Fine Engineering of d-Orbital Vacancies of ZnN₄ via High-Shell Metal and Nonmetal Single-Atoms for Efficient and Poisoning-Resistant ORR

Atomically dispersed metal-nitrogen-carbon (M-N-C) materials are active oxygen reduction reaction (ORR) catalysts. Among M-N-C catalysts, ZnN₄ single-atom catalysts (SACs) due to a nearly full 3d¹⁰ electronic configuration insufficiently activate oxygen and display low ORR activity. To finely engineer d-orbital vacancies of ZnN₄, we combine high-shell metal and nonmetal SAs as electronic regulators that are ZnN₄Cl and carbon vacancy-hosted -Cl motifs, which show complementary electron-withdrawing capacities versus the ZnN₄. Under that, the ZnN₄ exhibits significantly enhanced ORR activity with a half-wave potential (<i>E</i>_1/2) of 0.912 V_RHE relative to the unmodified ZnN₄ (<i>E</i>_1/2 = 0.822 V_RHE) and simultaneously robust durability (negligible activity loss after 10,000 potential cycles). Particularly, the engineered ZnN₄ possesses high resistance to SCN^- poisoning, which is rarely achieved among M-N-C SACs. Our works show that combining high-shell metal and nonmetal SAs can finely engineer d-orbital vacancies of metal centers to an optimal state, thereby intrinsically enhancing their catalytic performance.