Insights of Cu₂O/Zn₅(OH)₈Cl₂ photocathode architecture for an efficient photoelectrochemical CO₂ reduction to multi-carbon products

Photoelectrochemical (PEC) CO₂ reduction is a critical and sustainable method for significantly reducing greenhouse gas emissions while producing renewable fuels and chemicals. Copper(I) oxide (Cu₂O) is a significant photocathode material for CO₂ reduction; however, poor stability and low catalytic efficiency hinder its practical implementation. In this groundbreaking study, we introduce and rigorously investigate a novel photocathode architecture comprising Cu₂O and Zn₅(OH)₈Cl₂ (ZHC) that enhances the efficiency of PEC CO₂ reduction. The integration of ZHC effectively functions as a selectivity layer for CO* adsorption, driving the transformation into multi-carbon products, including methanol, ethanol, propylene, and butadiene. This transformation occurs at a compelling potential of 0.78 V vs. RHE, achieving a current density of approximately −1.2 mA/cm². Furthermore, first-principles density functional theory (DFT) calculations are employed to investigate CO₂ reduction on Cu₂O(100), ZHC, and the Cu₂O/ZHC (CZHC) heterostructure. This heterojunction architecture demonstrates enhanced CO₂ adsorption due to orbital delocalisation, which significantly improves the adsorption energy and promotes the formation of C₂ products. Our research decisively contributes valuable insights into the design of highly efficient copper-based photoelectrodes, ensuring improved selectivity in photoelectrochemical CO₂ reduction and ultimately producing high-value carbon products.