Recent progress on MN4 macrocycle-derived oxygen reduction reaction electrocatalysts for polymer electrolyte fuel cell application

Abstract

Transportation and power generation sectors have been garnering strong support for fuel cell-based technologies in recent times for emission-free energy conversion. However, the performance of these devices largely relies on the costly and scarce Pt-group metal-based electrocatalysts, which hinder their widespread commercialization. For the past few decades, a vast research effort has been made to develop cost-effective and efficient non-precious metal electrocatalysts for low-temperature fuel cells. Single-atom catalysts (SACs) have attracted the most attention due to their excellent electrocatalytic performance. Moreover, SACs derived from transition metal MN4 macrocycles have many advantages in terms of structural integrity of the active centers that are beneficial for superior electrocatalytic activity and durability. This feature article covers the recent reports focused on the development of the MN4 macrocycle-derived oxygen reduction reaction (ORR) electrocatalysts for proton exchange membrane fuel cell (PEMFC) and anion exchange membrane fuel cell (AEMFC), and summarizes the viability in energy applications, including their stability issues. This review aims to discuss the various factors that influence the fuel cell performance of cathode catalysts based on transition-metal macrocyclic complexes (metal porphyrins and phthalocyanines).