Photo-electrochemical Reduction of Carbon Dioxide into Methanol at CuFeO<sub>2</sub> Nanoparticle-Decorated CuInS<sub>2</sub> Thin-Film Photocathodes
Jiongliang Yuan, Chunhui Gu, Wenming Ding, Cunjiang Hao
Abstract
The conversion of CO 2 to useful chemicals is of great significance for the mitigation of global warming. Among many methods of CO 2 utilization, photo-electrochemical CO 2 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, CuFeO 2 nanoparticles (CFO NPs) are decorated on the CuInS 2 (CIS) thin-film surface by differential pulse voltammetry; at CFO NP-decorated CuInS 2 (CFO/CIS) thin-film photocathodes, CO 2 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 CO 2 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.