High-Density Accessible Iron Single-Atom Catalyst for Durable and Temperature-Adaptive Laminated Zinc-Air Batteries

Engineering p-d Orbital Coupling and Vacancy-Rich Structure in Triatomic Iron-Bismuth-Iron Sites for Rechargeable Zinc-Air Batteries

The rational design of heteroatomic sites with synergistic electronic modulation remains a critical challenge for achieving bifunctional oxygen electrocatalysis in sustainable energy technologies such as fuel cells and metal-air batteries. Herein, a triatomic Fe2BiN5 configuration embedded in nitrogen-doped carbon (Fe2BiN5/C) with atomically dispersed FeN2-BiN-FeN2 sites and vacancy-rich structures is synthesized via a pyrolysis and etching strategy. The triatomic architecture endows Fe2BiN5/C with exceptional bifunctional activity, delivering a high oxygen reduction reaction half-wave potential of 0.918 V and an oxygen evolution reaction overpotential of 245 mV at 10 mA cm-2, surpassing Pt/C and RuO2. In situ X-ray absorption fine structure and Raman spectroscopy reveal dynamic structural evolution during electrocatalysis, where Fe acts as the primary active center with Bi regulating the electron distribution via long-range interactions, thereby optimizing adsorption/desorption energetics of oxygen intermediates. The theoretical calculations further elucidate that the Bi-induced p-d orbital coupling leads to the alteration in Fe d-orbitals energy level, downshift d-band center, weaken binding strength to the oxygen-based intermediates, and reduced energy barrier for oxygen electrocatalysis. This work provides an understanding of bifunctional triatomic site with p-block metal as electronic modulators embedded in transition-metal atoms toward enhanced oxygen catalysis.

Emerging techniques and scenarios of scanning electrochemical microscopy for the characterization of electrocatalytic reactions

To fulfill the evergrowing energy consumption demands and the pursuit of sustainable and renewable energy, electrocatalytic reactions such as the water electrocatalysis reaction, the O2 reduction reaction, the N2 reduction reaction (NRR), the CO2 reduction reaction (CO2RR), etc., have drawn a lot of attention. Scanning electrochemical microscopy (SECM) is a powerful technique for in situ surface characterization, providing critical information about the local reactivity of electrocatalysts and unveiling key information about the reaction mechanisms, which are essential for the rational design of novel electrocatalysts. There has been a growing trend of SECM-based studies in electrocatalytic reactions, with a major focus on water splitting and O2 reduction reactions, and relying mostly on conventional SECM techniques. Recently, novel operation modes of SECM have emerged, adding new features to the functionality of SECM and successfully expanding the scope of SECM to other electrocatalytic reactions, i.e., the NRR, the NO3 - reduction reaction (NO3RR), the CO2RR and so on, as well as more complicated electrolysis systems, i.e. gas diffusion electrodes. In this perspective, we summarized recent progress in the development of novel SECM techniques and recent SECM-based research studies on the NRR, NO3RR, CO2RR, and so on, where quantitative information on the reaction mechanism and catalyst reactivity was uncovered through SECM. The development of novel SECM techniques and the application of these techniques can provide new insights into the reaction mechanisms of diverse electrocatalytic reactions as well as the in situ characterization of electrocatalysts, facilitating the pursuit of sustainable and renewable energy.

Honeycomb-like MnO/C hybrids with strong interfacial interactions for aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) have garnered significant attention for large-scale energy storage applications due to their high theoretical capacity, low cost, and inherent safety. However, the absence of cathode materials exhibiting superior electrochemical performance severely impedes their further development. In this study, we report a metal-organic framework (MOF)-derived honeycomb-like MnO/C hybrid as a high-performance cathode material for AZIBs. A facile synthesis method was employed to uniformly embed MnO nanoparticles within a carbon matrix, thereby forming a honeycomb-like structure with robust heterointerfaces. This unique architecture provides efficient pathways for ion and electron transport, significantly enhancing structural stability and electrochemical performance. The MnO/C hybrid exhibits a high discharge specific capacity of 388 mA h g-1 at a current density of 50 mA g-1 and demonstrates excellent cycling stability, with a capacity decay rate of only 0.01% per cycle over 1000 cycles at a high current density of 2000 mA g-1. Comprehensive material characterization and electrochemical testing reveal the underlying mechanisms responsible for the superior electrochemical performance. This work provides a new perspective on the development of high-performance manganese-based cathode materials for AZIBs.