Ni-Doping as a Design Strategy for Fe-Based Catalysts: Towards Efficient CO2 Activation and Dissociation Studied by Density Functional Theory

In this work, we investigate the activation of CO2 on bimetallic Ni–Fe catalysts, using Fe as the base metal and Ni as a dopant at low concentrations. Our aim is to evaluate how the presence of Ni, either as a substitutional atom or as an adatom, influences CO2 activation and facilitates subsequent C–O bond breaking. The catalytic surfaces were modeled using Fe(100) slabs, and the effect of Ni was examined in three configurations: (I) substitution of one Fe atom by Ni in the first layer, (II) Ni as an adatom, and (III) Fe as an adatom on the Ni-substituted Fe surface. In all cases, the optimized geometries lead to CO2 activation. The corresponding energy profiles for C–O bond dissociation were obtained and compared with those on pure Fe(100) (Eact = 0.84 eV). Among the three systems, the configuration with substitution of Fe by Ni in the first layer exhibits the lowest activation barrier for C–O bond breaking, just 0.48 eV—a substantial reduction of 0.36 eV relative to pristine Fe(100). Only the Niad-Fe(100) surface yields a higher barrier (0.93 eV). These results are rationalized by extracting the spin splitting from the spin-resolved LDOS of the metal d-band centers, revealing that the superior performance of Ni1-Fe(100) arises from a more efficient local spin reorganization during bond dissociation.