Selective photoelectrocatalytic reduction of CO2 to ethanol with a CuO–MoO3/TiO2NTs composite photoelectrode†

Abstract

Overusing fossil energy sources has led to global warming, seriously risking the habitability of the environments on which people depend. Photoelectrocatalytic (PEC) reduction of carbon dioxide (CO₂) is a promising strategy to reduce CO₂ into high-value-added chemicals and fuel products. However, photoelectrocatalysis faces problems related to low CO₂ conversion efficiency and uncontrollable product complexity. This study reports a CuO–MoO₃/TiO₂NTs composite photoelectrode prepared by pulsed electrodeposition for the photoelectrocatalytic (PEC) reduction of CO₂ to ethanol in a 1 M NaHCO₃ medium under visible light irradiation and at an applied potential of −0.3 V vs. SCE. Molybdenum trioxide plays a regulatory role in the structure and properties of the photoelectrode. Photoluminescence analysis suggests that this occurs by introducing new energy levels between those of CuO and TiO₂, which reduces the bandgap energy from 1.42 eV to 1.17 eV, promotes electron–hole pair separation, and significantly boosts photoelectrocatalytic activity. In addition, experimental results show that the doping of MoO₃ enhanced the adsorption strength of the intermediate products and promoted the C–C coupling process. The optimized composite photoelectrode achieves 89% Faraday efficiency for ethanol at −0.5 V versus SCE (saturated calomel electrode). No new phases were generated during the catalytic process, confirming the stability of the CuO–MoO₃/TiO₂NTs composite photoelectrode.