Activating C–H Bonds by Tuning Fe Sites and an Interfacial Effect for Enhanced Methanol Oxidation

Abstract

The interaction mechanism between the reacting species and the active site of α-Fe₂ O₃ -based photoanodes in photoelectrochemical methanol conversion reaction is still ambiguous. Herein, a simple two-step strategy is demonstrated to fabricate a porous α-Fe₂ O₃ /CoFe₂ O₄ heterojunction for the methanol conversion reaction. The influence of the electronic structure of active site and interfacial effect on the reaction are investigated by constructing two different FeO₆ octahedral configurations and heterogeneous structures. The optimal sample ZnFeCo-2 affords high photocurrent density of 1.17 mA cm^-2 at 0.5 V vs Ag/AgCl, which is 3.2 times than that of ZnFe (0.37 mA cm^-2 ). Meanwhile, the ZnFeCo-2 also exhibits 97.8% Faraday efficiency of CH₃ OH to HCHO, and long-term stability over 40 h. Furthermore, density functional theory calculations reveal that the heterostructured α-Fe₂ O₃ /CoFe₂ O₄ with favorable electron transfer effectively lowers methanol adsorption, C-H bond activation, and HCHO desorption energy relative to the pristine α-Fe₂ O₃ , resulting in excellent methanol conversion efficiency.