Oxidative Polyoxometalates Modified Graphitic Carbon Nitride for Visible-Light CO₂ Reduction

Abstract

Developing a photocatalysis system for converting CO₂ to valuable fuels or chemicals is a promising strategy to address global warming and fossil fuel consumption. Exploring photocatalysts with high-performance and low-cost has been two ultimate goals toward photoreduction of CO₂. Herein, noble-metal-free polyoxometalates (Co4) with oxidative ability was first introduced into g-C₃N₄ resulted in inexpensive hybrid materials (Co4@g-C₃N₄) with staggered band alignment. The staggered composited materials show a higher activity of CO₂ reduction than bare g-C₃N₄. An optimized Co4@g-C₃N₄ hybrid sample exhibited a high yield (107 μmol g^-1 h^-1) under visible-light irradiation (λ ≥ 420 nm), meanwhile maintaining high selectivity for CO production (94%). After 10 h of irradiation, the production of CO reached 896 μmol g^-1. Mechanistic studies revealed the introduction of Co4 not only facilitate the charge transfer of g-C₃N₄ but greatly increased the surface catalytic oxidative ability. This work creatively combined g-C₃N₄ with oxidative polyoxometalates which provide novel insights into the design of low-cost photocatalytic materials for CO₂ reduction.