Types, properties, and applications of non-precious oxygen reduction reaction electrocatalyst: A review

This review offers a comprehensive overview of non-precious group metal (non-PGM) electrocatalysts, with a particular focus on oxygen reduction reactions (ORR). The main challenge preventing the broad commercial use of polymer electrolyte membrane fuel cells (PEMFCs) is the dependence on noble metals, specifically electrocatalyst (EC) based on platinum (Pt) at the cathode, which is indispensable for assisting the oxygen reduction reaction (ORR) in fuel cells (FCs). Research on EC-containing non-noble metal (NNM) has been considerable over the past few decades to minimize costs and reduce the excessive loading of EC based on Pt. This review is aimed at improving the reliability and stability of non-precious metal EC. To achieve a feasible ORR, Pt-based EC is crucial for the widespread commercial applications of PEMFCs. The review emphasizes improving ORR performance, stability, and cost-effectiveness in catalysts that are not precious metals. The article examines the advancements in non-precious nanomaterial-based EC, highlighting different types that have improved ORR efficiency. The review suggests future possibilities and directions for further improvement in designing and constructing EC with high efficiency and low costs for PEMFCs.