Selective catalytic two-electron O2 reduction for onsite efficient oxidation reaction in heterogeneous electro-Fenton process

•Iron-copper embedded carbon aerogel (FeCuC) was a promising cathode for heterogeneous EF system.•Catalytic mechanism of ORR in heterogeneous electro-Fenton process was proposed.•Fe@Fe3C promotes ORR activity, Cu enhances the selectivity of 2e O2 reduction.•High TOC removal (88-99%) of many pollutants with FeCuC in 240 min was obtained.•Sanitary sewage were successively treated to meet the national discharge standard.

The selective two-electron oxygen reduction reaction (ORR) for an onsite Fenton oxidation reaction over an integrated cathode is a promising method for environmental restoration. Here, an economic iron-copper-embedded carbon aerogel (FeCuC) exhibited high ORR activity (half-wave potential of −0.19 V vs SCE). The electron transfer number (n) over FeCuC was 2.9. Indeed, Fe@Fe3C promoted the ORR activity, while Cu enhanced the selectivity of the two-electron ORR. Meanwhile, the simultaneous incorporation of Fe and Cu simultaneously facilitated the sequential Fenton oxidation induced by H2O2. The individual rate constants for ORR and the oxidation reaction successfully revealed the fact that the efficient Fenton oxidation reaction again promotes again the 2-electron O2 reduction pathway. The application of FeCuC as a cathode in the electro-Fenton (EF) process, involving both high ORR and high Fenton oxidation activities, exhibited efficient total organic carbon (TOC) removal (88-99%) in 240 min for dimethyl phthalate (DMP), imidacloprid (IMI), bisphenol A (BPA) and perfluorooctanoate (PFOA). Moreover, five types of sanitary sewage were successively treated to meet the national discharge standards (chemical oxygen demand (COD) < 50 mg L−1) with relatively low specific energy consumption (20-40 kW·h·(kgCOD)−1) using FeCuC in the heterogeneous EF process.