The oxygen reduction reaction (ORR) is one of the most important electrochemical reactions in energy conversion and storage technologies, such as fuel cells and metal–air batteries. However, the sluggish kinetics of the ORR is a key factor limiting the performance of these energy storage and conversion devices. Perovskite oxides are a promising family of electrocatalysts for the ORR because of their unique physical and chemical properties, such as variable crystal structure and non-stoichiometric chemistry. Studies have shown that the catalytic properties of perovskite oxides in the ORR are largely related to oxygen vacancies, which alter their electronic and crystal structures and surface chemistry. This review summarizes recent research advances on understanding the role of oxygen vacancies of the ABO₃ perovskite oxides in catalyzing the ORR. With a brief introduction of perovskite oxides, approaches to creating oxygen vacancies in the ABO₃ perovskite oxides and the role of oxygen vacancies in improving their catalytic performance for the ORR are discussed. Research perspectives in this important area are highlighted.

In this study, sea-urchin-like bimetal nickel–cobalt phosphide/phosphate (Ni–Co–P/PO_x) samples were first synthesized by a low-temperature phosphating method. The phosphide phase shows a crystal nanoparticle morphology distributed in the matrix of the amorphous phosphate phase. By theoretical calculations, it has been found that NiCoP shows a metallic conductivity property because the density of states crosses the Fermi level, and it exhibits better electrochemical activity than Ni₂P and CoP owing to the presence of more electrons close to the Fermi level; moreover, the effects of phosphorization and bimetallic properties on the charge storage performance of Ni–Co–P/PO_x have been investigated, and the results indicate improved electrochemical activity, rate capability and cycling stability. Ni–Co–P/PO_x with the Ni to Co molar ratio of 1 : 1 shows the best performance, and it exhibits electrochemical activity greater than and rate performance comparable to that of the oxide. Ni–Co–P/PO_x with the Ni to Co molar ratio of 1 : 1 shows a specific capacity of 647 C g⁻¹ at 1 A g⁻¹ and specific capacity retentions of 67% and 94% after the specific current increases by 50 times and after 1000 cycles, respectively; this indicates that high electrochemical activity, rate performance and cycling stability performances have been simultaneously achieved. In addition, a Ni–Co–P/PO_x//reduced graphene oxide hybrid supercapacitor was assembled, which showed good electrocapacitive performance.