Hybrid mesoporous Cu2ZnSnS4 (CZTS)–TiO2 photocatalyst for efficient photocatalytic conversion of CO2 into CH4 under solar irradiation

Abstract

A major concern facing global society is the ongoing excessive release of CO₂ into the atmosphere where it acts as a heat-trapping greenhouse gas. One approach to helping control atmospheric CO₂ concentrations is to use solar energy to convert CO₂ into useful products, namely hydrocarbons, by use of specifically designed photocatalytic materials. While numerous photocatalysts have been investigated for use in CO₂ reduction, the field remains in it's infancy with, overall, relatively poor photoconversion efficiencies and product selectivity. This study reports the synthesis and design of a mesoporous noble metal free p-type Cu₂ZnSnS₄ (CZTS)/n-type TiO₂ heterojunction photocatalyst for broad spectrum light absorption, enhanced charge separation and transfer that, in turn, enhances photocatalytic CO₂ conversion. A maximum methane production rate of 118.75 ppm g⁻¹ h⁻¹ is observed, which represents a methane evolution rate approximately 12 times greater than that of pure TiO₂. The key factors contributing to the enhanced photocatalytic performance seen in the mesoporous CZTS–TiO₂ samples include improved light absorption, high surface area, and effective charge separation.