Promoting oxygen reduction via coordination environment modulation through secondary metal-atom incorporation

Abstract

Fe-based single-atom catalysts (SACs) have been recognized as attractive candidates for the oxygen reduction reaction (ORR). However, several limitations such as unsatisfactory intrinsic activity and poor stability hinder their practical applications, motivating further optimization of Fe-SACs which requires precise control of their composition and coordination environment. Herein, we establish a facile solvothermal method to incorporate Cu into Fe-SACs to form heterometallic SACs. We observe that the adjacent Cu atoms can regulate the coordination environment of FeN₄ sites and significantly enhance the ORR activity. As a result, the heterometallic SACs show superior ORR catalytic performance compared to the mono-Fe-SAC counterpart (an enhancement factor of ∼5 times), delivering a half-wave potential (E_1/2) of 0.889 V vs. RHE and a high kinetic current density (j_k) of 4.77 mA cm⁻² at 0.9 V vs. RHE, and also outperform the state-of-the-art Pt/C catalyst under identical testing conditions.