Standalone photoconversion of CO2 using Ti and TiOx-sandwiched heterojunction photocatalyst of CuO and CuFeO2 films

Abstract

Artificial photoconversion of carbon dioxide to value-added chemicals remains a challenge. In this work, we synthesize heterojunction copper oxide and copper iron oxide (CuO/CuFeO2; CFO) films on transparent conducting substrates with metallic Ti layers, and deposit disordered TiOx particles on the CFO films. The Ti/CFO/TiOx samples convert CO2 into formate with ∼100% selectivity and drive O2 evolution under simulated sunlight in the absence of any electrical and chemical biases, achieving the overall solar-to-chemical energy conversion efficiency of ∼5%. The primary roles of the Ti underlayer are to create a robust contact between CFO and substrates and facilitate hole transfer. The TiOx (with unsaturated Ti atoms) delocalizes the electron density of the CFO and enhances electron transfer to the adsorbed CO2. Density functional theory calculations reveal that Ti/CFO/TiOx is the most suitable among the bare and modified CFO samples for efficient CO2 adsorption, formiloxyl intermediate formation, and formate desorption.