Atomically Incorporating Ni into Mesoporous CeO₂ Matrix via Synchronous Spray-Pyrolysis as Efficient Noble-Metal-Free...

Low-temperature catalytic CO oxidation is an important chemical process in versatile applications, such as the H₂ utilization for low-temperature H₂ air fuel cells. Pt-group metal catalysts are efficient but highly cost-consuming. This work demonstrates an excellent and sixpenny catalyst with earth-abundant Ni and Ce, in which Ni ions are atomically incorporated into the CeO₂ matrix (Ni-Ce-O) by synchronous spray-pyrolysis (SSP) of mixture nitrates of Ni and Ce. The Ni-Ce-O catalyst presents a mesoporous structure. Revealed by a model reaction of 1% CO, 1% O₂, and 98% balance He at a space velocity of 13,200 mL/g_cat/h, Ni-Ce-O catalysts display a typical volcano-shaped relationship between reactivity and Ni incorporation amount. The optimized Ni incorporation appears with a high Ni/Ce atomic ratio of 0.25, endowing the T₅₀ (temperature corresponding to a CO conversion of 50%), which is lower-shifted by 165 °C than that of pristine CeO₂ (266 °C). The density functional theory (DFT) calculations further indicate that the much-reduced oxygen vacancy formation energy at Ni-Ce single-atom sites boosted the adsorption activation of the CO molecule and therefore promoted the CO oxidation process. Besides, the₂ Ni-Ce-O from the SSP method presents better performance than the counterparts from immersion and hydrothermal methods. This work paves a way to access efficient noble-metal-free catalysts for low-temperature CO oxidation.