In situ construction of CuBi-MOF derived heterojunctions with electron-rich effects enhances localized CO₂ enrichment integrated with Si photocathodes for CO₂ reduction

Photoelectrochemical reduction of CO₂ (PEC-CO₂RR) to fuels or industrial feedstocks using photocathodes is a promising approach to addressing the climate crisis and energy shortage. The design of photocathode with suitable band structure and robust CO₂ capture remains challenging. In this work, a Cu₂O@Bi-300 (CuBi-300) catalyst was prepared in situ using Bi-MOF as a template, and a CuBi-300/Si photocathode was constructed. Due to the bridging effect of Cu-O-Bi bonds and the existence of the coordination unsaturated Bi sites, CuBi-300/Si exhibits excellent photoelectrochemical properties and reaction kinetics. The formate yield of CuBi-300/Si (101.1 µmol cm⁻² h⁻¹, Faraday efficiency = 95 %) are 10.2 times higher than those of Bi-300/Si at −0.3 V vs RHE, along with excellent stability for 50 hours. In situ FTIR and density functional theory calculations indicate that the Cu₂O-induced formation of electron-rich Bi enhances CO₂ chemisorption and stabilizes the key intermediate (*COOH). This work presents a novel approach for developing high-performance, low-energy consumption PEC-CO₂RR photocathode devices by in situ constructing heterojunctions to simultaneously enhance photovoltaic properties and CO₂ adsorption. © 2024 Elsevier B.V.