Electrosprayed BiVO4 nanopillars coated with atomic-layer-deposited ZnO/TiO2 as highly efficient photoanodes for solar water splitting

Abstract

We report the fabrication and the performance in photoelectrochemical water splitting of thin films of electrostatically sprayed nanotextured bismuth vanadate (BiVO4) pillars coated with thin ZnO/TiO2 passivation layers formed by atomic layer deposition. The thin ZnO and TiO2 layers deposited on the BiVO4 nanopillars formed a heterostructure that promoted electron-hole separation and the migration of electrons toward the ITO substrate. The photocurrent density (PCD) of the ZnO/TiO2 coated BiVO4 was 2.5 times higher (2.25 mA/cm(2) at 1.2 V (versus Ag/AgCl)) than that of pristine BiVO4 (0.9 mA/cm(2) at 1.2 V (versus Ag/AgCl)). We present incident/absorbed photon-to-current efficiency and electrochemical impedance measurements confirming that this improvement is a result of the heterojunction produced by the conformal ZnO/TiO2 coating and discuss the mechanism of this dramatic enhancement of PCD.