WO₃/W:BiVO₄/BiVO₄ graded photoabsorber electrode for enhanced photoelectrocatalytic solar light driven water oxidation

We demonstrate the dual advantages of graded photoabsorbers in mesoporous metal oxide-based hetero interfacial photoanodes in improving photogenerated charge carrier (e^-/h⁺) separation for the solar light-driven water-oxidation process. The pre-deposition of sol-gel-derived, tungsten-doped bismuth vanadate (W:BiVO₄) onto a primary BiVO₄ water oxidation layer forms graded interfaces, which facilitate charge transfer from the primary photoabsorber to the charge transport layer, thereby superseding the thickness-controlled charge recombination at the BiVO₄ water oxidation catalyst. As a result, the WO₃/BiVO₄ hetero photoanode containing the photoactive W:BiVO₄ interfacial layer showed 130% higher photocurrent than that of the interfacial layer-free hetero photoelectrode owing to the enhanced charge separation led water oxidation process.