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.