Photo-electrochemical Reduction of Carbon Dioxide into Methanol at CuFeO2 Nanoparticle-Decorated CuInS2 Thin-Film Photocathodes

The conversion of CO2 to useful chemicals is of great significance for the mitigation of global warming. Among many methods of CO2 utilization, photo-electrochemical CO2 reduction is promising; however, the low activity of the photoelectrodes and the poor selectivity of the reduction products inhibit its practical application. In this research, CuFeO2 nanoparticles (CFO NPs) are decorated on the CuInS2 (CIS) thin-film surface by differential pulse voltammetry; at CFO NP-decorated CuInS2 (CFO/CIS) thin-film photocathodes, CO2 is reduced photo-electrochemically to methanol and ethanol, with methanol as the main product. Compared to the CIS thin-film photoelectrode, CFO/CIS thin-film photocathodes exhibit high activity of CO2 reduction and good selectivity for methanol formation. The rate of methanol formation at the CFO/CIS thin-film photocathode at an overpotential of 0.17 V is estimated to be 15.40 mol h–1 m–2, which is three times that at the CIS thin-film photocathode. The enhanced activity is attributed to the low mass-transfer resistance at the electrode surface. At CFO/CIS [−1.0/–1.2 V] deposited for 20 s, the lowest mass-transfer resistance can be obtained; methanol yield is therefore the highest. Methanol yield shows strong relationship with *CO coverage on the CFO/CIS thin-film electrode surface, while it shows no obvious relationship with *H coverage. In addition, CFO/CIS thin-film electrodes have high stability within 9 h.