Catalysts with high H2O2 selectivity are critical for H2O2 electrosynthesis via the 2-electron oxygen reduction reaction (2e- ORR). The carbon-free active centers of transition metal compounds avoid them suffering the performance degradation induced by carbon corrosion, making them potential candidates as long-life catalysts for H2O2 electrosynthesis. Nevertheless, the H2O2 selectivity of transition metal compounds is generally lower than that of the state-of-the-art metal-free carbon materials and single-atom catalysts. Here, we introduce an alkali metal hydroxide-treatment strategy to improve the H2O2 selectivity of tungstate. We synthesized CdWO4via a hydrothermal method and soaked the as-prepared CdWO4 into four types of alkali metal hydroxides (LiOH, NaOH, KOH, and CsOH). It is found that alkali metal hydroxide-treated CdWO4 exhibited much higher H2O2 selectivity than as-prepared CdWO4, with the CsOH-treated CdWO4 (denoted as CdWO4-CsOH) delivering the highest H2O2 selectivity and still holding a H2O2 selectivity of 93.7% after 40 000 cyclic voltammetry (CV) cycles. Moreover, the CdWO4-CsOH catalyst retained an average faradaic efficiency (FE) of 84.3% during discharging at 100 mA cm-2 for 34 h in flow cell tests. Density functional theory (DFT) calculations suggest that W atoms in CdWO4-CsOH are the preferred active sites for H2O2 production.

Developing cost-effective bifunctional electrocatalysts for oxygen reduction and evolution reactions (ORR/OER) is crucial for rechargeable Zn-air batteries. Herein, we synthesize a novel catalyst comprising helical carbonaceous nanotubes encapsulating cobalt nanoparticles, using corn stigma agricultural waste, melamine and cobalt chloride as precursors. The curved surface of helical carbonaceous nanotubes promotes metal ion dispersion and charge separation within the carbon lattice. Applying strain engineering to these curved structures further tunes the electronic configuration of the active centers, boosting electrocatalytic performance. The as-prepared catalyst demonstrates remarkable electrocatalytic performance, achieving a high ORR half-wave potential of 0.869 V with minimal degradation (10 mV shift after 5000 CV cycles), along with a low OER overpotential of 350 mV at 10 mA cm−2. In liquid Zn-air batteries, the catalyst delivers a peak power density of 214.8 mW cm−2 and stable operation for over 390 h at 10 mA cm−2 with negligible voltage decay. Moreover, the corresponding flexible wearable Zn-air battery demonstrates excellent foldability and cyclic stability. These results highlight a promising strategy for designing durable, high-efficiency electrocatalysts for metal-air energy systems.

Iron-nitrogen-carbon (Fe-NC) materials have emerged as leading candidates among non-precious metal catalysts for the oxygen reduction reaction, offering a potential replacement for platinum-group metals in proton exchange membrane fuel cells (PEMFCs). However, the high intrinsic activity of current Fe-NC catalysts is often accompanied by rapid degradation, primarily due to the prevalence of M-Nx active sites embedded within microporous carbon frameworks, which exhibit limited resistance to demetallation. Here, we report the development of mesoporous carbon-dominated Fe-NC (MC-Fe-NC) catalysts featuring atomically dispersed Fe-N4 active sites (5.62 & times;1019 sites g-1 ), synthesized via a dual-coordination strategy combined with an assisted in-situ pore-forming approach. Mechanistic investigations reveal that the interconnected mesoporous architecture improves mass transport and water management at the electrode/membrane electrode assembly level, thereby mitigating carbon corrosion and structural degradation during durability testing. MC-Fe-NC demonstrates superior durability under stringent H2/air conditions, retaining 82% of initial current density at 0.6 V for 36 h, 92% of initial voltage at 0.2 A cm-2 for 100 hand enduring 30,000 square-wave voltage cycles-surpassing the performance of most previously reported Fe-NC systems. Distribution of relaxation time analysis further supports that the mesoporous structure alleviates water flooding and carbon corrosion-related transport deterioration. Density functional theory calculations reveal that the N-enriched local coordination environment downshifts the dband center, weakens OH-related perturbations, and reduces the driving force for metal dissolution, thereby enhancing the intrinsic anti-dissolution capability of the active sites. These results indicate that the improved durability originates from the synergistic effect of the interconnected mesoporous architecture and the N-enriched local coordination environment. This work offers a rational design pathway for stabilizing single-atom catalytic sites through the optimization of mesoporous structure and local coordination environment, advancing the practical deployment of non-precious metal catalysts in PEMFCs. (c) 2026 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

The development of efficient, stable, and low-cost non-precious metal electrocatalysts is pivotal for advancing water electrolysis for hydrogen production, where the oxygen evolution reaction (OER) remains the kinetic bottleneck. Herein, we report a self-supported S-NiCoFe(OH)x/NF electrode with Fe incorporation and S modification. The results reveal that the incorporation of Fe significantly boosts the intrinsic catalytic activity of the material, while the modification of S further enhances charge transfer efficiency and accelerates reaction kinetics. Electrochemical tests demonstrated that the S-NiCoFe(OH)x/NF electrode exhibited outstanding OER performance in 1.0 M KOH, requiring an overpotential of only 283 mV to achieve a current density of 100 mA cm-2, with a Tafel slope of 36.2 mV & sdot;dec-1. X-ray photoelectron spectroscopy (XPS) depth profiling confirms a gradient distribution of Fe and S from the surface to the bulk phase of the composite: Fe content increases from the surface to the bulk, whereas S is primarily enriched on the surface. This synergistic regulation of elemental composition and spatial distribution not only resolves the trade-off between activity and conductivity but also provides a versatile design principle for the development of high-performance hydroxide-based electrocatalysts toward practical water electrolysis.

The rational design of Pt-based alloy catalysts with dual resistance to CO poisoning and metal leaching, enabled by interfacial electronic modulation, remains a critical challenge for practical direct methanol fuel cells (DMFCs). Here, we report a highly stable catalyst comprising electron-enriched TiN-meditated PtNiCo (denoted as e-PtNiCo) for DMFCs, demonstrating stabilization mechanisms rooted in enhanced Pt-CO antibonding interactions and strengthened Pt-Co/Ni chemical bonds. The e-PtNiCo catalyst exhibits a voltage decay of 9.6% at 100 mA cm-2 over 50 h under practical DMFC operating conditionsa 4-fold improvement compared with the benchmarked PtNiCo (37.7%). Density functional theory calculations and post-mortem elemental analysis reveal that the developed catalysts possess tailored *CO adsorption energetics (-1.62 eV vs -1.27 eV for carbon-supported counterparts) and a 2-fold reduction in Ni/Co dissolution, governed by robust metal-support electronic coupling. This work establishes a mechanistic framework linking support-induced electronic effects to the stability of Pt-based alloys, offering a generalizable strategy for designing structurally durable, high-performance electrocatalysts in energy conversion technologies.

Atomically dispersed metal-nitrogen-carbon (M-N-C) materials, characterized by well-defined coordination structures, have emerged as promising candidates to supersede costly platinum-based catalysts for the oxygen reduction reaction (ORR). Although Fe-N-C catalysts exhibit the highest ORR activity among Pt-free systems, their practical application is hindered by durability challenges stemming from Fenton reaction-induced degradation. Fe-free M-N-C catalysts (MCo, Mn, Ni, etc.), which mitigate Fenton reactivity, have attracted significant attention; however, their catalytic activities remain markedly lower than those of Fe-based counterparts. Critical uncertainties persist in establishing structure-activity-stability relationships, particularly regarding the interplay between coordination architecture engineering, single-atom site density, and overall catalytic performance. This review critically examines ORR mechanisms underpinning M-N-C systems, evaluates innovative strategies to decouple activity and stability in Fe-free catalysts, and proposes frameworks to translate atomic-scale materials into enhanced device-level performance. Finally, a multidisciplinary roadmap integrating advanced synthesis, operando diagnostics, and machine learning to speed up the development of durable, high-performance ORR electrocatalysts is proposed.

Carbon-supported metal single-atom catalysts (M-SACs) are promising oxygen reduction reaction (ORR) catalysts. Their ORR activity and selectivity are significantly affected by the heteroatoms that coordinate the central metal atoms. Previous reports found that oxygen-coordinated M-SACs promoted a 2e- ORR rather than the 4e- ORR that is more desirable for fuel cells. Herein, we report for the first time that oxygen-coordinated M-SACs are capable of promoting the 4e- ORR in acid media. We prepared a Cr(acac)-NC catalyst with the central Cr atom coordinated by two O atoms. The Cr(acac)-NC catalyst not only exhibits excellent ORR activity and stability in acid media, but also delivers high proton exchange membrane fuel cell (PEMFC) performance comparable to N-coordinated M-SACs. Density functional theory (DFT) calculations reveal that Cr-O2 moieties located on the zigzag edge of the carbon support are the ORR-active sites.

Zinc dendrite, active iodine dissolution, and polyiodide shuttle caused by the strong interaction between liquid electrolyte and solid electrode are the chief culprits for the capacity attenuation of aqueous zinc-iodine batteries (ZIBs). Herein, mullite is adopted as raw material to prepare Zn-based solid-state electrolyte (Zn-ML) for ZIBs through zinc ion exchange strategy. Owing to the merits of low electronic conductivity, low zinc diffusion energy barrier, and strong polyiodide adsorption capability, Zn-ML electrolyte can effectively isolate the redox reactions of zinc anode and AC@I2 cathode, guide the reversible zinc deposition behavior, and inhibit the active iodine dissolution as well as polyiodide shuttle during cycling process. As expected, wide operating voltage window of 2.7 V (vs Zn2+/Zn), high Zn2+ transference number of 0.51, and low activation energy barrier of 29.7 kJ mol-1 can be achieved for the solid-state Zn//Zn cells. Meanwhile, high reversible capacity of 127.4 and 107.6 mAh g-1 can be maintained at 0.5 and 1 A g-1 after 3 000 and 2 100 cycles for the solid-state Zn//AC@I2 batteries, corresponding to high-capacity retention ratio of 85.2% and 80.7%, respectively. This study will inspire the development of mineral-derived solid electrolyte, and facilitate its application in Zn-based secondary batteries.

Exploring non-precious oxygen reduction reaction (ORR) catalysts is essential to fuel cells and seawater metal-air batteries. Transition metal nitrides are promising ORR catalysts with high corrosion resistance but fail to render satisfactory ORR performance. Herein, we introduce a novel method for the synthesis of carbon nanosheet-supported transition metal nitrides. Using dicyandiamine (DCDA) as the nitrogen and carbon source, we prepared carbon nanosheet-supported CrN nanoparticles (CrN/CNS) via a two-step pyrolysis method. The optimal CrN/CNS material has an ORR half-wave potential (E1/2) of 0.76 V vs. reversible hydrogen electrode (RHE) in acidic media and 0.50 V vs. RHE in simulated seawater, which is one of the best among those reported for transition metal nitrides. Furthermore, the optimal material has remarkable ORR stability in both acidic media and simulated seawater. Its ORR E1/2 shows 27 mV decay in acidic media and 20 mV increase in simulated seawater after stability tests, outperforming a commercial Pt/C catalyst and many transition metal nitrides. More importantly, the optimal CrN/CNS material-based seawater Zn-air batteries (ZABs) exhibit good stability within 200 h constant discharging. It is found that both the proportion of the Cr-N valence state and the Cr content in surfaces played a key role in the ORR activity of CrN/CNS materials. Carbon nanosheet-supported CrN nanoparticles render excellent ORR activity in acidic media and long-term stability in natural seawater Zn-air batteries.

With characteristics and advantages of functional composite materials, they are commendably adopted in numerous fields especially in oxygen electrocatalysis, which is due to the significant synergies between various components. Herein, a novel bifunctional oxygen electrocatalyst (Co-CNT@COF-Pyr) has been synthesized through in-situ growth of covalent organic frameworks (COFs) layers on the outer surface of highly conductive carbon nanotubes (CNTs) followed by coordination with Co(Ⅱ). For electrocatalytic OER, Co-CNT@COF-Pyr reveals a low overpotential (438 ​mV) in alkaline electrolyte (1.0 ​M aqueous solution of KOH) with a current density of 10 ​mA ​cm−2, which is comparable to most discovered COF-based catalysts. For electrocatalytic ORR, Co-CNT@COF-Pyr exhibits a low H2O2 yield range (9.0 ​%–10.1 ​%) and a reaction pathway close to 4e− (n ​= ​3.82–3.80) in alkaline electrolyte (0.1 ​M aqueous solution of KOH) within the test potential range of 0.1–0.6 ​V vs. RHE, which is superior to most reported COF-based catalysts. Hence, this research could not only offer an innovative insight into the construction of composites, but also facilitate the practical application of renewable fuel cells, closed water cycle, and rechargeable metal-air batteries.

The iron-nitrogen co-doped carbon (Fe-N-C) materials have considered one of the oxygen reduction reaction catalysts with the best potential. Unfortunately, their insufficient intrinsic activity and low active sites result in thick cathode catalytic layers of fuel cell, which has limited discharge performance of the Fe-N-C catalysts in the fuel cells. Herein, a supramolecular assembly strategy is designed to prepare accessible Fe-Nx sites and ultra-fine Fe3C nanoparticles in porous carbon nanosheet with optimized pore structure toward oxygen reduction electrocatalysis. It is found that supramolecular assembly strategy has significantly increased the specific surface area and Fe-Nx site content, and induced the formation of highly dispersed Fe3C nanoparticles, which contributes to the high electrochemical active surface area and catalytic activity. The obtained FeNC-900-S catalyst exhibits a high half-wave potential of 0.860 V and a current density of up to 8.28 mA/cm2 (Jk at 0.85 V) in 0.1 M KOH, outperforming the those of commercial Pt/C. More importantly, when the FeNC-900-S is employed as an air cathode catalyst towards zinc-air batteries, it obtains an open-circuit voltage of 1.548 V, a power density of 188.8 mW/cm2 and a specific capacity of 790.5 mAh/g.

Exploring non-precious efficient oxygen reduction reaction (ORR) catalysts is of great significance to fuel cells and Zn-air batteries (ZABs). CrN is a theoretically promising ORR catalyst, but its potential needs to be unlocked by proper supports that provide high conductivity and high exposure of active sites. In this work, we introduce a novel synthesis of carbon nanosheets-supported CrN nanoparticles (CrN/C) by annealing the mixture of CrCl3, 1, 10-phenanthroline and melamine via a two-step pyrolysis. The prepared CrN/C materials show good ORR activity and stability in acidic and alkaline media. The optimal CrN/C material has an ORR half-wave potential of 0.73 and 0.72 V (vs. reversible hydrogen electrode) in acidic and alkaline media, respectively. And it retains 82

Oxygen reduction reaction (ORR) is the heart of many new energy conversions and storage devices, such as metal-air batteries and fuel cells. However, ORR is currently facing the dilemma of sluggish intrinsic kinetics and the noble electrocatalysts of high price and low reserves. In this work, isolated Co atoms anchored on defective nitrogen-doped carbon graphene single-atom catalyst (Co-SAC/NC) are synthesized via the proposed movable type printing method. The prepared Co-SAC/NC catalyst demonstrates admirable ORR performance, with a high half-wave potential of 0.884 V in alkaline electrolytes and outstanding durability. In addition, an assembled zinc-air battery with prepared Co-SAC/NC as air-cathode catalyst displays a high-peak power density of 179 mW cm(-2) and a high-specific capacity (757 mAh g(-1)). Density functional theory calculations confirm that the true active sites of the prepared catalyst are Co-N-4 moieties, and further reveal a significantly electronic structure evolution of Co sites in the ORR process, in which the project density of states and local magnetic moment of Co atom varies during its whole reaction process. This work not only paves a new avenue for synthesizing SACs as robust electrocatalysts, but also provides an electronic-level insight into the evolution of the electronic structure of single-atom catalysts.

Synergistic effects have been demonstrated for binary single-atom catalysts (SACs), while it is still challenging to investigate the activity and performance of ternary SACs due to the lack of robust method to synthesize these materials. Herein, we provide a general approach for the preparation of ternary SACs, and the features of single atoms highly dispersed on the support have been identified and verified. As an illustration, trace platinum decorated iron-cobalt ternary single atom catalysts (PtFeCo/NC) possess an obviously enhanced bifunctional activity of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), as well as high stability. The density functional theory calculations reveal that the synergistic effects induced by the introduction of Pt enable modulating the adsorption strength of reaction intermediates both on the Fe-N4 and Co-N4 sites, thus enhancing the ORR and OER activity, respectively. In addition, the PtFeCo/NC-based Zn-air battery delivers a higher power density than that of commercial Pt/C-RuO2, and can be steadily operated over 188 h.

Developing cost-effective acidic oxygen reduction reaction (ORR) catalysts with high performance is of great significance for proton exchange membrane fuel cells (PEMFCs) but very challenging. Transition -metal oxynitrides have high tolerance to harsh acidic media due to their excellent corrosion resistance, but they suffer from low acidic ORR activity. Here we report the discovery of a carbon -supported bimetallic niobium -iron oxynitride as a highly active and robust ORR catalyst in acidic media. This catalyst shows much higher ORR activity than its monometallic niobium oxynitride counterpart and exhibits a record high ORR activity among transition -metal oxynitrides, with an optimal ORR half -wave potential of 0.75 V vs. RHE, approaching those of atomically dispersed metal -N -C materials. It is revealed that the optimal catalyst has two types of Fe species with low oxidation state and two additional oxygen adsorption sites with high reactivity in comparison to its monometallic niobium oxynitride counterpart, therefore resulting in its remarkable ORR activity. Our work provides a new direction to explore efficient acidic ORR catalysts with low costs.

Multimetallic alloys have demonstrated promising performance for the application of metal-air batteries, while it remains a challenge to design multimetallic single-atom catalysts (MM-SACs). Herein, metal-C3N4 and nitrogen-doped carbon are employed as cornerstones to synthesize MM-SACs by a general two-step method, and the inherent features of atomic dispersion and the strong electronic reciprocity between the multimetallic sites have been verified. The trimetallic FeCoZn-SACs and quatermetallic FeCoCuZn-SACs are both found to deliver superior oxygen evolution reaction and oxygen reduction reaction activity, respectively, as well as outstanding bifunctional durability. Density functional theory calculations elucidate the crucial contribution of Co sites of FeCoCuZn-SACs to the efficient catalysis of both the ORR and the OER. More importantly, Zn-air batteries with FeCoCuZn-SACs as cathodic catalysts exhibit a high power density (252 mW cm-2), high specific capacity (817 mAh gZn-1), and considerable stability (over 225 h) for charging-discharging processes. This work provides a visual perspective for the advantages of MM-SACs toward oxygen electrocatalysis.

Tetrazole-functionalized covalent organic frameworks via successive cycloaddition can be applied to efficient electrocatalytic H 2 O 2 production and Li–S batteries.

The practical application of carbon-supported Pt-based catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) still faces many limitations, including carbon corrosion and their weak interaction with Pt-based nanoparticles (NPs). Harnessing the strong metal-support interaction (SMSI) effects at the interface between Pt-based nanoparticles and alternative corrosion-resistant non-carbon support is an effective strategy to address these issues. The rational design of Pt-based catalysts with favorable SMSI and elucidation of the mechanisms underlying such interactions is indispensable for achieving desirable activity and stability. In this review, first, the basic principles of the ORR are briefly introduced. Next, the formation process of SMSI, construction strategies, and the advantages and drawbacks of representative supports, including transition metal oxides, nitrides, and carbides (TMOs, TMCs, and TMNs, respectively), are fully discussed. Finally, the challenges and prospects in promoting the practical applications of the SMSI effect for ORR are highlighted.

It is worthwhile to explore and develop multifunctional composites with unique advantages for energy con -version and utilization. Post-synthetic modification (PSM) strategies can endow novel properties to already excellent covalent organic frameworks (COFs). In this study, we prepared a range of COF-based composites via a multi-step PSM strategy. COF-Ph-OH was acquired by demethylation between anhydrous BBr3 and -OMe, and then, M@COF-Ph-OH was further obtained by forming the N -M -O structure. COF-Ph-OH exhibited a 2e- - dominatedoxygen reduction reaction (ORR) pathway with high H2O2 selectivity, while M@COF-Ph-OH exhibited a 4e--dominated ORR pathway with low H2O2 selectivity, which was due to the introduction of a metal salt with a d electron structure that facilitated the acquisition of electrons and changed the adsorption energy of the reaction intermediate (*OOH). It was proven that the d electron structure was effective at regu-lating the reaction pathway of the electrocatalytic ORR. Moreover, Co@COF-Ph-OH showed better 4e- ORR properties than Fe@COF-Ph-OH and Ni@COF-Ph-OH. In addition, compared with the other sulfur-impregnated COF-based composites examined in this study, S-Co@COF-Ph-OH had a larger initial capacity, a weaker impedance, and a stronger cycling durability in Li-S batteries, which was attributed to the unique porous structure ensuring high sulfur utilization, the loaded cobalt accelerating LiPS electrostatic adsorption and promoting LiPS catalytic conversion, and the benzoquinoline ring structure being ultra-stable. This work offers not only a rational and feasible strategy for the synthesis of multifunctional COF-based composites, but also promotes their application in electrochemistry.