Selective electrochemical H2O2 generation and activation on a bifunctional catalyst for heterogeneous electro-Fenton catalysis

[Display omitted] •A bifunctional catalyst was synthesized by carbonization of iron-based MOFs.•Pyridinic N and pyrrolic N were proposed to enhance H2O2 selectivity.•The strong interfacial interaction promoted electron transfer for Fe(III) reduction.•The bifunctional catalyst exhibited high mineralization ability and high stability. Heterogeneous electro-Fenton is attractive for pollutants removal, where H2O2 is in-situ generated and simultaneously activated to ·OH at the cathodic catalyst. However, the heterogeneous electro-Fenton efficiency is limited by low H2O2 production and slow Fe(II) regeneration, which can be improved by tuning oxygen reduction selectivity and facilitating electron transfer to Fe(III) centers. Herein, we designed a bifunctional catalyst with FeOx nanoparticles embedded into N-doped hierarchically porous carbon (FeOx/NHPC). The activity and selectivity for H2O2 production were improved by regulating N doping configurations and contents. The obtained FeOx/NHPC750 presented high catalytic activity for H2O2 production with a low overpotential of 190 mV and high H2O2 selectivity of 95%˜98% at -0.3 V to -0.8 V. The Fe(II) regeneration was enhanced by the strong interfacial interaction between FeOx and N-doped porous carbon support, which leaded to a rapid decomposition of H2O2 into ·OH. FeOx/NHPC750 exhibited excellent electro-Fenton performance for the degradation and mineralization of phenol, sulfamethoxazole, atrazine, rhodamine B and 2,4-dichlorophenol in neutral reaction solution. This study offered a new strategy to construct an efficient and durable bifunctional catalyst for heterogeneous electro-Fenton system for advanced treatment of refractory wastewater.