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 mu mol 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.