Nanohybrids photocatalyst AuPd/g-C3N4 nanosheets to promote CH4 oxidation into methanol under mild conditions

Abstract

Methanol is a platform molecule at the petrochemical industry, used in the synthesis of several chemical feedstocks, besides its central role in several large-scale industrial processes, e.g. biodiesel synthesis by transesterification process. Currently, at the industry, methanol is produced mostly from syngas (CO + H2) at high temperatures and pressure, an expensive and energy-intensive process. The methane direct oxidation to methanol can be a more sustainable and cheaper alternative, object of several studies recently, once natural gás (mostly composed by CH4) is abundant and cheap. Hutchings et al. recently published in the journal Science promising results for CH4 oxidation to methanol, using bimetallic nanoparticles of Au/Pd as catalyst under mild conditions. According to Hutchings et al., the reaction occurs by a radical mechanism with methane activation and consequent reaction with hydrogen peroxide. The study also suggests the efficiency of the reaction is strongly affected by the H2O2 decomposition rate, being favoured by the better stabilization of H2O2 on the catalyst surface.2In this project, we propose the use of a polymeric semi-conductor carbon nitride (g-C3N4) as support for Au/Pd nanoparticles. The g-C3N4 are capable of generating H2O2 from water, oxygen, and light, preventing the addition of this undesirable reagent for large-scale use, due to its relatively high cost and associated risks. Furthermore, g-C3N4 are known to be able to stabilize H2O2 on its surface, may favouring the oxidation reaction of CH4 which still presents very low yield (<1%). Thus, we believe strongly that nanohybrids photocatalyst AuPd/g-C3N4 nanosheets are able to produce and stabilize H2O2 in situ and consequently favour the CH4 oxidation to methanol, leading to higher yields for this important reaction.