Interfacial engineering of CuWO4/WO3 thin films precisely fabricated by ultrasonic spray pyrolysis for improved solar water splitting

Abstract

Herein, we proposed the interfacial engineering of CuWO₄/WO₃ thin film to improve the photoelectrochemical (PEC) performance for solar water splitting. Our theoretical calculation reveals the significantly accelerated charge separation in CuWO₄/WO₃ heterojunction due to an in situ formed built-in electric field. Accordingly, an efficient ultrasonic spray pyrolysis technique was developed to readily fabricate the heterostructural CuWO₄/WO₃ thin films on FTO glass substrates with accurately tunable thickness and composition. The resultant CuWO₄/WO₃ photoanode with an optimized CuWO₄/WO₃ composition (1 : 1) and thickness (∼4.0 μm) shows a high and stable photocurrent density of 0.66 mA cm⁻² (1.23 V vs. RHE) under AM 1.5 G illumination, which is ∼15 times higher than that of the CuWO₄ thin films (0.042 mA cm⁻²). The significantly enhanced light absorption and accelerated photoexcited charge separation and transfer enabled by the CuWO₄/WO₃ heterojunction are deemed to largely account for the highly improved PEC performance of the CuWO₄/WO₃ film for solar water splitting.