Mechanistic insights into NiMn bimetallic synergy driving efficient CO₂ to CH4 conversion

Abstract

CO₂ methanation represents a critical strategy to address environmental and energy challenges, though its reaction mechanism remains poorly understood. This study establishes a Mn-doped Ni (1 1 1) bimetallic catalytic model and employs density functional theory (DFT) calculations to systematically elucidate the unique mechanism of NiMn synergistic effects. At the CO₂ activation stage, Mn doping shortens the metal-O bond length from 2.34 Å to 2.08 Å and alters the active site charge from +0.036 e to −0.147 e, enhancing CO₂ adsorption and dissociation through d-orbital hybridization and charge redistribution. Concurrently, geometric modulation of Ni electronic structures reduces the rate-determining step activation energy to 1.28 eV. Through comparative analysis of three reaction pathways (CO₂^⁎ dissociation followed by CO^⁎ hydrogenation, HCOO^⁎ intermediate reduction, and COOH^⁎ intermediate reduction), the optimal reaction channel has been identified. This work provides theoretical guidance for designing efficient CO₂ conversion catalysts and offers predictive insights for subsequent experimental validation.