A Generalized Coordination Engineering Strategy for Single-Atom Catalysts toward Efficient Hydrogen Peroxide Electrosynthesis.

Designing non-noble metal single-atom catalysts (M-SACs) for two-electron oxygen reduction reaction (2e-ORR) is attractive for the hydrogen peroxide (H 2 O 2 ) electrosynthesis, in which the coordination configuration of the M-SACs essentially affects the reaction activity and product selectivity. Though extensively investigated, a generalized coordination engineering strategy has not yet been proposed, which fundamentally hinders the rational design of M-SACs with optimized catalytic capabilities. Herein, a generalized coordination engineering strategy is proposed for M-SACs toward H 2 O 2 electrosynthesis via introducing heteroatoms (e.g., oxygen or sulfur atoms) with higher or lower electronegativity than nitrogen atoms into the first sphere of metal-N 4 system to tailor their electronic structure and adjust the adsorption strength for * OOH intermediates, respectively, thus optimizing their electrocatalytic capability for 2e-ORR. Specifically, the (O, N)-coordinated Co SAC (Co-N 3 O) and (S, N)-coordinated Ni SAC (Ni-N 3 S) are precisely synthesized, and both present superior 2e-ORR activity (E onset : ≈0.80 V versus RHE) and selectivity (≈90%) in alkaline conditions compared with conventional Co-N 4 and Ni-N 4 sites. The high H 2 O 2 yield rates of 14.2 and 17.5 moL g -1  h -1 and long-term stability over 12 h are respectively achieved for Co-N 3 O and Ni-N 3 S. Such favorable 2e-ORR pathway of the catalysts is also theoretically confirmed by the kinetics simulations.