Atomic Co decorated free-standing graphene electrode assembly for efficient hydrogen peroxide production in acid

Electrochemical oxygen reduction reaction (ORR) in acids via a selective 2e − pathway offers great opportunities for electrosynthesis of H 2 O 2 , allowing on-site environmental treatment in industry. Unfortunately, despite some progress, the apparent activity of most electrocatalysts (especially in a flow cell reactor) still requires further improvement to meet the industrial demands, where high H 2 O 2 productivity with low energy input is desired. Herein, we report a free-standing ORR electrode comprising cobalt single atoms on a vertically aligned graphene nanosheet assembly (CoN 4 /VG), which is demonstrated to exhibit a hierarchical porous structure maximizing the utilization of catalytic active atoms without sacrificing the mass/charge transport efficiencies. Within a H-cell setup, the as-prepared ORR electrode gives a H 2 O 2 selectivity close to 100% from 0.3 to 0.5 V versus reversible hydrogen electrode (RHE) in 0.1 M HClO 4 , sustaining a record-breaking H 2 O 2 productivity of 706 mmol H 2 O 2 g catalyst −1 h −1 at 0.3 V vs. RHE for 36 hours. Further employing this electrode in a gas-diffusion flow reactor yields a peroxide concentration of 1100 mg L −1 (4000 mmol H 2 O 2 g catalyst −1 h −1 ) continuously at −1.8 V of cell voltage, corresponding to an energy consumption of 3.81 W h g H 2 O 2 −1 , which represents the most energy-efficient flow system for rapid H 2 O 2 generation in acidic media. A novel oxygen reduction reaction (ORR) electrode comprising isolated Co atom decorated vertically aligned graphene nanosheets is designed, which can enable the most energy-efficient, rapid acidic H 2 O 2 production in a flow-cell reactor.