Overview of Topics in Electrocatalysis for Sustainability: Reactions, Electrocatalysts, Degradation, and Mitigation

Abstract

Electrocatalysis provides an avenue for transitioning the global energy dependence from fossil fuels to renewable energy sources. While electrocatalytic reactions have been used for several decades, recently, there is a growing interest in electrocatalytic reactions that are useful from a sustainability perspective. The wide industrial applications of these sustainable electrocatalytic processes are largely limited by the degradation of the electrocatalysts. This review begins with an introduction to such reactions, followed by a detailed discussion of the electrocatalysts. Further, we describe the processes that are responsible for the degradation of electrocatalytic activity. Then, the strategies for reducing the degradation of electrocatalysts are discussed. This review also touches on the broader techno-economic and life-cycle considerations in catalyst development, linking fundamental research with practical sustainability.

1. Introduction

Developing sustainable and clean ways to produce energy and fuel is a major focus of the global scientific community today, as it has the potential to significantly reduce CO₂ emissions and secure our future energy. One of the most promising approaches to achieving this goal is through electrochemical conversion processes [1,2]. These processes involve using electricity to drive chemical reactions, which offers a route to convert renewable resources into valuable energy carriers or chemicals [3,4,5]. The efficacy of these technologies hinges not only on the intrinsic activity and selectivity of the electrocatalysts but, crucially, on their long-term durability under operational conditions [6,7,8].

Electrocatalysis is a process that accelerates an electrochemical reaction [9]. An electrochemical reaction is a combination of reduction and oxidation reactions. Although both of these reactions involve the transfer of electrons and occur at the interface of electrode and electrolyte, the directions of electron transfer are opposite to each other. In a reduction reaction, electrons are transferred from the electrode (cathode), while the oxidation reaction occurs simultaneously at the anode, where electrons are released by the oxidized species and flow through the external circuit to the cathode. The catalysts are required, as in any chemical reaction, to accelerate the rate of electron transfer by reducing the activation energy of the redox reaction.

Examples of electrochemical conversion include the splitting of water to produce hydrogen [10], the reduction of CO₂ to generate valuable hydrocarbons such as methane or ethylene [5,11,12], and nitrogen fixation for the production of ammonia [13]. Water electrolysis can convert water (H₂O) into hydrogen (H₂) and oxygen (O₂), a process that can provide a clean and sustainable source of hydrogen when powered by renewable electricity. Similarly, CO₂ reduction reactions can help mitigate greenhouse gas emissions by converting excess CO₂ into useful fuels or chemicals, such as carbon monoxide or formic acid. One of the goals is to develop processes where abundant molecules that are readily available in our environment, such as water, CO₂, and nitrogen, can be efficiently converted into higher-value products, such as clean fuels or chemical feedstock, with minimal environmental impact. In these electrochemical reactions, electrocatalysts play a vital role by enhancing the efficiency of electron transfer, lowering the activation energy of the reactions, and ensuring faster, more effective transformations.

Despite significant advancements in designing highly active and selective electrocatalysts, their stability remains a formidable challenge [14,15]. In regular applications, the electrocatalytic materials are exposed to harsh electrochemical environments, including varying potentials, fluctuating temperatures, and the presence of corrosive species or impurities. These conditions automatically lead to catalyst degradation, which manifests through a variety of complex mechanisms [8]. Understanding these degradation pathways is important for overcoming the current limitations toward the commercialization of these clean energy technologies.

This review aims to provide a concise overview of the field of electrocatalysis in the context of green and sustainable chemistry (Figure 1). First, we provide an overview of the key electrochemical reactions that are important from a sustainability perspective. Next, we present a brief survey of commonly used electrocatalysts. Then, we offer a timely discussion on electrocatalysts’ degradation, detailing the underlying mechanisms, the factors influencing these processes, and the emerging strategies aimed at mitigating them. Finally, we briefly explore the wider techno-economic and life-cycle aspects of catalyst development, bridging fundamental insights with real-world sustainability challenges.

2. Types of Electrocatalytic Reactions

Although a wide range of electrochemical reactions are being investigated for commercial applications, several are particularly vital for advancing sustainability. These reactions play a crucial role in addressing global energy and environmental challenges. In particular, electrocatalytic processes enable the conversion of abundant resources—such as water, carbon dioxide, and nitrogen—into valuable fuels and chemicals using renewable electricity. The primary electrocatalytic reactions of interest in this context include the following:

2.1. Oxygen Reduction Reaction (ORR)

The oxygen reduction reaction (ORR) is a key process for various electrochemical devices, most prominently fuel cells (e.g., Proton Exchange Membrane Fuel Cells (PEMFCs)) and metal–air batteries (such as Li–air and Zn–air). At the cathode of these devices, ORR converts oxygen into water (or hydroxide ions in alkaline media), enabling the flow of electricity [2,4,6]. Though it is a vital process, the ORR is kinetically sluggish due to its multi-electron transfer nature and the strong oxygen–oxygen bond in the O₂ molecule. The electrocatalysts have to be used to overcome this slow reaction rate and to achieve applicable current densities, which leads to a significant overpotential that limits overall device performance [6].

The ORR can proceed via two main pathways: the direct four-electron pathway, yielding water (2H₂O) in acidic media (${\mathrm{O}}_2+4{\mathrm{H}}^{+}+4{\mathrm{e}}^{-}\to 2{\mathrm{H}}_2\mathrm{O}$) or hydroxide ions (OH⁻) in alkaline media (${\mathrm{O}}_2+2{\mathrm{H}}_2\mathrm{O}+4{\mathrm{e}}^{-}\to 4\mathrm{O}{\mathrm{H}}^{-}$), and the two-electron pathway, producing hydrogen peroxide (H₂O₂) in acidic media (${\mathrm{O}}_2+2{\mathrm{H}}^{+}+2{\mathrm{e}}^{-}\to {\mathrm{H}}_2{\mathrm{O}}_2$) or hydroperoxide ions (${\mathrm{HO}}_2^{-}$) in alkaline media (${\mathrm{O}}_2+{\mathrm{H}}_2\mathrm{O}+2{\mathrm{e}}^{-}\to {\mathrm{HO}}_2^{-}+{\mathrm{OH}}^{-}$) [7]. The four-electron pathway is highly desirable for maximizing energy conversion efficiency and avoiding corrosive intermediates like ${\mathrm{H}}_2{\mathrm{O}}_2$, which can degrade catalyst materials and membranes [7]. Platinum (Pt) remains the benchmark catalyst for ORR in acidic environments due to its excellent activity and selectivity towards the four-electron pathway; however, its high cost and limited availability are significant barriers to widespread commercialization, driving the search for more sustainable alternatives [4,6].

2.2. Hydrogen Evolution Reaction (HER)

The Hydrogen Evolution Reaction (HER) is a critical cathodic reaction in water electrolysis, which offers a promising pathway for producing clean hydrogen fuel by following electrochemical reactions: in acid media $2{\mathrm{H}}^{+}+2{\mathrm{e}}^{-}\to {\mathrm{H}}_2$, and in alkaline media by $2{\mathrm{H}}_2\mathrm{O}+2{\mathrm{e}}^{-}\to {\mathrm{H}}_2+2{\mathrm{OH}}^{-}$ [16,17]. As a clean and sustainable energy carrier, hydrogen is envisioned as a key alternative to fossil fuels for the future fuel economy. However, the efficiency of water splitting, and thus the cost-effectiveness of hydrogen production, heavily relies on the performance of HER electrocatalysts.

While platinum (Pt) exhibits the lowest overpotential and fastest kinetics for HER, its high cost and scarcity hinder large-scale implementation [17]. Consequently, extensive research is dedicated to developing highly efficient, earth-abundant, and durable non-noble metal catalysts, as well as metal-free materials [16]. The HER mechanism typically involves initial proton adsorption, followed by either a Volmer–Heyrovsky or Volmer–Tafel step [18]. The optimization of these steps on the catalyst surface is crucial for high activity. Challenges include balancing activity with long-term stability and reducing the overpotential to make the process economically viable [16].

2.3. Hydrogen Oxidation Reaction (HOR)

The Hydrogen Oxidation Reaction (HOR) is the anodic reaction in fuel cells, particularly in PEMFCs, where hydrogen fuel is oxidized to produce protons and electrons (${\mathrm{H}}_2\to 2{\mathrm{H}}^{+}+2{\mathrm{e}}^{-}$) [19,20]. While the HOR is generally considered to be kinetically fast on platinum in acidic media, making the cathode (ORR) the primary performance bottleneck, its kinetics are found to be significantly slower in alkaline media [20,21]. This presents a major challenge for the development of anion-exchange membrane fuel cells (AEMFCs), which offer the advantage of potentially utilizing non-noble metal catalysts for ORR.

The sluggish kinetics of HOR in alkaline environments necessitate higher loadings of noble metal catalysts or the development of high-performance noble metal-free catalysts for the anode [20,21]. The exact mechanisms of alkaline HOR are still under debate, further complicating the rational design of electrocatalysts for this reaction [20]. Understanding the mechanistic insights, particularly the roles of various adsorbed intermediates and the influence of the electrolyte, is crucial for improving the performance of HOR catalysts. This is essential for unlocking the full potential of AEMFCs and other alkaline fuel cell technologies [20,22].

2.4. Oxygen Evolution Reaction (OER)

The Oxygen Evolution Reaction (OER) is the anodic half-reaction of water splitting, producing oxygen ($2{\mathrm{H}}_2\mathrm{O}\to {\mathrm{O}}_2+4{\mathrm{H}}^{+}+4{\mathrm{e}}^{-}$) [23,24]. It is also critical for rechargeable metal–air batteries, where it facilitates the regeneration of the metal anode [25,26]. Despite its importance, OER is kinetically sluggish due to the formation of a strong oxygen–oxygen bond and the involvement of multiple proton-coupled electron transfer steps, leading to high overpotentials [24,27]. This inherent kinetic barrier represents a major impediment to the overall efficiency of water electrolyzers and metal–air batteries.

Iridium (Ir) and ruthenium (Ru) oxides are currently the state-of-the-art OER catalysts, especially in acidic conditions, due to their superior activity [24]. However, their high cost, scarcity, and limited long-term stability (particularly Ru dissolution in acidic media) restrict their widespread application [24,28,29]. Consequently, there is a global effort to develop cost-effective, earth-abundant alternatives based on transition metals such as Fe, Co, Ni, and Mn, often in the form of oxides, hydroxides, chalcogenides, or phosphides [30,31,32,33,34]. The challenge lies in designing materials that can achieve high activity while maintaining robust stability under demanding OER operating conditions [24,27].

2.5. Carbon Dioxide Reduction Reaction (CO2RR)

The Electrocatalytic Carbon Dioxide Reduction Reaction (CO2RR) is a highly attractive approach for mitigating rising atmospheric CO₂ levels and generating valuable carbon-based chemicals and fuels (e.g., formate, methane, ethanol, ethylene) from renewable electricity [35,36]. This technology offers a promising route for artificial carbon recycling, potentially integrating carbon capture, utilization, and storage into sustainable energy cycles. However, the high thermodynamic stability of the CO₂ molecule requires a high overpotential for its activation, which remains a critical challenge.

Another major hurdle for CO2RR is achieving high selectivity towards a specific desired product, as CO₂ can be reduced into various ${\mathrm{C}}_1$ (e.g., CO, HCOOH, ${\mathrm{CH}}_3\mathrm{OH}$) or ${\mathrm{C}}_{2+}$ products (e.g., ${\mathrm{C}}_2{\mathrm{H}}_4$, ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}$) [37,38,39]. Furthermore, the CO2RR often competes with the energetically favorable HER, which reduces water to hydrogen and can significantly lower the Faradaic efficiency for carbon products [36,38,40]. Copper (Cu) and Cu-based materials are particularly interesting for CO2RR due to their unique ability to form ${\mathrm{C}}_{2+}$ products, but their selectivity and stability still need improvement [41]. Research focuses on developing catalysts that can efficiently activate ${\mathrm{CO}}_2$ while suppressing HER and controlling product distribution [42,43].

2.6. Nitrogen Reduction Reaction (NRR)

The Electrocatalytic Nitrogen Reduction Reaction (NRR) offers a sustainable and environmentally friendly alternative to the energy-intensive Haber–Bosch process for ammonia (NH₃) synthesis [44,45]. Ammonia is a vital chemical for fertilizers and is gaining recognition as a potential carbon-free energy carrier and liquid fuel due to its high energy density and hydrogen content [45,46,47]. The NRR aims to produce ${\mathrm{NH}}_3$ from ${\mathrm{N}}_2$ and water under ambient conditions (${\mathrm{N}}_2+6{\mathrm{H}}^{+}+6{\mathrm{e}}^{-}\to 2{\mathrm{NH}}_3$ in acidic media, or ${\mathrm{N}}_2+6{\mathrm{H}}_2\mathrm{O}+6{\mathrm{e}}^{-}\to 2{\mathrm{NH}}_3+6{\mathrm{OH}}^{-}$ in alkaline media) [48].

Despite its enormous potential, NRR faces significant challenges. The dinitrogen molecule (N₂) is extremely inert due to its strong triple bond, requiring high energy input for activation [45,49]. Moreover, the NRR competes intensely with the facile HER, which typically dominates, leading to low ammonia yields and poor Faradaic efficiencies [45,46,48]. Developing catalysts that can selectively activate N₂ and facilitate the multi-electron transfer steps while suppressing HER is a major research frontier [46]. Mitigation strategies often involve engineering the catalyst’s microenvironment to favor N₂ adsorption and activation over proton reduction [40].

Two principal mechanistic pathways have been proposed for the NRR: Associative and dissociative. In the associative pathway, N₂ first adsorbs intact on the catalyst surface and undergoes stepwise hydrogenation to form ^•N₂Hx intermediates, either via a distal mechanism (one N atom is hydrogenated fully before the other) or an alternating mechanism (hydrogenation proceeds on both N atoms sequentially) [46,48]. This pathway is generally favored on transition-metal-based and single-atom catalysts. By contrast, the dissociative pathway involves direct $N\equiv N$ bond cleavage followed by hydrogenation of two adsorbed N atoms (^•N), a route that is more relevant for certain nitrides but less feasible under ambient electrochemical conditions [45,49].

In addition to catalyst design, the electrolyte environment has been shown to significantly influence NRR performance. Alkali cations such as Li⁺ can interact with adsorbed N₂, facilitating bond polarization and simultaneously reducing HER by restructuring the interfacial water network. Larger cations such as K⁺ enhance the local electric field, stabilizing negatively charged intermediates (^•N₂⁻, ^•N₂Hx) and shifting the reaction toward NRR [40,45]. These findings emphasize that electrolyte engineering, alongside rational catalyst design, is crucial for improving selectivity and Faradaic efficiency.

3. Electrocatalysts

Electrocatalysts are essential materials that initiate and accelerate electrochemical reactions. They play a crucial role in determining the efficiency of these processes. In addition, they influence the selectivity and cost-effectiveness of various energy conversion and storage technologies. Their design involves modifying material properties, including composition, structure, and surface characteristics (such as two-dimensional surfaces [50]), to optimize interactions with reactants and intermediates. Based on their composition, electrocatalysts can be broadly categorized into noble metal-based, non-noble metal, and metal-free carbon-based materials (Figure 2).

3.1. Noble Metal-Based Electrocatalysts

Noble metal-based electrocatalysts, particularly those involving platinum (Pt) and other platinum group metals (PGMs) such as palladium (Pd), iridium (Ir), and ruthenium (Ru), have historically been the gold standard due to their exceptional intrinsic activity and stability for various electrochemical reactions.

3.1.1. Platinum (Pt)

Platinum is the benchmark catalyst for ORR in acidic media and HER. The superior electrocatalytic activity of platinum stems from its optimized binding energies for reaction intermediates. However, its scarcity and prohibitive cost pose significant barriers to widespread commercialization in applications like fuel cells [4,51,52]. To address these limitations, research on Pt-based catalysts focuses on maximizing Pt utilization and enhancing its durability.

Alloying Pt with transition metals (e.g., Fe, Co, Ni) has emerged as a key strategy to improve ORR activity and stability. The introduction of these secondary metals modifies the electronic structure of Pt (e.g., shifting the d-band center), which can weaken the adsorption of oxygenated species, thereby enhancing kinetics and mitigating poisoning [6,53,54,55]. Examples like ordered ${\mathrm{Pt}}_3\mathrm{Co}$ intermetallics demonstrate enhanced activity and durability [54]. The resulting lattice strain and ligand effects within these alloys play a crucial role in optimizing the binding energy of ORR intermediates [54].

Core–shell is an innovative design that minimizes Pt loading by confining it to the outer shell, while a less expensive core material (e.g., Pd, Au, Ni) provides the structural foundation and modulates the electronic properties of the Pt shell [51,53]. This maximizes the utilization of precious Pt atoms and enhances the catalytic performance and durability through beneficial strain and ligand effects [51,53].

Beyond nanoparticles, research explores Pt-based nanowires, nanotubes, and other porous structures. It is found that such structures show a great potential in improving overall catalyst performance in devices like fuel cells [52]. The greater performance of such morphologies is often attributed to the increase in the electrochemically active surface area.

3.1.2. Other PGMs (Pd, Ir, Ru)

Palladium (Pd)-based catalysts are investigated for both HOR and ORR, often as alternatives or alloys with Pt, showcasing promising activity and stability [22]. Iridium (Ir) and ruthenium (Ru) oxides are state-of-the-art catalysts for the OER due to their high activity, especially in acidic environments [24]. However, similar to Pt, their high cost and, particularly for Ru, significant dissolution in acidic media, limit their long-term applicability [24,28,29]. Research in this area involves doping and alloying strategies to enhance their stability [28,29].

3.2. Non-Noble Metal Electrocatalysts

The high cost and limited abundance of noble metals have spurred intensive research into non-noble metal electrocatalysts, which utilize earth-abundant transition metals (Fe, Co, Ni, Mn, Mo, W) and their compounds. These materials aim to provide cost-effective alternatives with comparable or superior performance, particularly in alkaline media.

3.2.1. Metal–Nitrogen–Carbon (M-N-C) Catalysts

These are a highly promising class, especially for ORR, often featuring atomically dispersed metal centers (e.g., Fe, Co) coordinated by nitrogen atoms within a porous carbon matrix. The synergistic interaction between the metal, nitrogen, and carbon support creates highly active sites [56,57]. Fe-N-C catalysts, for instance, have shown impressive initial ORR activity, sometimes rivaling that of Pt in alkaline environments [56]. Challenges include achieving high active site density, ensuring long-term stability in harsh conditions (especially acidic), and controlling the exact nature of the active sites [58]. They are also explored for NRR and CO2RR [59].

3.2.2. Metal Oxides and Hydroxides

Transition metal oxides (TMOs) and oxyhydroxides are extensively studied for OER and HER due to their tunable electronic properties and diverse structural possibilities. Examples include spinels (MFe₂O₄, where M=Ni, Co, Fe, Mn) [30,32,33], perovskites [60], and other mixed metal oxides [61]. Molecular metal oxides (polyoxometalates) show great potential as electrocatalysts in HER [62]. These materials often exhibit good activity in alkaline media, and their performance can be enhanced by optimizing their morphology (e.g., porous structures [63]), introducing oxygen vacancies, or doping with other elements [30,32]. Manganese-based oxides, for example, show promise for ORR and water splitting [33].

3.2.3. Metal Chalcogenides (Sulfides, Selenides)

Transition metal chalcogenides (TMCs), such as ${\mathrm{MoS}}_2$, ${\mathrm{WS}}_2$, and their analogues, are gaining significant attention for HER and OER due to their unique electronic structures and abundant active edge sites [31,64,65,66]. Defect engineering (e.g., creating sulfur vacancies) in two-dimensional TMCs has been shown to enhance their electrocatalytic activity [64,65]. Various selenides have also been investigated for selective CO2RR [67,68].

3.2.4. Metal Phosphides

Transition metal phosphides (TMPs) like MoP, CoP, and various nickel–molybdenum phosphides are emerging as highly active and stable catalysts for HER and OER [31,69]. Their metallic conductivity and unique electronic properties make them efficient for hydrogen and oxygen evolution. Hybrid structures, such as CoP-embedded nitrogen and phosphorus co-doped mesoporous carbon nanotubes, demonstrate enhanced HER efficiency [70].

3.2.5. Metal Carbides and Nitrides

Transition metal carbides (TMCs) and nitrides exhibit good metallic conductivity and often possess Pt-like electronic structures, making them attractive for various electrocatalytic reactions, including ORR, HER, and OER [23]. Examples like ${\mathrm{Mo}}_2\mathrm{C}$ have shown activity for CO2RR [42].

3.3. Metal-Free Carbon-Based Electrocatalysts

Metal-free carbon-based electrocatalysts offer a sustainable and cost-effective alternative to metal-containing catalysts, leveraging the earth-abundance, high electrical conductivity (for certain morphologies), and tunable surface properties of carbon materials. Their catalytic activity arises from intrinsic defects within the carbon lattice or from the deliberate incorporation of heteroatoms.

3.3.1. Heteroatom-Doped Carbons

Doping carbon nanostructures (e.g., graphene, carbon nanotubes, carbon quantum dots) with non-metal heteroatoms such as nitrogen (N), boron (B), sulfur (S), or phosphorus (P) is a primary strategy to enhance their electrocatalytic activity for ORR, HER, OER, and NRR [71,72,73]. Nitrogen doping is particularly effective, as the different nitrogen configurations (pyridinic-N, graphitic-N, pyrrolic-N) within the carbon lattice alter the charge distribution, creating active sites and improving oxygen adsorption and reduction kinetics [71,74]. Boron and sulfur doping can also introduce active sites and enhance electron transfer [72].

3.3.2. Defect-Engineered Carbons

Beyond heteroatom doping, creating intrinsic defects (e.g., vacancies, topological defects, Stone-Wales defects) within the carbon lattice itself can serve as active sites for various electrocatalytic reactions, including ORR, HER, and OER [75]. These defects can modify the local electronic structure and provide sites for reactant adsorption. The challenge lies in precisely controlling the type and density of these defects for optimal performance and stability.

3.3.3. Hybrid Carbon Materials

Carbon materials often serve as excellent supports or components in hybrid electrocatalysts, enhancing conductivity, providing large surface areas, and preventing the agglomeration of active metal nanoparticles. Examples include graphene-based electrocatalysts integrated with transition metal compounds for HER and electrocatalytic water splitting [76,77], or porous carbon architectures in lithium-based batteries [78]. Various morphologies of carbon-based anodes are often employed in sodium-ion batteries for efficient performance [79]. The interfacial engineering of carbon-based materials with heterogeneous components can create specific interfaces that act as active sites or major reaction sites for various reactions (OER, HER, ORR, CO2RR, and NRR) [71].

Following the discussion of various electrocatalyst families and their compositional diversity, it is essential to evaluate their functional performance using standardized electrochemical metrics. Overpotential, Tafel slope, and electrochemical stability are critical parameters for evaluating the performance of electrocatalysts. Overpotential denotes the additional potential required beyond the thermodynamic equilibrium to drive an electrochemical reaction; a lower overpotential implies higher catalytic efficiency and reduced energy input. The Tafel slope quantifies the relationship between overpotential and the logarithm of current density, providing insight into the reaction kinetics; a smaller Tafel slope indicates that a minor increase in overpotential yields a significant rise in current density, reflecting more favorable kinetics and enhanced catalytic activity. Electrochemical stability assesses the durability of the catalyst under prolonged operational conditions, which is essential for practical and scalable applications.

Table 1. Quantitative performance metrics of selected electrocatalysts discussed in this review. Overpotentials are reported at 10 mA/cm², with Tafel slopes and stability reflecting representative values under commonly studied conditions. Data are drawn from published articles and serve as a comparative benchmark across noble metal and emerging catalyst families.

Electrocatalyst	Reaction Type	Overpotential @10 mA/cm2 (mV)	Tafel Slope (mV/dec)	Stability (h)	Ref.
Pt/C	HER/ORR	∼30 (HER)	∼30	>100	[17,52]
IrO2	OER	∼300	∼40	>100	[24]
RuO2	OER	∼280	∼55	∼50	[24,29]
Pd/C	HOR, ORR	∼50 (HOR)	∼40	∼60	[22]
NiFe LDH	OER	∼270	∼35	>200	[30]
MoS2 (exfoliated)	HER	∼150	∼60	∼20	[64]
CoP	HER	∼120	∼50	∼80	[69]
Fe–N–C	ORR	∼400	∼70	30–50	[56]
MnOx	OER	∼350	60–80	∼50	[33]
Mo2C	HER/CO2RR	∼180 (HER)/∼600 (CO2RR)	∼50–70	∼40	[23,42]
MoSe2	CO2RR	∼500–700	-	∼10–20	[68]
N-doped graphene	ORR/NRR	∼350	∼80	∼40	[71,74]

summarizes representative values for key performance metrics such as overpotential at 10 mA/cm², Tafel slope, operational stability, and electrolyte conditions. These metrics help illustrate the trade-offs between noble-metal-based catalysts, which often offer superior activity, and emerging non-precious alternatives, which are typically more cost-effective and sustainable.

4. Mechanisms for Degradation

Despite significant advancements in their design and synthesis, electrocatalysts are inherently susceptible to degradation, which limits their long-term performance and widespread commercialization. These degradation processes are complex, often interconnected, and can occur due to the harsh electrochemical environment, material instability, or interaction with reaction intermediates and impurities. Figure 3 depicts an overview of such processes that lead to the degradation of electrocatalysts. Understanding these mechanisms is crucial for developing strategies to enhance catalyst durability.

4.1. Corrosion and Oxidation

Corrosion and oxidation are ubiquitous degradation pathways that impact both the active catalyst material and its support, particularly under high anodic potentials or during dynamic operational cycles.

4.1.1. Carbon Support Corrosion

In fuel cells, especially PEMFCs, the carbon support (e.g., carbon black) for PGM catalysts is highly vulnerable to electrochemical oxidation [7,80,81]. This corrosion occurs predominantly at high potentials (e.g., >0.8 $V_{\mathrm{RHE}}$) or during transient conditions like start-up and shut-down, where the cathode potential can spike [82]. The oxidation process converts carbon into carbon oxides (CO₂, CO), leading to a reduction in the electrical conductivity of the catalyst layer, a decrease in the active surface area of the catalyst due to detachment of particles, and ultimately, a decline in fuel cell performance [7,80,81,83]. Reactive oxygen species (ROS) such as hydrogen peroxide (H₂O₂) and super-oxide radicals, formed as undesired intermediates during the oxygen reduction reaction (ORR), can also chemically attack the carbon support, accelerating its degradation [7,81]. This loss of support integrity can lead to catalyst migration and agglomeration, further exacerbating performance decay [83]. Studies on carbon materials highlight how factors like graphitization degree, surface area, and pore structure influence their corrosion resistance [78,80].

4.1.2. Metal Oxidation and Dissolution

Active metal components, particularly noble metals like Pt, Ir, and Ru, undergo oxidation and subsequent dissolution, which are major degradation pathways. For Pt catalysts in fuel cells, the formation of platinum oxides (e.g., PtO, ${\mathrm{PtO}}_2$) at high potentials (e.g., above $0.8\text{–}0.9V_{\mathrm{RHE}}$) followed by their dissolution into the electrolyte as ${\mathrm{Pt}}^{2+}$ or ${\mathrm{Pt}}^{4+}$ ions is a primary cause of activity loss [7,51,82,84,85]. This process reduces the electrochemically active surface area over time. This phenomenon is particularly severe during fuel cell start-up/shut-down cycles due to large potential fluctuations [82]. Similarly, Ru-based catalysts, highly active for the OER, particularly in acidic media, suffer from significant dissolution [28,29]. This is often linked to the involvement of lattice oxygen in the OER mechanism, leading to the formation of unstable Ru oxide species that readily dissolve, limiting their long-term stability [28,29]. Tungsten-oxide-based catalysts for water splitting also face degradation due to the formation of less active oxide layers that can detach from the electrode surface [86]. For ${\mathrm{PbO}}_2$ electrodes, used in electrocatalytic degradation of organic pollutants, the degradation involves corrosion of the ${\mathrm{PbO}}_2$ layer itself and the underlying substrate, which is crucial for their long-term effectiveness in wastewater treatment [70,87].

4.2. Leaching of Active Sites

Leaching refers to the selective dissolution and removal of active metal components from the catalyst structure, leading to a direct reduction in the concentration of available active sites for the desired electrochemical reaction. This mechanism is particularly detrimental for noble metal nanoparticles and atomically dispersed catalysts.

For Pt and PGM nanoparticles, the dissolution of individual metal atoms from the particle surface is a fundamental degradation pathway. This dissolved metal can then re-deposit onto larger, more thermodynamically stable particles in a process known as Ostwald ripening [7,51,82,84,85]. This leads to an increase in the average particle size and a dramatic decrease in the total electrochemically active surface area over time, significantly reducing the catalyst’s performance. Alternatively, particle aggregation can occur, where individual nanoparticles merge, also resulting in a reduction in active surface area and accessibility of reaction sites [84,85]. Both Ostwald ripening and aggregation are accelerated at higher temperatures and during potential cycling, which promotes surface mobility and dissolution–reprecipitation events [82,84].

For Metal–Nitrogen–Carbon (M-N-C) catalysts, which are promising non-precious metal alternatives for the ORR, the demetalation of the active metal sites (e.g., iron from Fe-N-C) is a major cause of activity loss, especially in acidic environments [56,58]. These catalysts rely on atomically dispersed or nanostructured metal centers (often coordinated by nitrogen) embedded within a carbon matrix. Under acidic and oxidative conditions, these metal centers can leach out into the electrolyte, directly deactivating the catalyst [56]. This issue is a significant barrier to their widespread adoption in acidic PEMFCs, requiring substantial efforts in material design to improve the anchoring and stability of these active sites [58]. Similarly, the significant dissolution of Ru-based catalysts for OER, particularly in acidic media, exemplifies active site leaching, where the precious metal ions are lost from the catalyst, severely limiting its long-term stability and practical applicability [28].

4.3. Surface Reconstruction

Surface reconstruction refers to the dynamic atomic and electronic rearrangement of a catalyst’s surface under electrochemical operating conditions. These changes can be either beneficial and reversible, contributing to improved activity, or detrimental and irreversible, leading to long-term deactivation (Figure 4).

Dynamic restructuring, Figure 4a, transformations that typically enhance catalytic performance and can revert once the applied potential is removed. For example, transition metal oxides such as NiFeOx undergo in situ oxidation during the OER to form amorphous (oxy)hydroxide layers, which are considered the true catalytically active phase [61,88]. This restructuring increases active site density, modifies electronic states, and introduces defects that favor reaction kinetics [89,90,91].

In contrast, irreversible degradation, Figure 4b, involves structural or compositional changes that persist even after reaction conditions cease. Examples include the formation of thick, passivating oxide layers on Pt or Ni surfaces [61], lattice oxygen loss leading to dissolution in Ru-based catalysts [28,29], and metal ion leaching from atomically dispersed active sites [56,58]. These transformations reduce electrochemically active surface area and permanently compromise catalyst durability.

Discerning between these two surface reconstruction mechanisms requires in situ or operando techniques. Electrochemical liquid-phase transmission electron microscopy (ec-LPTEM) [89,90,91], X-ray absorption spectroscopy (XAS) [88], and Raman spectroscopy have been used to visualize restructuring at the nanoscale and differentiate between transient activation phenomena and irreversible degradation. Understanding this distinction is critical for designing catalysts that are not only active but also structurally robust under long-term operating conditions.

Operando techniques provide vital real-time insights into the structural, chemical, and electronic transformations of electrocatalysts under actual working conditions [92]. Operando Raman spectroscopy enables the detection of surface intermediates and phase transitions during electrocatalysis [93], while operando X-ray-based techniques are effective for monitoring oxidation states and chemical bonding changes on the catalyst surface [94,95]. Additionally, techniques like the electrochemical quartz crystal microbalance (EQCM) can sensitively track catalyst mass loss or gain during dissolution or deposition, providing quantitative insight into degradation processes [92,96]. Interpreting the complex, dynamic datasets from these operando methods often requires integration with computational modeling approaches such as density functional theory (DFT) or machine learning [97]. Acknowledging these challenges and limitations is essential for improving mechanistic understanding and enabling the rational design of electrocatalysts that can endure harsh operational environments.

4.4. Poisoning by Reaction Intermediates and Impurities

Catalyst poisoning is a significant degradation mechanism wherein foreign chemical species, either present as impurities in the reactant streams or generated as unwanted byproducts during the electrochemical reaction, irreversibly adsorb onto the active sites of the catalyst. This adsorption blocks the active sites, making them unavailable for the desired reaction and consequently diminishing the catalyst’s activity and selectivity.

In fuel cells, the primary catalysts are highly susceptible to poisoning from impurities in the fuel and air feeds. For instance, the Pt-anode catalyst is severely affected by carbon monoxide poisoning [98,99]. Even trace amounts of CO strongly adsorb on Pt sites, blocking them and leading to significant performance loss, especially at lower operating temperatures where CO desorption is slow [99,100]. Other sulfur-containing compounds (e.g., ${\mathrm{H}}_2\mathrm{S}$) and hydrocarbons present in impure hydrogen fuel can also adsorb on Pt surfaces, further contributing to poisoning [99,100]. On the cathode side, impurities in the air feed, such as SO₂ or NH₃, can adsorb on the active sites of ORR catalysts or interact with the proton exchange membrane, negatively impacting cell performance and stability [84,99,101].

Beyond external impurities, poisoning can also arise from undesired reaction intermediates. In the ORR, incomplete reduction of oxygen can lead to the formation of ROS like hydrogen peroxide (${\mathrm{H}}_2{\mathrm{O}}_2$) and super-oxide radicals. These species are not only detrimental because they represent inefficient energy conversion (two-electron pathway instead of four-electron) but also because they can chemically attack and degrade both the carbon support and the active metal sites, contributing to catalyst instability [7].

A critical challenge for multi-electron reactions like the CO2RR and the NRR is the intense competition from the kinetically facile HER [38,45,46]. In aqueous electrolytes, protons are readily available, and their reduction to hydrogen can preferentially occur on the catalyst surface. The strong adsorption of hydrogen intermediates (${\mathrm{H}}_{\mathrm{ad}}$) on the active sites effectively ‘poisons’ them, preventing the adsorption and activation of the less reactive ${\mathrm{CO}}_2$ or ${\mathrm{N}}_2$ molecules [38,40,46]. This competitive adsorption significantly reduces the selectivity and Faradaic efficiency for the desired carbon or nitrogen products, making it a major hurdle for the practical implementation of CO2RR and NRR [38,40]. Mitigation strategies often involve engineering the catalyst’s microenvironment to suppress HER or designing sites that selectively bind to ${\mathrm{CO}}_2$ or ${\mathrm{N}}_2$ over hydrogen intermediates [40].

5. Factors Influencing Degradation

The degradation of electrocatalysts is not solely an intrinsic material property but is significantly influenced by a complex interplay of various external operational conditions and the catalyst’s inherent characteristics. Understanding these influencing factors is paramount for designing more robust and durable electrocatalytic systems.

Potential cycling is one of the most critical and well-studied factors influencing degradation, particularly in fuel cells, often referred to as start-stop or load cycling [7,84]. During these dynamic operations, the catalyst is exposed to a wide range of potentials. For Pt catalysts in PEMFCs, repeated cycling between high potentials (e.g., $1.0\text{–}1.2V_{\mathrm{RHE}}$, characteristic of fuel starvation or air purging during shut-down) and low potentials (e.g., $0.6V_{\mathrm{RHE}}$, typical operating potential) severely accelerates degradation [7,82,85,99]. At high potentials, Pt oxidizes, forming surface oxides; upon potential reversal, these oxides are reduced, but some Pt atoms can dissolve into the electrolyte. This repeated oxidation-reduction-dissolution cycle leads to significant Pt loss, particle agglomeration, and a drastic reduction in the electrochemically active surface area [7,82,84,85]. Beyond Pt, carbon supports are also prone to oxidative corrosion at high potentials, leading to structural collapse and detachment of catalyst particles [80,82]. The rate and extent of degradation are highly dependent on the upper and lower potential limits, sweep rate, and duration of cycling.

Temperature plays a dual role in influencing catalyst degradation. Generally, elevated operating temperatures accelerate the kinetics of most chemical and electrochemical processes, including detrimental ones like dissolution, corrosion, and Ostwald ripening of catalyst nanoparticles [84,99]. Higher temperatures can increase the mobility of surface atoms, facilitating particle growth and agglomeration, which reduces the active surface area [85]. However, very low operating temperatures can also induce degradation, particularly in PEMFCs, where water freezing within the porous electrode structures can cause mechanical stress, cracking, and damage to the catalyst layer and membrane, leading to performance loss [84,99]. Therefore, maintaining an optimal temperature window is crucial for catalyst durability.

The pH of the electrolyte significantly impacts catalyst stability and the specific degradation pathways. The stability of many transition metal oxides and non-noble metal catalysts is highly sensitive to pH, with some being stable in alkaline environments but prone to dissolution in acidic conditions, and vice versa [28,60]. For instance, the kinetics of the HOR are markedly slower in alkaline media compared to acidic media, influencing the choice and stability of catalysts for anion exchange membrane fuel cells [20,21]. The presence of specific ions in the electrolyte can also affect dissolution rates (e.g., halide ions can promote Pt dissolution) or lead to poisoning [99]. Furthermore, the accumulation of corrosive species or reaction intermediates can lead to localized pH changes within the catalyst layer, creating a microenvironment that accelerates degradation even if the bulk electrolyte pH is controlled [99].

Electrolytes’ composition plays a critical role in determining the performance and durability of electrocatalytic systems, not only by providing ionic conductivity but also by directly influencing reaction pathways, intermediate stabilization, and catalyst stability (summarized in

Table 2. Summary of electrolyte effects on electrocatalysis.

Electrolyte Factor	Activity or Selectivity	Effect on Stability	Example Reactions
Li+	N2 polarization, HER suppression	Reduces local proton activity	NRR, CO2RR
K+ or Cs+	Stabilizes •N2−, •CO2− intermediates	Minimizes parasitic reactions	NRR, CO2RR
Halides (Cl−, Br−)	Modulate binding energies	Possible surface adsorption	HER, CO2RR
SO42− (anion)	Inert behavior, supports intrinsic activity	Minimal interaction	ORR, OER
Water-in-salt electrolytes	Suppress HER, improve selectivity	Reduce catalyst leaching	NRR, CO2RR
Organic co-solvents	Stabilize intermediates	Lower solvent- driven degradation	CO2RR, NRR

). While pH and bulk composition are well-established factors, emerging studies highlight the importance of specific ion effects and solvent environments in governing catalytic behavior. Alkali cations modulate the interfacial electric field and can stabilize key reaction intermediates [102]. For example, Li⁺ has been shown to strongly polarize N₂ and CO₂, facilitating their activation, while also suppressing the competing HER by reducing local proton activity [40]. Larger cations such as K⁺ and Cs⁺ generate a stronger interfacial electric field, which has been linked to enhanced stabilization of negatively charged intermediates (^•N₂⁻ or ^•CO₂⁻) and improved selectivity [40]. Electrolyte anions can also alter reaction pathways by specific adsorption or by modifying the double-layer structure. For instance, halides (e.g., Cl⁻, Br⁻) may interact with catalyst surfaces and tune the binding strength of intermediates [103,104], whereas non-coordinating anions (e.g., SO₄²⁻) tend to affect the microenvironment to improve intrinsic catalyst activity [105].

Beyond aqueous media, mixed-solvent systems and non-aqueous electrolytes have emerged as strategies to improve selectivity and stability. The use of aprotic or water-in-salt electrolytes can lower proton availability and suppress HER, enabling more favorable conditions for multi-electron transformations such as CO2RR and NRR [45]. Similarly, organic co-solvents have been employed to stabilize reactive intermediates or to modulate the solvation environment of key species, thereby influencing both activity and long-term catalyst durability [106,107]. Collectively, these findings underscore that electrolyte engineering—through deliberate choice of cations, anions, and solvent composition—is a powerful but underexplored lever for simultaneously improving catalytic activity, product selectivity, and material stability. Integrating these considerations alongside catalyst design represents a promising route toward practical and durable electrocatalytic systems.

Finally, mass transport limitations within the electrode structure can indirectly contribute to degradation. Inadequate supply of reactants or inefficient removal of products can lead to local concentration gradients. For example, in ORR, poor oxygen transport can result in the accumulation of reactive oxygen species (${\mathrm{H}}_2{\mathrm{O}}_2$) at the cathode, which can then attack the carbon support and the catalyst itself [7]. Similarly, the buildup of gaseous products (e.g., ${\mathrm{O}}_2$ bubbles in OER or ${\mathrm{H}}_2$ bubbles in HER) can block active sites, hinder mass transfer, and cause physical damage to the catalyst layer over time. These localized effects create conditions that are more conducive to various degradation mechanisms than the bulk operating environment might suggest [99]. The intrinsic material properties, such as electronic structure, surface facets, defect density, and chemical bonding within the catalyst, ultimately dictate its inherent resistance to these degradation pathways [75].

6. Mitigation Strategies

The persistent challenge of electrocatalysts’ degradation necessitates innovative strategies that integrate fundamental materials science with advanced engineering principles. Effective mitigation approaches often involve tailoring the catalyst’s composition, structure, and local environment to enhance its resilience against degradation mechanisms while maintaining high activity.

6.1. Composition Engineering

Catalyst design and compositional engineering are primary avenues for enhancing durability. For platinum-based catalysts, alloying Pt with transition metals (e.g., Fe, Co, Ni) introduces lattice strain and ligand effects that can modify the electronic structure of Pt, optimizing its binding energies for reaction intermediates and making it less susceptible to dissolution and poisoning [4,51,54,55]. These alloys, particularly ordered inter-metallic structures, demonstrate enhanced stability against Pt dissolution and improved ORR kinetics [54]. Core–shell structures represent another elegant solution, where a thin, protective Pt shell encapsulates a cheaper, often non-noble metal core. This design not only maximizes the utilization of precious Pt but also protects the core from dissolution and can tune the electronic properties of the surface Pt atoms, leading to both higher activity and improved durability [4,51,53]. For other metal catalysts, such as Ru-based OER catalysts, strategies like alloying with more stable elements are explored to mitigate their significant dissolution in acidic media [28,29].

6.2. Structure Modifications

Structural and morphological control also plays a crucial role in enhancing the durability of an electrocatalyst. Designing catalysts with controlled porous structures can improve mass transport kinetics, reduce local concentrations of corrosive species, and provide larger surface areas for active sites, all contributing to enhanced stability [63]. Furthermore, the choice of support material is critical. Using highly graphitized carbon supports significantly enhances their corrosion resistance against electrochemical oxidation compared to amorphous carbon, providing a more stable and robust platform for active metal nanoparticles and improving overall catalyst durability in fuel cells [78,80,85,108]. This approach directly addresses the carbon corrosion issue, a major degradation pathway.

6.3. Interfacial Engineering

Interfacial engineering focuses on optimizing the interactions at the boundaries between different catalyst components (e.g., metal/support, metal/metal oxide interfaces). Strong electronic and chemical interactions at these interfaces can stabilize active sites, prevent their leaching, and promote efficient electron transfer kinetics [52,61,71]. This can also be leveraged to induce beneficial surface reconstructions while suppressing detrimental ones, thereby guiding the catalyst towards more stable and active configurations during operation [61]. For instance, certain interfaces can stabilize atomically dispersed active sites, preventing their agglomeration or dissolution [58].

6.4. Microenvironment Engineering

Controlling the microenvironment involves tailoring the local chemical and physical environment around the active sites to favor desired reactions and suppress degradation pathways. For reactions facing strong competition from the HER, such as NRR and CO2RR, engineering a hydrophobic surface or controlling the local pH can effectively suppress HER by limiting proton access to the active sites, thereby enhancing selectivity and Faradaic efficiency for the target product [40,45]. This strategy creates a more favorable environment for the specific reactant (e.g., ${\mathrm{N}}_2$ or ${\mathrm{CO}}_2$) to adsorb and react.

6.5. Developing New Materials

Finally, the development of inherently robust materials and protective coatings offers direct approaches to combating degradation. This includes exploring new classes of stable transition metal compounds like specific phosphides and chalcogenides, or highly stable Metal–Organic Framework (MOF)-derived materials that are intrinsically designed to withstand harsh electrochemical environments [31,32,109]. Applying ultra-thin protective layers or functional coatings over catalyst particles can physically shield them from direct contact with corrosive electrolytes or reactive intermediates while still allowing reactants to access the active sites, thus extending their operational lifetime [110]. Combined, these multifaceted strategies are essential for bridging the gap between laboratory-scale catalyst performance and real-world durability requirements.

To provide a comprehensive overview, in

Table 3. Interrelationship between degradation mechanisms, reaction types, catalyst types, and mitigation strategies in electrocatalysis.

Degradation Mechanism	Reaction Types Affected	Typical Catalyst Types	Example Catalysts (Refs)	Mitigation Strategies (Refs)
Carbon Support Corrosion	ORR, OER (fuel cells, metal–air)	Pt/C, PGM/C (Pt, Pd, Ir, Ru)	Pt/C, PtCo/C [7,80,81]	Use graphitized carbon supports [80], alloy catalysts [54], protective coatings [110], control start-stop cycles [111]
Metal Oxidation & Dissolution	ORR, OER, HER	Pt, Ir, Ru, Pd	Pt [7], RuO2 [28,29], IrO2 [24]	Alloying with stable metals (PtCo, PtNi) [54], core–shell structures [51], potential cycling control [82]
Leaching of Active Sites	ORR, OER, NRR	M–N–C (Fe, Co), Ru-based	Fe–N–C [56,58], Ru-based OER [28,29]	Stronger metal–support interaction [29], interfacial engineering [112], anchoring atomically dispersed sites [56]
Ostwald Ripening & Aggregation	ORR, HER, CO2RR	Pt, Pd nanoparticles, Cu for CO2RR	Pt/C [84,85], Cu nanoparticles [41]	Optimize particle size [85], porous supports [113], stabilizers to suppress migration [54]
Surface Reconstruction	OER, HER, CO2RR	Transition metal oxides, chalcogenides	NiFeOx [30], MoS2 [64]	Operando monitoring [92], design self-reconstructing catalysts [61], interface stabilization [61]
Poisoning by Impurities	ORR, CO2RR, NRR	Pt (CO poisoning), Cu (CO2RR), Fe–N–C (NRR)	Pt (CO) [98,100], Cu (CO2RR) [38], Fe–N–C (NRR) [46]	Microenvironment engineering [40], hydrophobic layers, selective binding sites [40], impurity filtration [99]
Electrolyte Effects (pH/Ions)	HOR, HER, ORR, CO2RR, NRR	Pt, M–N–C, Cu	Pt (HOR) [20,21], Cu (CO2RR) [38], Fe–N–C (NRR) [46]	Electrolyte optimization [114], buffer layers [40], ion-selective membranes [99]

, we have summarized the interrelations between major degradation mechanisms, relevant electrocatalytic reactions, catalyst types, and corresponding mitigation strategies. Table 3 consolidates the detailed discussion presented above, highlighting how specific degradation pathways—such as carbon corrosion, metal dissolution, or poisoning by impurities—are directly linked to particular reactions and catalyst classes. This offers a clear perspective on how mitigation approaches such as alloying, interfacial engineering, microenvironment control, and electrolyte optimization can be strategically applied to enhance catalyst durability. Further, it serves as a practical guide for the rational design of stable and durable electrocatalysts under realistic operating conditions.

7. Techno-Economic and Life-Cycle Considerations

The development of high-performance electrocatalysts is increasingly being guided not only by activity and durability metrics but also by techno-economic feasibility and life-cycle impacts [115]. As the field moves closer to real-world implementation, assessing the overall sustainability of electrocatalytic systems—including cost of materials, availability of elements, synthesis scalability, and environmental footprint—is critical. This comparison is presented in

Table 4. Comparison of catalyst classes based on key sustainability and performance metrics.

Catalyst Class	Material Cost	Element Abundance	Synthetic Scalability	Recyclability	Life-Cycle Impact
Pt/C, IrO2, RuO2	High	Low	Moderate	Moderate	High
Fe–N–C, Co–N–C	Low	High	Moderate–High	High	Moderate
Metal Oxides	Low	High	High	High	Low
Metal Phosphides	Medium	Moderate	Moderate	Unknown	Moderate
MOF-derived Catalysts	Medium–High	Variable	Often Complex	Unknown	High

.

Noble metal catalysts like Pt and Ir, while exhibiting exceptional catalytic properties, remain prohibitively expensive and scarce, posing a major bottleneck for large-scale deployment in systems such as fuel cells and electrolyzers. In contrast, non-noble alternatives like Fe-N-C catalysts, transition metal oxides, and phosphides offer more favorable economic profiles and are composed of earth-abundant elements. However, long-term durability, recyclability, and manufacturing energy requirements still present challenges that impact their life-cycle performance.

Recent life-cycle assessment (LCA) studies have attempted to quantify these factors by analyzing the environmental impact of catalyst synthesis, energy input, chemical use, and end-of-life disposal or recyclability [116]. For example, catalysts with high-temperature or multi-step synthesis routes may carry higher embedded energy or CO₂ footprints, even if they use cheap raw materials. Moreover, metrics like cost per kilogram of hydrogen produced (for HER) or per mole of CO₂ converted (for CO2RR) are being used to connect catalyst design to system-level efficiency.

Though comprehensive techno-economic modeling is beyond the scope of most lab-scale catalyst studies, early consideration of these factors can help steer material development towards solutions that are both environmentally and economically viable at scale.

8. Conclusions

The widespread adoption of electrocatalysis in sustainable energy technologies hinges critically on overcoming the persistent challenge of catalyst degradation. While tremendous progress has been made in enhancing the activity and selectivity of electrocatalysts, their long-term durability under demanding operational conditions remains a formidable bottleneck. This review has illuminated the diverse and interconnected mechanisms that lead to catalyst degradation, including corrosion and oxidation, leaching of active sites, detrimental surface reconstruction, and poisoning by reaction intermediates and impurities. Each mechanism presents unique challenges that are further exacerbated by various operating factors such as potential cycling, elevated temperatures, and specific electrolyte compositions.

Addressing these complex degradation issues necessitates a concerted and systematic approach across the entire research and development pipeline. First and foremost, stability tests should become a norm for all studies that present new electrocatalysts. Moving beyond initial activity metrics to include rigorous, standardized, and long-term durability assessments under relevant operating conditions is crucial. This paradigm shift will facilitate a more realistic evaluation of catalyst viability, allowing for the prioritization of materials that not only exhibit high initial performance but also possess the inherent robustness required for practical applications.

Secondly, given that degradation mechanisms for each electrocatalyst are not only distinct but also highly dependent on various intrinsic and extrinsic factors, there is an urgent need for developing standardized protocols to assess the temporal stability of electrocatalytic performance. Such standardization would enable truly meaningful and reproducible comparisons across different research groups and materials, significantly accelerating the identification, optimization, and scale-up of durable electrocatalysts. These protocols should ideally simulate real-world operating conditions and include accelerated stress tests to quickly gauge long-term performance.

Finally, to avoid speculative or false assignments of degradation mechanisms, it is imperative that hypotheses regarding these mechanisms are rigorously verified via complementary experimental or theoretical methods. The integration of advanced in situ and operando characterization techniques (e.g., ec-LPTEM, XAS, operando spectroscopy) with sophisticated computational modeling (e.g., DFT, machine learning) can provide unprecedented atomic-level insights into dynamic catalyst transformations and active site evolution under reaction conditions. This multi-pronged approach will foster a deeper fundamental understanding, allowing for the rational design of more robust and long-lasting electrocatalysts that can withstand the rigors of continuous operation and ultimately drive the energy transition towards a sustainable future.

As the field moves closer to real-world deployment, life-cycle assessment (LCA) is becoming increasingly important in evaluating the full sustainability of electrocatalytic systems. Factors such as raw material cost and scarcity, synthesis scalability, energy use, and recyclability significantly influence a catalyst’s environmental and economic viability. While detailed techno-economic modeling may exceed the scope of early-stage research, incorporating simplified LCA considerations in early development can help steer material choices toward solutions that balance performance, durability, and sustainability at scale.

Taken together, these efforts can bridge the gap between fundamental catalyst research and real-world deployment, accelerating the transition toward cleaner, more resilient energy systems.