Search Results (1,053)

By modulating the mass ratio of hydrothermal agents to cobalt/iron precursors, Co₃O₄ nanowires were successfully integrated into spinel-type Co/Fe@NF, forming a heterojunction anode for alkaline water electrolysis (AWE) hydrogen production. This Co₃O₄ nanowire-assembled CoFe₂O₄ nanosheet anode (Co/Fe(5:1)@NF) exhibits exceptional electrochemical oxygen evolution reaction (OER) performance, requiring only 221 mV overpotential to achieve 10 mA cm⁻². Sulfamethoxazole (SMX) was employed as a model pollutant to investigate the anode sacrificial material; it achieved approximately 95% SMX degradation efficiency, reducing the OER potential of 50 mV/10 mA cm⁻². SMX oxidation coupled with Co/Fe heterojunction structure partially substitutes the OER. Co/Fe heterojunction generates an internal magnetic field, which induces the formation of novel active species within the system. ·O₂⁻ is the newly formed active oxygen species, which enhanced the proportion of indirect SMX oxidation. Quantitative analysis reveals that superoxide radical-mediated indirect oxidation of SMX accounts for approximately 38.5%, Fe(VI) for 9.4%, other active species for 6.1%, and direct oxidation for 46.0%. The nanowire–nanosheet assembly stabilizes a high-spin configuration on the catalyst surface, redirecting oxygen intermediate pathways toward triplet oxygen (³O₂) generation. Subsequent electron transfer from nanowire tips facilitates rapid ³O₂ reduction, forming superoxide radicals (·O₂⁻). This study effectively driven by indirect oxidation, with cathodic hydrogen production, providing a novel strategy for utilizing renewable electricity and reducing OER while offering insights into the design of Co/Fe-based catalyst. Full article

Municipal wastewater treatment relies primarily on biological methods, yet effective disposal of residual sludge remains a major challenge. Converting sludge into biochar via oxygen-limited pyrolysis presents a novel approach for waste resource recovery. This study prepared sludge-based biochar (SBC) through one-step pyrolysis of sewage sludge and applied it to activate peroxymonosulfate (PMS) for degrading diverse contaminants. Characterization (SEM, XPS, FTIR) revealed abundant pore structures and diverse surface functional groups on SBC. Using Acid Orange 7 (AO7) as the target pollutant, SBC effectively degraded AO7 across pH 3.0–9.0 and catalyst dosages (0.2–2.0 g·L⁻¹), achieving a maximum observed rate constant (k_obs) of 0.3108 min^–1. Salinity and common anions showed negligible inhibition on AO7 degradation. SBC maintained 95% degradation efficiency after four reuse cycles and effectively degraded sulfamethoxazole, sulfamethazine, and rhodamine B besides AO7. Mechanistic studies (chemical quenching and ESR) identified singlet oxygen (¹O₂) and superoxide radicals (O₂^•− ) as the dominant reactive oxygen species for AO7 degradation. XPS indicated a 39% reduction in surface carbonyl group content after cycling, contributing to activity decline. LC-MS identified five intermediates, suggesting a potential degradation pathway driven by SBC/PMS system. ECOSAR model predictions indicated significantly reduced biotoxicity of the degradation products compared to AO7. This work provides a strategy for preparing sludge-derived catalysts for PMS activation and pollutant degradation, enabling effective solid waste resource utilization. Full article

The advancement of efficient energy conversion and storage technologies is fundamentally linked to the development of electrochemical systems, including fuel cells, batteries, and electrolyzers, whose performance depends on key electrocatalytic reactions: hydrogen evolution (HER), oxygen evolution (OER), oxygen reduction (ORR), carbon dioxide reduction (CO₂RR), and nitrogen reduction (NRR). Beyond catalyst design, the electrolyte microenvironment significantly influences these reactions by modulating charge transfer, intermediate stabilization, and mass transport, making electrolyte engineering a powerful tool for enhancing performance. This review provides a comprehensive analysis of how fundamental electrolyte properties, including pH, ionic strength, ion identity, and solvent structure, affect the mechanisms and kinetics of these five reactions. We examine in detail how the electrolyte composition and individual ion contributions impact reaction pathways, catalytic activity, and product selectivity. For HER and OER, we discuss the interplay between acidic and alkaline environments, the effects of specific ions, interfacial electric fields, and catalyst stability. In ORR, we highlight pH-dependent activity, selectivity, and the roles of cations and anions in steering 2e⁻ versus 4e⁻ pathways. The CO₂RR and NRR sections explore how the electrolyte composition, local pH, buffering capacity, and proton sources influence activity and the product distribution. We also address challenges in electrolyte optimization, such as managing competing reactions and maximizing Faradaic efficiency. By comparing the electrolyte’s effects across these reactions, this review identifies general trends and design guidelines for enhancing electrocatalytic performance and outlines key open questions and future research directions relevant to practical energy technologies. Full article

Nitrogen oxides (NO_x) emissions pose environmental and health risks. Selective catalytic reduction (SCR) is effective for NO_x removal, and using CO as a reductant can eliminate both NO_x and CO. This study explores CuCe catalysts on SiO₂, Al₂O₃, and TiO₂ for CO-SCR. Results show catalytic activity relates to the synergy between lattice oxygen and CuCe species. TiO₂ enhances this interaction, promoting Cu⁺ and lattice oxygen for NO adsorption and dissociation. The CuCe/TiO₂ catalyst achieves 100% NO conversion at 300 °C and 40.2% at 100 °C, indicating excellent low-temperature performance. These findings are valuable for developing efficient SCR catalysts. Full article

Dexamethasone (DXM) is a glucocorticoid widely used in treating various diseases, but its extensive use raises environmental concerns due to poor absorption and rapid excretion, leading to its presence in aquatic environments. In this study, aqueous DXM was treated via heterogeneous solar photocatalysis (HSP) using a Zn-doped TiO₂ catalyst supported on zeolite clinoptilolite (TiO₂-Zn(II)-ZC), synthesized by electrodeposition. The catalyst was characterized by IR spectroscopy, SEM-EDS, XRD, atomic absorption spectroscopy, and P_zc determination. A Box–Behnken design was applied to evaluate the influence of initial DXM concentration (5–15 mg/L), hydraulic retention time (HRT: 30–60 min), and catalyst dose (0.5–1.5 g/L), using DXM (UV–Vis) and COD as response variables. Optimal conditions (12.5 mg/L DXM, 60 min HRT, 1.0 g/L catalyst) achieved 80% DXM removal (UV–Vis), 88.71% (HPLC), 85.29% COD removal, and 82.86% TOC reduction at 67 °C, 325.12 kJ/L, and 38.77 W/m². Additionally, a treated sample of chocolate industry wastewater enriched with 12.5 mg/L DXM (DXM-WW) achieved 67.88% (HPLC), 93.02% (COD), and 92.38% (TOC) removal. The catalyst reduced the bandgap, enabling sunlight-driven generation of e⁻/h⁺ pairs and reactive oxygen species (^•OH, H₂O₂, and O₂^•−), facilitating DXM degradation. Full article

The development of efficient non-noble metal catalysts is critical for advancing sustainable fuel-cell technologies. This study investigates the effect of carbon support microstructure on the oxygen reduction reaction (ORR) performance of Fe-N-C catalysts. By precisely tuning the pyrolysis temperature of activated carbon (AC) between 600 and 1000 °C, we elucidate the mechanistic influence of the physicochemical characteristics of the carbon support on the ORR activity of the supported catalyst. Increasing the pyrolysis temperature enhanced the electrical conductivity of the carbon support, thereby improving the ORR performance of the catalyst. However, while the defect density and specific surface area of the carbon support initially increased with increasing pyrolysis temperature, they declined when elevated temperatures were used (e.g., 1000 °C), leading to reduced ORR activity. The AC-900 support, pyrolyzed at 900 °C, exhibited an optimal balance of a high surface area, abundant defects, and superior conductivity. An Fe phthalocyanine/AC-900 catalyst synthesized using the AC-900 support exhibited excellent ORR activity (E_1/2: 0.89 V and E_on: 0.95 V vs. reversible hydrogen electrode (RHE)) in 0.1 M KOH. This work highlights the pivotal role of carbon support microstructure in governing the ORR activity of the supported catalyst and provides a rational strategy for designing high-performance non-noble metal electrocatalysts. Full article

Biomass carbon materials exhibit a significant specific surface area, carbon defects, and oxygen-containing functional groups during the electrochemical cathodic oxygen reduction (ORR) process, resulting in an enhanced adsorption–desorption of reaction intermediates (e.g., *OH and *OOH) by the catalyst. In this study, a cost-effective biomass-derived carbon material (HBC-500) was prepared through low-temperature pyrolysis at 500 °C using Spirulina as a precursor for H₂O₂ production. By employing surface engineering modification of the carbon-based material to promote the ORR process’s two-electron selectivity, HBC-500 demonstrated consistent experimental results with the RRDE findings at pH = 5, yielding 238.40 mg·L⁻¹ of hydrogen peroxide within a 90 min duration at a current density of 50 mA·cm⁻². Furthermore, HBC-500 accomplished over 95% degradation within 30 min at pH = 5 and maintained approximately 91.79% electrocatalytic activity after undergoing five consecutive electrocatalytic cycles lasting 300 min. These results establish HBC-500 biomass carbon material as a highly suitable candidate for H₂O₂ production and Fenton degradation of organic wastewater. Full article

High-entropy alloy (HEA) catalysts have attracted significant attention from researchers. In many cases, HEAs exhibit high activity and selectivity for catalytic reactions due to four “core effects”: high entropy effect, lattice distortion effect, slow diffusion effect, and mixing effect. However, a systematic summary of HEA catalyst design and understanding is lacking. In this review, the reasons for the outstanding performance of HEA catalysts are first discussed from multiple perspectives, such as excellent mechanical properties, ultra-high-performance stability, and the potential for compositional optimization. Furthermore, to deepen our understanding of HEA catalysts, the rational design of HEA catalysts is introduced, covering design principles, element selection, and the use of algorithms for prediction. Next, several common preparation methods for HEAs are introduced, including chemical co-reduction, solution combustion, mechanical alloying, and sol–gel methods. Finally, the research progress of HEA catalysts in hydrogen evolution reactions, oxygen evolution reactions, and oxygen reduction reactions is presented. Unlike existing reviews, this work establishes a unified framework connecting HEA fundamentals (entropy effects), computational design, scalable synthesis, and application-specific performance, while identifying underexplored pathways like lattice-oxygen-mediated mechanisms (LOM) for future research. Full article

Metal–air batteries have excellent theoretical energy density and economic advantages through abundant anode materials and open cathode structures. However, the actual energy efficiency of metal–air batteries is much lower than the theoretical value due to the effect of polarization voltage during battery operation, limiting the power output and thus hindering their practical application. This review systematically dissects the origins of polarization: slow oxygen reduction/evolution reaction (ORR/OER) kinetics, interfacial resistance, and mass transfer bottlenecks. We highlight cutting-edge strategies to mitigate polarization, including atomic-level engineering of air cathodes (e.g., single-atom catalysts, low Pt catalysts), biomass-derived 3D porous electrodes, and electrolyte innovations (additives to inhibit corrosion, solid-state electrolytes to improve stability). In addition, breakthroughs in metal–H₂O₂ battery design using concentrated liquid oxygen sources are discussed. Together, these advances alleviate the battery polarization bottleneck and pave the way for practical applications of metal–air batteries in electric vehicles, drones, and deep-sea devices. Full article

In this study, cerium with different ratios (x = 0 (zero), 0.1, 0.15, 0.5) was added to the PrMn structure as an A-site material to evaluate characteristic behavior as a potential cathode material for solid oxide fuel cells. The Pr_xCe_1−xMnO_3−δ electrocatalysts were synthesized using the sol–gel combustion method and were assessed for their electrochemical, phase, and structural properties, as well as desorption and reducibility capabilities. Phase changes, from orthorhombic to cubic structures observed upon cerium additions, were evaluated via the X-Ray diffraction method. X-Ray photoelectron spectroscopy (XPS) showed the valence states of the surface between the Ce⁴⁺/Ce³⁺ and Pr⁴⁺/Pr³⁺ redox pairs, while oxygen temperature programmed desorption (O₂-TPD) analysis was used to evaluate the oxygen adsorption and desorption behavior of the electrocatalysts. Redox characterization, evaluated via hydrogen atmosphere temperature-programmed reduction (H₂-TPR), revealed that a higher cerium ratio in the structure lowered the reduction temperature, suggesting a better dynamic oxygen exchange capability at a lower temperature for the Pr_0.5Ce_0.5MnO_3−δ catalyst compared to the electrochemical behavior analysis by the electrochemical impedance spectroscopy method. Moreover, the symmetrical cell tests with Pr_0.5Ce_0.5MnO_3−δ electrodes showed that, when combined with scandia-stabilized zirconia (ScSZ) electrolyte, the overall polarization resistance was reduced by approximately 28% at 800 °C compared to cells with yttria-stabilized zirconia (YSZ) electrolyte. Full article

Developing cost-effective, sustainable, and high-performance air electrode catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) remains a significant challenge in the advancement of rechargeable zinc–air batteries (ZABs). Herein, we successfully construct a vacancy-rich heterogeneous perovskite La_0.85Y_0.15Ni_0.7Fe_0.3O₃ (LYNF) hybridized with Co₃O₄ spinel nanoparticles using a simple chemical bath-assisted method. The Co₃O₄ composite LYNF material is systematically evaluated as the bifunctional catalyst for ZABs in the proportion of 25 wt%, 50w t%, and 75 wt% (denoted as LYNF-xCo₃O₄, x = 0.25, 0.5, 0.75). The results confirm an intimate coupling between the perovskite and spinel phases, along with a significant increase in oxygen vacancy concentration. Among the composites, LYNF-0.5Co₃O₄ exhibits the best performance, achieving an ORR onset potential of 0.813 V vs. RHE at −0.1 mA cm⁻² and a lower OER overpotential of 441 mV at 10 mA cm⁻². When applied as the air electrode catalyst in ZABs, LYNF-0.5Co₃O₄ displays the highest discharge voltage and a peak power density of 115 mW cm⁻², representing a 20% improvement over pristine LYNF. The enhanced performance of the LYNF-0.5Co₃O₄ composite is attributed to the accumulation of Co₃O₄ nanoparticles within the LYNF matrix, which introduces numerous electrochemically active sites and facilitates the charge and mass transport during the catalytic process in ZABs. Full article

Atomically dispersed metal–nitrogen–carbon (M-N-C) catalysts are regarded as ideal catalytic materials for the oxygen reduction reaction (ORR) under alkaline conditions. Compared with other ORR catalysts, M-N-C catalysts exhibit notable advantages, including low cost, high atomic utilization efficiency, and considerable catalytic potential. We provide a systematic review of recent research advances in enhancing the ORR performance of M-N-C catalysts, focusing on catalytic activity and stability. First, the reaction mechanism of the ORR on the surfaces of the M-N-C catalysts is elucidated. Second, the primary strategies employed in recent years to improve their catalytic activity and stability are summarized. Finally, critical research directions that should be prioritized to expedite the commercialization of M-N-C catalysts are outlined. Full article

A major challenge for Li-O₂ batteries is the slow kinetics of oxygen reduction (ORR) and evolution (OER) reactions. This work presents a high-performance Pt₃Rh/C composite cathode where Pt-Rh nanoalloys are uniformly dispersed on 3D nanoporous carbon. The bimetallic architecture demonstrates significantly enhanced ORR/OER activity compared to conventional catalysts. Super P, with a large specific surface area and omnipresent pores with diverse size distribution, provided sufficient storage space for Li₂O₂ and facilitated transport channels for Li⁺ and O₂, while the highly conductive Pt₃Rh NPs optimized catalytic efficiency. XPS reveals a prominent electron transfer process between Pt and Rh; the Rh sites in Pt₃Rh/C alloy can effectively act as electron donors to improve the oxygen/lithium peroxide (O₂/Li₂O₂) redox chemistry in LOB. Therefore, the Pt₃Rh/C electrode shows the minimum overpotential (0.60 V) for efficient oxygen reduction and evolution under an upper-limit capacity of 2000 mAh g⁻¹. This work introduces a Pt₃Rh/C nanoalloy synthesis method that boosts Li-O₂ battery efficiency by accelerating oxygen reaction kinetics. Full article

High-Temperature Proton-Exchange Membrane Fuel Cells (HT-PEMFCs) represent a promising clean energy technology and are valued for their fuel flexibility and simplified balance of plant. Their commercialization, however, is critically hindered by the prohibitive cost and resource scarcity of platinum-group metal (PGM) catalysts. The challenge is amplified in the phosphoric acid (PA) electrolyte of HT-PEMFCs, where the severe anion poisoning of PGM active sites necessitates impractically high catalyst loadings. This review addresses the urgent need for cost-effective alternatives by providing a comprehensive assessment of recent advancements in non-precious metal (NPM) catalysts for the oxygen reduction reaction (ORR) in HT-PEMFCs. It systematically explores synthesis strategies and structure–performance relationships for emerging catalyst classes, including transition metal compounds, metal–nitrogen–carbon (M-N-C) materials, and metal-free heteroatom-doped carbons. A significant focus is placed on M-N-C catalysts, particularly those with atomically dispersed Fe-Nx active sites, which have emerged as the most viable replacements for platinum due to their high intrinsic activity and notable tolerance to phosphate poisoning. This review critically analyzes key challenges that impede practical application, such as the trade-off between catalyst activity and stability, mass transport limitations in thick electrodes, and long-term degradation in the harsh PA environment. Finally, it outlines future research directions, emphasizing the need for a synergistic approach that integrates computational modeling with advanced operando characterization to guide the rational design of durable, high-performance catalysts and electrode architectures, thereby accelerating the path to commercial viability for HT-PEMFC technology. Full article

The advancement of catalytic materials is critical to improving the performance, reducing the cost and enhancing the sustainability of Proton Exchange Membrane (PEM) fuel cells and electrolyzers. Although Platinum Group Metal (PGM)-based electrocatalysts exhibit high electrochemical activity, their limited availability and the environmentally intensive extraction pose significant challenges. This study aims to demonstrate the direct reuse of recycled impure platinum (Pt) precursors for the synthesis of effective Pt/C electrocatalysts as a viable step toward circular hydrogen economy implementation. A low-cost and eco-friendly chlorine-based hydrometallurgical method was successfully employed to recycle over 99% of Pt from End-of-Life (EoL) Membrane Electrode Assemblies (MEAs), with an industrial perspective. Recycled metal precursor was used without purification to synthesize Pt/C electrocatalyst via a scalable and sustainable method. The catalyst was structurally and chemically characterized, and their electrochemical performance towards the Oxygen Reduction Reaction (ORR) was conducted under conditions simulating real operating environments. The recycled-metal-derived catalyst demonstrated comparable activity toward ORR (170 A/gPt) relative to a commercial catalyst, indicating its potential as viable alternative to conventional PGM-based catalysts. By integrating energy-efficient recycling with advanced material design, this work supports the development of cost-effective and green solutions for clean energy technologies aligned with a circular hydrogen economy model. Full article