Photoelectrochemical behaviors and photocatalytic activities of mixed CuO and CuFeO2 films with Ti and Ni underlayers for CO2 conversion

This study synthesizes heterojunction CuO and CuFeO2 (CFO) films via electrodeposition on Ti and Ni-deposited transparent conducting substrates and examines their photoelectrochemical behavior and unassisted photocatalytic activities for CO2 conversion in aqueous bicarbonate solutions at circumneutral pH. Deposition of 15 nm and 50 nm-thick metal layers increases the electrical conductivity of the substrate, improving the deposition kinetics of the CFO precursors and establishing firm contact between CFO and the substrate. CFO films with Ti and Ni underlayers (Ti/CFO and Ni/CFO) exhibit higher photocurrent generation than bare CFO, owing to the rapid charge transfer and low interfacial charge-transfer resistance. Despite comparable apparent solar-to-chemical conversion (STC) efficiencies (∼1%), the C1 chemical (formate) is the sole product in the bare CFO film, whereas mixed C1–C4 chemicals are produced in Ti- and Ni-underlayered CFO films. When estimated based on transmitted light, the Ti/CFO and Ni/CFO films exhibit STCs of ∼7% and 3%, respectively. [Display omitted] •CFO films with Ti and Ni underlayers are electrochemically synthesized.•Metal-underlayered CFO films exhibit high solar CO2 conversion efficiencies.•Metal-underlayered CFO films produce C-C coupled aliphatic acid anions from CO2.•The metals provide good conductivity and robust contact between CFO and FTO.•The high Wf value of metals leads to fast charge separation in CFO film.