Engineering NiO Lattice Distortion by Doping Pr ³⁺ Cations in Internal Bulk: An Effective Way for Improving the Mobility of Lattice Oxygen

Doping is crucial for regulating oxygen vacancies and improving the catalytic performance in transition metal oxides (TMOs). While prior research has extensively explored the effects of dopant valence and ionic radius, the role of the dopant spatial distribution in determining TMO performance has received limited attention. This study systematically examines praseodymium (Pr) doping in nickel oxide (NiO), with a focus on the spatial distribution of dopants. By precisely controlling the placement of Pr either at the surface or within the bulk lattice, we demonstrate that bulk doping induces lattice distortion, which increases the oxygen migration rates. This enhancement in oxygen mobility results in improved catalytic performance compared with surface doping. The study establishes a structure–activity relationship in doped TMOs and proposes an unexpected strategy for optimizing the catalytic performance through controlled dopant positioning.