Carbon Free and Noble Metal Free Ni 2 Mo 6 S 8 Electrocatalyst for Selective Electrosynthesis of H 2 O 2

Abstract Electrocatalytic two‐electron reduction of oxygen is a promising method for producing sustainable H 2 O 2 but lacks low‐cost and selective electrocatalysts. Here, the Chevrel phase chalcogenide Ni 2 Mo 6 S 8 is presented as a novel active motif for reducing oxygen to H 2 O 2 in an aqueous electrolyte. Although it has a low surface area, the Ni 2 Mo 6 S 8 catalyst exhibits exceptional activity for H 2 O 2 synthesis with >90% H 2 O 2 molar selectivity across a wide potential range. Chemical titration verified successful generation of H 2 O 2 and confirmed rates as high as 90 mmol H 2 O 2 g cat −1 h −1 . The outstanding activities are attributed to the ligand and ensemble effects of Ni that promote H 2 O 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 H 2 O 2 with high turn‐over frequencies of ≈30 s −1 . In addition, the Ni 2 Mo 6 S 8 catalyst has a stable crystal structure that is resistive for oxidation and delivers good catalyst stability for continuous H 2 O 2 production. The described Ni‐Mo 6 S 8 active motif can unlock new opportunities for designing Earth‐abundant electrocatalysts to tune oxygen reduction for practical H 2 O 2 production.