Single-Atom Zinc Sites with Synergetic Multiple Coordination Shells for Electrochemical H2 O2 Production

Abstract

Precise manipulation of the coordination environment of single-atom catalysts (SACs), particularly the simultaneous engineering of multiple coordination shells, is crucial to maximize their catalytic performance but remains challenging. Herein, we present a general two-step strategy to fabricate a series of hollow carbon-based SACs featuring asymmetric Zn-N₂ O₂ moieties simultaneously modulated with S atoms in higher coordination shells of Zn centers (n≥2; designated as Zn-N₂ O₂ -S). Systematic analyses demonstrate that the synergetic effects between the N₂ O₂ species in the first coordination shell and the S atoms in higher coordination shells lead to robust discrete Zn sites with the optimal electronic structure for selective O₂ reduction to H₂ O₂ . Remarkably, the Zn-N₂ O₂ moiety with S atoms in the second coordination shell possesses a nearly ideal Gibbs free energy for the key OOH* intermediate, which favors the formation and desorption of OOH* on Zn sites for H₂ O₂ generation. Consequently, the Zn-N₂ O₂ -S SAC exhibits impressive electrochemical H₂ O₂ production performance with high selectivity of 96 %. Even at a high current density of 80 mA cm^-2 in the flow cell, it shows a high H₂ O₂ production rate of 6.924 mol g_cat ^-1 h^-1 with an average Faradaic efficiency of 93.1 %, and excellent durability over 65 h.

Keywords: Coordination Environment; H2O2 Production; Hollow Structure; Single-Atom Catalysts; Synergetic Effects.