The emergence of single-atom-layer catalysis

To improve the utilization efficiency of noble metals as well as lower their mass loading in electrocatalysis, the research community has contributed significant efforts to nanostructure noble metal catalysts in various dimensions during recent decades, such as porous structures (3D), nanosheets (2D), nanowires (1D), nanoclusters (0D), and individual atoms (i.e., single-atom catalyst). Recently, with the development of the well-controlled synthesis of atom-thin materials (e.g., the noble metal layer or two-dimensional materials), a new type of catalyst defined as the single-atom-layer catalyst, has emerged, allowing nearly all the atoms at the monolayer to be accessible to catalytic reactions. In this perspective, we first introduced the unique properties of this catalyst and distinguished it from current single-atom catalysts, then highlighted its recent theoretical and experimental progress, and finally discussed critical challenges toward catalytic applications.