Are Fe–N–C Electrocatalysts an Alternative to Pt-Based Electrocatalysts for the Next Generation of Proton Exchange Membrane Fuel Cells?

Notable progress has been made for low Pt-based and Fe–N–C electrocatalysts for proton exchange membrane fuel cell (PEMFC) applications. In particular, the research and development of cost-effective Fe–N–C’s have witnessed significant improvements in recent years due to the need for an alternative candidate for the scare and expensive platinum. Numerous studies have explored the design and optimization of Fe–N–C’s and generally make simple performance comparisons with commercial Pt/C catalysts on the basis of rotating disk electrode (RDE) and/or membrane electrode assembly (MEA), thus arguing that said materials are comparable, or could even surpass, Pt/C electrocatalysts. The resulting question, i.e., “Are Fe–N–C’s an alternative to Pt-based electrocatalysts in PEMFCs?”, is the centerpiece of this review. Here, the interconnectedness and differences between Fe–N–C’s and Pt-based materials are discussed from fundamental insights to applications in PEMFCs, covering the oxygen reduction reaction (ORR) mechanism, the nature of active sites and its effect on the intrinsic activity, the rational design of the catalyst layer, the electrocatalysts’ performance in PEMFCs, and their durability in operating conditions. This review provides a global picture of the current state of research in the field of PEMFC electrocatalysts, focusing on the two most important types of cathode materials and aiming to shed light on the potential of Fe–N–C’s as a replacement for Pt-based catalysts along with pointing out the research directions toward the next generation of PEMFCs.