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.