Chemical microenvironment regulation of single-atom catalysts in photocatalysis

The emerging single-atom catalysts (SACs) have garnered significant attention in photocatalytic energy conversion processes due to their high atomic efficiency and unique structural characteristics. The geometric structure and electronic properties of SACs are primarily governed by their chemical microenvironment, which almost entirely determines their photocatalytic performance. Herein, we highlight the recent advances in the microenvironment engineering of SACs, focusing on the regulation of coordinating atoms and metal center sites. Moreover, we summarize the achievements in microenvironment modulation across various photocatalytic applications, including CO₂ reduction, CH₄ conversion, N₂ fixation, H₂O splitting and pollutant degradation. The fundamental impacts of SACs' microenvironment on photocatalytic activity, selectivity, and stability are further explored. Finally, we summarize the challenges in the development of microenvironment engineering and provide an outlook on future opportunities and challenges. This comprehensive review offers guidance for the design and fabrication of highly active SACs and is expected to foster the progress of microenvironment engineering.