Herein, we investigate the morphological effect of WO3 interfacial blocking layer on the PEC performance of WO3 nanoflakes grown on fluorine-doped tin oxide (FTO) glass as a model photoanode system. We found that the mesoporous WO3 interfacial blocking layer is much more effective than the random WO3 nanoparticle interfacial layer in reducing the interfacial recombination. With the mesoporous interfacial blocking layer, the photocurrent density of WO3 photoanode reaches 2.6 mA cm(-2) at 1.23 V vs RHE. This PEC system in 1 M H2SO4 solution produces high-value added peroxydisulfate (S2O82-) and hydrogen efficiently at over similar to 95% faradaic efficiency. (C) 2017 Elsevier Ltd. All rights reserved.