Cu2In/In core–shell interface regulating Cu0/+ enables selective *OCHO capture for efficient CO2-to-formate conversion across a wide potential range

Abstract

Integrating Cu–In bimetallic systems with core–shell interface engineering represents a promising strategy for constructing efficient electrocatalysts for CO₂ reduction. Herein, a well-defined Cu₂In/In core–shell interface catalyst (denoted as Cu₂In/In) is synthesized via a simple hydrogen gas (H₂) reduction method. The synergistic interaction between the electron-donating Cu₂In core and the electron-accepting In shell induces interfacial electronic reconstruction, enabling regulation of Cu^0/+ species. The Cu₂In/In delivers a formate faradaic efficiency above 80% across −0.9 to −1.3 V vs. RHE, reaching a peak of 93.6%. In addition, Cu valence states can be effectively tuned by the In content, thereby enriching Cu^0/+ species while suppressing Cu²⁺ formation. Cu K-edge XANES reveals that the absorption edge and dipole-allowed 1s → 4p transition of Cu₂In/In lie between those of Cu⁰ and Cu⁺, indicating electron transfer from Cu to In. DFT calculations reveal that interfacial electronic reconstruction in Cu₂In/In drives charge transfer, creating electron-deficient Cu sites that anchor *OCHO and an electron-rich In shell that stabilizes it. This synergistic effect results in a low energy barrier of only 0.156 eV for the reaction pathway from CO₂ to *OCHO.