Mechanism of Particle-Mediated Inhibition of Demetalation for Single-Atom Catalytic Sites in Acidic Electrochemical Environments

Demetalation, caused by the electrochemical dissolution of metal atoms, poses a significant challenge to the practical application of single-atom catalytic sites (SACS) in proton exchange membrane-based energy technologies. One promising approach to inhibit SACS demetalation is the use of metallic particles to interact with SACS. However, the mechanism underlying this stabilization remains unclear. In this study, we propose and validate a unified mechanism by which metal particles can inhibit the demetalation of Fe SACS. Metal particles act as electron donors, decreasing the Fe valence by increasing the electron density at the FeN4 position, thereby strengthening the Fe-N bond, and inhibiting electrochemical Fe dissolution. Different types, forms, and contents of metal particles increase the Fe-N bond strength to varying extents. A linear correlation between Fe valence, Fe-N bond strength, and electrochemical Fe dissolution amount supports this mechanism. Our screening of a particle-assisted Fe SAC led to a 78% reduction in Fe dissolution, enabling continuous operation for up to 430 hours in a fuel cell. These findings contribute to the development of stable SACS for energy applications.