Vertical graphene array for efficient electrocatalytic reduction of oxygen to hydrogen peroxide

Hydrogen peroxide (H2O2) is a green chemical oxidant that finds widespread use in the chemical industry. The electrocatalytic oxygen reduction reaction (ORR) is presently attracting a lot of attention as an environmentally friendly synthetic route towards H2O2. However, the efficient reduction of O-2 & nbsp;to produce H2O2 & nbsp;at high current densities (> 100 mA cm(-2)), thereby achieving viable H2O2 & nbsp;yields, remains a challenge. Herein, we demonstrate that vertical graphene arrays grown on carbon paper (denoted herein as VG array) via plasma-enhanced chemical vapor deposition show outstanding activity for ORR to H2O2 & nbsp;in alkaline media at high current densities. The VG array electrode delivered a Faradaic efficiency of 94% and a H2O2 & nbsp;production rate of 61.3 mg h(-1)& nbsp;cm(-2) at 100 mA cm(-2), and similarly impressive performance at 200 mA cm(-2)& nbsp;(81% and 102.8 mg cm-2 h(-1), respectively), outperforming most catalysts reported to date for electrochemical H2O2 & nbsp;synthesis. The remarkable performance of the VG array electrode is ascribed to the interconnected network of graphene nanosheets which ensures a high availability of graphene edge active sites (thus a high H2O2 selectivity) and fast electron transfer during ORR. Further, gas-liquid-solid three-phase interfaces formed between the graphene nanosheets facilitate a steady supply of O-2 & nbsp;from the gas phase when the electrode was applied in a flow cell. Results encourage the application array electrodes in electrochemical H2O2 & nbsp;synthesis, whilst also offering a roadmap to future industrial H2O2 & nbsp;production.

Automated summary

This study investigates the electrocatalytic oxygen reduction reaction (ORR) activity of vertically grown graphene arrays on carbon paper (VG array) in alkaline media at high current densities. The VG array electrode demonstrates remarkable performance with a Faradaic efficiency of 94% and a H2O2 production rate of 61.3 mg h(-1) cm(-2) at 100 mA cm(-2). The interconnected network of graphene nanosheets and gas-liquid-solid three-phase interfaces contribute to the high activity and selectivity of the VG array electrode.