Sacrificial Template Synthesis of Copper Tungstate: Influence of Preparing Conditions on Morphology and Photoactivity

Morphology-controlled synthesis of ternary transition metal oxides is very important for their application in many fields. As a typical n-type semiconductor ternary oxide, CuWO4 finds application in solar water splitting as a photoanode material. In this work, we successfully prepared the CuWO4 nanoflakes (NFs), nanoneedles (NNs) and nanoparticles (NPs) films via a thermal solid-state reaction using different WO3 as sacrificial templates. We systematically investigated the effect of the morphology, size, and crystal type of the WO3 templates on the resulting CuWO4. We found that the morphology and size of WO3 templates and the reaction temperature were crucial factors that dominated the formation and morphology of CuWO4. The well-crystallized CuWO4 NFs and NPs were obtained at 550 degrees C, whereas, the crystalline CuWO4 NNs could be obtained at a much lower temperature of 475 degrees C. All the obtained CuWO4 samples exhibited activity and good stability for photoelectrochemical (PEC) water oxidation. Among the CuWO4 samples, the NFs exhibited the highest activity, which was attributed to (1) the high light absorption efficiency obtained from the perpendicularly oriented NF structure and (2) the large electron density. This work reveals the dependence of morphology, crystallinity, and photoactivity of CuWO4 on the preparation conditions during sacrificial template synthesis.