Interfacial charge redistribution in nickel hydroxide@multimetallic MXene heterojunctions for selective carbon dioxide electroreduction to methane.

Electrocatalytic carbon dioxide reduction reaction (CO2RR) is a promising approach to achieve carbon cycle balance by selectively converting carbon dioxide into valuable methane (CH4). However, developing electrocatalysts that exhibit high activity, selectivity, and stability simultaneously remains a challenge. In this study, a three-dimensional porous nickel hydroxide@multimetallic MXene (Ni(OH)2@MX) heterojunction was successfully constructed, which leveraged the excellent electrical conductivity of MX and the intrinsic catalytic activity of Ni(OH)2, resulting in a powerful synergistic effect at their interface. When tested in an H-type cell, the Ni(OH)2@MX heterojunction achieved a Faradaic efficiency of up to 81% for CH4 at -1.2 V versus reversible hydrogen electrode (vs. RHE) and maintained stable operation for 24 h under a current density of 45 mA cm-2. Ab initio molecular dynamics (AIMD) simulations showed that MX coupling reorganized the interfacial water orientation and disrupted the continuous hydrogen-bond network favorable for hydrogen evolution reaction (HER). Density functional theory (DFT) calculations further demonstrated that the heterointerface induced directional electron transfer from MX to Ni(OH)2, optimized the adsorption of CO2RR intermediates, lowered the thermodynamic barrier for *CO hydrogenation, and weakened competitive *H adsorption. This work highlighted interfacial charge redistribution and solvent microenvironment regulation as effective strategies for designing non-Cu-based electrocatalysts toward selective CO2-to-CH4 conversion.