Activating Lattice Oxygen in Perovskite Oxide by B‐Site Cation Doping for Modulated Stability and Activity at Elevated Temperatures

Doping perovskite oxide with different cations is used to improve its electro-catalytic performance for various energy and environment devices. In this work, an activated lattice oxygen activity in Pr_0.4 Sr_0.6 Co_x Fe_{0.9- x} Nb_0.1 O_{3- δ} (PSCxFN, x = 0, 0.2, 0.7) thin film model system by B-site cation doping is reported. As Co doping level increases, PSCxFN thin films exhibit higher concentration of oxygen vacancies ( V o • • ) as revealed by X-ray diffraction and synchrotron-based X-ray photoelectron spectroscopy. Density functional theory calculation results suggest that Co doping leads to more distortion in FeO octahedra and weaker metaloxygen bonds caused by the increase of antibonding state, thereby lowering V o • • formation energy. As a consequence, PSCxFN thin film with higher Co-doping level presents larger amount of exsolved particles on the surface. Both the facilitated V o • • formation and B-site cation exsolution lead to the enhanced hydrogen oxidation reaction (HOR) activity. Excessive Co doping until 70%, nevertheless, results in partial decomposition of thin film and degrades the stability. Pr_0.4 S_r0.6 (Co_0.2 Fe_0.7 Nb_0.1 )O₃ with moderate Co doping level displays both good HOR activity and stability. This work clarifies the critical role of B-site cation doping in determining the V o • • formation process, the surface activity, and structure stability of perovskite oxides.