Effects of Different Synthesis Methods on the Photo Electrochemical Performance of CdS Nanoparticles

Abstract

In the present study, nanoparticles (NPs) of CdS were synthesized using three different approaches viz. solvothermal (CdS-s), hydrothermal (CdS-h) and chemical reduction (CdS-c) methods for analyzing the effects of these synthesis procedures on the electrocatalytic as well as photocatalytic activity of CdS NPs. The Optical properties of as prepared CdS NPs were characterized using UV-Visible spectroscopy and Photoluminescence spectroscopy. The optical energy gap calculated from Tauc’s relation using Kubelka-Munk function depicted a decrease in energy gap from CdS-s to CdS-c. This may be due to the formation of trap states in between HOMO and LUMO levels of CdS-c NPs. Photoluminescence (PL) spectroscopy also depicted quenching in emission peaks of CdS-c and CdS-h NPs, attributed to the inclusions of trap states. Structural characterization using X-Ray Diffraction (XRD) revealed the hexagonal structure of as synthesized CdS NPs. The size of CdS-c NPs calculated from Transmission Electron Microscopy (TEM) image using imageJ software came out to be 7.07 ± 0.66 nm. The enhanced electrocatalytic activity of CdS-c NP catalysts was investigated by performing electrochemical techniques: Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The CdS-c NPs exhibited highest photocurrent density of ~1.57 mA/cm² at 1.5 V (vs SHE) and lowest charge transfer resistance (R_ct) of 13 Ω.