As the core functional unit of the flow battery system, the surface and interface microenvironment of carbon electrode materials determine the electrochemical polarization behavior and energy storage performance. From the perspectives of microstructural regulation and electronic structure modulation, this review systematically examines carbon electrode surface/interface modification strategies and their mechanisms for enhancing flow battery performance. It systematically discusses how microstructural regulation and electronic structure modulation can effectively optimize mass transport kinetics, charge transfer efficiency, and electrocatalytic activity, consequently mitigating electrode polarization. Particular emphasis is placed on unveiling the underlying structure–performance relationships and the structure–function interplay between the electrode microenvironments and their resultant electrochemical properties. Furthermore, advanced characterization techniques, including synchrotron radiation, X-ray absorption spectroscopy, in situ Raman spectroscopy, and first-principles calculations, are summarized to elucidate the dynamic evolution of carbon electrodes. These methods provide crucial insights into how surface chemical modifications reconstruct electronic structures and active sites, leading to suppressed concentration and electrochemical polarization. Building on recent progress in atomically dispersed metal electrocatalysts, we also propose the rational design of single-atom catalyst-modified carbon electrodes. Moreover, synergistic strategies integrating high-throughput computation with machine learning are envisioned to establish multidimensional predictive models based on band structure, adsorption energy, and reaction pathways, thereby addressing the bottlenecks of metal utilization efficiency and structure–performance correlation. Overall, this review delivers a multidimensional theoretical framework and technological roadmap for the rational design and practical deployment of high-performance carbon electrodes in next-generation flow batteries.

Single-atom catalysts (SACs) are considered as the most promising nonprecious metal alternatives for oxygen reduction reactions (ORR) in proton exchange membrane fuel cells because of their high atomic utilization and excellent catalytic performance. However, the inadequate activity and long-term stability of SACs under operational conditions significantly hinder their practical application. Therefore, this paper focuses on understanding the micro- and electronic structures that synergistically enable the activity and stability of oxygen reduction. It provides a comprehensive summary of the effects for improving the ORR catalytic activity and stability of SACs from a multilevel, multi-angle perspective, including macroscale adjustments to the overall catalyst structure, nanoscale optimization of the catalyst microstructure, and atomic-scale regulation of the active sites. Additionally, it emphasizes the importance of advanced simulation, computational methods, and characterization techniques in understanding the catalytic and degradation mechanisms of SACs during the ORR process. This review aims to provide a theoretical foundation for the synergistic catalytic mechanisms and long-term stable operation of catalytic sites in complex heterogeneous environments, thereby advancing research on low-cost, high-efficiency, and highly stable single-atom catalysts.