Hierarchically confined Pt3Co intermetallic nanoparticles in porous Co-N-doped carbon nanofiber for highly active and durable oxygen reduction reaction

Graphitic-N induced asymmetric charge distribution of carbon sites accelerates O2 activation for efficient oxygen reduction reaction.

An oxalate anion-assisted strategy mediated densely edge-hosted atomic FeN4 sites for enhanced oxygen reduction reaction in Zn-air batteries.

Developing active and durable platinum-based catalysts is critical for advancing proton-exchange membrane fuel cells (PEMFCs). To overcome the Cu dissolution and poor stability of PtCu intermetallics, we propose a Mn-doping strategy to fabricate L10-ordered PtCuMn nanocatalysts. Mn incorporation modulates the Pt electronic structure, enhances L10 ordering, and induces compressive strain within a Pt-rich shell. Consequently, the catalyst demonstrates exceptional oxygen reduction reaction (ORR) activity with a half-wave potential of 0.921 V, a mass activity (MA) of 0.96 A mgPt-1 and a negligible half-wave potential shift after 30 000 cycles. In PEMFCs, it delivers peak power densities of 1.31 W cm-2 (H2-air) and 2.23 W cm-2 (H2-O2). Furthermore, its MA reaches 0.78 A mgPt-1, which exceeds the U.S. Department of Energy (DOE) 2025 target. Operando characterizations and theoretical calculations confirm that Mn doping downshifts the Pt d-band center, accelerates the conversion kinetics of the key *OH intermediate, and thereby optimizes the ORR performance.

Studying the influence of the distance between dopant and transition metal (TM) atom (dTM-N) on the local atomic/electronic structures of the active centers is beneficial for fine-tuning the catalytic performance toward optimal efficiency. In this work, the oxygen reduction reaction (ORR) activity and selectivity of TM1N4@carbon single-atom catalysts (TM = Fe, Co and Ni) were systematically modulated by adjusting the dTM-N values using density functional theory simulations. The results show that nitrogen doping at any position lowers the d-band center, thereby enhancing d-p orbital hybridization, reducing chemical activity, and increasing adsorption free energy. The difference in adsorption free energy (ΔGdoped - ΔGpristine) is mainly determined by both the nature of the adsorbed species and the type of TM atom, with clear power-law relationships identified between these factors. The catalytic performance of TM1N4@carbon is primarily governed by the intrinsic chemical activity of the TM atoms and can be further optimized through precise control of dTM-N. With appropriate nitrogen doping, Co1N4@carbon exhibits exceptionally low ORR overpotentials for the two-electron path (η2e = 0.018 V and 0.026 V when nitrogen is doped at positions 1 and 2, respectively). This approach offers a promising strategy for the rational design of high-activity and selectivity single-atom catalysts.

Nitrogen-rich biochar electrodes from urban green waste for microbial CO2 electroreduction in bioelectrochemical systems.

ABSTRACT Single‐atom catalysts (SACs) are attractive due to their high metal utilization efficiency and intriguing properties. Developing a facile and general method to synthesize SACs with tunable geometric and electronic structure is critical for realizing their widespread application. Here we report a continuous‐flow spray pyrolysis approach to SACs (including iron, cobalt, nickel, copper, and platinum) with control over the crumple structure of the graphene substrate and the electronic structure of the single‐atom sites. Notably, the formation of single‐atom sites and morphologic engineering of the substrate are simultaneously achieved within the single‐step droplet‐to‐particle conversion process. Taking Co SACs for catalyzing the 2‐electron oxygen reduction reaction (ORR) as a representative example, the Co moieties possess a deformed local geometric structure and electron deficiency that are dependent on the crumpling degree of the graphene substrate, leading to controllable ORR activity and selectivity. The optimal catalyst achieves an unprecedently high mass activity of 456 ± 4 A g −1 at 0.65 V, along with a high H 2 O 2 selectivity of up to 97%. Furthermore, a flow‐cell electrolyzer assembled with this catalyst demonstrates an averaged H 2 O 2 productivity of 23.78 mol g −1 catalyst h −1 , sustained over 120 h of operation.

High-temperature annealing often induces severe sintering of Pt nanoparticles in Pt/C catalysts, resulting in activity degradation. Here, a carbon nitride–assisted thermal treatment strategy is proposed to enhance the thermal stability of Pt/C. TG-FTIR and XPS analysis reveal that nitrogen-containing species generated during carbon nitride decomposition play a key role in suppressing Pt nanoparticle coalescence at intermediate temperatures. Although the carbon nitride framework decomposes at high temperatures, residual graphitic and pyridinic nitrogen species are retained and interact electronically with Pt, leading to a reduced Pt binding energy. As a result, the carbon nitride–assisted Pt/C maintains a narrow particle size distribution after annealing. Electrochemical measurements demonstrate that the assisted catalyst retains oxygen reduction reaction activity comparable to commercial Pt/C after thermal treatment at 700 °C, while the untreated sample shows pronounced performance loss. Moreover, the assisted catalyst exhibits significantly improved durability after 20 000 cycles. This work offers a simple and effective approach to improving the thermal robustness of Pt-based electrocatalysts for PEM fuel cells.

Inorganic nanoparticles serve as robust nanozymes mimicking natural enzymes' catalytic activity and selectivity, yet their on-demand design is hindered by insufficient atom-level mechanistic insights. Herein, we develop a biomimetic ligand engineering approach to reproduce natural peroxidase (POD) catalytic environments on the surface of metal nanoparticles, boosting their POD-like activity. Using atomically precise Au25(Cys)18 (Cys = l-cystine) nanoclusters (NCs) as a model nanozyme, customized cysteine-proline (CP), cysteine-histidine (CH), and cysteine-arginine (CR) dipeptides are anchored on their surfaces via stepwise ligand exchange. Combined absorption spectroscopy, nuclear magnetic spectroscopy, and mass spectrometry examinations evidence the spatial proximity of CP, CH, and CR on the surface of resultant Au25(Cys/CP/CH/CR)18 NCs, mimicking the catalytic microenvironment of horseradish peroxidase. Thereby, Au25(Cys/CP/CH/CR)18 NCs exhibit significantly enhanced POD-like catalytic activity, which stems from improved H2O2 adsorption affinity and reduced energy barrier for their conversion to the OOH species. The ligand engineering process concurrently boosts the electrocatalytic oxygen reduction reaction (ORR) activity and selectivity of Au25 NCs toward H2O2. Synergizing the ORR and POD-like catalytic activities of Au25(Cys/CP/CH/CR)18 NCs enables direct •OH generation from O2 for the efficient removal of organic pollutants and bacteria from waters. This work provides a facile nanozyme customization method while revealing atom-level ligand effects on enzyme-mimetic behaviors.

Development of efficient and durable oxygen reduction reaction (ORR) electrocatalysts is of great interest yet remains challenging. Herein, we predicted and screened a bilayer graphite carbon-supported Ir-N4/Fe-N4 catalyst with high ORR activity using density functional theory calculations. Subsequently, various bimetallic single atom supported on 3D ordered macroporous carbon were rationally designed and experimentally synthesized via a colloidal microsphere template-confined reaction method. As anticipated, the resulting Ir-N4/Fe-N4 bimetallic single-atom catalysts (IrFe-SACs) exhibit superior ORR activity and durability, reaching a half-wave potential of 0.928V. The IrFe-SACs also demonstrate outstanding performance in Zn-air batteries, including a high discharge power density (314mW cm⁻2) and excellent cycling stability (~ 1650 cycles over 550h). Further experimental characterizations and theoretical analysis reveal that introducing interlayer-adjacent Ir-N4 sites facilitates the transition of Fe-N4 from a low-spin state to a medium-spin state, which optimizes the spin polarization of Fe 3d orbitals and enhances the non-localization of the Fe-O/OH molecular orbital, thereby significantly improving the ORR intrinsic activity and durability of atomic Fe-N4 sites.

This paper reports on the template-assisted synthesis of Pt-based catalysts featuring a porous structure. The influence of various gadolinium precursors on the synthesis of Pt-Gd oxide catalysts is systematically investigated, with the objective of optimizing their crystalline structure and correlating it with their performance in the oxygen reduction reaction (ORR). Transmission electron microscopy analyses reveal complex morphological features, while synchrotron radiation experiments, combined with an innovative and robust approach based on the Debye Scattering Equation (DSE), enable a more accurate correlation between the electrochemical performance and the actual morphology of the catalysts. Although this work does not claim the development of a breakthrough catalyst, the observed ORR activity is comparable to that of commercial benchmarks (e.g., TKK). More importantly, it underscores the value of DSE-based XRD analysis as a statistically rigorous and complementary technique for nanoparticle morphology characterization, offering significant advantages over conventional TEM in this context.

ABSTRACT Catalyst support materials play an important role in oxygen electrocatalysis by providing a stable platform to disperse and anchor electrocatalysts for their enhanced activity and durability. MXenes, a class of two‐dimensional van der Waals materials, have gained significant attention as support materials in oxygen electrocatalysis due to their exceptional conductivity, hydrophilicity, tailorable surface functionality, and mechanical stability. This review highlights the role of MXenes as the support for the whole spectrum of oxygen electrocatalysis, including the Oxygen Evolution Reaction (OER), Oxygen Reduction Reaction (ORR), and bifunctional activity. We begin by discussing the fundamental properties of MXenes that make them effective catalyst supports, followed by a mechanistic analysis of OER in both alkaline and acidic environments. Recent advancements in MXene‐supported catalysts for OER are reviewed, focusing on their impact on reaction kinetics and stability. Similarly, we examine ORR mechanisms in different media, detailing both the two‐electron and four‐electron pathways and the role of MXenes in optimizing selectivity and efficiency. Further, we discuss the bifunctional catalytic performance of MXene‐based systems, highlighting their potential applications in metal–air batteries. The review ends by outlining the major challenges that remain and offers perspectives on future research paths to further improve the performance of MXene‐based catalysts.

DFT insights into synergistic interactions and ORR mechanisms of BN-supported dual-atom catalysts.

Pt electrooxidation in fuel cell membrane electrodes: mechanisms and effects on oxygen reduction reaction activity based on in-situ Raman and electrochemical impedance spectroscopy

Efficient oxygen reduction at the cathode remains a critical bottleneck in advancing bio-electrochemical energy conversion, necessitating integrated experimental and atomistic-level understanding. 2D polymeric nanomaterials offer stable, nitrogen-rich frameworks as sustainable alternatives to platinum catalysts. However, their poor conductivity and low active-site density hinder oxygen reduction reactions (ORR), create an inefficient two-electron pathway, and limit the use of bio(electrochemical) devices for power generation. Lanthanide incorporation, owing to their unique redox and electronic properties, offers a promising route to overcome these shortcomings. In this investigation, lanthanides (RE) were incorporated into graphitic carbon nitride nanoparticles (g-C3N4 NPs) via one-pot synthesis, resulting in structural and electronic modifications confirmed by experiments and simulations, thereby enhancing their suitability for bio(electrochemical) systems. High-resolution TEM (HR-TEM) shows lattice distortion and nanosheet corrugation after lanthanide incorporation. X-ray photoelectron spectroscopy (XPS) confirms mixed RE3+/RE4+ states and valence-band modulation, which agrees well with density of states (DOS) calculations indicating Ce/Gd 4f-π hybridization near the Fermi level. Density functional theory (DFT) charge-density and adsorption analyses reveal that lanthanide sites stabilize key ORR intermediates and lower the reaction overpotential, favoring a four-electron pathway. This is consistent with the experimentally observed electron transfer number of n ≈ 3.9. Electrochemical tests show improved ORR activity for Gd-g-C3N4 NPs, with an onset potential of 0.81 V vs RHE and performance approaching Pt/C. When used as a microbial fuel cell cathode, Gd-g-C3N4 NPs deliver higher power output and COD removal, along with low peroxide yield, good stability, and strong methanol tolerance. When Gd-g-C3N4 NPs are used in microbial fuel cells (MFCs) as cathode catalysts, they achieve a peak power density of 447 mW m-2 and 83% chemical oxygen demand (COD) removal, outperforming both pristine and Ce-based variants. The catalyst also demonstrated a low peroxide yield (< 5%), excellent stability, and superior methanol tolerance compared with Pt/C. This investigation offers mechanistic insights from integrated experimental and computational approaches to advance efficient electrocatalysts for power generation in MFCs and clean energy and water systems.

Heavy-duty vehicle (HDV) fuel cells require oxygen reduction reaction (ORR) catalysts with exceptional activity and durability under stringent operating conditions. However, conventional solid-solution Pt-based ORR catalysts often fail to simultaneously meet the requirements of high-power density and long-term stability, due to their inherent activity-stability trade-offs and mass-transport limitations at working conditions of fuel cells. Herein, we report a universal ligand-tuned co-reduction strategy to efficiently load Pt-based intermetallic compound (IMC) nanoparticles with high density (>50 wt% metal content and ∼3 nm particle size) and a high degree of ordering into hollow mesoporous carbon (HMC) by narrowing the reduction-potential gap between Pt and other transition metal precursors to achieve stable high-power HDV fuel cells. The dense and ordered IMCs ensure the efficient and stable ORR, while the mass-transport-favorable HMC promotes oxygen transport to the active sites. This design greatly enhances HDV fuel cell ORR activity, stability, and mass-transport efficiency. Under the HDV-relevant conditions (250 kPaabs and cathode loading of 0.15 mgPt cm-2), the optimized H-L10-PtCo/HMC catalyst achieves an exceptional current density of 1.73 A cm-2 at 0.7 V and retains 85% after 90,000 accelerated durability cycles, significantly exceeding the U.S. Department of Energy targets. The findings establish H-L10-PtCo/HMC as a next-generation cathode electrocatalyst for HDV applications.

ABSTRACT Oxygen reduction reaction (ORR) with two‐electron transfer pathway is the key reaction for aprotic lithium‐oxygen (Li‐O 2 ) batteries with high theoretical energy density. Herein, we present that capturing ORR superoxide (O 2 •‒ ) intermediate can promote ORR rate and stability by using pyrrolidinium bis(trifluoromethanesulfonyl)imide (Py‐TFSI). Py + cation can bind O 2 •‒ absorbed on the surface of solid catalyst and transfer it into electrolyte, in which the coordination chemistry not only inhibits the generation and disproportionation of LiO 2 on the electrode surface to enhance ORR rate, but also stabilize O 2 •‒ to inhibit its related side reactions for better ORR stability. Over fivefold enhancement of ORR activity is observed. Moreover, Py‐TFSI promotes the uniform lithium deposition through enriching inorganics in solid‐electrolyte‐interphase and electrostatic shielding effect on Li metal surface, resulting in 2.5 times increase of cycling stability of Li electrode. As a result, the Li‐O 2 batteries demonstrate a cycle lifespan of 47 days with a high areal capacity of 5 mAh cm ‒2 . This study presents the deep understanding of intermediate manipulation mechanism for ORR and provides the effective way to improve the performance of metal‐O 2 batteries.

Efficient bifunctional oxygen electrocatalysts are crucial for overcoming the high overpotentials and sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable zinc-air batteries (ZABs). Iron-based single-atom catalysts exhibit promising ORR activity, however, their excessive adsorption of oxygen-containing intermediates, together with the scaling relationships between these intermediates, limits their bifunctional performance. Herein, a unique Fe-Dy dual-atom catalyst (FeDy-DAC) is constructed, leveraging the strong orbital coupling between Fe-3d and Dy-4f orbitals to precisely modulate the electronic structure of the Fe sites. This modulation effectively weakens the overly strong adsorption of oxygen-containing intermediates on Fe sites, facilitating *OH desorption. Meanwhile, the unique dual-site co-adsorption configuration of *O drives efficient O─O bond coupling, ultimately leading to a significant reduction in the rate-determining energy barriers of both ORR and OER. Therefore, FeDy-DAC exhibits outstanding bifunctional catalytic performance, with a high ORR half-wave potential of 0.90V and a narrow ORR/OER potential gap of 0.68V. Moreover, FeDy-DAC maintains stable operation for over 2500 h in ZABs, showcasing excellent long-term durability. This work provides a novel strategy and insights for high-performance bifunctional electrocatalyst design.

The electrochemical synthesis of hydrogen peroxide (H2O2) via the oxygen reduction reaction (ORR) offers a promising alternative to the anthraquinone process, addressing environmental concerns without requiring expensive hydrogen. However, developing catalysts that selectively promote the two-electron ORR pathway while maintaining stability remains challenging. Here, we report Ruddlesden-Popper (RP) perovskite oxides as efficient catalysts for selective H2O2 production. Among the tested LaSrBO4 compositions (B = Ni, Co, Fe, Mn), LaSrNiO4 (LSN) showed the best two-electron ORR selectivity (∼87%) and activity. Integrated into a photovoltaic-electrochemical system, LSN achieved a solar-to-chemical conversion efficiency of 4.85%, producing a H2O2 production rate of 149.2 μmol cm-2 h-1 with good stability over 50 h. Density functional theory calculations attributed this performance to favorable H2O2 formation and desorption kinetics at the Ni B-site. Overall, RP perovskites offer earth-abundant, efficient, and sustainable catalysts for electrochemical H2O2 generation, providing an alternative to carbon- or noble-metal-based systems.

Dual-atom catalysts (DACs) have emerged as a new frontier in heterogeneous catalysis, offering improved stability and superior performance in key electrocatalytic reactions. However, identifying optimal multimetallic DACs combination for a multistep reaction is challenging due to the vast chemical space. Herein, we develop a machine learning (ML) framework to expedite the screening of DACs, which consist of a heterometallic dimer embedded in the surface layer of a metal host, for improved oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) performance. We encode the solid-state-derived d-band descriptors to accurately train the ML model and effectively capture the nonmonotonic bifunctional activity on DACs, without requiring expensive DFT calculations. Interestingly, we identify the nonscaling behavior of these DACs, with CoPd and CoCu dimer exhibiting superior OER and ORR activity. Furthermore, we employ the surface charging method to evaluate the potential-dependent activity and reveal the nonlinear relationship between catalytic activity and electrode potential. Overall, this study established the pivotal role of d-states in governing the catalytic performance and offers a practical pathway to accelerate the discovery of next-generation electrocatalysts for fuel cell applications.