Recent Advances in Electrocatalysts for Proton Exchange Membrane Fuel Cells and Alkaline Membrane Fuel Cells

Inhibiting demetalation of ZnNC via bimetallic CoZn alloy for an efficient and durable oxygen reduction reaction

Inhibition of demetalation due to electrochemical dissolution of metal active centers is a major challenge for the real-world commercialization of transition metals and nitrogen co-doped carbon (MNC) material catalysts. This research utilized a microchannel reactor to synthesize zeolitic imidazolate framework-8@zeolitic imidazolate framework-67, resulting in a CoZn/ZnNC material produced through a core-shell pyrolysis strategy. Direct synergistic interaction of CoZn alloy nanoparticles and ZnNC improves the activity and durability of the oxygen reduction reaction. In proton-exchange membrane fuel cell tests, the CoZn/ZnNC achieved a peak power density of 380.1 mW/cm2. Furthermore, it demonstrated excellent stability in Zn-air battery charge/discharge cycles, lasting up to 480 h. Experimental tests and density functional theory calculations confirmed the presence of strong interactions between the CoZn alloy and ZnNC, which could inhibit demetalation by strengthening the ZnN bond. Furthermore, a moderate rise in the d-band center optimized the adsorption and desorption capacities of oxygen-containing intermediates (*O, *OH, and *OOH). Overall, this research presents a new strategy based on interactions between alloy nanoparticles and single atoms.

Cost trajectory of hydrogen fuel cell technology in China

Reducing the cost of hydrogen fuel cell technology is crucial in propelling the hydrogen economy and achieving decarbonized energy systems. This study identifies the hydrogen fuel cell cost trajectory through a multi-stage learning curve model, highlighting technology learning mechanisms across different stages. Findings show that innovation and production contribute to cost reduction, and the learning by researching holds a more significant role presently, while the learning by doing takes precedence in the long term, achieving a 14% learning rate. The cost predictions imply that the system cost of hydrogen fuel cell is expected to fall below 1,000 yuan/kW after 2031. Moreover, the scenario analyses highlight the conducive role of various hydrogen production technologies and the evolution of cost influencing factors on cost reduction. Our research provides critical insights into the evolving dynamics of technological learning and cost trajectory in the hydrogen fuel cell industry, with significant implications for policy-making.

Designing Flexible Carbon Nanofiber Membranes by Electrospinning and Cross-Linking for Proton Exchange Membrane Fuel Cells

Traditional carbon-based materials suffer from fragility, low mechanical strength, and electrical conductivity when they are used as a gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs), resulting in low power density. In this study, a flexible carbon nanofiber membrane (CFM) was studied for use as a GDL, prepared by polyacrylonitrile (PAN) electrospinning with the incorporation of carboxylated multiwalled carbon nanotubes (MWCNTs), polyethylenimine (PEI) impregnation, glutaraldehyde (GA) cross-linking, and thermal treatment. The concentrations of MWCNTs in the electrospinning solution and PEI in the impregnation solution were investigated. Interestingly, the mechanical strength and electrical conductivity of CFM showed a triangle trend with the MWCNTs or PEI concentration. The optimal sample (CNT1.5/PEI7/GA-CFM) demonstrated good flexibility, with an in-plane resistivity of 18.60 mΩ cm, a tensile strength of 7.94 MPa, and a bending strength of 20.65 MPa. The peak power density and maximum current density were respectively 1169 mW cm-2 and 2720 mA cm-2, exceeding those of commercial Toray and Cetech GDLs under identical testing conditions. These results illustrate the potential of high-performance electrospun CFMs for GDL applications.

Oxygen spillover on supported Pt-cluster for anti-CO-poisoning hydrogen oxidation

Reducing Pt loading in the anodic hydrogen oxidation reaction (HOR) and concurrently increasing mass activity and CO tolerance are essential for advancing proton exchange membrane fuel cells (PEMFCs). Here, an electrocatalyst of 1.7 wt% Pt clusters loaded on a hollow bowl-like W3O/WC heterostructure is designed to increase the anti-CO-poisoning HOR. Due to its unique electron delocalization effect, the W3O/WC heterostructure serves as a warehouse to share electrons with Pt; this simultaneously lowers the HOR barrier and accumulates the hydroxyl radicals (•OH) to accelerate CO oxidation. The Pt‒O bond originating from the oxygen spillover effect of W3O promotes hydrogen and CO oxidation, whereas the lattice‒O consumed in W3O replenished through water dissociation. The resultant electrocatalyst exhibits mass activity of 469 A g‒1 at 50 mV and anti-toxicity even at 2000 ppm CO. The PEMEC delivers a peak power density of 1.63 W cm‒2 and maintains considerable anti-CO poisoning performance.

Atomic Cobalt-Doped Palladium Metallene toward Efficient Oxygen Reduction Electrocatalysis

Designing a high-efficiency catalyst for the cathode oxygen reduction reaction (ORR) in fuel cells still faces enormous challenges due to the stringent requirements for high power density and long-term durability. Palladium (Pd) metallene, on account of its unique properties and high Pd utilization efficiency, is recognized as a prospective candidate for enhancing the ORR catalytic performance. Herein, we present atomic cobalt (Co)-doped Pd metallene (Co-Pdene), featuring an ultrathin and highly curved morphology, developed via a straightforward wet-chemical approach for efficient ORR electrocatalysis in alkaline media. Resulting from the metallene structure and transition metal Co doping, the Co-Pdene catalyst demonstrates exceptional electrocatalytic performance, achieving an electrochemical mass activity (MA) of 3.14 A per milligram palladium at 0.85 V while maintaining structural integrity over 30000 potential cycles. Theory simulations (DFT) manifest that the single-atom Co sites optimize the electronic structure of palladium in the Co-Pdene, thereby lowering the theoretical overpotential to 0.29 V. This work proposes an innovative design strategy of single-atom transition metal-doped Pd metallene as a highly efficient ORR electrocatalyst.

Nanoscale Fe3O4 Electrocatalysts for Oxygen Reduction Reaction

This study presents a straightforward hydrothermal synthesis approach to fabricate uniform and highly dispersed nanoscale Fe3O4 electrocatalysts for the oxygen reduction reaction (ORR). FeSO4·7H2O is used as the precursor, and sodium dodecyl sulfate (SDS) is incorporated as a dispersing agent to optimize particle size and dispersion. The SDS concentration plays a crucial role in controlling the particle size and distribution, with higher SDS concentrations resulting in smaller, well-dispersed particles (30-40 nm), compared to the agglomerated particles formed without SDS. The Fe3O4 catalyst demonstrates significant enhancement in ORR performance, with a half-wave potential of 0.091 V vs. Hg/HgO and a limiting diffusion current density of -5.50 mA cm2, surpassing the performance of agglomerated Fe3O4 and approaching that of state-of-the-art 20% Pt/C catalysts. Additionally, the Fe3O4 catalyst exhibits superior stability and resistance to methanol and CO poisoning, presenting a promising alternative to platinum-based catalysts for ORR applications. This work introduces an efficient approach for the synthesis of high-performance and evenly distributed Fe3O4 electrocatalysts, offering a new pathway for the development of metal oxide-based ORR catalysts with enhanced activity and durability.

Co-Motif-Engineered RuO2 Nanosheets for Robust and Efficient Acidic Oxygen Evolution

The development of efficient and reliable acidic oxygen evolution reaction (OER) electrocatalysts represents a crucial step in the process of water electrolysis. RuO2, a benchmark OER catalyst, suffers from limited large-scale applicability due to its tendency toward the less stable lattice oxygen mechanism (LOM). This work reports the synthesis of Co-doped RuO2 nanosheets with a unique porous morphology composed of interconnected grains via a facile molten salt method. Co doping modulates the grain size, effectively increasing the specific surface area and introducing oxygen vacancies. These oxygen vacancies, coupled with the Co dopants, form Co-O(V) motifs that tune the electronic configuration of Ru. This structural engineering promotes a shift in the OER mechanism from the detrimental LOM pathway to the more efficient adsorbate evolution mechanism (AEM), significantly enhancing the stability of the RuO2 matrix in acidic environments. The optimized Co0.108-RuO2 catalyst exhibits a low overpotential of 214 mV at 10 mA cm-2 and remarkable stability over commercial RuO2 and undoped counterparts, owing to the synergistic effect of the increased surface area, Co-O(V) motifs, and favored AEM pathway. This strategy of utilizing Co doping to engineer morphology, electronic structure, and reaction mechanism offers a promising avenue for developing high-performance OER electrocatalysts.

Isolated p-Block Antimony Atoms Activated CuO@Co-CN Enable High Performances for Water Splitting and Zn-Air Batteries

This study reports an effective strategy for designing 3D electrocatalyst via the deposition of ZIF67-derived Co-CN shell layer over CuO nanoarrays to form a CuO@Co-CN hybrid, followed by incorporation with p-block Sb single atoms (CuO@Co-CN/Sb) to obtain highly activated catalytic behaviors. Inheriting both the excellent intrinsic catalytic activity of the components and their synergy, the CuO@Co-CN/Sb material serves as a high-efficiency multifunctional catalyst for overall water splitting and zinc (Zn)-air batteries. The material yields a current density of 10 mA cm-2 at a low overpotential of 72 and 250 mV for the hydrogen evolution reaction and oxygen evolution reaction, respectively. Furthermore, an electrolyzer based on CuO@Co-CN/Sb shows remarkable performance with a derived current density of 0.5 A cm-2 at low cell voltage of 2.67 V and good stability for 50 h continuous operation at a high current density of 0.5 A cm-2. Simultaneously, Zn-air battery using the CuO@Co-CN/Sb material as air cathode yields a high open circuit voltage of 1.455 V and a discharge power density of 131.07 mW cm-2.

Microkinetic Modelling of Electrochemical Oxygen Evolution Reaction on Ir(111)@N-Graphene Surface

We have explored the thermodynamics and microkinetic aspects of oxygen evolution catalysis on low loading of Ir(111) on nitrogen-doped graphene at constant potential. The electronic modification induced by N-doping is the reason for the reduced overpotential of OER. The N-induced defect in the charge density is observed with increasing charge-depleted region around the Ir atoms. The lattice contraction shifts the d-band center away from the Fermi level, which increases the barrier for OH* and O* formation on Ir(111) supported on NGr (Ir(111)@NGr). Thus, highly endothermic O* formation reduces the OOH* formation, which is the potential determining step. For comparison, all electronic and binding energy calculations were also performed against Ir NP supported on Gr (Ir(111)@Gr). The stepwise potential-dependent activation barrier (G a ${{G}_{a}}$ ) was obtained using the charge extrapolation method. The third step remains the RDS in all ranges of water oxidation potentials. The potential dependentG a ${{G}_{a}}$ is further applied to the Eyring rate equation to obtain the current density (j O E R ${{j}_{OER}}$ ) and correlation betweenj O E R ${{j}_{OER}}$ and pH dependence, i. e., OH- concentration. The microkineticj O E R ${{j}_{OER}}$ progression leads to a Tafel slope value of 30 mV dec-1 at pH=14.0, requiringη k i n e t i c = 0 . 33 V ${{\eta }_{kinetic}=0.33\ V}$ .

Optimized Adsorption of Had and OHad over Amorphous SrRuPtOxHy Nanobelts towards Efficient Alkaline Fuel Cell Catalysis

PtRu-based catalysts toward hydrogen oxidation reaction (HOR) suffer from low efficiency, CO poisoning and over-oxidation at high potentials. In this work, an amorphization strategy is adopted for preparation of amorphous SrRuPtOxHy nanobelts (a-SrRuPtOxHy NBs). The a-SrRuPtOxHy NBs has optimized adsorption of intermediates (H and OH), increased number of active sites, highly weakened CO poisoning and enhanced anti-oxidation ability owing to the special amorphous structure. Consequently, a-SrRuPtOxHy NBs displays superior HOR performance with a mass activity of 7.5 A/mgPt+Ru, 25 and 5 times of that of SrRuPt(OH)x NBs and commercial PtRu/C, respectively, and long-lasting stability. Besides, a peak power density of 750 mW/cm2 and a specific power of 14.8 W/mgPt+Ru have been achieved for a-SrRuPtOxHy NBs at a low loading of 0.05 mgPt+Ru/cm2, surpassing many reported HOR catalysts. Mechanism investigation indicates that Pt and Ru are present in oxide/hydroxide forms and H in a-SrRuPtOxHy NBs participates in HOR. Ab initio molecular dynamics (AIMD) simulations and density functional theory (DFT) calculations show that there are three catalytic mechanisms participating in a-SrRuPtOxHy NBs, which all exhibit low catalytic barrier and highly improved HOR efficiency. This work provides a new strategy for designing high-performance catalysts towards fuel cells.

Advanced Anion Exchange Membranes: Structural Insights and Property Optimization

With the increasing demand for clean energy, driven by advancements in science and technology, anion exchange membrane fuel cells (AEMFCs) have emerged as a promising solution for efficient and clean energy conversion. As the core component of AEMFCs, anion exchange membranes (AEMs) are crucial for ion transport and the separation of the cathode and anode. The performance of AEMs primarily depends on two key factors: ionic conductivity and stability, which often require a delicate balance. The ion conduction process is closely linked to the membrane's microscopic structure. This concept article reviews the development of various AEM types, including homogeneous polymer membranes, hybrid membranes, and nanoporous framework membranes, with a focus on their structural characteristics. Additionally, it explores the design and optimization of AEMs in relation to key properties such as ionic conductivity, dimensional stability, and alkali resistance, providing a reference for future innovations in ion-exchange membranes for AEMFCs.

Empowering telecommunication towers employing improved war strategy optimization method

In the field of telecommunication towers, specifically focusing on Base Transceiver Station (BTS) units, this research presents a revolutionary power supply system that is characterized by optimization and environmental cleanliness. The primary goal is to develop a reliable and continuous energy supply for these isolated units. In order to accomplish this objective, the use of PEMFCs (Proton Exchange Membrane Fuel Cells) is utilized. To provide a constant and controlled voltage of output from the PEMFC to the BTS, a proportional-integral (PI) controller based on improved war strategy optimization is used. The purpose of this controller is to improve the efficacy of the model and efficiently adjust to different operating situations. By conducting a comparison study with other methodologies, the suggested system showcases its advantages in terms of both efficiency and dependability. The research results presented in this study provide a substantial and noteworthy addition to the domain of sustainable energy solutions for communications infrastructure. Through the use of PEMFCs and the integration of modern control algorithms, the suggested system presents a very favorable method for supplying power to telecommunication towers. This approach not only enhances the operational efficiency of these towers but also contributes to the reduction of their environmental footprint.

The Role of Alkali Metal Ions in Cooperative Electrocatalysis by Bifunctional Co-Mn-Mixed Phosphates

Developing cost-effective, non-precious metal bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial for advancing sustainable energy storage and conversion technologies, including zinc-air batteries, fuel cells, and water electrolyzers. This study presents a one-pot synthesis of cobalt-manganese mixed phosphates as effective bifunctional electrocatalysts for both ORR and OER. Among the catalysts tested, Na-Co-Mn-P [NaCo1.5Mn1.5(HPO4)2(PO4)] exhibited the highest catalytic activity, with a minimal ΔE of 0.86 V, indicating superior performance. The incorporation of alkali metals and the synergistic effects of metal and phosphate components enhance conductivity, electrochemical surface area, and mixed valency of transition metals, contributing to improved electrocatalytic activity. This work highlights a straightforward synthesis method and the beneficial role of metal-phosphate synergy in oxygen electrocatalysis.

Atomic insights into the ion-conducting channels of poly(arylene piperidinium) anion exchange membranes

Anion exchange membranes (AEMs) are crucial in green energy devices such as water electrolyzers, fuel cells, and CO2 electroreduction. Among the reported AEMs, the quaternary ammonia poly(N-methyl-piperidine-co-p-terphenyl) (QAPPT) AEM is notable for its high OH- conductivity. However, the underlying mechanisms responsible for this high OH- conductivity have remained elusive. Recent experiments have developed the poly(p-quaterphenyl dimethyl piperidinium) (QAQPP) AEM, which has a similar structure to the QAPPT AEM but exhibits much lower conductivity. This discrepancy further complicates our understanding of the superior performance of the QAPPT AEM. To clarify the origin of QAPPT AEM's enhanced conductivity, we perform molecular dynamics simulations to investigate the differences in the underlying causes of the OH- conductivity between QAPPT and QAQPP AEMs. We observe higher OH- diffusion with larger ion-conducting channels in the QAPPT AEM, which is in good agreement with experimental results. Further analysis of the conformations with varying water contents shows that the ion-conducting channels in QAPPT AEMs become larger due to polymer chain folding and dispersion, thereby enhancing OH- transport. In contrast, the channels in QAQPP remain limited in size because the chains maintain their compactness regardless of the water content. Such pronounced conformational changes in QAPPT compared to QAQPP are essentially due to the greater sensitivity of its backbone phenyl rings to water. These findings highlight that conformational evolution in response to water is key to the enhanced conductivity of QAPPT AEMs, providing new insights for more efficient AEM design.

Galvanic replacement mediated morphological adjustments boost nanoparticle performance in electrocatalytic alcohol oxidation

The PdPtCo core-shell nanostructure, fabricated via galvanic replacement by rapidly incorporating Pd into PtCo nanoalloys at room temperature, excels in alcohol oxidation (AOR). Synergistic effects lower Pt electron density, promoting C-C cleavage, while increased Co coverage reduces COads adsorption, enhancing CO tolerance. This work offers a novel strategy for high-performance AOR catalysts.

Durable Acidic Oxygen Evolution Via Self-Construction of Iridium Oxide/Iridium-Tantalum Oxide Bi-Layer Nanostructure with Dynamic Replenishment of Active Sites

Proton exchange membrane (PEM) water electrolysis presents considerable advantages in green hydrogen production. Nevertheless, oxygen evolution reaction (OER) catalysts in PEM water electrolysis currently encounter several pressing challenges, including high noble metal loading, low mass activity, and inadequate durability, which impede their practical application and commercialization. Here we report a self-constructed layered catalyst for acidic OER by directly using an Ir-Ta-based metallic glass as the matrix, featuring a nanoporous IrO2 surface formed in situ on the amorphous IrTaOx nanostructure during OER. This distinctive architecture significantly enhances the accessibility and utilization of Ir, achieving a high mass activity of 1.06 A mgIr-1 at a 300 mV overpotential, 13.6 and 31.2 times greater than commercial Ir/C and IrO2, respectively. The catalyst also exhibits superb stability under industrial-relevant current densities in acid, indicating its potential for practical uses. Our analyses reveal that the coordinated nature of the surface-active Ir species is effectively modulated through electronic interaction between Ir and Ta, preventing them from rapidly evolving into high valence states and suppressing the lattice oxygen participation. Furthermore, the underlying IrTaOx dynamically replenishes the depletion of surface-active sites through inward crystallization and selective dissolution, thereby ensuring the catalyst's long-term durability.

Advanced electrocatalysts for fuel cells: Evolution of active sites and synergistic properties of catalysts and carrier materials

Proton exchange-membrane fuel cell (PEMFC) is a clean and efficient type of energy storage device. However, the sluggish reaction rate of the cathode oxygen reduction reaction (ORR) has been a significant problem in its development. This review reports the recent progress of advanced electrocatalysts focusing on the interface/surface electronic structure and exploring the synergistic relationship of precious-based and non-precious metal-based catalysts and support materials. The support materials contain non-metal (C/N/Si, etc.) and metal-based structures, which have demonstrated a crucial role in the synergistic enhancement of electrocatalytic properties, especially for high-temperature fuel cell systems. To improve the strong interaction, some exciting synergistic strategies by doping and coating heterogeneous elements or connecting polymeric ligands containing carbon and nitrogen were also shown herein. Besides the typical role of the crystal surface, phase structure, lattice strain, etc., the evolution of structure-performance relations was also highlighted in real-time tests. The advanced in situ characterization techniques were also reviewed to emphasize the accurate structure-performance relations. Finally, the challenge and prospect for developing the ORR electrocatalysts were concluded for commercial applications in low- and high-temperature fuel cell systems.

Modulating Electronic Spin State of Perovskite Fluoride by Ni─F─Mn Bond Activating the Dynamic Site of Oxygen Reduction Reaction

Establishing the relationship between catalytic performance and material structure is crucial for developing design principles for highly active catalysts. Herein, a type of perovskite fluoride, NH4MnF3, which owns strong-field coordination including fluorine and ammonia, is in situ grown on carbon nanotubes (CNTs) and used as a model structure to study and improve the intrinsic catalytic activity through heteroatom doping strategies. This approach optimizes spin-dependent orbital interactions to alter the charge transfer between the catalyst and reactants. As a result, the oxygen reduction reaction (ORR) activity of NH4MnF3 on CNTs is significantly enhanced by partial substitution of Mn sites with Ni, such as a half-wave potential (E1/2) of 0.86 V and a limiting current density of 5.26 mA cm-2, which are comparable to those of the commercial Pt/C catalysts. Experimental and theoretical calculations reveal that the introduction of Ni promotes lattice distortion, adjusts the electronic states of the active Mn centers, facilitates the transition from low-spin to intermediate-spin states, and shifts the d-band center closer to the Fermi level. This study establishes a novel approach for designing high-performance perovskite-based fluoride electrocatalysts by modulating spin states.

Two novel lanthanide metal-organic frameworks based on tetraphenylethylene for ultra-high proton conduction

Two novel isostructural anionic lanthanide metal-organic frameworks, (Me2NH2)[Ln(HTCBPE-F)·(HCOO)·DMF]·4.5DMF·2H2O (Eu-MOF and Dy-MOF), based on tetraphenylethylene carboxylate ligands were successfully constructed and characterized. These two MOFs possess porous structures and water stabilities with uncoordinated carboxylate groups and dimethyl ammonium cations, which allow for high proton conductivities (5.35 × 10-2 and 1.22 × 10-2 S cm-1) at 98% RH (relative humidity) and 90 °C. Based on the structural characteristics and activation energy, the proton transfer mechanism is proposed.

Precisely designing asymmetrical selenium-based dual-atom sites for efficient oxygen reduction

Owing to their synergistic interactions, dual-atom catalysts (DACs) with well-defined active sites are attracting increasing attention. However, more experimental research and theoretical investigations are needed to further construct explicit dual-atom sites and understand the synergy that facilitates multistep catalytic reactions. Herein, we precisely design a series of asymmetric selenium-based dual-atom catalysts that comprise heteronuclear SeN2-MN2 (M = Fe, Mn, Co, Ni, Cu, Mo, etc.) active sites for the efficient oxygen reduction reaction (ORR). Spectroscopic characterisation and theoretical calculations revealed that heteronuclear selenium atoms can efficiently polarise the charge distribution of other metal atoms through short-range regulation. In addition, compared with the Se or Fe single-atom sites, the SeFe dual-atom sites facilitate a reduction in the conversion energy barrier from *O to *OH via the coadsorption of *O intermediates. Among these designed selenium-based dual-atom catalysts, selenium-iron dual-atom catalysts achieves superior alkaline ORR performance, with a half-wave potential of 0.926 V vs. a reversible hydrogen electrode. In addition, the SeN2-FeN2-based Zn-air battery has a high specific capacity (764.8 mAh g-1) and a maximum power density (287.2 mW cm-2). This work may provide a good perspective for designing heteronuclear DACs to improve ORR efficiency.

Cooperative Atomically Dispersed Fe-N4 and Sn-Nx Moieties for Durable and More Active Oxygen Electroreduction in Fuel Cells

One grand challenge for deploying porous carbons with embedded metal-nitrogen-carbon (M-N-C) moieties as platinum group metal (PGM)-free electrocatalysts in proton-exchange membrane fuel cells is their fast degradation and inferior activity. Here, we report the modulation of the local environment at Fe-N4 sites via the application of atomic Sn-Nx sites for simultaneously improved durability and activity. We discovered that Sn-Nx sites not only promote the formation of the more stable D2 FeN4C10 sites but also invoke a unique D3 SnNx-FeIIN4 site that is characterized by having atomically dispersed bridged Sn-Nx and Fe-N4. This new D3 site exhibits significantly improved stability against demetalation and several times higher turnover frequency for the oxygen reduction reaction (ORR) due to the shift of the reaction pathway from a single-site associative mechanism to a dual-site dissociative mechanism with the adjacent Sn site facilitating a lower overpotential cleavage of the O-O bond. This mechanism bypasses the formation of the otherwise inevitable intermediate that is responsible for demetalation, where two hydroxyl intermediates bind to one Fe site. As a result, a mesoporous Fe/Sn-PNC catalyst exhibits a positively shifted ORR half-wave potential and more than 50% lower peroxide formation. This, in combination with the stable D3 site and enriched D2 Fe sites, significantly enhanced the catalyst's durability as demonstrated in membrane electrode assemblies using complementary accelerated durability testing protocols.

CuFe Cooperativity at the Membrane-Electrode Interface Elicits a Tandem 2e-+2e- Mechanism for Exclusive O2-To-H2O Electroreduction

High O2 reduction reaction (ORR) kinetics and exclusive 4e- pathway selectivity are keys to realizing a sustainable society. However, nonprecious electrocatalysts at present cannot enhance the ORR turnover frequency and H2O Faradaic efficiency (FE) concurrently. To address these two challenges, hybrid bilayer membrane (HBM) electrodes with earth-abundant metal centers are developed to control proton-coupled electron transfer (PCET) in ORR. Here, an oxidase-inspired CuFe active site is supported on a tris(2-pyridylmethyl)amine HBM and explored as a unique interface for efficient ORR. This bimetallic HBM displayed an ORR activity 1.4 times higher than the monometallic systems and exhibited the highest FE for H2O (∼94%) among Cu-, Fe-, Ni-, and Co-based HBMs. Contrary to previous studies where the ORR current decreases upon embedding the metal center in a hydrophobic lipid environment, here, the incorporation of a nitrile-terminated proton carrier at the HBM interface boosts the ORR current by 1.7 folds relative to the case where the catalytic site is directly exposed to protons in solution. This intriguing dual improvement is supported by density function theory calculations where an additional 2e-+2e- mechanism occurs in parallel to the direct 4e- pathway, highlighting the synergistic effect of the CuFe HBM for facilitating high-performance ORR. A Zn-air battery is constructed using this CuFe HBM for the first time, further demonstrating that the knowledge gained from this HBM technology holds practical values in real-life applications. These findings on interfacial PCET are envisioned to spark new design principles for future catalysts with optimal electrochemical properties for advanced energy conversion schemes.

Cobalt Nitride-Implanted PtCo Intermetallic Nanocatalysts for Ultrahigh Fuel Cell Cathode Performance

Stable and active oxygen reduction electrocatalysts are essential for practical fuel cells. Herein, we report a novel class of highly ordered platinum-cobalt (Pt-Co) alloys embedded with cobalt nitride. The intermetallic core-shell catalyst demonstrates an initial mass activity of 0.88 A mgPt-1 at 0.9 V with 71% retention after 30,000 potential cycles of an aggressive square-wave accelerated durability test and loses only 9% of its electrochemical surface area, far exceeding the US Department of Energy 2025 targets, with unprecedented stability and only a minimal voltage loss under practical fuel cell operating conditions. We discover that regulating the atomic ordering in the core results in an optimal lattice configuration that accelerates the oxygen reduction kinetics. The presence of cobalt nitride decorated within PtCo superlattices guarantees a larger barrier to Co dissolution, leading to the excellent endurance of the electrocatalysts. This work brings up a transformative structural engineering strategy for rationally designing high-performing Pt-based catalysts with a unique atomic configuration for broad practical uses in energy conversion technology.

Formation and Dynamics of Imidazole Supramolecular Chains Investigated by Deep Potential Molecular Dynamics Simulation

Imidazole-based materials have attracted considerable attention due to their promising potential for facilitating anhydrous proton transport at high temperatures. Herein, a machine learning-based deep potential (DP) model for bulk imidazole with first-principles accuracy is developed. The trained model exhibits remarkable accuracy in predicting energies and forces, with minor errors of 4.71 × 10-4 eV/atom and 3.23 × 10-2 eV/Å, respectively. Utilizing DP molecular dynamics simulations, we have systematically investigated the temperature-dependent formation and dynamics of imidazole supramolecular chains through the partial radial distribution function, quantification of hydrogen bond numbers, incoherent intermediate scattering function, and diffusion coefficient. The findings reveal the influence of temperature on the proton transport path following either the "Grotthuss" and "vehicle" mechanism.

DFT-guided synthesis of N, B dual-doped porous carbon from saccharina japonica for enhanced oxygen reduction catalysis

Introduction

The oxygen reduction reaction (ORR) is a crucial determinant of the energy transformation capacity of fuel cells. This study investigates the performance of N and B dual-doped carbon in ORR.

Methods

Six models using density functional theory (DFT) are developed to compare the performance of different doping strategies. A highly efficient dual-doped carbon ORR catalyst (S-850-1) is synthesized from Saccharina japonica, containing 4.54 at% N and 1.05 at% B atom.

Results

Electrochemical analysis reveals that S-850-1 significantly outperforms the nitrogen mono-doped carbon S-850, exhibiting a higher half-wave potential of 0.861 V and a greater limited current density of -5.60 mA cm⁻2, compared to S-850's 0.838 V and -5.24 mA cm⁻2. Furthermore, S-850-1 surpasses the performance of 20% Pt/C, demonstrating enhanced durability and exceptional resistance to CO and methanol. The 1.40 V open circuit voltage produced by S-850-1 when integrated into a Zn-air battery can power an LED light.

Discussion

Both theoretical and practical evaluations validate the excellent ORR performance of nitrogen and boron dual-doped carbon, as evidenced by the agreement between the electrochemical results and DFT calculations. This work not only extends the range of ORR catalysts derived from biomass but also provides guidance on creating and producing affordable, effective catalysts that utilize natural resources.

Crystal-Phase- and B-Content-Dependent Electrochemical Behavior of Pd─B Nanocrystals toward Oxygen Reduction Reaction

The manipulation of crystal phases in metal-nonmetal interstitial alloy nanostructures has attracted considerable attention due to the formation of unique electronic structures and surface atomic arrangements, resulting in unprecedented catalytic performances. However, achieving simultaneous control over crystal phase and nonmetal elements in metal-nonmetal interstitial alloy nanostructures has remained a formidable challenge. Here, a novel synthesis approach is presented for Pd─B interstitial alloy nanocrystals (NCs) that allows investigation of the crystal-phase- and B-content-dependent catalytic performance. Through comparison of the oxygen reduction reaction (ORR) properties of Pd─BX interstitial alloy NCs with different crystal phases and B contents, achieved by precise control of reaction temperature and time, the influences of crystal phase and B contents in the Pd─BX interstitial alloy NCs on ORR are precisely investigated. The hexagonal closed packed (hcp) PdB0.5 NCs exhibit superior catalytic activity, with mass activities reaching 2.58 A mg-1, surpassing Pd/C by 10.3 times, attributed to synergistic effects by the hcp crystal phase and relatively high B contents. This study not only provides a novel approach to fabricate interstitial alloy nanostructures with unconventional crystal phases and finely controlled nonmetal elements but also elucidates the importance of crystal phase and nonmetal element content in optimizing electrocatalytic efficiency.

Growth Modulation of High-Entropy Alloys for Electrocatalytic Methanol Oxidation Reaction

High-entropy alloy (HEA) electrocatalysts have exhibited remarkable catalytic performance because of their synergistic interactions among multiple metals. However, the growth mechanism of HEAs remains elusive, primarily due to the constraints imposed by the current synthesis methodologies for HEAs. In this work, an innovative electrodeposition method was developed to fabricate Pt-based nanocomposites (Pt1Bi2Co1Cu1Ni1/CC), comprising HEA nanosheets and carbon cloths (CCs). The reaction system could be effectively monitored by taking samples out from the system during the reaction process, facilitating in-depth insight into the growth mechanism underlying the material formation. In particular, Pt1Bi2Co1Cu1Ni1/CC nanocomposites show superior methanol oxidation reaction (MOR) performance (mass activity up to 5.02 A mgPt-1). Upon structural analysis, the d-band center of Pt1Bi2Co1Cu1Ni1/CC is lower in comparison with that of Pt1Bi2/CC and Pt/CC, demonstrating the formation of a rich-electron structure. Both the uniformity of HEAs and the carbon-supported effect could provide additional active sites. These findings suggest that the strong electronic interaction within HEAs and additional active sites can effectively modulate the catalytic structure of Pt, which benefits the enhanced CO tolerance and MOR performance.

Precise Construction of the Triple-Phase Boundary and Its Antiphosphate Poisoning Effect in the Confined Region

As a critical component for the oxygen reduction reaction (ORR), platinum (Pt) catalysts exhibit promising catalytic performance in High-temperature-proton exchange membrane fuel cells (HT-PEMFCs). Despite their success, HT-PEMFCs primarily utilize phosphoric acid-doped polybenzimidazole (PA-PBI) as the proton exchange membrane, and the phosphoric acid within the PBI matrix tends to leach onto the Pt-based layers, easily causing toxicity. Herein, we first propose UiO-66@Pt3Co1-T composites with precisely engineered interfacial structures. The UiO-66@Pt3Co1-T exhibits an octahedral porous framework with uniform structural dimensions and even distribution of surface nanoparticles, which demonstrate superior ORR performance compared to commercial Pt/C. The unique structure and morphology of the composites also exhibit a favorable half-wave potential in different concentrations of phosphoric acid electrolyte, regulated by the phosphoric acid adsorption site and intensity.This finding suggests that the incorporation of Co could effectively modulate the Pt d-band center, thereby enhancing the ORR performance. Furthermore, the selective adsorption of phosphoric acid by ZrO2 enables precise control over the phosphoric acid distribution. Notably, the retention of the octahedral framework post high-temperature treatment facilitates the establishment of dual transport pathways for gases and protons, leading to a stable and efficient triple-phase boundary.

Carbothermal Reduction-Assisted Synthesis of a Carbon-Supported Highly Dispersed PtSn Nanoalloy for the Oxygen Reduction Reaction

Exploring high-performance and low-platinum-based electrocatalysts to accelerate the oxygen reduction reaction (ORR) at the air cathode of zinc-air batteries remains crucial. Herein, by combining electroless deposition and carbothermal reduction, a nitrogen-doped carbon-supported highly dispersed PtSn alloy nanocatalyst (PtSn/NC) was prepared for a high-efficiency ORR process. Electrochemical measurements show that PtSn/NC exhibits excellent electrocatalytic ORR activity with a half-wave potential of 0.850 V versus reversible hydrogen electrode (RHE), which is higher than that of commercial Pt/C (0.815 V). The PtSn/NC-based (20 μgPt cm-2) rechargeable Zn-air battery exhibited astonishing performance with a maximum power density of up to 150.1 mW cm-2, as well as excellent rate performance and charge/discharge stability. Physical characterization reveals that carbothermal reduction could compel the transformation of Sn oxide into metallic Sn, which then alloys with the deposited Pt atoms to form the PtSn nanoalloy, in which electrons are transferred from Sn atoms to neighboring Pt atoms, thereby improving the ability of Pt-based active sites to catalyze the ORR process in PtSn/NC by optimizing the unoccupied d-band of Pt atoms. This work provides a reliable and innovative route for the rational design of highly dispersed Pt-based alloy ORR electrocatalysts.

Insights into the pH effect on hydrogen electrocatalysis

Hydrogen electrocatalytic reactions, including the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR), play a crucial role in a wide range of energy conversion and storage technologies. However, the HER and HOR display anomalous non-Nernstian pH dependent kinetics, showing two to three orders of magnitude sluggish kinetics in alkaline media compared to that in acidic media. Fundamental understanding of the origins of the intrinsic pH effect has attracted substantial interest from the electrocatalysis community. More critically, a fundamental molecular level understanding of this effect is still debatable, but is essential for developing active, stable, and affordable fuel cells and water electrolysis technologies. Against this backdrop, in this review, we provide a comprehensive overview of the intrinsic pH effect on hydrogen electrocatalysis, covering the experimental observations, underlying principles, and strategies for catalyst design. We discuss the strengths and shortcomings of various activity descriptors, including hydrogen binding energy (HBE) theory, bifunctional theory, potential of zero free charge (pzfc) theory, 2B theory and other theories, across different electrolytes and catalyst surfaces, and outline their interrelations where possible. Additionally, we highlight the design principles and research progress in improving the alkaline HER/HOR kinetics by catalyst design and electrolyte optimization employing the aforementioned theories. Finally, the remaining controversies about the pH effects on HER/HOR kinetics as well as the challenges and possible research directions in this field are also put forward. This review aims to provide researchers with a comprehensive understanding of the intrinsic pH effect and inspire the development of more cost-effective and durable alkaline water electrolyzers (AWEs) and anion exchange membrane fuel cells (AMFCs) for a sustainable energy future.

Proton-Enriched Alginate-Graphene Hydrogel Microreactor for Enhanced Hydrogen Peroxide Photosynthesis

Efficient synthesis of H2O2 via photocatalytic oxygen reduction without sacrificial agents is challenging due to inadequate proton supply from water and difficulty in maintaining O-O bond during O2 activation. Herein, we developed a straightforward strategy involving a proton-rich hydrogel cross-linked by metal ions [M(n)], which is designed to facilitate the selective production of H2O2 through proton relay and metal ion-assisted detachment of crucial intermediates. The hydrogel comprises CdS/graphene and alginate cross-linked by metal ions via O=C-O-M(n) bonds. Efficient O2 reduction and hydrogenation occurred, benefitting from the collaboration between proton-rich alginate and the photocatalytically active CdS/graphene. Meanwhile, the O=C-O-M(n) bonds enhance the electron density of α-carbon sites on graphene, crucial for O2 activation and *OOH intermediate detachment, preventing deeper O-O bond cleavage. The role of metal ions in promoting *OOH desorption was demonstrated through Lewis acidity-dependent activity, with Y(III) having the highest activity, followed by Lu(III), La(III), and Ca(II).

Electron regulation of CeO2 on CoP multi-shell hetero-junction micro-sphere towards highly efficient water oxidation

CeO2 has been identified as a significant cocatalyst to enhance the electrocatalytic activity of transition metal phosphides (TMPs). However, the electrocatalytic mechanism by which CeO2 enhances the catalytic activity of TMP remains unclear. In this study, we have successfully developed a unique CeO2-CoP-1-4 multishell microsphere heterostructure catalyst through a simple hydrothermal and calcination process. CeO2-CoP-1-4 exhibits great potential for electrocatalytic oxygen evolution reaction (OER), requiring only an overpotential of 254 mV to achieve a current density of 10 mA cm-2. Moreover, CeO2-CoP-1-4 demonstrates excellent operating durability lasting for 55 h. The presence of CeO2 as a cocatalyst can regulate the microsphere structure of CoP, the resulting multishell microsphere structure can shorten the mass transfer distance, and improve the utilization rate of the active site. Furthermore, in situ Raman and ex situ characterizations, and DFT theoretical calculation results reveal that CeO2 can effectively regulates the electronic structure of Co species, reduces the reaction free energy of rate-limiting step, thus increase the reaction kinetic. Overall, this study provides experimental and theoretical evidence to better comprehend the mechanism and structure evolution of CeO2 in enhancing the OER performance of CoP, offering a unique design inspiration for the development of efficient hollow heterojunction electrocatalysts.

Advanced Hollow Cubic FeCo-N-C Cathode Electrocatalyst for Ultrahigh-Power Aluminum-Air Battery

The exploration of electrocatalysts toward oxygen reduction reaction (ORR) is pivotal in the development of diverse batteries and fuel cells that rely on ORR. Here, a FeCo-N-C electrocatalyst (FeCo-HNC) featuring with atomically dispersed dual metal sites (Fe-Co) and hollow cubic structure is reported, which exhibits high activity for electrocatalysis of ORR in alkaline electrolyte, as evidenced by a half-wave potential of 0.907 V, outperforming that of the commercial Pt/C catalyst. The practicality of such FeCo-HNC catalyst is demonstrated by integrating it as the cathode catalyst into an alkaline aluminum-air battery (AAB) paring with an aluminum plate serving as the anode. This AAB demonstrates an unprecedented power density of 804 mW cm-2 in ambient air and an impressive 1200 mW cm-2 in an oxygen-rich environment. These results not only establish a new benchmark but also set a groundbreaking record for the highest power density among all AABs reported to date. Moreover, they stand shoulder to shoulder with state-of-the-art H2-O2 fuel cells. This AAB exhibits robust stability with continuous operation for an impressive 200 h. This groundbreaking achievement underscores the immense potential and forward strides that the present work brings to the field.

Recent advances of doping strategy for boosting the electrocatalytic performance of two-dimensional noble metal nanosheets

Benefiting from the ultrahigh specific surface areas, massive exposed surface atoms, and highly tunable microstructures, the two-dimensional (2D) noble metal nanosheets (NSs) have presented promising performance for various electrocatalytic reactions. Nevertheless, the heteroatom doping strategy, and in particular, the electronic structure tuning mechanisms of the 2D noble metal catalysts (NMCs) yet remain ambiguous. Herein, we first review several effective strategies for modulating the electrocatalytic performance of 2D NMCs. Then, the electronic tuning effect of hetero-dopants for boosting the electrocatalytic properties of 2D NMCs is systematically discussed. Finally, we put forward current challenges in the field of 2D NMCs, and propose possible solutions, particularly from the perspective of the evolution of electron microscopy. This review attempts to establish an intrinsic correlation between the electronic structures and the catalytic properties, so as to provide a guideline for designing high-performance electrocatalysts.

Spin Polarization Enhances the Catalytic Activity of Monolayer MoSe2 for Oxygen Reduction Reaction

The key factors in achieving high energy efficiency for proton exchange membrane fuel cells are reducing overpotential and increasing the oxygen reduction rate. Based on first-principles calculations, we induce H atom adsorption on 4 × 4 × 1 monolayer MoSe2 to induce spin polarization, thereby improving the catalytic performance. In the calculation of supercells, the band unfolding method is used to address the band folding effect in doped systems. Furthermore, it is evident from analyzing the unique energy band configuration of MoSe2 that a higher valley splitting value has better catalytic effects on the oxygen reduction reaction. We believe that the symmetries of the distinct adsorption site result in different overpotentials. In addition, when an even number of hydrogen atoms is adsorbed, the monolayer MoSe2 has no spin polarization. The spin can affect the electron transfer process and alter the hybrid energy with the reaction products, thereby regulating its catalytic performance.

PGM-free single atom catalysts for the oxygen reduction reaction in proton exchange membrane fuel cells

The progress of proton exchange membrane fuel cells (PEMFCs) in the clean energy sector is notable for its efficiency and eco-friendliness, although challenges remain in terms of durability, cost and power density. The oxygen reduction reaction (ORR) is a key sluggish process and although current platinum-based catalysts are effective, their high cost and instability is a significant barrier. Single-atom catalysts (SACs) offer an economically viable alternative with comparable catalytic activity for ORR. The primary concern regarding SACs is their operational stability under PEMFCs conditions. In this article, we review current strategies for increasing the catalytic activity of SACs, including increasing active site density, optimizing metal center coordination through heteroatom doping, and engineering porous substrates. To enhance durability, we discuss methods to stabilize metal centers, mitigate the effects of the Fenton reaction, and improve graphitization of the carbon matrix. Future research should apply computational chemistry to predict catalyst properties, develop in situ characterization for real-time active site analysis, explore novel catalysts without the use of platinum-based catalysts to reduce dependence on rare and noble metal, and investigate the long-term stability of catalyst under operating conditions. The aim is to engineer SACs that meet and surpass the performance benchmarks of PEMFCs, contributing to a sustainable energy future.

Five years of scanning electrochemical cell microscopy (SECCM): new insights and innovations

Scanning electrochemical cell microscopy (SECCM) is a nanopipette-based technique which enables measurement of localised electrochemistry. SECCM has found use in a wide range of electrochemical applications, and due to the wider uptake of this technique in recent years, new applications and techniques have been developed. This minireview has collected all SECCM research articles published in the last 5 years, to demonstrate and celebrate the recent advances, and to make it easier for SECCM researchers to remain well-informed. The wide range of SECCM applications is demonstrated, which are categorised here into electrocatalysis, electroanalysis, photoelectrochemistry, biological materials, energy storage materials, corrosion, electrosynthesis, and instrumental development. In the collection of this library of SECCM studies, a few key trends emerge. (1) The range of materials and processes explored with SECCM has grown, with new applications emerging constantly. (2) The instrumental capabilities of SECCM have grown, with creative techniques being developed from research groups worldwide. (3) The SECCM research community has grown significantly, with adoption of the SECCM technique becoming more prominent.

Iridium-Based Alkaline Hydrogen Oxidation Reaction Electrocatalysts

The hydroxide exchange membrane fuel cells (HEMFCs) are promising but lack of high-performance anode hydrogen oxidation reaction (HOR) electrocatalysts. The platinum group metals (PGMs) have the HOR activity in alkaline medium two to three orders of magnitude lower than those in acid, leading to the high required PGMs amount on anode to achieve high HEMFC performance. The mechanism study demonstrates the hydrogen binding energy of the catalyst determines the alkaline HOR kinetics, and the adsorbed OH and water on the catalyst surface promotes HOR. Iridium (Ir) has a unique advantage for alkaline HOR due to its similar hydrogen binding energy to Pt and enhanced adsorption of OH. However, the HOR activity of Ir/C is still unsatisfied in practical HEMFC applications. Further fine tuning the adsorption of the intermediate on Ir-based catalysts is of great significance to improve their alkaline HOR activity, which can be reasonably realized by structure design and composition regulation. In this concept, we address the current understanding about the alkaline HOR mechanism and summarize recent advances of Ir-based electrocatalysts with enhanced alkaline HOR activity. We also discuss the perspectives and challenges on Ir-based electrocatalysts in the future.

Fabrication of N and S co-doped lignin-based porous carbon aerogels loaded with FeCo alloys and their application to oxygen evolution and reduction reactions in Zn-air batteries

Zn-air batteries are a highly promising clean energy sustainable conversion technology, and the design of dual-function electrocatalysts with excellent activity and stability is crucial for their development. In this work, FeCo alloy loaded biomass-based N and S co-doped carbon aerogels (FeCo@NS-LCA) were fabricated from chitosan and lignosulfonate-metal chelates via liquid nitrogen pre-frozen synergistic high-temperature carbonization with application in electrocatalytic reactions. The abundant oxygen-containing functional groups on lignosulfonates have a chelating effect on metal ions, which can avoid the aggregation of metal nanoparticles during carbonation and catalysis, facilitating the construction of a nanoconfinement catalytic system with biomass carbon as the domain-limiting body and FeCo nanoparticles as the active sites. FeCo@NS-LCA exhibited catalytic activity (E1/2 = 0.87 V, JL = 5.7 mA cm-2) comparable to the commercial Pt/C in the oxygen reduction reaction (ORR), excellent resistance to methanol toxicity and stability. Meanwhile, the overpotential of oxygen evolution reaction (OER) was 324 mV, close to that of commercial RuO2 catalysts (351 mV). This study utilizes the coordination action of lignosulfonate to provide a novel and environmentally friendly method for the preparation of confined nano-catalysts and provides a new perspective for the high-value utilization of biomass resources.

Boosting Formate Electrooxidation by Heterostructured PtPd Alloy and Oxides Nanowires

Direct formate fuel cells (DFFCs) receive increasing attention as promising technologies for the future energy mix and environmental sustainability, as formate can be made from carbon dioxide utilization and is carbon neutral. Herein, heterostructured platinum-palladium alloy and oxides nanowires (PtPd-ox NWs) with abundant defect sites are synthesized through a facile self-template method and demonstrated high activity toward formate electrooxidation reaction (FOR). The electronic tuning arising from the heterojunction between alloy and oxides influence the work function of PtPd-ox NWs. The sample with optimal work function reveals the favorable adsorption behavior for intermediates and strong interaction in the d-p orbital hybridization between Pt site and oxygen in formate, favoring the FOR direct pathway with a low energy barrier. Besides the thermodynamic regulation, the heterostructure can also provide sufficient hydroxyl species to facilitate the formation of carbon dioxide due to the ability of combining absorbed hydrogen and carbon monoxide at adjacent active sites, which contributes to the improvement of FOR kinetics on PtPd-ox NWs. Thus, heterostructured PtPd-ox NWs achieve dual regulation of FOR thermodynamics and kinetics, exhibiting remarkable performance and demonstrating potential in practical systems.

Strong Interaction between Titanium Carbonitride Embedded in Mesoporous Carbon Nanofibers and Pt Enables Durable Oxygen Reduction

Platinum (Pt) supported on high surface area carbon has been the most widely used electrocatalyst in proton exchange membrane fuel cell (PEMFC). However, conventional carbon supports are susceptible to corrosion at high potentials, leading to severe degradation of electrochemical performance. In this work, titanium carbonitride embedded in mesoporous carbon nanofibers (m-TiCN NFs) are reported as a promising alternative to address this issue. Benefiting from the interpenetrating conductive pathways inside the one-dimensional (1D) nanostructures and the embedded TiCN nanoparticles (NPs), m-TiCN NFs exhibit excellent stability at high potentials and interact strongly with Pt NPs. Subsequently, m-TiCN NFs-supported Pt NPs deliver remarkably enhanced oxygen reduction reaction (ORR) activity and durability, with negligible activity decay and less than 5% loss of electrochemical surface area（ECSA） after 50 000 cycles. Moreover, the fuel cell assembled by this catalyst delivers a maximum power density of 1.22 W cm-2 and merely 3% loss after 30 000 cycles of accelerated durability tests under U.S. Department of Energy (DOE) protocols. The improved ORR activity and durability are attributed to the superior corrosion resistance of the m-TiCN NF support and the strong interaction between Pt and m-TiCN NFs.

Tailoring Oxygen Reduction Reaction Kinetics of Fe-N-C Catalyst via Spin Manipulation for Efficient Zinc-Air Batteries

The interaction between oxygen species and metal sites of various orbitals exhibits intimate correlation with the oxygen reduction reaction (ORR) kinetics. Herein, a new approach for boosting the inherent ORR activity of atomically dispersed Fe-N-C matrix is represented by implanting Fe atomic clusters nearby. The as-prepared catalyst delivers excellent ORR activity with half-wave potentials of 0.78 and 0.90 V in acidic and alkaline solutions, respectively. The decent ORR activity can also be validated from the high-performance rechargeable Zn-air battery. The experiments and density functional theory calculations reveal that the electron spin-state of monodispersed Fe active sites is transferred from the low spin (LS, t2g 6 eg 0) to the medium spin (MS, t2g 5 eg 1) due to the involvement of Fe atomic clusters, leading to the spin electron filling in σ∗ orbit, by which it favors OH- desorption and in turn boosts the reaction kinetics of the rate-determining step. This work paves a solid way for rational design of high-performance Fe-based single atom catalysts through spin manipulation.

Oxygen-Vacancy-Induced Formation of Pt-Based Intermetallics on MXene with Strong Metal-Support Interactions for Efficient Oxygen Reduction Reaction

The Pt-based alloys can moderate the binding energies of oxygenated species on the catalytic surface, endowing the superior catalytic performance towards oxygen reduction reaction (ORR). Nevertheless, it is still challenging to explore general methods to synthesize structurally ordered intermetallics with uniform distributions. Herein, the strong metal-support interaction is employed to facilitate the interdiffusion of Pt/M atoms by establishing a tunnel of oxygen vacancy on ultrathin Ti3C2Tx (MXene) sheets, synthesizing the ordered PtFe, PtCo, PtZn, PdFe, PdZn intermetallics loaded onto Ti3C2Tx. Furthermore, the in-situ generation of Ti-O from Ti3C2Tx could be bonded with Pt and forming Pt-O-Ti, resulting in charge redistribution through Pt-O-Ti structure. Theoretical calculations demonstrate that the valuable charge redistribution can be observed at the interface and extended even to at the distance of two nanometers from the interface, which can modulate the Pt-Pt distance, optimize Pt-O binding energy and enhance intrinsic activity towards ORR. The strong coupling interaction between PtFe and Ti3C2Tx containing the titanium oxide layer endows the high stability of the composites. This work not only presents a general synthesis strategy for intermetallics but also provides a new insight that metal-support interaction is essential for the structural evolution of intermetallics on materials with oxygen vacancies.

Catalytically Active Carbon for Oxygen Reduction Reaction in Energy Conversion: Recent Advances and Future Perspectives

The shortage and unevenness of fossil energy sources are affecting the development and progress of human civilization. The technology of efficiently converting material resources into energy for utilization and storage is attracting the attention of researchers. Environmentally friendly biomass materials are a treasure to drive the development of new-generation energy sources. Electrochemical theory is used to efficiently convert the chemical energy of chemical substances into electrical energy. In recent years, significant progress has been made in the development of green and economical electrocatalysts for oxygen reduction reaction (ORR). Although many reviews have been reported around the application of biomass-derived catalytically active carbon (CAC) catalysts in ORR, these reviews have only selected a single/partial topic (including synthesis and preparation of catalysts from different sources, structural optimization, or performance enhancement methods based on CAC catalysts, and application of biomass-derived CACs) for discussion. There is no review that systematically addresses the latest progress in the synthesis, performance enhancement, and applications related to biomass-derived CAC-based oxygen reduction electrocatalysts synchronously. This review fills the gap by providing a timely and comprehensive review and summary from the following sections: the exposition of the basic catalytic principles of ORR, the summary of the chemical composition and structural properties of various types of biomass, the analysis of traditional and the latest popular biomass-derived CAC synthesis methods and optimization strategies, and the summary of the practical applications of biomass-derived CAC-based oxidative reduction electrocatalysts. This review provides a comprehensive summary of the latest advances to provide research directions and design ideas for the development of catalyst synthesis/optimization and contributes to the industrialization of biomass-derived CAC electrocatalysis and electric energy storage.

Biphase Pd Nanosheets with Atomic-Hybrid RhOx/Pd Amorphous Skins Disentangle the Activity-Stability Trade-Off in Oxygen Reduction Reaction

The activity-stability trade-off relationship of oxygen reduction reaction (ORR) is a tricky issue that strikes the electrocatalyst population and hinders the widespread application of fuel cells. Here neoteric biphase Pd nanosheets that are structured with ultrathin two-dimensional crystalline Pd inner cores and ≈1 nm thin atomic-hybrid RhOx/Pd amorphous skins, named c/a-Pd@PdRh NSs, for disentangling this trade-off dilemma for alkaline ORR are developed. The superthin amorphous skins significantly amplify the quantity of flexibly low-coordinated atoms for electrocatalysis. An in situ selected oxidation of the top-surface Rh dopants creates atomically hybrid RhOx/Pd disorder surfaces. Detailed energy spectra and theoretical simulation confirm that these RhOx/Pd interfaces can arouse a surface charge redistribution, causing significant electron deficiency and lowered d-band center for surface Pd. Meanwhile, anticorrosive Rh/RhOx species can thermodynamically passivate the neighboring Pd atoms from oxidative dissolution. Thanks to these amplified interfacial effects, the biphase c/a-Pd@PdRh NSs simultaneously exhibit a superhigh ORR activity (5.92 A mg-1, 22.8 times that of Pt/C) and an outstanding long-lasting stability after 100k cycles of accelerated durability test, showcasing unprecedented electrocatalysts for breaking the activity-stability trade-off relationship of ORR. This work paves a bran-new strategy for designing high-performance electrocatalysts through creating modulated amorphous skins on low-dimensional nanomaterials.

Precisely Engineering Asymmetric Atomic CoN4 by Electron Donating and Extracting for Oxygen Reduction Reaction

The development of nonpyrolytic catalysts featuring precisely defined active sites represents an effective strategy for investigating the fundamental relationship between the catalytic activity of oxygen reduction reaction (ORR) catalysts and their local coordination environments. In this study, we have synthesized a series of model electrocatalysts with well-defined CoN4 centers and nonplanar symmetric coordination structures. These catalysts were prepared by a sequential process involving the chelation of cobalt salts and 1,10-phenanthroline-based ligands with various substituent groups (phen(X), where X=OH, CH3, H, Br, Cl) onto covalent triazine frameworks (CTFs). By modulating the electron-donating or electron-withdrawing properties of the substituent groups on the phen-based ligands, the electron density surrounding the CoN4 centers was effectively controlled. Our results demonstrated a direct correlation between the catalytic activity of the CoN4 centers and the electron-donating ability of the substituent group on the phenanthroline ligands. Notably, the catalyst denoted as BCTF-Co-phen(OH), featuring the electron-donating OH group, exhibited the highest ORR catalytic activity. This custom-crafted catalyst achieved a remarkable half-wave potential of up to 0.80 V vs. RHE and an impressive turnover frequency (TOF) value of 47.4×10-3 Hz at 0.80 V vs. RHE in an alkaline environment.

Drop-cast gold nanoparticles are not always electrocatalytically active for the borohydride oxidation reaction

The next-generation of energy devices rely on advanced catalytic materials, especially electrocatalytic nanoparticles (NPs), to achieve the performance and cost required to reshape the energy landscape towards a more sustainable and cleaner future. It has become imperative to maximize the performance of the catalyst, both through improvement of the intrinsic activity of the NP, and by ensuring all particles are performing at the level of their capability. This requires not just a structure-function understanding of the catalytic material, but also an understanding of how the catalyst performance is impacted by its environment (substrate, ligand, etc.). The intrinsic activity and environment of catalytic particles on a support may differ wildly by particle, thus it is essential to build this understanding from a single-entity perspective. To achieve this herein, scanning electrochemical cell microscopy (SECCM) has been used, which is a droplet-based scanning probe technique which can encapsulate single NPs, and apply a voltage to the nanoparticle whilst measuring its resulting current. Using SECCM, single AuNPs have been encapsulated, and their activity for the borohydride oxidation reaction (BOR) is measured. A total of 268 BOR-active locations were probed (178 single particles) and a series of statistical analyses were performed in order to make the following discoveries: (1) a certain percentage of AuNPs display no BOR activity in the SECCM experiment (67.4% of single NPs), (2) visibly-similar particles display wildly varied BOR activities which cannot be explained by particle size, (3) the impact of cluster size (#NP at a single location) on a selection of diagnostic electrochemical parameters can be easily probed with SECCM, (4) exploratory statistical correlation between these parameters can be meaningfully performed with SECCM, and (5) outlying "abnormal" NP responses can be probed on a particle-by-particle basis. Each one of these findings is its own worthwhile study, yet this has been achieved with a single SECCM scan. It is hoped that this research will spur electrochemists and materials scientists to delve deeper into their substantial datasets in order to enhance the structure-function understanding, to bring about the next generation of high-performance electrocatalysts.

Enhancing Interaction between Lanthanum Manganese Cobalt Oxide and Carbon Black through Different Approaches for Primary Zn-Air Batteries

Due to the need for decarbonization in energy generation, it is necessary to develop electrocatalysts for the oxygen reduction reaction (ORR), a key process in energy generation systems such as fuel cells and metal-air batteries. Perovskite-carbon material composites have emerged as active and stable electrocatalysts for the ORR, and the interaction between both components is a crucial aspect for electrocatalytic activity. This work explores different mixing methods for composite preparation, including mortar mixing, ball milling, and hydrothermal and thermal treatments. Hydrothermal treatment combined with ball milling resulted in the most favorable electrocatalytic performance, promoting intimate and extensive contact between the perovskite and carbon material and improving electrocatalytic activity. Employing X-ray photoelectron spectroscopy (XPS), an increase in the number of M-O-C species was observed, indicating enhanced interaction between the perovskite and the carbon material due to the adopted mixing methods. This finding was further corroborated by temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) techniques. Interestingly, the ball milling method results in similar performance to the hydrothermal method in the zinc-air battery and, thus, is preferable because of the ease and straightforward scalability of the preparation process.

Nanostructure Engineering of Cathode Layers in Proton Exchange Membrane Fuel Cells: From Catalysts to Membrane Electrode Assembly

The membrane electrode assembly (MEA) is the core component of proton exchange membrane fuel cells (PEMFCs), which is the place where the reaction occurrence, the multiphase material transfer and the energy conversion, and the development of MEA with high activity and long stability are crucial for the practical application of PEMFCs. Currently, efforts are devoted to developing the regulation of MEA nanostructure engineering, which is believed to have advantages in improving catalyst utilization, maximizing three-phase boundaries, enhancing mass transport, and improving operational stability. This work reviews recent research progress on platinum group metal (PGM) and PGM-free catalysts with multidimensional nanostructures, catalyst layers (CLs), and nano-MEAs for PEMFCs, emphasizing the importance of structure-function relationships, aiming to guide the further development of the performance for PEMFCs. Then the design strategy of the MEA interface is summarized systematically. In addition, the application of in situ and operational characterization techniques to adequately identify current density distributions, hot spots, and water management visualization of MEAs is also discussed. Finally, the limitations of nanostructured MEA research are discussed and future promising research directions are proposed. This paper aims to provide valuable insights into the fundamental science and technical engineering of efficient MEA interfaces for PEMFCs.

Hierarchical Sea Urchin-like Fe-doped Heazlewoodite for High-Efficient Oxygen Evolution

Electrochemical water-splitting to produce hydrogen is potential to substitute the traditional industrial coal gasification, but the oxygen evolution kinetics at the anode remains sluggish. In this paper, sea urchin-like Fe doped Ni3S2 catalyst growing on nickel foam (NF) substrate is constructed via a simple two-step strategy, including surface iron activation and post sulfuration process. The NF-Fe-Ni3S2 obtains at temperature of 130 °C (NF-Fe-Ni3S2-130) features nanoneedle-like arrays which are vertically grown on the particles to form sea urchin-like morphology, features high electrochemical surface area. As oxygen evolution catalyst, NF-Fe-Ni3S2-130 exhibits excellent oxygen evolution activities, fast reaction kinetics, and superior reaction stability. The excellent OER performance of sea urchin-like NF-Fe-Ni3S2-130 is mainly ascribed to the high-vertically dispersive of nanoneedles and the existing Fe dopants, which obviously improved the reaction kinetics and the intrinsic catalytic properties. The simple preparation strategy is conducive to establish high-electrochemical-interface catalysts, which shows great potential in renewable energy conversion.