Search Results (186)

Developing electrocatalysts that are efficient and durable for the oxygen evolution reaction (OER) is essential for improving the energy efficiency of alkaline water splitting. Spinel-type transition-metal oxides have emerged as promising non-noble alternatives; however, their catalytic performance is often limited by sluggish charge transport and insufficient utilization of active sites. Herein, we present a systematic comparative study of electrodeposited Co₃O₄ (CO-300) and Cu-substituted Co₂CuO₄ (CCO-300) nanosheet films directly grown on Ni foam. Structural, morphological, and spectroscopic analyses reveal that Cu²⁺ integration into Co-oxide spinel lattice modifies the local electronic environment and produces a more open and interconnected nanosheet architecture, thereby enhancing conductivity and increasing the density of accessible redox-active sites. As a result, the optimized CCO-300 exhibits superior catalytic performance at higher current densities, along with a smaller Tafel slope (44 mV dec^–1), a larger electrochemically active surface area (ECSA), and reduced charge-transfer resistance compared to CCO-300, indicating accelerated reaction kinetics and improved electron-ion transport. Furthermore, the multistep chronopotentiometry measurements and long-term stability tests over 100 h at current densities of 10 and 250 mA cm^–2 highlight the excellent operational stability of the CCO-300 catalyst. Full article

The electrochemical water splitting process represents a promising and sustainable route for generating high-purity hydrogen with minimal environmental impact. The development of efficient and economically viable electrocatalysts is crucial for enhancing the kinetics of the oxygen evolution reaction (OER), which is a major bottleneck in overall water splitting. In this study, a Co₃V₂O₈/PEG-CTAB electrocatalyst was synthesized and systematically evaluated for its OER activity in alkaline conditions. The nanosheet-like architecture of the PEG-CTAB-assisted Co₃V₂O₈ electrocatalyst facilitates effective interfacial contact, thereby improving charge transport and catalytic accessibility. Among the examined compositions, the Co₃V₂O₈/PEG-CTAB catalyst exhibited superior OER performance, requiring a low overpotential of 298 mV to deliver a current density of 10 mA cm⁻² and displaying a Tafel slope of 90 mV dec⁻¹ in 1 M KOH. Furthermore, the catalyst demonstrated outstanding durability, retaining its electrocatalytic activity after 5000 consecutive CV cycles and prolonged chronopotentiometric testing. The Co₃V₂O₈/PEG-CTAB || Pt-C asymmetric cell required a cell voltage of 1.83 V to reach the threshold current density, confirming its ability to efficiently sustain overall water splitting under alkaline conditions. The enhanced performance is attributed to the synergistic effect of the electrocatalyst, which promotes active site exposure and structural stability. These findings highlight the potential of the Co₃V₂O₈/PEG-CTAB system as a cost-effective and robust electrocatalyst for practical water oxidation applications. Full article

To optimize the electrocatalytic reaction process through the synergistic effects of V and Ni, this study employed a two-step hydrothermal method to successfully construct a V₂O₅ composite structure grown on a Ni(OH)₂ substrate (denoted V₂O₅/Ni(OH)₂-2). Electrochemical evaluation revealed that this catalyst exhibits efficient bifunctional activity in 1.0 M KOH electrolyte. For the hydrogen evolution reaction (HER), it requires a mere 89.6 mV overpotential to achieve a current density of −10 mA cm⁻². The catalyst also demonstrates excellent performance in the oxygen evolution reaction (OER), demanding only 198 mV overpotential to drive a current density of 10 mA cm⁻², while maintaining low overpotential increases even at high current densities. Furthermore, it exhibits outstanding long-term stability during a 12 h continuous test. When assembled as a dual-electrode overall water splitting device, the system requires a voltage of only 2.82 V to drive a high current density of 100 mA cm⁻², showcasing its significant potential for practical applications. Full article

Aquaponics is a water-reusing, circular form of controlled-environment agriculture, but its sustainability benefits depend on reliable, constraint-aware nutrient dosing under delayed inflow effects. Aquaponics involves coupling hydroponics with aquaculture but is difficult to control because the greenhouse/crop state at the current time step ($t$) must anticipate water-quality changes that arrive at the next time step ($t+1$), under hard EC–pH and dose constraints. We propose the Analysis System for Nutrient Requirements in Hydroponics (ASNRH), a two-module, constraint-aware framework that directly regresses next-step elemental supplementation (N, P, K; mg·L⁻¹). First, the Fish-farm By-product Prediction Module (FBPM) uses a lightweight GRU forecaster to predict inflow chemistry at $t+1$ (e.g., NH₄⁺/NO₂⁻/NO₃⁻, alkalinity) from standard aquaculture sensors. Second, the Nutrient Requirement Prediction Module (NRPM) encodes the current hydroponic and crop state at t in parallel with the FBPM inflow at $t+1$ via a dual-branch architecture and fuses both representations to produce non-negative dose recommendations while penalizing forecasted EC/pH violations and excessive actuation volatility. The data pipeline assumes low-cost greenhouse and aquaculture sensors with chronological, leakage-free splits. A protocol-first simulation evaluates ASNRH against time-series and rule-based baselines using accuracy metrics (MAE/RMSE/R²), EC/pH violation rates, and robustness under missingness/noise; ablations isolate the contributions of the inflow branch, constraint-aware losses, and lightweight physics priors. The framework targets deployability in decoupled or coupled aquaponics by structurally resolving $t$ vs. $t+1$ asynchrony and internalizing domain constraints during learning; procedures are specified to support reproducibility and subsequent field trials. By operationalizing anticipatory dosing from reused aquaculture byproducts under EC/pH feasibility constraints, ASNRH is designed to support sustainability goals such as reduced nutrient wastage and fewer corrective water exchanges in coupled or decoupled aquaponics. Full article

The oxygen evolution reaction (OER) in water splitting involves complex multi-electron–proton transfer processes and represents the rate-determining step limiting overall electrolysis efficiency. Developing non-noble-metal catalysts with high activity and stability is therefore essential. Herein, a heterogeneous synthesis strategy was employed to in situ construct an iron-rich layered sulfate precursor (Fe_0.42Co_0.58-SO₄/NF) on nickel foam, which underwent deep self-reconstruction in alkaline electrolyte to form nanoflower-like Fe_0.42Co_0.58OOH/NF. The optimized catalyst maintained its iron-rich composition and hierarchical structure, delivering outstanding OER performance with an overpotential of 220 mV at 10 mA·cm⁻², a Tafel slope of 31.9 mV·dec⁻¹, and stability exceeding 12 h at 600 mA·cm⁻². Synchrotron analyses revealed dynamic transitions between mono-μ-O and di-μ-O Fe–M (M = Fe, Co) oxygen bridges during reconstruction, which enhanced both structural robustness and active-site density. The Fe-rich environment promoted the formation of Fe³⁺–O–Fe³⁺ units that synergized with Co⁴⁺ species to activate the lattice oxygen mechanism (LOM), thereby accelerating OER kinetics. This work elucidates the key role of oxygen-bridge geometry in optimizing catalytic activity and durability, providing valuable insights into the rational design of Fe–Co-based non-noble-metal catalysts with high iron content for efficient water oxidation. Full article

The escalating global energy crisis has intensified the demand for sustainable hydrogen production through electrochemical water splitting. Herein, we report a novel oxygen-vacancy-rich bifunctional electrocatalyst, Pt-NiSe@NiFe-LDH-Ov, synthesized via a facile electrodeposition and reduction method. It demonstrates exceptional performance, requiring low overpotentials of 280 mV for the HER and 344 mV for the OER to achieve current densities of 50 and 100 mA cm⁻², respectively, in 1.0 M KOH. When employed for overall water splitting, the system requires a cell voltage of only 1.878 V to reach 50 mA cm⁻². Notably, in an anion exchange membrane water electrolyzer (AEMWE), the performance shows significant enhancement with increasing operating temperature (20 to 60 °C), particularly at high current densities (>200 mA cm⁻²), highlighting its excellent thermal adaptability. The superior activity is attributed to the synergistic effect between the Pt-NiSe and NiFe-LDH interfaces and the abundant oxygen vacancies, which collectively enhance charge transfer and optimize the adsorption of reaction intermediates. Full article

Single-atom catalysts are highly efficient electrocatalysts for water splitting with exceptional atomic utilization, but atomic aggregation can impair their catalytic performance. To address this challenge, a Fe-Co-Ni single-atom bifunctional catalyst supported on nitrogen-doped graphene oxide was designed and employed for overall water splitting in alkaline electrolyte. The catalyst’s composition, structure, and morphology were systematically characterized using XRD, XPS, SEM, and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Electrochemical evaluations were performed to assess its activity and stability toward both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The results demonstrate that strong metal-nonmetal interactions between the Fe, Co and Ni single atoms and the nitrogen-doped graphene oxide support facilitate stable and uniform anchoring of the metal centers on the wrinkled carbon framework. The total metal loading reaches approximately 6.78 wt%, ensuring a high density of accessible active sites. Furthermore, synergistic electronic coupling among the Fe, Co, and Ni centers enhances charge transfer kinetics and modulates the D-band electronic states of the metal atoms. This effect weakens the adsorption strength of hydrogen and oxygen-containing intermediates, thus promoting faster reaction kinetics for both HER and OER. Consequently, the FeCoNi/CNG catalyst delivers low overpotentials of 77 mV for HER and 355 mV for OER at a current density of 10 mA cm⁻² in alkaline conditions. When integrated into an alkaline water electrolyzer, the system achieves a cell voltage of only 1.68 V to attain a current density of 10 mA cm⁻², underscoring its outstanding bifunctional catalytic performance. Full article

Electrocatalytic water splitting offers a promising route to sustainable H₂, but the oxygen evolution reaction (OER) in alkaline media remains the principal bottleneck for activity and durability. This review focuses on alkaline OER and integrates mechanism, kinetics, materials design, and cell-level considerations. Reaction mechanisms are outlined, including the adsorbate evolution mechanism (AEM) and the lattice oxygen mediated mechanism (LOM), together with universal scaling constraints and operando reconstruction of precatalysts into active oxyhydroxides. Strategies for electronic tuning, defect creation, and heterointerface design are linked to measurable kinetics, including iR-corrected overpotential, Tafel slope, charge transfer resistance, and electrochemically active surface area (ECSA). Representative catalyst families are critically evaluated, covering Ir and Ru oxides, Ni-, Fe-, and Co-based compounds, carbon-based materials, and heterostructure systems. Electrolyte engineering is discussed, including control of Fe impurities and cation and anion effects, and gas management at current densities of 100–500 mA·cm⁻² and higher. Finally, we outline challenges and directions that include operando discrimination between mechanisms and possible crossover between AEM and LOM, strategies to relax scaling relations using dual sites and interfacial water control, and constant potential modeling with explicit solvation and electric fields to enable efficient, scalable alkaline electrolyzers. Full article

The development of durable and efficient catalysts capable of driving both hydrogen and oxygen evolution reactions is essential for advancing sustainable hydrogen production through overall water electrolysis. In this study, we developed a corrosion-mediated approach, where Ni ions originate from the self-corrosion of the nickel foam (NF) substrate, to construct Pt-modified NiFe layered double hydroxide (Pt-NiFeO_xH_y@NiFe-LDH) under ambient conditions. The obtained catalyst exhibits a hierarchical architecture with abundant defect sites, which favor the uniform distribution of Pt clusters and optimized electronic configuration. The Pt-NiFeO_xH_y@NiFe-LDH catalyst, constructed through the interaction between Pt sites and defective NiFe layered double hydroxide (NiFe-LDH), demonstrates remarkable hydrogen evolution reaction (HER) activity, delivering an overpotential as low as 29 mV at a current density of 10 mA·cm⁻² and exhibiting a small tafel slope of 34.23 mV·dec⁻¹ in 1 M KOH, together with excellent oxygen evolution reaction (OER) performance, requiring only 252 mV to reach 100 mA·cm⁻². Moreover, the catalyst demonstrates outstanding activity and durability in alkaline seawater, maintaining stable operation over long-term tests. The Pt-NiFeO_xH_y@NiFe-LDH electrode, when integrated into a two-electrode system, demonstrates operating voltages as low as 1.42 and 1.51 V for current densities of 10 and 100 mA·cm⁻², respectively, and retains outstanding stability under concentrated alkaline conditions (6 M KOH, 70 °C). Overall, this work establishes a scalable and economically viable pathway toward high-efficiency bifunctional electrocatalysts and deepens the understanding of Pt-LDH interfacial synergy in promoting water-splitting catalysis. Full article

Developing highly efficient and stable electrocatalysts from inexpensive and earth-abundant elements represents a significant advancement in overall water splitting (OWS). This study focuses on the synthesis and evaluation of palladium-modified cobalt–phosphorus (PdCoP) and cobalt–iron–phosphorus (PdCoFeP) coatings for use as electrocatalysts in hydrogen evolution (HER), oxygen evolution (OER) and overall water splitting (OWS) in alkaline media. A facile electroless plating method is adopted to deposit the CoP and CoFeP coatings onto a copper surface (Cu sheet), with sodium hypophosphite (NaH₂PO₂) acting as the reducing agent. Pd crystallites were incorporated on CoP and CoFeP coatings using the galvanic displacement method. This study details morphological characterization (using SEM, EDX, and XRD), as well as electrochemical activity testing, for both HER and OER using linear sweep voltammetry (LSV) at different temperatures. The stability of the catalysts for HER was evaluated using chronoamperometry (CA) and chronopotentiometry (CP). The results show that the Pd-modified CoFeP and CoP catalysts exhibited lower overpotentials of 207 and 227 mV, respectively, for HER and 396 mV for OER at a current density of 10 mA cm⁻² compared to the unmodified CoFeP and CoP catalysts. The innovation achieved in this study lies in combining a facile, low-cost deposition method (electroless plating followed by galvanic displacement) with a novel, highly effective ternary composition (PdCoFeP) that exploits synergistic electronic and morphological effects to achieve superior bifunctional performance for alkaline OWS, achieving a low cell voltage of 1.69 V at a current density of 10 mA cm⁻². Overall, this research demonstrates that these synthesized materials are promising candidates for sustainable and economical hydrogen production. Full article

Electrochemical water splitting has emerged as a pivotal strategy for advancing sustainable and renewable energy technologies. However, its practical deployment is often hampered by sluggish reaction kinetics, large overpotentials, and the high cost of efficient electrocatalysts. To overcome these critical challenges, a novel bifunctional electrocatalyst based on electropolymerized CeO₂-NiO with polyacrylic acid (Ce-Ni-PAA) has been rationally engineered for overall water splitting. The strategic incorporation of conductive polymer framework enables effective modulation of the local electronic structure, enhances charge transport pathways, and maximizes the density of electrochemically accessible active sites, thereby substantially boosting catalytic performance. When evaluated in a 1 M KOH alkaline medium, the optimized Ce-Ni-PAA_0.5/NF hybrid demonstrates remarkable catalytic activity with 366.5 mV overpotential at 50 mA cm⁻², coupled with lower Tafel slope of 93.5 mV dec⁻¹. Additionally, the Ce-Ni-PAA_0.5/NF electrocatalyst exhibits exceptional ECSA of 1092.3 cm², which confirms the presence of a significantly larger number of electrochemically active sites. The electrocatalyst retains its performance even after 5000 continuous cycles of operation. The superior performance is attributed to the synergistic effects arising from the enriched composition, efficient electron transport channels, and abundant catalytic centers. Collectively, this study not only highlights the significance of rational structural and compositional design but also offers valuable insights toward the development of next-generation, cost-effective bifunctional electrocatalysts with strong potential for scalable water splitting and clean energy applications. Full article

With the aim of reducing catalysts’ cost while maintaining high performance in water splitting, ZnO and RuO₂ were combined into composites with ZnO to RuO₂ mass ratios of 1:1, 2:1, and 10:1. The ZnO/RuO₂ composites were prepared by microwave processing of a suspension containing Zn(OH)₂ in situ precipitated onto RuO₂ powder, and subsequently thermally modified at 600 °C to promote heterojunction formation and alter the defect chemistry. Phase composition, crystal structure, morphology, and optical properties were analyzed in detail employing XRD, TEM/HRTEM, HAADF-STEM with EDS, PL and XPS spectroscopy. The photoelectrocatalytic (PEC) activity of the composites toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) was evaluated by linear sweep voltammetry in alkaline electrolyte (0.1 M NaOH, pH 13), before and after one hour of electrochemical system illumination. The analysis focused on surface and bulk oxygen vacancies, which may have a crucial impact in PEC activity, by (1) promoting charge separation and increasing the number of active sites thus enhancing PEC activity, or (2) acting as electron–hole traps and recombination centers, reducing the lifetime of photo-induced charge carriers and thus deteriorating PEC activity. The presented results demonstrate that the combination of ZnO with RuO₂ in a specific mass ratio, along with controlled defect structure, offers a worthwhile route for developing bifunctional, noble-metal-reduced catalysts for green hydrogen and oxygen production. Full article

Among various H₂ production methods, splitting water using renewable electricity for H₂ production is regarded as a promising approach due to its high efficiency and zero carbon emissions. The oxygen evolution reaction (OER) is an important part of splitting water, but also the main bottleneck. The anodic oxygen evolution reaction (OER) for water electrolysis technology involves multi-electron/proton transfer and has sluggish reaction kinetics, which is the key obstacle to the overall efficiency of electrolyzing water. Therefore, it is necessary to develop highly efficient and cheap OER electrocatalysts to drive overall water splitting. Herein, a series of efficient RuO₂-Co₃O₄ composites were synthesized via a straightforward three-step process comprising solvothermal synthesis, ion exchange, and calcination. The results indicate that using 10 mg of RuCl₃·xH₂O and 15 mg of Co-MOF precursor in the second ion exchange step is the most effective way to acquire the Co₃O₄-RuO₂-10 (RCO-10) composite with the largest specific area and the best electrocatalytic performance after the calcination process. The optimal Co₃O₄-RuO₂-10 composite powder catalyst displays low overpotential (η₁₀ = 272 mV), a small Tafel slope (64.64 mV dec⁻¹), and good electrochemical stability in alkaline electrolyte; the overall performance of Co₃O₄-RuO₂-10 surpasses that of many related cobalt-based oxide catalysts. Furthermore, through integration with a carbon cloth substrate, Co₃O₄-RuO₂-10/CC can be directly used as a self-supporting electrode with high stability. This work presents a straightforward method to design Co₃O₄-RuO₂ composite array catalysts for high-performance electrocatalytic OER performance. Full article

The development of ternary metal oxide electrocatalysts with optimized electronic structures and surface morphologies has emerged as one of the effective strategies to improve the performance of electrochemical water splitting. In this work, ternary CoMoCe (CMC)-oxide electrocatalysts were successfully synthesized on nickel foam substrates via a hydrothermal technique and employed for their catalytic activity in an alkaline electrolyte. For comparison, binary counterparts (CoMo, CoCe, and MoCe) were also fabricated under similar conditions. The synthesized catalysts’ electrodes exhibited diverse surface architectures, including microporous-flake hybrids, ultrathin flakes, nanoneedle-assembled microspheres, and randomly oriented hexagonal structures. Among them, the ternary CoMoCe-oxide electrode exhibited outstanding bifunctional electrocatalytic activity, delivering low overpotentials of 124 mV for the hydrogen evolution reaction (HER) at −10 mA cm⁻², and 340 mV for the oxygen evolution reaction (OER) at 100 mA cm⁻², along with excellent durability. Furthermore, in full water-splitting configuration, the CMC||CMC and RuO₂||CMC electrolyzers required cell voltages of 1.69 V and 1.57 V, respectively, to reach a current density of 10 mA cm⁻². Remarkably, the CMC-based electrolyzer reached an industrially relevant current density of 1000 mA cm⁻² at a cell voltage of 2.18 V, maintaining excellent stability over 100 h of continuous operation. These findings underscore the impact of an optimized electronic structure and surface architecture on design strategies for high-performance ternary metal oxide electrocatalysts. Herein, a robust and straightforward approach is comprehensively presented for fabricating highly efficient ternary metal-oxide catalyst electrodes, offering significant potential for scalable water splitting. Full article

Hydrogen generation has become a popular research subject in light of currently pressing issues, such as the rapidly increasing environmental pollution, the depleting fossil fuel reserves, and the looming energy crisis. Sustainable electrochemical water splitting is regarded as one of the most desirable methods for obtaining green hydrogen. Considering this state of affairs, the water splitting electrocatalytic activity of glassy carbon electrodes modified with birnessite-type K₂Mn₄O₈ and mixed-valence iron phosphate Fe₃(PO₃OH)₄(H₂O)₄ materials were evaluated in electrolyte solutions having different pH values. Both compounds were characterized by X-ray diffraction and FT-IR spectroscopy in order to analyze their phase purity and their structural features. The most catalytically active birnessite-type K₂Mn₄O₈-based electrode was manufactured using a catalyst ink containing only the electrocatalyst dispersed in ethanol and Nafion solution. In 0.1 M H₂SO₄, it exhibited an oxygen evolution reaction (OER) overpotential of 1.07 V and a hydrogen evolution reaction (HER) overpotential of 0.957 V. The Tafel slopes obtained in the OER and HER experiments were 0.180 and 0.142 V/dec, respectively. The most catalytically active mixed-valence iron phosphate Fe₃(PO₃OH)₄(H₂O)₄-based electrode was obtained with a catalyst ink containing the specified material mixed with carbon black and dispersed in ethanol and Nafion solution. In a strongly alkaline medium, it displayed a HER overpotential of 0.515 V and a Tafel slope value of 0.122 V/dec. The two electrocatalysts have not been previously investigated in this way, and the acquired data provide insights into their electrocatalytic activity and improve the scientific understanding of their properties and applicative potential. Full article