Fe2PO5-Encapsulated Reverse Energetic ZnO/Fe2O3 Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water

Graphical A passive catalyst? A Fe 2 O 3 shell was grown onto a ZnO core to protect the surface from corrosion and increase the charge-separation efficiency. PH 3 treatment onto the core–shell nanowire creates a Fe 2 PO 5 with dual functionality: a catalyst and passivating overlayer. Zinc oxide is regarded as a promising candidate for application in photoelectrochemical water oxidation due to its higher electron mobility. However, its instability under alkaline conditions limits its application in a practical setting. Herein, we demonstrate an easily achieved wet-chemical route to chemically stabilize ZnO nanowires (NWs) by protecting them with a thin layer Fe 2 O 3 shell. This shell, in which the thickness can be tuned by varying reaction times, forms an intact interface with ZnO NWs, thus protecting ZnO from corrosion in a basic solution. The reverse energetic heterojunction nanowires are subsequently activated by introducing an amorphous iron phosphate, which substantially suppressed surface recombination as a passivation layer and improved photoelectrochemical performance as a potential catalyst. Compared with pure ZnO NWs (0.4 mA cm −2 ), a maximal photocurrent of 1.0 mA cm −2 is achieved with ZnO/Fe 2 O 3 core–shell NWs and 2.3 mA cm −2 was achieved for the PH 3 -treated NWs at 1.23 V versus RHE. The PH 3 low-temperature treatment creates a dual function, passivation and catalyst layer (Fe 2 PO 5 ), examined by X-ray photoelectron spectroscopy, TEM, photoelectrochemical characterization, and impedance measurements. Such a nano-composition design offers great promise to improve the overall performance of the photoanode material.