Efficient Electrocatalytic Oxidation of o -Phenylenediamine to 2,3-Diaminophenazine on Nitrogen-Doped Graphene for Low-Voltage Hydrogen Production

Confronting the challenges of high energy consumption and low value-added products associated with the oxygen evolution reaction (OER) in traditional water electrolysis. The electrochemical oxidation reaction of o-phenylenediamine (oPD), termed the DAOR, is employed as an alternative to the OER, which not only reduces the decomposition voltage of water splitting but also yields the high-value-added product 2,3-diaminophenazine (DAP). The carbon felt enriched with nitrogen-doped graphene structures (N-GS/CF) exhibits high catalytic activity for DAOR. A two-electrode system with N-GS/CF and Pt/C requires only 0.78 V (theoretical value) to reach a current density of 10 mA cm⁻², reducing energy consumption compared to conventional water electrolysis systems. Density functional theory (DFT) calculations revealed that the theoretical energy barrier of the DAOR corresponds to a potential of 0.46 V. Depolarization experiments demonstrated a polarization gap of 230 mV for the DAOR, caused by mass-transfer limitations at the electrode interface. The outstanding catalytic performance of N-GS/CF results from nitrogen-doping-driven electron redistribution, which significantly enhances the oPD adsorption energy and stabilizes reaction intermediates through π-π stacking interactions (adsorption distance: 3.234 Å).