Self-Assembled Urchin-Like CuWO₄/WO₃ Heterojunction Nanoarrays as Photoanodes for Photoelectrochemical Water Splitting

With attractive visible-light response and chemical stability, CuWO₄ has emerged to be a promising candidate as a photoanode for photoelectrochemical (PEC) water oxidation. In this work, we report a one-step hydrothermal method to prepare CuWO₄-based films directly grown on a conductive glass substrate from a stable precursor solution. By controlling the reaction duration, CuWO₄/WO₃ heterojunctions with urchin-like nanoarray morphology are obtained. The CuWO₄/WO₃ film obtained with an optimized hydrothermal reaction time exhibits an onset potential of 0.6 V and a photocurrent density of 0.48 mA cm⁻² at 1.23 V vs. RHE, which is almost five times that of bare CuWO₄. The superior structure of the urchin-like array with large surface area, optimizing film thickness for adequate light absorption and formation of heterojunctions for efficient charge separation conjointly, contributes to the improved performance as well as robust stability.