Manipulation of CO adsorption over Me₁/CeO₂ by heterocation doping: Key roles of single-atom adsorption energy

The performance of metal atoms chemically bonded to oxide supports cannot be explained solely by the intrinsic properties of the metals such as the d-band center. Herein, we present an in-depth study of the correlation between metal-oxide interactions and the properties of the supported metal using CO adsorption on Me₁ (Fe₁, Co₁, and Ni₁) loaded over CeO₂ (111) doped with divalent (Ca, Sr, and Ba), trivalent (Al, Ga, Sc, Y, and La), and quadrivalent (Hf and Zr) heterocations. CO adsorption over Me₁ is strongly dependent on the binding energies of Me₁. Two factors led to this trend. First, the extent of the Me₁-surface oxygen (Me₁-O) bond relaxation during CO adsorption played a key role. Second, the d-band center shifted drastically because of charge transfer to the oxides. The shift is related to the oxophilicity of metals. Adsorption energies of Me₁ over oxides include the contributions of the factors described above. Therefore, we can predict the activities of Me₁ using the strength of anchoring by oxide supports. Results show that smaller ionic radii of the doped heterocations were associated with more tightly bound Me₁. This finding sheds light on the possibility of heterocation-doping manipulating the reactivity of the Me₁ catalyst based on theoretical predictions.