Shifting electrochemical oxygen reduction towards 2e– pathway to hydrogen peroxide (H2O2), instead of the traditional 4e– to water, becomes increasingly important as a green method for H2O2 generation. Here, through a flexible control of oxygen reduction pathways on different transition metal single atom coordination in carbon nanotube, we discovered Fe-C-O as an efficient H2O2 catalyst, with an unprecedented onset of 0.822 V versus reversible hydrogen electrode in 0.1 M KOH to deliver 0.1 mA cm−2 H2O2 current, and a high H2O2 selectivity of above 95% in both alkaline and neutral pH. A wide range tuning of 2e–/4e– ORR pathways was achieved via different metal centers or neighboring metalloid coordination. Density functional theory calculations indicate that the Fe-C-O motifs, in a sharp contrast to the well-known Fe-C-N for 4e–, are responsible for the H2O2 pathway. This iron single atom catalyst demonstrated an effective water disinfection as a representative application. Hydrogen peroxide can be produced alternatively using green inputs such as air, water, and sunlight but this requires a selective catalyst. Here the authors report an iron single atom catalyst that can convert oxygen into hydrogen peroxide with a selectivity of above 95% in both alkaline and neutral pH.