Photoelectrochemical CO₂ reduction to formic acid using as cuprous oxide-based photocathodes

The use of novel Cu-based photoelectrodes for photoelectrochemical CO₂ reduction to produce hydrocarbon fuels offers a promising strategy to address the energy and environmental crisis. In this study, we have developed a Cu₂O/Ga₂O₃/TiO₂/In multilayer photoelectrode, where CO₂ on the photoelectrode surface could gain electrons and be reduced to chemicals such as HCOOH. A bundled Cu₂O photoelectrode is constructed by optimizing the traditional electrodeposition method. We elucidated its synthesis mechanism and reported its enhancement of photoelectrocatalytic CO₂ reduction performance. By constructing a Cu₂O/Ga₂O₃/TiO₂/In multilayer photoelectrode, the photocurrent density can achieve 2.21 mA/cm² (at a potential of −0.9 V (vs. Ag/AgCl)), along with the capability to reduce CO₂ to HCOOH. Notably, the Faradaic selectivity for formic acid reaches 62.1 %, and the photocathode sample exhibits stability lasting up to 180 min. The findings of this paper provide feasible strategies for designing and manufacturing highly active photoelectrochemical CO₂ reduction photocathodes.