Band structure engineering of carbon nitride hybrid photocatalysts for CO2 reduction in aqueous solutions

Abstract

Through the co-polymerisation of dicyandiamide and barbituric acid precursors, a series of visible light active carbon nitride photocatalysts has been prepared and characterized, and their photocatalytic activity has been evaluated. Structural and electronic characterisation has enabled variations in observed activity towards water splitting and CO₂ reduction to be understood, both in the presence and absence of the iron porphyrin co-catalyst Fe^III tetra(4-carboxylphenyl)porphyrin (FeTCPP). A combination of the most active carbon nitride catalyst using 5 wt% barbituric acid and FeTCPP provides a hybrid system where the alignment of band structure with appropriate reduction potentials and enhanced carrier lifetimes is capable of CO₂ reduction in an aqueous solution with >60% selectivity for CO production. This study is one of only a few that achieves selective CO₂ reduction using a hybrid molecular catalyst-carbon nitride photocatalyst in aqueous solution.