In situ photoemission from semiconducting WO 3 electrodes

Abstract

Both anodic and cathodic photocurrents have been observed from illuminated WO 3 electrodes and their dependences on electrode potential and incident photon energy have been explored. With the semiconductor/electrolyte junction biased into accumulation, anodic photocurrents are observed with a threshold equal to the band gap of WO 3 and independent of potential. As the potential is made more negative, the shape of the spectral response curve changes and at −0.6 V (SCE) the photocurrent changes sign. This effect is reversible and shows hysteresis. At slightly more positive potentials interference between anodic and cathodic photocurrents is observed. The hysteresis and change in color of the electrode suggests growth of a H x WO 3 layer on the surface and electron emission from this layer. The threshold for electron emission shifts linearly with potential and agrees with the threshold observed for electron emission from metals. The electron emission from H x WO 3 shows structure in the spectral response.