Cation Concavities Induced d-Band Electronic Modulation on Co/FeO x Nanostructure to Activate Molecular and Interfacial Oxygen for CO Oxidation.

Cobalt-based catalysts have been identified for effective CO oxidation, but their activity is limited by molecular O 2 and interfacial oxygen passivation at low temperatures. Optimization of the d-band structure of the cobalt center is an effective method to enhance the dissociation of oxygen species. Here, we developed a novel Co/FeO x catalyst based on selective cationic deposition to anchor Co cations at the defect site of FeO x , which exhibited superior intrinsic low-temperature activity (100%, 115 °C) compared to that of Pt/Co 3 O 4 (100%, 140 °C) and La/Co 2 O 3 (100%, 150 °C). In contrast to catalysts with oxygen defects, the cationic Fe defect in Co/FeO x showed an exceptional ability to accept electrons from the Co 3d orbital, resulting in significant electron delocalization at the Co sites. The Co/FeO x catalyst exhibited a remarkable turnover frequency of 178.6 per Co site per second, which is 2.3 times higher than that of most previously reported Co-based catalysts. The d-band center is shifted upward by electron redistribution effects, which promotes the breaking of the antibonding orbital *π of the O═O bond. In addition, the controllable regulation of the Fe-O v -Co oxygen defect sites enlarges the Fe-O bond from 1.97 to 2.02 Å to activate the lattice oxygen. Moreover, compared to Co x Fe 3- x O 4 , Co/FeO x has a lower energy barrier for CO oxidation, which significantly accelerates the rate-determining step, *COO formation. This study demonstrates the feasibility of modulating the d-band structure to enhance O 2 molecular and interfacial lattice oxygen activation.