Surface Modification and Optimization of Semiconductor ns-TiO₂–WO₃ Admixed Photoelectrode in Regard to Solar Hydrogen Production

Abstract

To minimize the harmful effects of commercial energies like fossil fuel and nuclear energy on our environment, research is going on to find clean and renewable sources of energy. The main efforts of researchers nowadays is to harness solar energy for the production of clean hydrogen fuels by a photoelectrochemical (PEC) cell which represents a very attractive but challenging alternative. Some strategies have been developed to improve PEC performances of the photoelectrode materials, including doping for enhancing visible light absorption in the wide bandgap semiconductor or promoting charge transport in the narrow bandgap semiconductor, respectively. This chapter deals with the investigation on the optimization of ns-WO₃–TiO₂ admixed/Ti with respect to optimum photoelectrode area for semiconductor septum (SC-SEP) PEC solar cell. The motivation of the present work was to prepare an electrode having high-effective surface area and hence better quantum yield and improved PEC activity. Several attempts have been made to bring spectral response of TiO₂ into visible or near visible region. It is known that the spectral response of the TiO₂ films can be improved through admixing with appropriate oxides. The surface morphology, structural, and PEC characterization of the bare TiO₂ as well as the TiO₂ overlaid with WO₃ thin film admixtures have been investigated in relation to hydrogen production through SC-SEP PEC solar cell. The PEC response of ns-WO₃–TiO₂ photo electrodes for four different electrode areas has been measured to explore the effect of electrode area on the output power in a chemical fuel (i.e., H₂) produced by SC-SEP PEC cell. This was done for determining the electrode area for optimum electrical output and hydrogen production. The PEC cell having ns-WO₃–TiO₂ admixed/Ti photoanode of several geometric areas like 0.5, 1.0, 1.5, 2.0, and 2.5 cm² were fabricated and characterized. It has been found that the photoanode area corresponding to optimum electrical output and hydrogen production rate corresponds to 1.0 cm². The ns-WO₃–TiO₂ exhibited a high photocurrent and photovoltage of 15.6 mA cm^–2, 960 mV, respectively. The ns-WO₃–TiO₂ electrode exhibited a higher hydrogen gas evolution rate of 13.8 l h^–1 m⁻².