Inorganic non-carbon supported Pt catalysts and synergetic effects for oxygen reduction reaction

Oxygen reduction reaction (ORR) is regarded as the rate-determining step in a fuel cell or a metal-air battery because of the kinetically retarded four-electron process. Among the substantial types of catalysts developed for decades, Pt-based catalysts are almost still the most promising electrode materials with outstanding comprehensive performance and commercial potential. For the widely used Pt/C catalysts, the rapid degradation of performance in ORR tests exposed serious problems due to severe carbon corrosion and Pt deterioration. Non-carbon supports can avoid the direct connection between Pt and carbon materials, resulting in reduction (or elimination) of carbon oxidative dissolution and stabilization of Pt nanoparticles. More importantly, non-carbon supports for Pt-based catalysts may bring favorable anchoring and synergetic effects, which have been widely proved to enhance the durability and catalytic activity. In this review, the inorganic non-carbon support materials are classified as metal oxides, carbides, nitrides, and other metal compounds. Among them, the metal oxide supports manifest excellent stability during the ORR process but may lack electrical conductivity, while metal carbides and nitrides possess both high stability and high electrical conductivity in suitable electrolytes. We aim to summarize the applications of non-carbon supported Pt catalysts in ORR, the relevant mechanisms and the properties of the hybrid catalysts, with emphasis on the anchoring and synergetic effects.