Oxygen-rich hierarchical activated coke-based gas diffusion electrode enables highly efficient H2O2 synthesis via O2 electroreduction

Abstract

Large-scale application of H2O2 production through 2-electron oxygen reduction reaction (2eORR) greatly depends on the cost of electrode materials and configuration. In this work, engineered coal-derived oxygen-rich hierarchical activated coke (AC), which is low-cost and highly tunable in porosity and surface chemistry, was used as catalyst to fabricate gas diffusion electrodes (GDEs) for efficient H2O2 production. Results showed that Fenton’s reagents treatment could significantly increase the contents of CO and –COOH on AC, leading to an increased hydrophilicity. However, the higher O contents do not necessarily enhance the selectivity of AC towards 2eORR (i.e., F-5-AC, F-10-AC), especially that F-20-AC exhibited a complete 4e pathway. GDEs were then fabricated with AC and oxidized AC as catalyst, key fabrication parameters including the PTFE binder and AC particle size, and operating parameters such as current intensity, electrolyte pH, and O2 flow rate were optimized. Up to 747 mg/L H2O2 were generated within 90 min. Results showed that oxidized AC exhibited a decreased H2O2 yield, due to the flooding of GDEs caused by super-hydrophilicity property. Finally, DFT calculations were employed to reveal the synergistic effect of different O groups considering the fact of high O contents on AC.