Carbon Free and Noble Metal Free Ni_2Mo_6S_8 Electrocatalyst for Selective Electrosynthesis of H_2O_2

摘要

Electrocatalytic two-electron reduction of oxygen is a promising method for producing sustainable H2O2 but lacks low-cost and selective electrocatalysts. Here, the Chevrel phase chalcogenide Ni2Mo6S8 is presented as a novel active motif for reducing oxygen to H2O2 in an aqueous electrolyte. Although it has a low surface area, the Ni2Mo6S8 catalyst exhibits exceptional activity for H2O2 synthesis with 90 H2O2 molar selectivity across a wide potential range. Chemical titration verified successful generation of H2O2 and confirmed rates as high as 90 mmol H2O2 g(cat)(-1) h(-1). The outstanding activities are attributed to the ligand and ensemble effects of Ni that promote H2O dissociation and proton-coupled reduction of O-2 to HOO*, and the spatial effect of the Chevrel phase structure that isolates Ni active sites to inhibit O-O cleavage. The synergy of these effects delivers fast and selective production of H2O2 with high turn-over frequencies of approximate to 30 s(-1). In addition, the Ni2Mo6S8 catalyst has a stable crystal structure that is resistive for oxidation and delivers good catalyst stability for continuous H2O2 production. The described Ni-Mo6S8 active motif can unlock new opportunities for designing Earth-abundant electrocatalysts to tune oxygen reduction for practical H2O2 production.