Selective Alcohol on Dark Cathodes by Photoelectrochemical CO₂ Valorization and Their In Situ Characterization

Valorization of CO2 into chemical fuel by photoelectrochemical CO2 reduction competes with hydrogen evolution reaction. Considering that CO2 reduction reaction (CO2RR) occurs on the interface of the cathode in artificial photosynthesis, selectivity and faradaic efficiency depend on the performance of the cathode itself. Herein, we report a Nafion-coated TiO2 dark cathode to produce alcohol as a selective liquid product from CO2RR. The mechanism for selective alcohol production is investigated by in situ extended X-ray absorption fine structure and in situ electron paramagnetic resonance spectroscopy measurement for the intermediate CO2 radical detection. The Nafion functional layer on the TiO2 dark electrode suppresses the dimerization of monocarbon radical intermediates due to the efficient one-pot reactions of proton-coupled multiple electron transfer. As a result, the dimerization of monocarbon radical intermediates is suppressed due to decreased lifetime of the intermediate, facilitating the exclusive methanol production.