Interfacial charge redistribution in nickel hydroxide@multimetallic MXene heterojunctions for selective carbon...

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.