Atomically dispersed dual-metal-site PGM-free electrocatalysts for oxygen reduction reaction: Opportunities and challenges

Atomically dispersed and nitrogen coordinated single metal site (MNx, M = Fe, Co, or Mn) moieties embedded in partially graphitized carbon (denoted as M-N-C) are recognized as the most promising platinum group metal-free catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. However, simply regulating their coordination environments and local structures of single metal sites cannot fundamentally change active site structure, which leads to insufficient activity and stability. A second transition metal can be incorporated to design dual-metal sites, offering a new opportunity to modulate the electronic and geometric structures of M-N-C catalysts. Therefore, exploring optimal atomically dispersed dual-metal-site is essential to designing new active sites with enhanced ORR activity, and stability, especially breaking the activity-stability trade-off. This review provides a comprehensive analysis of the advances in developing atomically dispersed dual-metal site catalysts for the ORR, including innovative synthesis methods, primary structural configurations, and the mechanisms to promote catalytic performance. We aim to elucidate the crucial structure-property correlation, emphasizing the inherent electronic and geometric effects of dual metal sites. Finally, we discuss the current challenges of dual-metal site catalysts concerning rational design, precise synthesis, and high-fidelity structural characterization.

Automated summary

This review provides a comprehensive analysis of the advances in developing atomically dispersed dual-metal site catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. It explores the structure-property correlation and inherent effects of dual metal sites, and discusses the challenges in rational design, precise synthesis, and high-fidelity structural characterization of dual-metal site catalysts.