Polyoxometalate-based nanostructures for electrocatalytic and photocatalytic CO 2 reduction

Electro/photocatalytic carbon dioxide (CO₂) reduction to value-added chemicals and fuels is being actively studied as a promising pathway for renewable energy storage and climate change mitigation. Because of inert molecular properties and competing hydrogen generation reactions, high-performance electrocatalysts with high Faradaic efficiency and product selectivity but low overpotential are urgently needed. Polyoxometalates (POMs) are a class of polynuclear metal oxide clusters with a precise atomic structure, providing an ideal research platform to reveal the relationship between macroscopic properties and microstructures. Moreover, their highly tunable redox properties and abundant transition metal atom composition ensure thriving research for POM-based nanostructures toward CO₂ reduction. In this review, we first introduce the specific roles of POMs in electro/photocatalytic CO₂ reduction. Recent advances in POM-based nanostructures ranging from single clusters, assemblies, organic–inorganic hybrids to derivatives are systematically summarized. In particular, the structure–performance relationship of POM-based nanostructures is discussed at the atomic and molecular levels. Finally, the challenges and opportunities in the design of high-efficiency POM-based nanostructures are discussed to promote electro/photocatalytic CO₂ reduction.