Nitrogen (N) and nitrogen/sulphur (N/S) co-doped graphene aerogels were synthesized by hydrothermal method using graphene oxide and urea or thiourea as precursors following a freezing-drying process. The determination of the number of the electrons involved in the mechanism of electro-reduction of oxygen (ORR) in alkaline medium was assessed. The mechanism of 4e(-) was obtained with N/S-doped graphene aerogels showing good electrocatalytic behavior and larger kinetic current densities. The 2e(-) ORR process (involving in situ H2O2 generation) was mainly obtained using N-doped graphene aerogels and it was related to the content of N functionalities as well as to the porous texture of the samples. Carbon-magnetic catalyst was synthesized to promote the decomposition of H2O2 to HO for the degradation of acetaminophen (ACE) in heterogeneous electro-Fenton (EF) process. The highest pollutant removal (71.0%) and mineralization (51.6%) were obtained with N-doped materials and carbon-Fe3O4 catalyst, showing good stability and low iron leaching (0.33 mg L-1). (C) 2019 Elsevier Inc. All rights