Fe/Fe₃C Boosts H₂O₂ Utilization for Methane Conversion Overwhelming O₂ Generation

Abstract

H₂ O₂ as a well-known efficient oxidant is widely used in the chemical industry mainly because of its homolytic cleavage into ^. OH (stronger oxidant), but this reaction always competes with O₂ generation resulting in H₂ O₂ waste. Here, we fabricate heterogeneous Fenton-type Fe-based catalysts containing Fe-N_x sites and Fe/Fe₃ C nanoparticles as a model to study this competition. Fe-N_x in the low spin state provides the active site for ^. OH generation. Fe/Fe₃ C, in particular Fe₃ C, promotes Fe-N_x sites for the homolytic cleavages of H₂ O₂ into ^. OH, but Fe/Fe₃ C nanoparticles (Fe⁰ as the main component) with more electrons are prone to the undesired O₂ 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, O₂ generation was suppressed 68 %. This work provides guidance for the efficient utilization of H₂ O₂ in the chemical industry.