Electrocatalysts for the Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells: Significant Advances, Major Challenges, and Future Directions

Electrocatalysts are indispensable in proton exchange membrane fuel cells (PEMFCs) for enhancing the oxygen reduction reaction (ORR). ORR is also an essential step for several important energy conversion technologies including metal-air batteries and hydrogen peroxide production. Because of their high energy density, high conversion efficiency, and very low pollution levels, PEMFCs have received extraordinary attention as one of the most promising options for stationary, automotive, and mobile applications in the future. However, the cost and the sluggish kinetics of ORR at the cathode are some of the major contributors to the efficiency losses in the PEMFCs. This article examines the latest breakthroughs in metal and metal-alloy electrocatalysts, as well as explores the current developments in Pt-free alternative options. We critically assessed the significance of electrocatalyst synthesis methods, alternative catalyst support systems, and design and optimization of the cathode layer. The report delivers an insightful discussion on possible future research directions about ORR electrocatalysis in PEMFCs. Finally, it advocates for an expanded research perspective that integrates environmentally friendly synthesis methods with innovative materials engineering, along with computational studies, machine learning, and data science to gain deeper insights. By fostering advanced discussions and a visionary perspective, this work aims to pave the way for a more cost-effective and efficient future in energy technology and hydrogen infrastructure development.