Enhanced Photoelectrocatalytic Activities for CH₃ OH-to-HCHO Conversion on Fe₂ O₃ /MoO₃ : Fe-O-Mo Covalency Dominates the Intrinsic Activity

The catalytic conversion of alcohols under mild conditions is a great challenge because it is constrained by low selectivity and low activity. Herein, we demonstrate a hollow nanotube Fe₂ O₃ /MoO₃ heterojunction (FeMo-2) for the photoelectrocatalytic conversion of small-molecule alcohols. Experimental and theoretical analyses reveal that the optical carrier transfer rate is enhanced by constructing interfacial internal electric fields and Fe-O-Mo charge transfer channels. For the formox process, heterojunctions possess superior HCHO-selective reaction paths and free energy transitions, optimizing the selectivity of HCHO and enhancing the reactivity. FeMo-2 shows a greatly improved performance compared to single Fe₂ O₃ ; the photocurrent density of FeMo-2 reaches 0.66 mA cm^-2 , which is 3.88 times that of Fe₂ O₃ (0.17 mA cm^-2 ), and the Faraday efficiency of the CH₃ OH-to-HCHO conversion is 95.7 %. This work may deepen our understanding of interfacial charge separation and has potential for the production of HCHO and for conversion reactions of other small-molecule alcohols at cryogenic temperatures.