Oxygen-deficient non-crystalline tungsten oxide thin films for solar-driven water oxidation

The preparation of metal oxide semiconductors in non-stoichiometric (oxygen-deficient) form can lead to significant change in their optical and electronic properties, and hence affect the photoelectrochemical performance. The controlled introduction of oxygen vacancy can improve the charge separation and increases the charge carrier density, which can significantly contribute to the enhancement of photoelectrocatalytic activity. Herein, we report fabrication of non-crystalline tungsten oxide films from metallic tungsten target using DC reactive sputtering technique. The oxygen flow rate was regulated to control the composition, structure and morphology of the films. The as-prepared films are amorphous in nature with distinct surface morphology and optical properties. The presence of oxygen vacancies were confirmed by the surface analysis. The non-stoichiometric films were evaluated for PEC performance by monitoring the water oxidation reaction under the UV–visible radiation. The findings reveal a correlation between photoelectrocatalytic activity, optical band gap, morphology, and, more importantly, oxygen content of the films.