Regulating Catalytic Properties and Thermal Stability of Pt and PtCo Intermetallic Fuel-Cell Catalysts via Strong Coupling Effects between Single-Metal Site-Rich Carbon and Pt

Fe2P as cocatalyst for ultra-low Pt oxygen reduction reaction catalyst

The preparation of low Pt catalysts for oxygen reduction reaction (ORR) has been the focus research in fuel cell. Here, Pt&Fe2P@NC with ultra-low Pt loading (∼2 wt% Pt, one tenth of the commercial 20 wt% Pt/C) is prepared by introducing Fe2P cocatalyst into Pt-based catalyst through a simple two-step pyrolysis method. Pt&Fe2P@NC shows excellent ORR electrocatalytic performance in 0.1 M KOH electrolyte with oxygen reduction peak potential of 0.91 V (vs. RHE), half-wave potential of 0.877 V (vs. RHE) and a nearly direct 4e reaction pathway. By comparing Pt@NC, Fe2P@NC and Pt&Fe2P@NC, Fe2P plays a dual role in Pt&Fe2P@NC: on one hand, Fe2P, as an electron donor, transfers electrons to Pt, thus optimizing the adsorption of oxygen intermediates on Pt; on the other hand, Fe2P has a Pt-like electron configuration and can also serve as an active site to co-catalyze the ORR together with Pt. This study provides a new strategy for the preparation of ultra-low Pt catalysts for ORR.

Competitive adsorption and strain modulation induced by low electronegative elements to improve phosphate tolerance in HT-PEMFC

The cathode Pt-based electrocatalyst, a core component of high-temperature proton exchange membrane fuel cells (HT-PEMFCs), significantly influences fuel cell efficiency. At high temperatures and strongly acidic pH, phosphoric acid tends to adsorb onto the Pt surface by forming PtO bonds, covering the catalyst's active sites. Phosphoric acid anions' toxicity towards Pt significantly impairs the oxygen reduction reaction (ORR) kinetics, posing a major obstacle to the commercial viability of this technology. In this study, we activated the carbon layer by introducing boron (B) to anchor intermetallic compounds clusters, which competitively adsorb desorbed phosphate anions in HT-PEMFCs. This approach mitigates phosphoric acid poisoning. Additionally, the core-shell configuration induces compressive strain in PtMn intermetallic compounds, inhibits transition metal solvation, and regulates the d-band center, optimizing the adsorption energy of oxygen reduction intermediates and enhancing the catalyst's activity and stability in high-temperature phosphoric acid. At 80 °C, experiments showed the E1/2 value of PtMn/BC was 0.854 V, 53 mV higher than commercial Pt/C. Additionally, the mass activity (MA) and specific activity (SA) were 5.2 and 2.6 times higher than those of commercial Pt/C, respectively. The maximum power density of the HT-PEMFC in an H2/O2 atmosphere reached 1108.3 mW cm-2, significantly higher than that of commercial Pt/C. This value is also higher than most reported ORR catalysts, demonstrating the potential of this catalyst for HT-PEMFC applications.

Advances in the Structure-Activity Relationship of Electrocatalytic C-N Coupling: From Nanocatalysis to Single Metal Site Catalysis

C-N coupling is crucial for constructing amides and amines and involves various fields, including medicine, chemical industries, agriculture, and energy. With the rapid development of electrocatalytic C-N coupling and the continuous improvement of catalytic performance, this field has aroused extensive research interest. A comprehensive review is urgently needed to summarize the structure-activity relationship, key challenges, and future development directions. This review provides a concise overview of the recent advancements from nanocatalysis to single metal site catalysis for electrocatalytic C-N coupling reactions. We summarize the C-N coupling mechanisms using different nitrogen sources and further analyze the influences of various active metal centers and different coordination environments on the C-N coupling performance, thereby elucidating the structure-activity relationship. Moreover, we discuss the dynamic structural evolution of active metal sites during the reaction. Finally, we present current challenges and perspectives in this field. This review aims to provide valuable insights into the development of advanced nano/single metal site catalysts for electrocatalytic C-N coupling reactions along with a deeper understanding of catalytic mechanisms.

Facile chemical synthesis of a high-performance Pt/C catalyst displaying a specialized morphology

Here, we report a unique process of urea-enhanced glycol reduction for the facile synthesis of Pt/C catalyst with morphology resembling a strawberry and its seeds. It exhibited 0.87 V half-wave potential and 1.57 W cm-2 power density with Pt loading of 0.1 mg cm-2; it lost only ∼2% ECSA and ∼2 mV half-wave potential after 50 000 cycles of accelerated degradation testing (ADT).

Unlocking Proton Exchange Membrane Fuel Cell Performance with Porous PtCoV Alloy Catalysts

Carbon-supported Pt-based catalysts in fuel cells often suffer from sulfonate poisoning, reducing Pt utilization and activity. Herein, a straightforward strategy is developed for synthesizing a porous PtCoV nanoalloy embedded within the porous structures of carbon nanofibers. Incorporation of vanadium (V) atoms into the PtCo alloy optimizes the oxygen binding energy of Pt sites, while heightening the dissolution energy barrier for both Pt and Co atoms, leading to a significantly enhanced intrinsic activity and durability of the catalyst. By encapsulating the nanoalloys within porous nanofibers, a non-contact Pt-ionomer interface is created to mitigate the poisoning effect of sulfonate groups to Pt sites, while promoting oxygen permeation and allowing proton transfer. This rational architecture liberates additional active Pt sites, while the evolved porous nanostructure of the PtCoV alloy extends its exposed surface area, thereby boosting Pt utilization within the catalytic layer and overall fuel cell performance. The optimized catalyst demonstrates an exceptional peak power density of 29.0 kW gPt -1 and an initial mass activity of 0.69 A mgPt -1, which exceeds the U.S. Department of Energy 2025 targets. This study provides a promising avenue for developing highly active and durable low-Pt electrocatalysts for fuel cell applications.

Toward Hydrogen Mobility: Challenges and Strategies in Electrocatalyst Durability for Long-Term PEMFC Operation

Proton exchange membrane fuel cells (PEMFCs) are emerging as a key technology in the transition to hydrogen-based energy systems, particularly for heavy-duty vehicles (HDVs) that face operational challenges, such as frequent startup-shutdown cycles and fuel starvation. However, the widespread adoption of PEMFCs has been limited by their durability and long-term performance issues, which are crucial for heavy-duty applications. This Perspective focuses on recent advancements in PEMFC catalysts and supports, with an emphasis on strategies to enhance their durability. We introduce Pt-based intermetallic catalysts, including Pt transition metal (TM) alloys, which offer improved stability and activity through regular atomic arrangements and strengthened metal-support interactions. Hybrid catalysts combining Pt with M-N-C (M = Fe, Co) have shown promise in boosting performance by enhancing the catalytic activity while reducing the platinum content. Moreover, stringent conditions must be met to meet the HDV requirements. Consequently, alternative support materials, such as metal oxides and graphitized carbons, have been introduced to enhance both the corrosion resistance and the electrical conductivity, thereby addressing the limitations of conventional carbon supports. Structural innovations and material advancements are essential for optimizing catalysts and supports to achieve long-term PEMFC performance. This Perspective provides a comprehensive overview of key developments in catalyst and support design, offering insights into current challenges and future directions for achieving durable and cost-effective PEMFCs.

Ultrafine intermetallic platinum-cobalt with a contracted Pt-Pt pair for efficient acidic oxygen reduction reactions

Ultrafine ordered intermetallic nanoparticles are emerging as promising electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. However, they are difficult to obtain because high-temperature annealing inevitably leads to metal sintering, resulting in larger crystallites. Additionally, the resulting electronic effects are difficult to control, limiting both performance and stability improvements. Herein, we present an ultrafine ordered intermetallic platinum-cobalt alloy encaged in nitrogen-doped carbon (Pt3Co/NC) with a small particle size of 4.18 ± 1.00 nm and a high electrochemically active surface area (ECSA) of 73.16 m2 gPt-1. The contraction of the Pt-Pt pair induces strong electron coupling, resulting in electron transfer from Co to Pt. Using in situ spectroscopies, we revealed that incorporating the cost-effective transition metal Co into the Pt lattice induces Pt-Pt contraction and generates additional Pt d-band occupancy, which accelerates the protonation of *O to *OH, thereby significantly enhancing the kinetics of the four-electron ORR process. The meticulously designed catalyst achieves a superior half-wave potential of 0.89 V versus RHE and a remarkable mass activity of 0.79 A mgPt-1. More importantly, after 10 000 cycles, the particle size expansion is marginal (5.01 ± 0.92 nm), alongside slight reductions in mass activity (6%) and specific activity (2%), demonstrating excellent catalytic stability in an acidic medium.

MOF-derived ordered porous nitrogen-doped carbon integrated with Pt3Co alloy catalyst for efficient oxygen reduction reaction

Here, we report a structurally ordered Pt3Co alloy integrated within a 3D porous nitrogen-doped carbon carrier. The optimal Pt3Co-NC-800 demonstrated high ORR catalytic activity and enhanced durability, achieving negligible half-potential after 30 000 cycles.

Switching CO2 Electroreduction toward C2+ Products and CH4 by Regulating the Dimerization and Protonation in Platinum/Copper Catalysts

Copper (Cu)-based catalysts exhibit distinctive performance in the electrochemical CO2 reduction reaction (CO2RR) with complex mechanism and sophisticated types of products. The management of key intermediates *CO and *H is a necessary factor for achieving high product selectivity, but lack of efficient and versatile strategies. Herein, we designed Pt modified Cu catalysts to effectively modulate the competitive coverage of those intermediates. The Pt single-atoms and Pt nanoparticles modified Cu catalysts (denoted as Cu-Pt1 and Cu-PtNPs) precisely regulated the protonation and dimerization, with the faradaic efficiency (FE) of C2+ products up to 70.4 % and the FE of CH4 reaching 57.7 %, respectively. CO stripping experiments reveal that Pt1 sites could enhance the adsorption of *CO, while PtNPs exhibit *CO tolerance for H2O dissociation. In situ spectroscopic results further confirms that high coverage of *CO is achieved on Cu-Pt1, while *CHO on Cu-PtNPs might generate by additional water dissociation. As elucidated by theoretical studies, the interfacial sites of Cu-Pt1 would favor the *CO coverage promoting the evolution of *OCCO for C2+ products while PtNPs supplementarily accelerate H2O dissociation achieving *CHO for CH4. This work provides insights for efficient and targeted CO2 conversion by atomically design of active sites with engineered key intermediates coverage.

Platinum-Nickel Oxide Cluster-Cluster Heterostructure Enabling Fast Hydrogen Evolution for Anion Exchange Membrane Water Electrolyzers

Carbon black has been extensively employed as the support for noble metal catalysts for electrocatalysis applications. However, the nearly catalytic inertness and weak interaction with metal species of carbon black are two major obstacles that hinder the further improvement of the catalytic performance. Herein, we report a surface functionalization strategy by decorating transition metal oxide clusters on the commercial carbon black to offer specific catalytic activity and enhanced interaction with metal species. In the case of NiOx cluster-decorated carbon black, a strongly coupled cluster-cluster heterostructure consisting of Pt clusters and NiOx clusters (Pt-NiOx/C) is formed and delivers greatly enhanced alkaline hydrogen evolution kinetics. The NiOx clusters can not only accelerate the hydrogen evolution process as the co-catalyst, but also optimize the adsorption of H intermediates on Pt and stabilize the Pt clusters. Notably, the anion exchange membrane water electrolyzer with Pt-NiOx/C as the cathode catalyst (with a loading of only 50 μgPt cm-2) delivers the most competitive electrochemical performance reported to date, requiring only 1.90 V to reach a current density of 2 A cm-2. The results demonstrate the significance of surface functionalization of carbonaceous supports toward the development of advanced electrocatalysts.

COF-Assisted Construction of Steric Mass-Charge Channels to Boost Activity for High-Performance Fuel Cells

The two-dimensional lamellar materials disperse platinum sites and minimize noble-metal usage for fuel cells, while mass transport resistance at the stacked layers spurs device failure with a significant performance decline in membrane electrode assembly (MEA). Herein, we implant porous and rigid sulfonated covalent organic frameworks (COF) into the graphene-based catalytic layer for the construction of steric mass-charge channels, which highly facilitates the activity of oxygen reduction reactions in both the rotating disk electrode (RDE) measurements and MEA device tests. Specifically, the normalized mass activity is remarkably boosted by 3.7 times to 1.56 A mgpt -1 after additions of suitable COF modifications in the RDE tests. Especially, an excellent maximum power density of 1.015 W cm-2 is realized on the MEA in H2/Air condition, representing a 22 % improvement through such constructions of steric mass-charge channels. Meanwhile, the open-circuit voltage of fuel cells demonstrates only 0.8 % reductions after 10,000 cycles of stability tests. We further extended such methodology of constructing mass-charge channels to granular PtCo and commercial Pt/C catalysts, which demonstrates a significant impetus for stimulating the catalytic activity in fuel cells.

Pt catalyst protected by graphene nanopockets enables lifetimes of over 200,000 h for heavy-duty fuel cell applications

Proton exchange membrane fuel cells feature considerable scalability advantages over lithium-ion batteries for heavy-duty-vehicle applications. The different driving behaviours and operating conditions of heavy-duty vehicles pose challenging requirements, particularly on fuel cell lifetime and efficiency. Here we report the design of a graphene-nanopocket-protected, pore-confined and electrochemically accessible Pt nanocatalyst supported on Ketjenblack carbon for heavy-duty-vehicle applications. The membrane electrode assembly made from these nanocatalysts delivers an initial mass activity of 0.74 A mgPt-1 and a high rated power density of 1.08 W cm-2, as well as extraordinary long-term durability with an ultrasmall rated power loss of 1.1% after 90,000 aggressive square-wave cycles. The remarkable activity and durability throughout the operation conditions promise an unprecedentedly long fuel cell lifetime of over 200,000 h and high peak efficiency of 71.9%, making it highly attractive for emerging heavy-duty fuel cell applications.

Integrating PtCo Intermetallic with Highly Graphitized Carbon Toward Durable Oxygen Electroreduction in Proton Exchange Membrane Fuel Cells

Exploiting robust and high-efficiency electrocatalysts for sluggish oxygen reduction reaction (ORR) is essential for proton exchange membrane fuel cells (PEMFCs) toward long-term operation for practical applications, yet remains challenging. Herein, the ordered PtCo intermetallic is reported with a Pt-rich shell loaded on a highly graphitized carbon carrier (O-PtCo@GCoNC) prepared by an impregnation annealing strategy. Systematic X-ray spectroscopic, operando electrochemical techniques and theoretical calculations reveal that thanks to the synergistic interaction of the core-shell PtCo intermetallic structure with a tailor-made Pt electronic configuration and highly graphitized carbon, O-PtCo@GCoNC exhibits significantly enhanced activity and stability toward ORR. Crucially, O-PtCo@GCoNC delivers a much-enhanced mass activity of 0.83 A mgPt -1 at 0.9 V versus reversible hydrogen electrode (RHE) in 0.1 m HClO4, which only drops by 26.5% after 70 000 cycles (0.6-1.0 V vs RHE), and 10.8% after 10 000 cycles (1.0-1.5 V vs RHE), apparently overmatching Pt/C (0.19 A mgPt -1, 73.7%, and 63.1%). Moreover, O-PtCo@GCoNC employed as the cathode catalyst in H2/air PEMFC achieves a superb peak power density (1.04 W cm-2 at 2.06 A cm-2), outperforming that of Pt/C (0.86 W cm-2 at 1.79 A cm-2). The cell voltage loss at 0.8 A cm-2 is 28 mV after 30 000 cycles, outstripping the United States Department of Energy 2025 target.

Double Confinement Design to Access Highly Stable Intermetallic Nanoparticles for Fuel Cells

Maintaining the stability of low Pt catalysts during prolonged operation of proton exchange membrane fuel cells (PEMFCs) remains a substantial challenge. Here, a double confinement design is presented to significantly improve the stability of intermetallic nanoparticles while maintaining their high catalytic activity toward PEMFCs. First, a carbon shell is coated on the surface of nanoparticles to form carbon confinement. Second, O2 is introduced during the annealing process to selectively etch the carbon shell to expose the active surface, and to induce the segregation of surface transition metals to form Pt-skin confinement. Overall, the intermetallic nanoparticles are protected by carbon confinement and Pt-skin confinement to withstand the harsh environment of PEMFCs. Typically, the double confined Pt1Co1 catalyst exhibits an exceptional mass activity of 1.45 A mgPt -1 at 0.9 V in PEMFCs tests, with only a 17.3% decay after 30 000 cycles and no observed structure changes, outperforming most reported PtCo catalysts and DOE 2025 targets. Furthermore, the carbon confinement proportion can be controlled by varying the thickness of the coated carbon shell, and this strategy is also applicable to the synthesis of double-confined Pt1Fe1 and Pt1Cu1 intermetallic nanoparticles.

Copper dual-doping strategy of porous carbon nanofibers and nickel fluoride nanorods as bi-functional oxygen electrocatalysis for effective zinc-air batteries

Designing and developing efficient, low-cost bi-functional oxygen electrocatalysts is essential for effective zinc-air batteries. In this study, we propose a copper dual-doping strategy, which involves doping both porous carbon nanofibers (PCNFs) and nickel fluoride nanoparticles with copper alone, successfully preparing copper-doped nickel fluoride (NiF2) nanorods and copper nanoparticles co-modified PCNFs (Cu@NiF2/Cu-PCNFs) as an efficient bi-functional oxygen electrocatalyst. When copper is doped into the PCNFs in the form of metallic nanoparticles, the doped elemental copper can improve the electronic conductivity of composite materials to accelerate electron conduction. Meanwhile, the copper doping for NiF2 can significantly promote the transformation of nickel fluoride nanoparticles into nanorod structures, thus increasing the electrochemical active surface area and enhancing mass diffusion. The Cu-doped NiF2 nanorods also possess an optimized electronic structure, including a more negative d-band center, smaller bandgap width and lower reaction energy barrier. Under the synergistic effect of these advantages, the obtained Cu@NiF2/Cu-PCNFs exhibit outstanding bi-functional catalytic performances, with a low overpotential of 0.68 V and a peak power density of 222 mW cm-2 in zinc-air batteries (ZABs) and stable cycling for 800 h. This work proposes a one-step way based on the dual-doping strategy, providing important guidance for designing and developing efficient catalysts with well-designed architectures for high-performance ZABs.

Enhancing Oxygen Reduction Reaction of Single-Atom Catalysts by Structure Tuning

Deciphering the fine structure has always been a crucial approach to unlocking the distinct advantages of high activity, selectivity, and stability in single-atom catalysts (SACs). However, the complex system and unclear catalytic mechanism have obscured the significance of exploring the fine structure. Therefore, we endeavored to develop a three-component strategy to enhance oxygen reduction reaction (ORR), delving deep into the profound implications of the fine structure, focusing on central atoms, coordinating atoms, and environmental atoms. Firstly, the mechanism by which the chemical state and element type of central atoms influence catalytic performance is discussed. Secondly, the significance of coordinating atoms in SACs is analyzed, considering both the number and type. Lastly, the impact of environmental atoms in SACs is reviewed, encompassing existence state and atomic structure. Thorough analysis and summarization of how the fine structure of SACs influences the ORR have the potential to offer valuable insights for the accurate design and construction of SACs.

Turning the Surface Electronic Effect Over Core-Shell CoS2─FexCo1-xS2 Nanooctahedra Toward Electrochemical Water Splitting in the Alkaline Medium

The long-term challenge in overall water splitting is the conflict in the pH condition of electrolytes for achieving efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at the same time, in addition to the typical cost issue in catalysts. It hence raises an intense research interest in seeking cost-efficient non-noble metal electrocatalysts as well as compromising electrolyte conditions for electrocatalytic HER and OER. To tackle the problems, various approaches are demonstrated to engineer the electronic effect on the active sites of catalysts for enhancing the activities. In this work, the core-shell CoS2─FexCo1-xS2 nanooctahedra is fabricated with a tunable Fe content over the surface and took them as the model catalyst for systematic studies in alkaline OER and HER. By various X-ray spectroscopies as well as electron microscopy, the results showed that the shells of CoS2─FexCo1-xS2 nanooctahedra formed the {111} surfaces of Fe0.9Co1.0S2 and Fe0.25Co0.75S2 with and without the promotion by OH- anions during the syntheses. Catalyzed by the CoS2, Fe0.25Co0.75S2, and Fe0.9Co1.0S2 {111} surfaces, the results of alkaline OER and HER indicated the Fe0.9Co1.0S2 the most superior activities by virtue of the optimized Fe─Co electronic effect. From the predictions by density functional theory (DFT) calculations in reaction thermodynamics, the energy barriers in OER and HER both follow the order of Fe0.9Co0.1S2(111) < Fe0.25Co0.75S2(111) < CoS2(111). However, FeS2(111) is worse than Fe0.9Co0.1S2(111). From the confirmations by in-situ X-ray spectroscopies in reaction kinetics, the Co sites of Fe0.9Co0.1S2(111) on the core-shell nanooctahedra exhibited much higher activities than those of CoS2(111) under the applied potentials for OER and HER, which reflected the electronic benefits from the existing Fe neighbors.

Interfacial Reactivity-Triggered Oscillatory Lattice Strains of Nanoalloys

Understanding the structure evolution of nanoalloys under reaction conditions is vital to the design of active and durable catalysts. Herein, we report an operando measurement of the dynamic lattice strains of dual-noble-metal alloyed with an earth-abundant metal as a model electrocatalyst in a working proton-exchange membrane fuel cell using synchrotron high-energy X-ray diffraction coupled with pair distribution function analysis. The results reveal an interfacial reaction-triggered oscillatory lattice strain in the alloy nanoparticles upon surface dealloying. Analysis of the lattice strains with an apparent oscillatory irregularity in terms of frequency and amplitude using time-frequency domain transformation and theoretical calculation reveals its origin from a metal atom vacancy diffusion pathway to facilitate realloying upon dealloying. This process, coupled with surface metal partial oxidation, constitutes a key factor for the nanoalloy's durability under the electrocatalytic oxygen reduction reaction condition, which serves as a new guiding principle for engineering durable or self-healable electrocatalysts for sustainable fuel cell energy conversion.

Second-Shell Coordination Environment Modulation for MnN4 Active Sites by Oxygen Doping to Boost Oxygen Reduction Performance

As a category of transition metal-nitrogen-carbon (M-N-C) catalysts, Mn-based single-atom catalysts (SACs) are considered as promising non-precious metal catalysts for stable oxygen reduction reaction (ORR) due to their Fenton-inactive character (versus Fe) and more abundant earth reserves (versus Ni, Co). However, their ORR activity is unsatisfactory. Besides, the structure-activity relationship via tuning the coordination environment of the second coordination shell for transition metal single sites is still elusive. Here, a Mn SAC with O doping in the second-shell of atomically dispersed Mn centers (MnSAC-O/C) as highly efficient and stable ORR catalyst is developed. X-ray absorption spectroscopy combined with theoretical calculations verifies the O doping in the second-shell of Mn center, and reveals the distortion of local environment of Mn center in the MnSAC-O/C. The MnSAC-O/C exhibits high ORR performance with a half-wave potential of 0.898 V, superior to MnSAC-C, commercial Pt/C and most reported non-noble metal-based SACs. More importantly, MnSAC-O/C based zinc-air batteries (ZABs) deliver outstanding durability with stable operation exceeding 930 h. Theoretical calculations confirm that O doping breaks the symmetry of charge distribution of MnN4 active center and facilitates OH* desorption, thus attributing to the promoted ORR activity.

Strong Metal-Support Interactions in Heterogeneous Oxygen Electrocatalysis

Molecular oxygen redox electrocatalysis involves oxygen reduction and evolution as core reactions in various energy conversion and environmental technology fields. Strong metal-support interactions (SMSIs) based nanomaterials are regarded as desirable and state-of-the-art heterogeneous electrocatalysts due to their exceptional physicochemical properties. Over the past decades, considerable advancements in theory and experiment have been achieved in related studies, especially in modulating the electronic structure and geometrical configuration of SMSIs to enable activity, selectivity, and stability. In this focuses on the concept of SMSI, explore their various manifestations and mechanisms of action, and summarizes recent advances in SMSIs for efficient energy conversion in oxygen redox electrocatalysis applications. Additionally, the correlation between the physicochemical properties of different metals and supports is systematically elucidated, and the potential mechanisms of the structure-activity relationships between SMSIs and catalytic performance are outlined through theoretical models. Finally, the obstacles confronting this burgeoning field are comprehensively concluded, targeted recommendations and coping strategies are proposed, and future research perspectives are outlined.

N-doped CoO-anchored ultrafine Pt nanoparticles for acidic hydrogen evolution reaction

An efficient hydrogen evolution reaction catalyst of ultrafine Pt nanoparticles loaded onto N-doped CoO was synthesized. This catalyst displayed high electrocatalytic activity and stability. The outstanding performance is attributed to the interactions between the active sites and support, as well as the regulation of the electronic structure through covalent nitrogen bridging.

Oxygen Vacancy-Mediated Synthesis of Inter-Atomically Ordered Ultrafine Pt-Alloy Nanoparticles for Enhanced Fuel Cell Performance

Pt-based intermetallics are expected to be the highly active catalysts for oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells but still face great challenges in controllable synthesis of interatomically ordered and ultrafine intermetallic nanoparticles. Here, we propose an oxygen vacancy-mediated atomic diffusion strategy by mechanical alloying to reduce the energy barrier of the transition from interatomic disordering to ordering, and to resist interparticulate sintering via strong M-O-C bonding. This synthesis results in a nanosized core/shell structure featuring an interatomically ordered PtM core and a Pt shell of two to three atomic layers in thickness and can be extended to the multicomponent PtM (M = Co, FeCo, FeCoNi, FeCoNiGa) systems. The electron enrichment in the Pt outer shell induced by the compressive strain leads to the enhanced antibonding orbital occupation below the Fermi level and accelerated OH* desorption kinetics. The optimized PtCo-O/C-6 catalyst presents excellent ORR activity (mass activity = 1.28 A mgPt-1 at 0.9 ViR-free, peak power densities = 2.38/1.25 W cm-2 in H2-O2/-air) and durability (∼1% activity loss in over 50 h in air condition) in fuel cells at a total Pt loading of 0.1 mgPt cm-2. Furthermore, we establish a systematic correlation to elucidate the formation mechanisms of highly ordered intermetallic catalysts underlying oxygen vacancies. This study provides a general approach for the large-scale production of highly ordered and nanosized Pt-dispersed intermetallic catalysts.

Atom-glue stabilized Pt-based intermetallic nanoparticles

Pt-based nanoparticles (NPs) have been widely used in catalysis. However, this suffers from aggregation and/or sintering at working conditions. We demonstrate a robust strategy for stabilizing PtCo NPs under high temperature with strong interaction between M-N-C and PtCo NPs with Pt-M-N coordination, namely, "atom glue." Such atom glue for stabilizing Pt-based NPs can be extended to Zn, Mn, Fe, Ni, Co, and Cu, being a versatile strategy for stabilizing PtCo NPs, which substantially promotes the performance toward oxygen reduction reaction (ORR) and fuel cell. Impressively, the mass activity (MA) reaches 2.99 A mgPt-1 for ORR over g-Zn-N-C/PtCo, and 79.3% of the initial MA is maintained after 90K cycles in fuel cell. This work provides a versatile strategy for stabilizing Pt-based NPs via atom glue, which is likely to spark widespread interest across various fields.

Entropy-Driven Ostwald Ripening Reversal Promotes the Formation of Low-Platinum Intermetallic Fuel Cell Catalysts

Strain engineering has been widely used to optimize platinum-based oxygen reduction reaction (ORR) catalysts for proton exchange membrane fuel cells (PEMFCs). PtM3 (M is base metals), a well-known high-compressive-strain intermetallic alloy, shows promise as a low platinum ORR catalyst due to high intrinsic activity. However, during the alloying of Pt with a threefold amount of M, a notable phase separation between Pt and M may occur, with M particles rapidly sintering while Pt particles grow slowly, posing a challenge in achieving a well-defined PtM3 intermetallic alloy. Here, an entropy-driven Ostwald ripening reversal phenomenon is discovered that enables the synthesis of small-sized Pt(FeCoNiCu)3 intermetallic ORR catalysts. High entropy promotes the thermodynamic driving force for the alloying Pt with M, which triggers the Ostwald ripening reversal of sintered FeCoNiCu particles and facilitates the formation of uniform Pt(FeCoNiCu)3 intermetallic catalysts. The prepared Pt(FeCoNiCu)3 catalysts exhibit a high specific activity of 3.82 mA cm-2, along with a power density of ≈1.3 W cm-2 at 0.67 V and 94 °C with a cathode Pt loading of 0.1 mg cm-2 in H2-air fuel cell.

Pt3(CoNi) Ternary Intermetallic Nanoparticles Immobilized on N-Doped Carbon Derived from Zeolitic Imidazolate Frameworks for Oxygen Reduction

Pt-based intermetallic compound (IMC) nanoparticles have been considered the most promising catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFC). Herein, we propose a strategy for producing ordered Pt3(CoNi) ternary IMC nanoparticles supported on N-doped carbon materials. Particularly, the Co and Ni are originally embedded into ZIF-derived carbon, which diffuse into Pt nanocrystals to form Pt3(CoNi) nanoparticles. Moreover, a thin layer of carbon develops outside of Pt3(CoNi) nanoparticles during the cooling process, which contributes to stabilizing the Pt3(CoNi) on carbon supports. The optimal Pt3(CoNi) nanoparticle catalyst has achieved significantly enhanced activity and stability, exhibiting a half-wave potential of 0.885 V vs reversible hydrogen electrode (RHE) and losing only 16 mV after 10,000 potential cycles between 0.6 and 1.0 V. Unlike the direct-use commercial carbon (VXC-72) for depositing Pt, we utilized ZIF-derived carbon containing dispersed Co and Ni nanocluster or nanoparticles to prepare ordered Pt3(CoNi) intermetallic catalysts.

Strong Electronic Metal-Support Interactions Enable the Increased Spin State of Co-N4 Active Sites and Performance for Acidic Oxygen Reduction Reaction

Nonprecious metal catalysts, particularly M-N-C catalysts, are widely recognized as promising contenders for the oxygen reduction reaction (ORR). However, a notable performance gap persists between M-N-C catalysts and Pt-based catalysts under acidic conditions. In this study, hybrid catalysts comprising single Co atoms and ultralow concentrations of Pt3Co intermetallic nanoparticles (NPs) are introduced to enhance ORR performance. Under acidic conditions, these hybrid catalysts demonstrate ORR efficiency with a half-wave potential of 0.895 V, negligible decay even after 80 000 cycles, and a high maximum power density of 1.34 W cm-2 in fuel cells. This performance surpasses those of Co-N-C and Pt/Co-N-C catalysts. Both experimental findings and theoretical computations suggest that the heightened ORR activity stems from an increase in the spin density of Co sites induced by noble metal NPs, facilitating the activation of O-O bonds via side-on overlapping and enabling a transition in the reaction pathway from associative to dissociative processes. This research offers a promising avenue for the systematic design of M-N-C cathodes with an enhanced performance for acidic fuel cells.

Metal bond strength regulation enables large-scale synthesis of intermetallic nanocrystals for practical fuel cells

Structurally ordered L10-PtM (M = Fe, Co, Ni and so on) intermetallic nanocrystals, benefiting from the chemically ordered structure and higher stability, are one of the best electrocatalysts used for fuel cells. However, their practical development is greatly plagued by the challenge that the high-temperature (>600 °C) annealing treatment necessary for realizing the ordered structure usually leads to severe particle sintering, morphology change and low ordering degree, which makes it very difficult for the gram-scale preparation of desirable PtM intermetallic nanocrystals with high Pt content for practical fuel cell applications. Here we report a new concept involving the low-melting-point-metal (M' = Sn, Ga, In)-induced bond strength weakening strategy to reduce Ea and promote the ordering process of PtM (M = Ni, Co, Fe, Cu and Zn) alloy catalysts for a higher ordering degree. We demonstrate that the introduction of M' can reduce the ordering temperature to extremely low temperatures (≤450 °C) and thus enable the preparation of high-Pt-content (≥40 wt%) L10-Pt-M-M' intermetallic nanocrystals as well as ten-gram-scale production. X-ray spectroscopy studies, in situ electron microscopy and theoretical calculations reveal the fundamental mechanism of the Sn-facilitated ordering process at low temperatures, which involves weakened bond strength and consequently reduced Ea via Sn doping, the formation and fast diffusion of low-coordinated surface free atoms, and subsequent L10 nucleation. The developed L10-Ga-PtNi/C catalysts display outstanding performance in H2-air fuel cells under both light- and heavy-duty vehicle conditions. Under the latter condition, the 40% L10-Pt50Ni35Ga15/C catalyst delivers a high current density of 1.67 A cm-2 at 0.7 V and retains 80% of the current density after extended 90,000 cycles, which exceeds the United States Department of Energy performance metrics and represents among the best cathodic electrocatalysts for practical proton-exchange membrane fuel cells.

Integration Construction of Hybrid Electrocatalysts for Oxygen Reduction

There is notable progress in the development of efficient oxygen reduction electrocatalysts, which are crucial components of fuel cells. However, these superior activities are limited by imbalanced mass transport and cannot be fully reflected in actual fuel cell applications. Herein, the design concepts and development tracks of platinum (Pt)-nanocarbon hybrid catalysts, aiming to enhance the performance of both cathodic electrocatalysts and fuel cells, are presented. This review commences with an introduction to Pt/C catalysts, highlighting the diverse architectures developed to date, with particular emphasis on heteroatom modification and microstructure construction of functionalized nanocarbons based on integrated design concepts. This discussion encompasses the structural evolution, property enhancement, and catalytic mechanisms of Pt/C-based catalysts, including rational preparation recipes, superior activity, strong stability, robust metal-support interactions, adsorption regulation, synergistic pathways, confinement strategies, ionomer optimization, mass transport permission, multidimensional construction, and reactor upgrading. Furthermore, this review explores the low-barrier or barrier-free mass exchange interfaces and channels achieved through the impressive multidimensional construction of Pt-nanocarbon integrated catalysts, with the goal of optimizing fuel cell efficiency. In conclusion, this review outlines the challenges associated with Pt-nanocarbon integrated catalysts and provides perspectives on the future development trends of fuel cells and beyond.

Bridged Pt-OH-Mn Mediator in N-coordinated Mn Single Atoms and Pt Nanoparticles for Electrochemical Biomolecule Oxidation and Discrimination

The rational design of efficient catalysts for uric acid (UA) electrooxidation, as well as the establishment of structure-activity relationships, remains a critical bottleneck in the field of electrochemical sensing. To address these challenges, herein, a hybrid catalyst that integrates carbon-supported Pt nanoparticles and nitrogen-coordinated Mn single atoms (PtNPs/MnNC) is developed. The metal-metal interaction during annealing affords the construction of metallic-bonded Pt-Mn pairs between PtNPs and Mn single atoms, facilitating the electron transfer from PtNPs to the support and thereby optimizing the electronic structure of catalysts. More importantly, experiments and theoretical calculations provide visual proof for the 'incipient hydrous oxide adatom mediator' mechanism for UA oxidation. The Pt-Mn pairs first adsorb OH* to construct the bridged Pt-OH-Mn mediators to serve as a highly active intermediate for N-H bond dissociation and proton transfer. Benefiting from the unique electronic and geometric structure of the catalytic center and reactive intermediates, PtNPs/MnNC exhibits superior electrooxidation performance. The electrochemical sensor based on PtNPs/MnNC enables sensitive detection and discrimination of UA and dopamine in serum samples. This work offers new insights into the construction of novel electrocatalysts for sensitive sensing platforms.

Advances of Synergistic Electrocatalysis Between Single Atoms and Nanoparticles/Clusters

Combining single atoms with clusters or nanoparticles is an emerging tactic to design efficient electrocatalysts. Both synergy effect and high atomic utilization of active sites in the composite catalysts result in enhanced electrocatalytic performance, simultaneously provide a radical analysis of the interrelationship between structure and activity. In this review, the recent advances of single-atomic site catalysts coupled with clusters or nanoparticles are emphasized. Firstly, the synthetic strategies, characterization, dynamics and types of single atoms coupled with clusters/nanoparticles are introduced, and then the key factors controlling the structure of the composite catalysts are discussed. Next, several clean energy catalytic reactions performed over the synergistic composite catalysts are illustrated. Eventually, the encountering challenges and recommendations for the future advancement of synergistic structure in energy-transformation electrocatalysis are outlined.

Decoupling the Synergy Between PGM and PGM-Free Moieties toward Oxygen Reduction Reaction

Recently, coupling the conventional low Pt-group-metal (low-PGM, LP) and emerging PGM-free (PF) moiety to form a composite LP/PF catalyst is proposed to be an advanced strategy to improve the intrinsic activity and stability of oxygen reduction reaction (ORR) catalysts. Milestones in terms of ORR mass activity are created by this type of catalyst. However, the specific synergy between LP and PF moieties has not been well elucidated. Herein, two model catalysts are synthesized, i.e., atomically dispersed Co/N/C supporting Pt single atoms (Co/N/C@Pt-SAs) and PtCo nanoparticles (Co/N/C@PtCo-NPs). Interestingly, the Co/N/C@PtCo-NPs catalyst presents higher ORR mass activity prior to Co/N/C@Pt-SAs. This is theoretically due to the dual "built-in electric field" in Co/N/C@PtCo-NPs: one electric field with a direction from Pt to Co in NPs and another from Pt to Co/N/C; that is, Pt gains higher electron density in Co/N/C@PtCo-NPs than that in Co/N/C@Pt-SAs, thus forming an asymmetric electron cloud, and regulating the adsorption and activation of oxygen-containing species. In addition, the existence of Co significantly decreases the average valence state of PtCo NPs, indicating a stronger affinity between PtCo NPs and Co/N/C substrate, to account for the enhanced stability.

Catalase-like Fe Nanoparticles and Single Atoms Catalysts with Boosted Activity and Stability of Oxygen Reduction for Pesticide Detection

Although oxygen reduction reaction (ORR) as an effective signal amplification strategy has been extensively investigated for the improvement of sensitivity of electrochemical sensors, their activity and stability are still a great challenge. Herein, single-atom Fe (FeSA) and Fe nanoparticles (FeNP) on nitrogen-doped carbon (FeSA/FeNP) catalysts demonstrate a highly active and stable ORR performance, thus achieving the sensitive and stable electrochemical sensing of organophosphorus pesticides (OPs). Experimental investigations indicate that FeNP in FeSA/FeNP can improve the ORR activity by adjusting the electronic structure of FeSA active sites. Besides, owing to the excellent catalase-like activity, FeSA/FeNP can rapidly consume in situ generated H2O2 in the ORR process and avoid the leakage of active sites, thereby improving the stability of ORR. Utilizing the excellent ORR performance of FeSA/FeNP, an electrochemical sensor for OPs is established based on the thiocholine-induced poison of the active sites, demonstrating satisfactory sensitivity and stability. This work provides new insight into the design of high performance ORR catalysts for sensitive and stable electrochemical sensing.

Strategies for Achieving Ultra-Long ORR Durability-Rh Activates Interatomic Interactions in Alloys

The stability of platinum-based alloy catalysts is crucial for the future development of proton exchange membrane fuel cells, considering the potential dissolution of transition metals under complex operating conditions. Here, we report on a Rh-doped Pt3Co alloy that exhibits strong interatomic interactions, thereby enhancing the durability of fuel cells. The Rh-Pt3Co/C catalyst demonstrates exceptional catalytic activity for oxygen reduction reactions (ORR) (1.31 A mgPt -1 at 0.9 V vs. the reversible hydrogen electrode (RHE) and maintaining 92 % of its mass activity after 170,000 potential cycles). Long-term testing has shown direct inhibition of Co dissolution in Rh-Pt3Co/C. Furthermore, tests on proton exchange membrane fuel cells (PEMFC) have shown excellent performance and long-term durability with low Pt loading. After 50,000 cycles, there was no voltage loss at 0.8 A cm-2 for Rh-Pt3Co/C, while Pt3Co/C experienced a loss of 200 mV. Theoretical calculations suggest that introducing transition metal atoms through doping creates a stronger compressive strain, which in turn leads to increased catalytic activity. Additionally, Rh doping increases the energy barrier for Co diffusion in the bulk phase, while also raising the vacancy formation energy of the surface Pt. This ensures the long-term stability of the alloy over the course of the cycle.

MnF2 Surface Modulated Hollow Carbon Nanorods on Porous Carbon Nanofibers as Efficient Bi-Functional Oxygen Catalysis for Rechargeable Zinc-Air Batteries

Developing highly efficient bi-functional noble-metal-free oxygen electrocatalysts with low-cost and scalable synthesis approach is challenging for zinc-air batteries (ZABs). Due to the flexible valence state of manganese, MnF2 is expected to provide efficient OER. However, its insulating properties may inhibit its OER process to a certain degree. Herein, during the process of converting the manganese source in the precursor of porous carbon nanofibers (PCNFs) to manganese fluoride, the manganese source is changed to manganese acetate, which allows PCNFs to grow a large number of hollow carbon nanorods (HCNRs). Meanwhile, manganese fluoride will transform from the aggregation state into uniformly dispersed MnF2 nanodots, thereby achieving highly efficient OER catalytic activity. Furthermore, the intrinsic ORR catalytic activity of the HCNRs/MnF2@PCNFs can be enhanced due to the charge modulation effect of MnF2 nanodots inside HCNR. In addition, the HCNRs stretched toward the liquid electrolyte can increase the capture capacity of dissolved oxygen and protect the inner MnF2, thereby enhancing the stability of HCNRs/MnF2@PCNFs for the oxygen electrocatalytic process. MnF2 surface-modulated HCNRs can strongly enhance ORR activity, and the uniformly dispersed MnF2 can also provide higher OER activity. Thus, the prepared HCNRs/MnF2@PCNFs obtain efficient bifunctional oxygen catalytic ability and high-performance rechargeable ZABs.

Engineering a High-Loading Sub-4 nm Intermetallic Platinum-Cobalt Alloy on Atomically Dispersed Cobalt-Nitrogen-Carbon for Efficient Oxygen Reduction in Fuel Cells

Developing a high-performance membrane electrode assembly (MEA) poses a formidable challenge for fuel cells, which lies in achieving both high metal loading and efficient catalytic activity concurrently for MEA catalysts. Here, we introduce a porous Co@NC carrier to synthesize sub-4 nm PtCo intermetallic nanocrystals, achieving an impressive Pt loading of 27 wt %. The PtCo-CoNC catalyst demonstrates exceptional catalytic activity and remarkable stability for the oxygen reduction reaction. Advanced characterization techniques and theoretical calculations emphasize the synergistic effect between PtCo alloys and single Co atoms, which enhances the desorption of the OH* intermediate. Furthermore, the PtCo-CoNC-based cathode delivers a high power density of 1.22 W cm-2 in the MEA test owing to the enhanced mass transport, which is verified by the simulation results of the O2 distributions and current density inside the catalyst layer. This study lays the groundwork for the design of efficient catalysts with practical applications in fuel cells.

Enhanced Activity of Small Pt Nanoparticles Decorated with High-Loading Single Fe─N4 for Methanol Oxidation and Oxygen Reduction via the Assistive Active Sites Strategy

Decorating platinum (Pt) with a single atom offers a promising approach to tailoring their catalytic activity. In this study, for the first time, an innovative assistive active sites (AAS) strategy is proposed to construct high-loading (3.46wt.%) single Fe─N4 as AAS, which are further hybridized with small Pt nanoparticles to enhance both oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) activities. For ORR, the target catalyst (Pt/HFeSA-HCS) exhibits a higher mass activity (MA) of 0.98 A mgPt -1 and specific activity (SA) of 1.39 mA cmPt -2 at 0.90 V versus RHE. As for MOR, Pt/HFeSA-HCS shows exceptional MA (3.21 A mgPt -1) and SA (4.27 mA cmPt -2) at peak values, surpassing commercial Pt/C by 15.3 and 11.5 times, respectively. The underlying mechanism behind this AAS strategy is to find that in MOR, Fe─N4 promotes water dissociation, generating more *OH to accelerate the conversion of *CO to CO2. Meanwhile, in ORR, Fe─N4 acts as a competitor to adsorb *OH, weakening Pt─OH bonding and facilitating desorption of *OH on the Pt surface. Constructing AAS that can enhance dual functionality simultaneously can be seen as a successful "kill two birds with one stone" strategy.

Surface Engineered Single-atom Systems for Energy Conversion

Single-atom catalysts (SACs) are demonstrated to show exceptional reactivity and selectivity in catalytic reactions by effectively utilizing metal species, making them a favorable choice among the different active materials for energy conversion. However, SACs are still in the early stages of energy conversion, and problems like agglomeration and low energy conversion efficiency are hampering their practical applications. Substantial research focus on support modifications, which are vital for SAC reactivity and stability due to the intimate relationship between metal atoms and support. In this review, a category of supports and a variety of surface engineering strategies employed in SA systems are summarized, including surface site engineering (heteroatom doping, vacancy introducing, surface groups grafting, and coordination tunning) and surface structure engineering (size/morphology control, cocatalyst deposition, facet engineering, and crystallinity control). Also, the merits of support surface engineering in single-atom systems are systematically introduced. Highlights are the comprehensive summary and discussions on the utilization of surface-engineered SACs in diversified energy conversion applications including photocatalysis, electrocatalysis, thermocatalysis, and energy conversion devices. At the end of this review, the potential and obstacles of using surface-engineered SACs in the field of energy conversion are discussed. This review aims to guide the rational design and manipulation of SACs for target-specific applications by capitalizing on the characteristic benefits of support surface engineering.

An excellent bismuth-doped perovskite cathode with high activity and CO2 resistance for solid-oxide fuel cells operating below 700 °C

Lowering the operating temperatures of solid-oxide fuel cells (SOFCs) is critical, although achieving success in this endeavor has proven challenging. Herein, Bi0.15Sr0.85Co0.8Fe0.2O3-δ (BiSCF) is systematically evaluated as a carbon dioxide (CO2)-tolerant and highly active cathode for SOFCs. BiSCF, which features Bi3+ with an ionic radius similar to Ba2+, exhibits activity (e.g., 0.062 Ω cm2 at 700 °C) comparable to that of Ba0.5Sr0.5Co0.8Fe0.2O3-δ and PrBaCo2O5+δ, while demonstrating a considerable advantage over Bi-doped cathodes. Moreover, BiSCF exhibits long-term stability over a period of 500 h, and an anode-supported cell with BiSCF achieves a power density of 912 mW cm-2 at 650 °C. The CO2-poisoned BiSCF exhibits quick reversibility or slight activation after returning to normal conditions. The exceptional CO2 tolerance of BiSCF can be attributed to its reduced basicity and high electronegativity, which effectively restrict surface Sr diffusion and hinder subsequent carbonate formation. These findings highlight the substantial potential of BiSCF for SOFCs operating below 700 °C.

Uncovering Structural Evolution during the Dealloying Process in Pt-Based Oxygen-Reduction Catalyst

The comprehensive understanding toward the dealloying process is crucial for designing alloy catalysts employed in the oxygen reduction reaction (ORR). However, the specific leaching procedure and subsequent reconstruction of the dealloyed catalyst still remain unclear. Herein, we employ in situ X-ray absorption fine structure spectroscopy to monitor the dealloying process of a two-dimensional PtTe ordered alloy, known for its enhanced ORR activity. Our findings reveal the unsynchronous evolutions of Pt and Te sites, wherein the Pt component undergoes a structural transformation prior to the complete leaching of Te, leading to the formation of a defect-rich Pt catalyst. This dealloyed catalyst exhibits a significant enhancement in ORR activity, featuring a half-wave potential of 0.90 V versus the reversible hydrogen electrode and a mass activity of 0.62 A mgPt-1, outperforming the performance of commercial Pt/C counterpart. This in-depth understanding of the dealloying mechanism enriches our knowledge for the development of high-performance Pt-based alloy catalysts.

Designing and Engineering Atomically Dispersed Metal Catalysts for CO2 to CO Conversion: From Single to Dual Metal Sites

The electrochemical CO2 reduction reaction (CO2 RR) is a promising approach to achieving sustainable electrical-to-chemical energy conversion and storage while decarbonizing the emission-heavy industry. The carbon-supported, nitrogen-coordinated, and atomically dispersed metal sites are effective catalysts for CO generation due to their high activity, selectivity, and earth abundance. Here, we discuss progress, challenges, and opportunities for designing and engineering atomic metal catalysts from single to dual metal sites. Engineering single metal sites using a nitrogen-doped carbon model was highlighted to exclusively study the effect of carbon particle sizes, metal contents, and M-N bond structures in the form of MN4 moieties on catalytic activity and selectivity. The structure-property correlation was analyzed by combining experimental results with theoretical calculations to uncover the CO2 to CO conversion mechanisms. Furthermore, dual-metal site catalysts, inheriting the merits of single-metal sites, have emerged as a new frontier due to their potentially enhanced catalytic properties. Designing optimal dual metal site catalysts could offer additional sites to alter the surface adsorption to CO2 and various intermediates, thus breaking the scaling relationship limitation and activity-stability trade-off. The CO2 RR electrolysis in flow reactors was discussed to provide insights into the electrolyzer design with improved CO2 utilization, reaction kinetics, and mass transport.

Rare Earth Evoked Subsurface Oxygen Species in Platinum Alloy Catalysts Enable Durable Fuel Cells

Alleviating the degradation issue of Pt based alloy catalysts, thereby simultaneously achieving high mass activity and high durability in proton exchange membrane fuel cells (PEMFCs), is highly challenging. Herein, we provide a new paradigm to address this issue via delaying the place exchange between adsorbed oxygen species and surface Pt atoms, thereby inhibiting Pt dissolution, through introducing rare earth bonded subsurface oxygen atoms. We have succeeded in introducing Gd-O dipoles into Pt3 Ni via a high temperature entropy-driven process, with direct spectral evidence attained from both soft and hard X-ray absorption spectroscopies. The higher rated power of 0.93 W cm-2 and superior current density of 562.2 mA cm-2 at 0.8 V than DOE target for heavy-duty vehicles in H2 -air mode suggest the great potential of Gd-O-Pt3 Ni towards practical application in heavy-duty transportation. Moreover, the mass activity retention (1.04 A mgPt -1 ) after 40 k cycles accelerated durability tests is even 2.4 times of the initial mass activity goal for DOE 2025 (0.44 A mgPt -1 ), due to the weakened Pt-Oads bond interaction and the delayed place exchange process, via repulsive forces between surface O atoms and those in the sublayer. This work addresses the critical roadblocks to the widespread adoption of PEMFCs.

Manipulation of Electronic States of Pt Sites via d-Band Center Tuning for Enhanced Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells

Expediting the torpid kinetics of the oxygen reduction reaction (ORR) at the cathode with minimal amounts of Pt under acidic conditions plays a significant role in the development of proton exchange membrane fuel cells (PEMFCs). Herein, a novel Pt-N-C system consisting of Pt single atoms and nanoparticles anchored onto the defective carbon nanofibers is proposed as a highly active ORR catalyst (denoted as Pt-N-C). Detailed characterizations together with theoretical simulations illustrate that the strong coupling effect between different Pt sites can enrich the electron density of Pt sites, modify the d-band electronic environments, and optimize the oxygen intermediate adsorption energies, ultimately leading to significantly enhanced ORR performance. Specifically, the as-designed Pt-N-C demonstrates exceptional ORR properties with a high half-wave potential of 0.84 V. Moreover, the mass activity of Pt-N-C reaches 193.8 mA gPt-1 at 0.9 V versus RHE, which is 8-fold greater than that of Pt/C, highlighting the enormously improved electrochemical properties. More impressively, when integrated into a membrane electrode assembly as cathode in an air-fed PEMFC, Pt-N-C achieved a higher maximum power density (655.1 mW cm-2) as compared to Pt/C-based batteries (376.25 mW cm-2), hinting at the practical application of Pt-N-C in PEMFCs.

Tailoring Local Chemical Ordering via Elemental Tuning in High-Entropy Alloys

Due to the large multi-elemental space desired for property screening and optimization, high-entropy alloys (HEAs) hold greater potential over conventional alloys for a range of applications, such as structural materials, energy conversion, and catalysis. However, the relationship between the HEA composition and its local structural/elemental configuration is not well understood, particularly in noble-metal-based HEA nanomaterials, hindering the design and development of nano-HEAs in energy conversion and catalysis applications. Herein, we determined precise atomic-level structural and elemental arrangements in model HEAs composed of RhPtPdFeCo and RuPtPdFeCo to unveil their local characteristics. Notably, by changing just one constituent element in the HEA (Rh to Ru), we found dramatic changes in the elemental arrangement from complete random mixing to a local single elemental ordering feature. Additionally, we demonstrate that the local ordering in RuPtPdFeCo can be further controlled by varying the Ru concentration, allowing us to toggle between local Ru clustering and distinct heterostructures in multicomponent systems. Overall, our study presents a practical approach for manipulating local atomic structures and elemental arrangements in noble-metal-based HEA systems, which could provide in-depth knowledge to mechanistically understand the functionality of noble-metal-based HEA nanomaterials in practical applications.

Integrated PtxCoy-Hierarchical Carbon Matrix Electrocatalyst for Efficient Hydrogen Evolution Reaction

Pt-based catalysts are regarded as state-of-the-art electrocatalysts for producing clean hydrogen energy; however, their wide application is restricted by their low abundance, high cost, and poor stability. Herein, we report an integrated PtxCoy-hierarchical carbon matrix electrocatalyst (Pt/Co@NCNTs, Pt3Co@NCNTs, PtCo@NCNTs, and PtCo3@NCNTs) that is developed using a thermally driven Co migration strategy forming alloy nanoparticles to achieve efficient hydrogen evolution reaction (HER). Benefiting from its electronic regulation effect and unique hierarchical hollow structure, the Pt3Co@NCNTs catalyst loaded with 11.5 wt % Pt exhibits superior catalytic performance and durability for HER compared with commercial 20 wt % Pt/C. Under both alkaline and acidic conditions, Pt3Co@NCNTs exhibits excellent HER activity with overpotentials of 21 and 45 mV at 10 mA cm-2, respectively. Density functional theory (DFT) results further verify that the interaction between Pt and Co in Pt3Co@NCNTs can modulate electronic rearrangement, optimize the d-band center, and accelerate water dissociation and *H desorption, thereby enhancing HER activity.

An Ultrasmall Ordered High-Entropy Intermetallic with Multiple Active Sites for the Oxygen Reduction Reaction

Controlling multimetallic ensembles at the atomic level is significantly challenging, particularly for high-entropy alloys with more than five elements. Herein, we report an innovative ultrasmall (∼2 nm) PtFeCoNiCuZn high-entropy intermetallic (PFCNCZ-HEI) with a well-ordered structure synthesized by using the space-confined strategy. By exploiting these combined metals, the PFCNCZ-HEI nanoparticles achieve an ultrahigh mass activity of 2.403 A mgPt-1 at 0.90 V vs reversible hydrogen electrode for the oxygen reduction reaction, which is up to 19-fold higher than that of state-of-the-art commercial Pt/C. A proton exchange membrane fuel cell assembled with PFCNCZ-HEI as the cathode (0.03 mgPt cm-2) exhibits a power density of 1.4 W cm-2 and a high mass-normalized rated power of 45 W mgPt-1. Furthermore, theoretical calculations reveal that the outer electrons of the non-noble-metal atoms on the surface of the PFCNCZ-HEI nanoparticle are modulated to show characteristics of multiple active centers. This work offers a promising catalyst design direction for developing highly ordered HEI nanoparticles for electrocatalysis.

Intermetallic Nanocrystals for Fuel-Cells-Based Electrocatalysis

Electrocatalysis underpins the renewable electrochemical conversions for sustainability, which further replies on metallic nanocrystals as vital electrocatalysts. Intermetallic nanocrystals have been known to show distinct properties compared to their disordered counterparts, and been long explored for functional improvements. Tremendous progresses have been made in the past few years, with notable trend of more precise engineering down to an atomic level and the investigation transferring into more practical membrane electrode assembly (MEA), which motivates this timely review. After addressing the basic thermodynamic and kinetic fundamentals, we discuss classic and latest synthetic strategies that enable not only the formation of intermetallic phase but also the rational control of other catalysis-determinant structural parameters, such as size and morphology. We also demonstrate the emerging intermetallic nanomaterials for potentially further advancement in energy electrocatalysis. Then, we discuss the state-of-the-art characterizations and representative intermetallic electrocatalysts with emphasis on oxygen reduction reaction evaluated in a MEA setup. We summarize this review by laying out existing challenges and offering perspective on future research directions toward practicing intermetallic electrocatalysts for energy conversions.

Au Doping PtNi Nanodendrites for Enhanced Electrocatalytic Methanol Oxidation Reaction

To boost the electrocatalytic methanol oxidation reaction (MOR) of Platinum (Pt), making binary PtM (M = transition metals, for example, Fe, Cu, and Ni) with specific morphology is known as a promising method. Although great progress has been made in the synthesis of shaped PtM catalysts toward MOR, enhancing the catalytic performance of the PtM to enable it to be commercialized is still a hotspot. In this work, the Au-doped PtNi dendritic nanoparticles (Au-PtNi DNPs) were obtained by doping a small amount of gold (Au) into initially prepared PtNi DNPs, greatly improving their MOR catalytic activity and durability. The energy-dispersive X-ray spectroscopy mapping (EDXS) indicates that the surface of DNPs is mainly composed of Au dopant and PtNi, while the core is mainly Pt, indicating the formation of Au-doped PtNi/Pt core-shell-like DNP structures. The electrocatalytic performance of the prepared Au-PtNi DNPs with different compositions for the MOR was evaluated using cyclic voltammetry, chronoamperometry, and CO-stripping tests. The experimental findings indicate that the Au-PtNi DNPs showed better MOR performance in comparison with PtNi DNPs and commercial Pt catalysts. Among all the catalysts, 6% Au-PtNi DNPs showed 4.3 times improved mass catalytic activity for the MOR in comparison with commercial Pt catalysts. In addition, all the prepared Au-PtNi DNPs display a remarkable CO tolerance compared to that of PtNi DNPs and commercial Pt catalysts. The dendritic structure of Au-PtNi DNPs can effectively enhance catalytic performance, combined with the electronic effect of Au, Pt, and Ni.