Microenvironment regulation strategies of single-atom catalysts for advanced electrocatalytic CO2 reduction to CO

The electrocatalytic CO2 reduction reaction (CO2RR) is an effective and sustainable route to achieve carbon neutrality by generating valuable fuels and feedstocks from renewable electricity. CO as one of the most economically valuable products, has been used for a wide range of applications in the synthesis of commodity and specialty chemicals. Single atom catalysts (SACs) are emerging as highly-active electrocatalysts for CO product from CO2RR due to high atomic utilization, adjustable coordination environment and strong metal-support interactions. Thus, the significant progresses force a comprehensive and critical summary reporting the microenvironment regulation strategies of SACs for CO2 to CO, however, has been rarely reported. In this review, we focus on the current developed various design of microenvironment regulation strategies, including the design of metal catalytic center, the regulation of coordination environment (unsaturated coordination, oversaturated coordination, and heteroatom doping), support effect, and defect effect, to conduct the summary. It is generally believed that the change of microenvironment has an important effect on the electron distribution of the active site and the adsorption energy of the reaction intermediates. Here, we attempt to reveal the essential source of single-atom catalytic activity through in-depth understanding of microenvironment regulation. And we hope to provide help for large-scale application of advanced SACs.