Decentralized on-site production of hydrogen peroxide (H2O2) relies on the discovery of efficient, robust and inexpensive electrocatalysts for the selective two-electron (2e-) oxygen reduction reaction (ORR). Here we combine computations and experiments to demonstrate cobalt pyrite (CoS2), an earth-abundant transition metal compound, catalyzes 2e- ORR in acidic solution with excellent activity and selectivity. CoS2 nanomaterials drop-casted on rotating ring-disk electrode (RRDE) showed selective and efficient H2O2 formation in 0.05 M H2SO4 at high catalyst loadings, with their operational stability evaluated by structural and surface analyses. CoS2 nanowires directly grown on high-surface-area carbon fiber paper electrode boosted the overall performance of bulk ORR electrolysis and the produced H2O2 was chemically quantified by a ceric sulfate titration method, yielding a ~70% H2O2 selectivity at 0.5 V vs. RHE, in good agreement with the RRDE results. Computations suggested the modest binding of OOH* adsorbate on the single Co site of CoS2 and the kinetically disfavored O-O bond scission due to the lack of active site ensembles in the CoS2 structure, predicting the experimentally observed activity and selectivity. This work opens up new opportunities to explore diverse earth-abundant transition metal compounds in search of highly active and selective electrocatalysts for efficient H2O2 production.

Electrocatalytic production of H2O2 by selective oxygen reduction using Earth-abundant cobalt pyrite (CoS2)

2019 Fall National Meeting

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