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

Demetalation, caused by the electrochemical dissolutionof metalatoms, poses a significant challenge to the practical applicationof single-atom catalytic sites (SACSs) in proton exchange membrane-basedenergy technologies. One promising approach to inhibit SACS demetalationis the use of metallic particles to interact with SACSs. However,the mechanism underlying this stabilization remains unclear. In thisstudy, we propose and validate a unified mechanism by which metalparticles can inhibit the demetalation of Fe SACSs. Metal particlesact as electron donors, decreasing the Fe oxidation state by increasingthe electron density at the FeN4 position, thereby strengtheningthe Fe-N bond, and inhibiting electrochemical Fe dissolution.Different types, forms, and contents of metal particles increase theFe-N bond strength to varying extents. A linear correlationbetween the Fe oxidation state, Fe-N bond strength, and electrochemicalFe dissolution amount supports this mechanism. Our screening of aparticle-assisted Fe SACS led to a 78% reduction in Fe dissolution,enabling continuous operation for up to 430 h in a fuel cell. Thesefindings contribute to the development of stable SACSs for energyapplications.