Activation of Surface Lattice Oxygen by Ni-Doped CeO₂ To Enhance CO-SCR Reactivity and Antioxidant Performance Testing: Density Functional Theory Study

Selective catalytic reduction of nitric oxide using carbon monoxide from industrial flue gas is considered an economical and environmentally friendly method of denitrification (CO-SCR). Ni-doped CeO₂ catalysts exhibited high denitrification performance, where the distribution and number of oxygen vacancies were the key factors affecting the performance. In this paper, Ni-doped CeO₂ (1 1 1) surface CO reduction of NO has been thoroughly investigated and its reactivity has been evaluated by using density functional theory, electronic structure analysis, and transition state theory. The negative oxygen vacancy formation energy of the Ni-CeO₂ (1 1 1) surface is manifested by the easier activation of the surface lattice oxygen. The Ni-CeO₂ (1 1 1)-O1_VO5_V structure the reaction path that generates N₂ via the ONCO intermediate has the lowest energy barrier and is the best reaction path. When oxygen is present, not only does it compete with NO for the active site, but the adsorption of O₂ at other sites also changes the position of already adsorbed NO. It also destroys ONNO and ONCO intermediates, thus blocking or hindering subsequent reactions. When trace amounts of oxygen are present in the reaction system, only the trioxide vacancy CeO₂ (1 1 1)-O1_VO5_VO7v structure via the N₂O₂ intermediate to generate the N₂ reaction pathway can go through. However, the reactivity was reduced. In this study, the intrinsic mechanism of Ni doped CeO₂ catalysts with high denitrification performance was deeply elucidated at the atomic level, and the effect of O₂ on the reaction process was also revealed.