Transition-metal-oxide-based catalysts for the oxygen reduction reaction

Anion-exchange membrane fuel cells (AEMFCs) are promising energy storage and conversion devices that provide opportunities and advantages in the application of low-cost transition metal oxide (TMO)-based catalysts. However, the oxygen reduction reaction (ORR) activity of these catalysts is still greatly inferior to that of Pt-based catalysts. In this review, the key factors to develop high performance TMO-based catalysts have been carefully detailed, including strategies to enhance their electrical conductivity, recent advances in the understanding of their intrinsic activity, and their morphology and structure design. Finally, we discussed the existing challenges and future research directions for further development of TMO-based ORR catalysts.