The degradation of pesticide diuron has been explored by photoelectrocatalysis (PEC) under visible light illumination using two different WO3 nanostructures, obtained by anodization of tungsten. The highest degradation efficiency (73%) was obtained for WO3 nanosheets synthesized in the presence of small amounts of hydrogen peroxide (0.05 M). For that nanostructure, the kinetic coefficient for diuron degradation was 133% higher than that for the other nanostructure (anodized in the presence of fluoride anions). These results have been explained by taking into account the different architecture and dimensions of the two WO3 nanostructures under study. •Two different WO3 nanostructures were fabricated by anodization in two electrolytes.•Photocurrent densities were higher for WO3 nanosheets formed in the H2O2 solution.•Diuron photoelectrodegradation proceeded through the cleavage of the aromatic ring.•Degradation efficiencies of 73% and mineralization degrees of 50% were obtained.