Concentration specific and tunable photoresponse of bismuth vanadate functionalized hexagonal ZnO nanocrystals based photoanodes for photoelectrochemical application

Abstract In the present work, dual layer BiVO 4 /ZnO photoanode is instigated for photo-electrochemical (PEC) water splitting applications. Two different photocatalytic layers ZnO and BiVO 4 , reduces charge carrier recombination and charge transfer resistance at photoanode/electrolyte junction. The concentration-specific, tunable and without ‘spike and overshoot’ features, photocurrent density response is originated by varying BiVO 4 concentration in the BiVO 4 /ZnO photoanode. The crystal structure of ZnO (hexagonal wurtzite structure) and BiVO 4 (monoclinic scheelite structure) is confirmed by X-ray diffraction studies. The band gap of BiVO 4 /ZnO was estimated to be ca. 2.42 eV through Kubler-Munk function F(R ∞ ) using diffuse reflectance spectroscopy. Electrochemical behavior of samples was analyzed with photocurrent measurements, electrochemical impedance, Mott-Schottky plots, bulk separation efficiency and surface transfer efficiency. The maximum photocurrent density of BiVO 4 /ZnO photoanode was found to be 2.3 times higher than pristine ZnO sample.0.038 M BiVO 4 /ZnO exhibited the highest separation efficiency of 72% and surface transfer efficiency of 64.7% at +1.23 V vs. RHE. Mott-Schottky study revealed the maximum charge carrier density in the same sample.