Electrochemical and optical studies on photoactive BiVO4-TiO2/poly 3,4-ethylenedioxythiophene assemblies in gel electrolyte: Role of inorganic/organic interfaces in surface functionalization

Abstract

Inorganic/organic interface assemblies were created from poly 3,4-ethylenedioxythio­phene (PEDOT) interfaced with amorphous BiVO4 and with BiVO4-TiO2. Electrochemical cells-based thermoplastic gel electrolytes containing KI/I2 were used to study the photoelectrochemical behavior of the Inorganic/organic interface electrodes. Optical studies show that doping BiVO4 with TiO2 narrowed the optical band gap to allow more absorption in the visible region and increases solar energy conversion. Evidence for both direct and indirect band gaps was observed. Refractive index data indicates that BiVO4 and BiVO4/TiO2 obey the anomalous dispassion multiple-oscillator model. Chronoampero­metry of these assemblies shows the phenomena of dark current, which correlates to the presence of random electron/hole generation in the depletion layer. PEDOT enhances the photoactivity of BiVO4 only. Electrochemical impedance spectroscopy studies indicated that both kinetic and diffusional control at high and low frequencies, respectively. Furthermore, studies show that as frequency increases, the conductivity increases due to dispersion and charge carrier hopping. All photoactivity outcomes were reproducible.