Small molecular amine mediated synthesis of hydrophilic CdS nanorods and their photoelectrochemical water splitting performance

Photoelectrochemical (PEC) water splitting is a promising route for solar energy harvesting and storage, but it has been highly limited by the performance of the semiconductor photoelectrodes. Herein, we report a small molecular amine-mediated solvothermal method for synthesizing CdS nanorods. The obtained CdS nanorods are hydrophilic and can be easily dispersed in water. Furthermore, the small molecular amine, activating elemental sulfur and mediating the growth of CdS, all play a role similar to that of long-chain surfactant molecules in non-aqueous systems. Thus, the obtained CdS nanorods show uniform shape with monodispersed size, the length of which can be tuned by the sulfur dosage. In addition, the CdS nanorods show a broader light absorption than CdS nanoparticles. Their photoelectrochemical water splitting performances were then tested. Under light irradiation of lambda > 200 nm, the photocurrent density of CdS nanorods at -0.2 V bias potential (vs. Ag/AgCl) is found to be 25 times of that obtained with CdS nanoparticles. The present finding demonstrates that small amine molecules could be efficient mediators for the synthesis of hydrophilic sulfides with high quality. The simple synthesis method and the good photoelectrochemical properties illustrate the hydrophilic CdS nanorods are potential candidate for photoelectrochemical applications.