H<sub>2</sub> O<sub>2</sub> as a well-known efficient oxidant is widely used in the chemical industry mainly because of its homolytic cleavage into <sup>.</sup> OH (stronger oxidant), but this reaction always competes with O<sub>2</sub> generation resulting in H<sub>2</sub> O<sub>2</sub> waste. Here, we fabricate heterogeneous Fenton-type Fe-based catalysts containing Fe-N<sub>x</sub> sites and Fe/Fe<sub>3</sub> C nanoparticles as a model to study this competition. Fe-N<sub>x</sub> in the low spin state provides the active site for <sup>.</sup> OH generation. Fe/Fe<sub>3</sub> C, in particular Fe<sub>3</sub> C, promotes Fe-N<sub>x</sub> sites for the homolytic cleavages of H<sub>2</sub> O<sub>2</sub> into <sup>.</sup> OH, but Fe/Fe<sub>3</sub> C nanoparticles (Fe<sup>0</sup> as the main component) with more electrons are prone to the undesired O<sub>2</sub> generation. With a catalyst benefiting from finely tuned active sites, 18 % conversion rate for the selective oxidation of methane was achieved with about 96 % selectivity for liquid oxygenates (formic acid selectivity over 90 %). Importantly, O<sub>2</sub> generation was suppressed 68 %. This work provides guidance for the efficient utilization of H<sub>2</sub> O<sub>2</sub> in the chemical industry.