Tungsten and molybdenum based polyoxometalates for photo and electrocatalytic carbon dioxide conversion - A critical review

Today, carbon dioxide (CO2) is one of the most pervasive greenhouse gases in the atmosphere, mainly because of the burning of fossil fuels. The carbon dioxide reduction reaction by photocatalysis and electrocatalysis is one approach that holds a lot of promise for easing the global crisis on the environmental and energy fronts. Developing and constructing high-performance photo-and electrocatalysts is a challenge that is being studied. The class of anionic metal-oxo clusters known as polyoxometalates (POMs) brings diverse and interesting chemical and physical characteristics that can be modified easily. The studies reveal that POMs are emerging to be distinctive photo/electrocatalysts for these reactions because of their unmatched advantages, like thermal and redox stability, light-absorbing capacity, quasi-semiconductor properties, etc. Numerous studies have demonstrated the capability of tungsten and molybdenum-based photo-and electrocatalysts for CO2 reduction and conversion into value-added products. This review has covered the most recent developments in tungsten and molybdenum-based POMs that convert CO2 into multiple products (CO, H2, HCOOH, HCHO, CH3OH, etc.). Perspectives for designing and constructing different kinds of POM-based catalytic systems have been offered.