Efficient CO2 reduction to C2 products in a Ce-TiO2 photoanode-driven photoelectrocatalysis system using a Bnanometer Cu2O cathode

Abstract

Excessive emission of CO₂ into the atmosphere has caused significant environmental issues. Photoelectrocatalytic (PEC) reduction of CO₂ is an effective method that combines the benefits of both photo- and electrocatalysis. This process effectively minimizes CO₂ emissions, enhances the efficiency of CO₂ reduction, and diminishes energy consumption during the reduction process. In this work, we have successfully developed a photoelectrochemical (PEC) system, integrating a Ce-doped TiO₂ film as the photoanode and Cu₂O as the dark cathode, in which the 4 % Ce-TiO₂ film photoanode demonstrated the best performance. Electrochemical performance data revealed that the Cu₂O catalysts, characterized by their octahedral geometry that optimally presents active sites for CO₂ reduction, displayed superior activity in converting CO₂. Through a straightforward hydrothermal synthesis, we crafted three-dimensional, flower-like TiO₂ thin films. The strategic incorporation of cerium into the TiO₂ matrix not only enhanced the material's crystallinity but also resulted in a uniform and compact morphology. This modification significantly narrowed the band gap of TiO₂, thereby boosting its photocatalytic capabilities. In the system where a 4 % Ce-TiO₂ thin film photoanode was used to drive the PEC reduction of CO₂, the octahedral Cu₂O catalyst demonstrated the highest selectivity for C₂ products. This occurred at a reaction voltage of −1.4 V vs. RHE, resulting in a total Faraday efficiency of 67.33 %. Notably, this Faraday efficiency is double the one produced from the electrocatalytic (EC) system. This work demonstrates that the use of a 4 % Ce-TiO₂ film as a photoanode is able to solve the photocorrosion problem of the Cu₂O catalyst while employing a photovoltaic combination to enhance the selectivity to C₂ products.