Low-Temperature Methane Conversion over Single-Atom Photocatalysts (a Review)

Single-atom catalysts (SACs) are the latest generation of nanoheterogeneous catalysts. They consist of active metal sites dispersed into single atoms on the surface of a solid support and, thus, exhibit unique catalytic performance including enhanced activity and high selectivity. Semiconductor materials are used to prepare single-atom photocatalysts designed for photo-driven chemical processes, generally without external heating. Photoinduced low-temperature methane conversion over SAC-based photocatalysts offers new prospects for methane chemistry. This review summarizes, systematizes, and analyzes recent publications on dry reforming of methane (DRM) and nonoxidative coupling of methane (NOCM) in the presence of single-atom photocatalysts. Despite the unfavorable thermodynamics of these types of reactions over wide ranges of low and high temperatures, they can be carried out at room temperature under photocatalytic conditions. The review discusses the performance of SACs in photoinduced DRM and NOCM compared to heterogeneous nanocatalysts. It further provides a comparative assessment of the SAC behaviors in DRM and NOCM under photocatalytic and conventional thermocatalytic conditions.