Visible-light sensitization of anodic tungsten oxide layers with CuWO4

Abstract

Anodic tungsten oxide is an attractive material for photoelectrochemical water splitting under solar irradiation, however due to several limitations, it absorbs only UV light and, therefore, one of the challenges is to transfer its photoresponse to the visible light region. In this paper, for the first time, it is proposed sensitization of anodic WO3 layers with copper tungstate by a wet impregnation method. The CuWO4–WO3 materials are obtained by immersion of anodic layers in a copper acetate solution and annealing at 500 °C in air atmosphere. As-received materials are characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), and Raman spectroscopy, Mott–Schottky measurements and photoelectrochemical (PEC) tests. Proposed visible-light sensitization with CuWO4 results in an enhanced photoelectrochemical response to visible light. Moreover, narrowing of the band gap (from 2.88 to 2.47 eV) with a prolonged impregnation time is also observed.