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 Pr0.4Sr0.6CoxFe0.9-xNb0.1O3-delta (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 (Vo center dot center dot) 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 Vo center dot center dot 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 Vo center dot center dot 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. Pr0.4Sr0.6(Co0.2Fe0.7Nb0.1)O-3 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 Vo center dot center dot formation process, the surface activity, and structure stability of perovskite oxides.