Review of CO2 reduction photocatalysts with sustainability perspective

Abstract

The most frequently used semiconductors and co-catalysts for the photocatalytic CO2 reduction are reviewed with sustainability perspectives; the material availability and supply risk, sustainability of production routes, CO2 reduction performance and operational stability, and end-of-life degradation patterns were used as the criteria to assess the sustainability of semiconductor and co-catalyst alternatives. It was found that g-C3N4 is the most sustainable semiconductor, followed by TiO2, among the most frequently used alternatives while Cu2O/CuO, ZnO, GO/g-GO, ZnS can be considered as moderately sustainable alternatives. BiVO4 cannot be treated as sustainable material due to the supply risks associated with both Bi and V while CsPbBr3 and CdS should be avoided due to high toxicity of Pb and Cd respectively. Among the semiconductor alternatives Cu, Fe and Ni seems to be sustainable choices while the precious metal co-catalysts may not be sustainable due to low availability and supply risks, price fluctuations and environmental impacts they may impose during mining and refining stages. Cobalt should be also avoided du to its high toxicity and environmental burden through its life cycle.