Phase engineering Governing reaction pathways in Phosphorus-Doped copper oxide for selective CO2 electroreduction to CH4 and Multicarbon products

Abstract

Copper-based catalysts exhibit moderate adsorption energy for *CO intermediates and have attracted significant attention for CO₂ electroreduction to fuels and high-value chemicals, but their low activity and poor selectivity remain challenges. Herein, we synthesized phosphorus-doped copper oxide (CuO_xP_y) and demonstrated that phosphorus governs the phase transition, creating distinct interfaces that regulate proton donors or local OH^– concentrations, thereby modulating the reaction pathway and directing CO₂ electroreduction selectively towards CH₄ or multi-carbon (C₂₊) products. Notably, the P-Cu₂O/Cu interface derived from amorphous CuO_xP_y exhibits a Faradaic efficiency (FE) for CH₄ of 53 % ± 4.99 % at a current density of 0.4 A cm⁻². In contrast, the Cu₂P₂O₇/Cu₂O interface obtained from crystalline CuO_xP_y achieves a FE_C2+ of 74.3 % ± 1.75 % at 0.8 A cm⁻². Experiments and theoretical calculations reveal that the accumulation of proton donors at the P-Cu₂O/Cu interface facilitates the protonation of the *CO intermediate, thereby enhancing CH₄ production. The Lewis acid sites of Cu²⁺ at the Cu₂P₂O₇/Cu₂O interface enhance the local OH^– concentration and lower the energy barrier for C-C coupling, resulting in high selectivity towards C₂₊ products. This study presents a novel paradigm for the rational regulation of selectivity in CO₂ electroreduction products through modulation of the interfacial microenvironment.