Efficiency and stability aspects of CdS photoanode for solar hydrogen generation technology

Abstract

Photoelectrochemical (PEC) cell based technology is expected to be one of the easiest green technologies to harness and to convert available solar energy into hydrogen [1]. Among the known systems of GaAs, Si, GaP and CdS- Cadmium sulphide is one of the best suited PEC materials that display a balance between its efficiency and stability. It has capability to absorb the visible light photons (E∼1.5eV - 3eV), and displays the band- energetics that suits for water-splitting reaction (H2O→H2+O2), that ultimately is based on the electronic and optical structure of the sulphides. However, the photo-induced dissolution of CdS in an electrolyte during its photo-illumination in PEC cell is its major drawback [2]. Though arsenides and phosphides show higher efficiency however CdS exhibits significant stability. In contrast though TiO2/ ZnO show good stability but CdS displays good optical response towards visible light photons as compared null response of titanate like systems. This necessitates one to identify the practical way to inhibit the photocorrosion in case of CdS photoanodes which is mainly facilitated due to interaction of photogenerated holes with CdS lattice. In past, Pt/ RuO2/ Ru modified CdS surface were found to control the unwanted photocorrosion [3]. Commercially, usage of such materials is un-economic option for any technological usage. The present work discusses that with advent of present day new synthetic routes how the dynamics of photo generated holes and electrons can be controlled to improve the stability and efficiency of the sulphide photoanodes, which in turn shows an an improvement in the performance and stability of the PEC cell for desirable technological applications.