Single‐atom catalysts (SACs) have attracted extensive interest to catalyze the oxygen reduction reaction (ORR) in fuel cells and metal–air batteries. However, the development of SACs with high selectivity and long‐term stability is a great challenge. In this work, carbon vacancy modified Fe–N–C SACs (Fe _H –N–C) are practically designed and synthesized through microenvironment modulation, achieving high‐efficient utilization of active sites and optimization of electronic structures. The Fe _H –N–C catalyst exhibits a half‐wave potential ( E _1/2 ) of 0.91 V and sufficient durability of 100 000 voltage cycles with 29 mV E _1/2 loss. Density functional theory (DFT) calculations confirm that the vacancies around metal–N ₄ sites can reduce the adsorption free energy of OH*, and hinder the dissolution of metal center, significantly enhancing the ORR kinetics and stability. Accordingly, Fe _H –N–C SACs presented a high‐power density and long‐term stability over 1200 h in rechargeable zinc–air batteries (ZABs). This work will not only guide for developing highly active and stable SACs through rational modulation of metal–N ₄ sites, but also provide an insight into the optimization of the electronic structure to boost electrocatalytical performances.

Developing energy production, storage, and conversion technologies based on sustainable or renewable energy is essential to address the energy and environmental crisis. Electrochemical water splitting is one of the most promising approaches to realize the production of green hydrogen. The design of catalytic materials with low cost, high activity, and long‐term stability and the exploration of specific reaction mechanisms are the key focus for the involved electrochemical hydrogen evolution reaction (HER). Recently, substantial efforts have been devoted to the rational design and synthesis of non‐noble metallic heterostructures with fascinating synergistic effects among different components. These heterostructured materials demonstrate comprehensive properties exceeding the estimations by the rule of mixtures and display high activity and long‐term stability in industrial conditions for HER. Herein, the reaction mechanism and key parameters for improving catalytic performance in the HER process are discussed in detail. The latest advances in heterostructures based on synthetic methods and electrocatalytic characteristics from experimental and computational perspectives are summarized according to the role of various components. Herein, insights are provided in this review into an in‐depth understanding of the heterostructures as HER electrocatalysts, and the opportunities and challenges to scale up future‐oriented developments are highlighted.

Carbon-coated SnSe₂/C–N composites with optimized hetero-atom doping and electrical conductivity exhibit superior electrochemical performance in lithium-ion batteries and sodium-ion batteries.