Progress of electrochemical CO2 reduction reactions over polyoxometalate-based materials

Graphical Abstract Electrochemical CO2 reduction to value-added fuels and chemicals is recognized as a promising strategy to alleviate energy shortages and global warming owing to its high efficiency and economic feasibility. Recently, understanding the activity origin, selectivity regulation, and reaction mechanisms of CO2 reduction reactions (CO2RRs) has become the focus of efficient electrocatalyst design. Polyoxometalates (POMs), a unique class of nanosized metal-oxo clusters, are promising candidates for the development of efficient CO2RR electrocatalysts and, owing to their well-defined structure, remarkable electron/proton storage and transfer ability, and capacities for adsorption and activation of CO2, are ideal models for investigating the activity origin and reaction mechanisms of CO2RR electrocatalysts. In this review, we focus on the activity origin and mechanism of CO2RRs and survey recent advances that were achieved by employing POMs in electrocatalytic CO2RRs. We highlight the significant roles of POMs in the electrocatalytic CO2RR process and the main factors influencing selectivity regulation and catalytic CO2RR performance, including the electrolyte, electron-transfer process, and surface characteristics. Finally, we offer a perspective of the advantages and future challenges of POM-based materials in electrocatalytic CO2 reduction that could inform new advancements in this promising research field.