Exactly regulated copper catalysts exploiting isolated photoelectrochemical reduction of cuprous oxides and random mesh-structured TiO2 for enhanced photoelectrochemical CO2 conversion

Abstract

Photoelectrochemical (PEC) CO₂ reduction for the direct conversion of solar energy into carbon-based chemical fuels has received considerable attention owing to it being an inherently sustainable and green process. However, complex photocathode architectures and processes involving protective layers and co-catalysts typically hinder product selectivity and stable PEC operation. Cu is the only electrocatalyst that yields products containing multiple carbon molecules during the electrochemical CO₂ reduction reaction (CO₂RR). In this study, Cu nanoparticles were artificially fabricated on the surface of Cu₂O from a light absorption layer using isolated photoelectrochemical reduction, which was designed from a negative photocorrosive reaction. Using hydrogen evolution reaction (HER) and CO₂RR electrolytes, HER-Cu (H-Cu) and CO₂RR-Cu (C-Cu) catalysts were respectively fabricated by artificially controlling photoelectrochemical self-photocorrosion (SPC) at the atomic level. Additionally, we adopted a partially installed random-mesh (RM) structured protective TiO₂ layer with ultimately thin thickness and the optimal structure displays resistant to photocorrosion by forming individual catalyst particles on the uncovered RM-TiO₂. The designed Cu₂O/RM-TiO₂/H-Cu displays a remarkable cathodic-photocurrent density of −1.57 mA cm⁻² at 0.4 V_RHE, CO formation with 98% efficiency, and improved stability under illumination. The utilization of an RM-structured TiO₂ layer mitigates loss of charge via recombination, while also imposing a physical barrier that restricts direct interaction between the Cu₂O surface without the Cu catalyst and the electrolyte. This study provides mechanistic insights into the CO₂RR pathways and suggests an innovative approach that exploits the intrinsic corrosion reaction to design efficient PEC CO-producing catalysts.