Advanced Noncarbon Materials as Catalyst Supports and Non-noble Electrocatalysts for Fuel Cells and Metal–Air Batteries

Electrochemical energy systems such as fuel cells and metal–air batteries can be used as clean power sources in the field of electric transportation and possess great potential in the reduction of various energy and environmental issues. In these systems, the oxygen reduction reaction (ORR) at the cathode is the rate-determining factor for overall system performance, and up to now, platinum group metals supported on carbon materials, especially Pt, remain the highest performing and the most practical ORR electrocatalysts. However, corresponding carbonaceous catalyst supports are extremely susceptible to corrosion under electrochemical operation, and therefore, the extensive exploration of alternative stable materials for ORR electrocatalysts with both high electrochemical stability and catalytic performance is essential. Here, noncarbon materials with high corrosion resistance have been explored to substitute traditional carbon supports or even act directly as low-cost non-noble metal electrocatalysts, and based on this, this review will present a comprehensive overview and deep analysis of the recent progress in noncarbon materials, including metals, oxides, nitrides, carbides, sulfides, and so on. Overall, general attributes associated with noncarbon materials include high corrosion resistance, strong metal–support interaction, and impressive porous structure retention. However, major drawbacks include low electrical conductivity, insufficient chemical stability in acidic or alkaline media, and poor electrochemical stability at ORR electrode potentials. To overcome these challenges, this review will also summarize efficient strategies such as combining with highly conductive materials, introducing dopants and forming vacancies to result in promising electrocatalytic ORR performances. Finally, this review will propose possible research directions to facilitate future research and development toward the practical application of noncarbon-based ORR electrocatalysts.