CuBi2O4/Cu2O nano-enabled stable photocathodes promoting CO2 to methyl acetate conversion under low bias potential and solar irradiation

The use of Cu₂O-based photocathodes has demonstrated the promising activity of these earth-abundant materials for the photoelectrochemical CO₂ reduction reaction (CO₂RR), particularly in producing methanol. However, their application in long-term devices is hindered by severe photocorrosion. To address this limitation, photocathode designs incorporating Schottky barriers, heterojunctions, and scaffolding layers have been explored. In this work, a CuBi₂O₄/CuO thin layer was employed as a scaffold to support Cu₂O films with either seeded or grown morphologies for enhanced photoelectrochemical CO₂RR. Photoelectrochemical testing in CO₂-saturated electrolyte revealed that 0.55 V vs. reversible hydrogen electrode (RHE) yielded the highest activity and stability for methanol (CH₃OH) production, outperforming more negative potentials. Furthermore, the present work highlighted that electrolyte engineering can be used to promote the generation of alternative products such as methyl acetate (CH₃COOCH₃). The presence of CuBi₂O₄/CuO scaffold was critical for allowing this pathway, providing both enhanced stability and improved charge transfer on the Cu₂O surface. The generation of CH₃COOCH₃ is attributed to locally modified microenvironments that facilitate the esterification reaction when acetate is present in solution. These findings highlight the role of scaffold engineering in improving photocathode performance and electrolyte tuning in steering product selectivity toward scarcely explored, added-value compounds such as methyl acetate.