Efficient H2O2 generation and spontaneous OH conversion for in-situ phenol degradation on nitrogen-doped graphene: Pyrolysis temperature regulation and catalyst regeneration mechanism

[Display omitted] •Pyrolysis temperature of N-doped graphene on enhanced OH production was regulated.•A facile preparation of N-GE for high N content, H2O2 selectivity and pollutant removal.•Graphite N and pyridinic N conversions are important in ORR and OH conversion.•Mechanism of a simple regeneration process of N-GE in EAOPs was firstly clarified.•Pyridinic N-oxide to pyridinic N is critical to catalyst stability and sustainability. H2O2 is a green and valuable chemical that can be electrochemically synthesis from oxygen reduction, offering in-situ application for organic pollutants removal in environmental remediation. However, how to improve activity and further convert into powerful radicals is a still challenge. Herein, we show a facile and general approach to fabricate nitrogen-doped graphene (N-GE) catalyst via pyrolysis temperature regulation. The optimal N-GE at 400 °C exhibited the highest active N content (12.2 wt.%) and H2O2 selectivity (85.45 %) and spontaneous OH production (19.42 μM), achieving a high phenol degradation (93.58 %) at 180 min in neutral pH condition. Importantly, a simple catalyst regeneration method and mechanism was disclosed. It is proposed that the conversion of graphite N and pyridinic N in N-GE plays an important role in oxygen reduction reaction (ORR) and OH conversion, while the conversion of pyridinic N-oxide to pyridinic N is critical to catalyst stability and sustainability. This study provides a new insight into structure design of electro-catalyst about stability of nitrogen-doped carbon materials for efficient H2O2 generation and cost-effective pollutants removal.