Chemical synthesis of orthorhombic Ag8SnS6/zinc oxide nanorods photoanodes for photoelectrochemical salt-water splitting

Orthorhombic Ag8SnS6/ZnO nanorods grown onto indium-tin-oxide conductive glass substrates were prepared using a simple chemical synthesis method for the application in photoelectrochemical salt-water splitting. For the deposition of ZnO nanorods on substrates, the concentrations of ammonium hydroxide in the solution bath were changed to obtain the pristine ZnO nanorods with good morphology for the growth of silver-tin-sulfide layer. Pristine ZnO nanorods prepared with concentration of 5.5 M for ammonium hydroxide in the reaction solution has the highest intensity of (0 0 2) crystal plane, which indicates that pristine ZnO nanorods sample has good morphology for the preparation of the Ag8SnS6 core/shell photoanode. From the results of X-ray diffraction patterns and energy-dispersive X-ray spectroscopy analysis for samples, with decreasing [Ag]/[Ag + Sn] molar ratio in the reaction solution, crystal phases of samples changed from Ag2S/SnS/ZnO, orthorhombic Ag8SnS6/ZnO to Ag8SnS6/SnS/ZnO mixing phases. The values of sample's energy band gap were located in the range of 1.36 similar to 1.79 eV. At the [Ag]/[Ag + Sn] molar ratio of 0.4 in the reaction solution, the maximum photoelectrochemical activity of 0.79 mA cm(-2) for samples was obtained with the external bias set at + 1.5 V vs. an Ag/AgCl electrode in 0.5 M NaCl aqueous solution. The photoelectrochemical activity of sample could remain at least 2000 s without any decay in the salt-water solution.

Automated summary

Orthorhombic Ag8SnS6/ZnO nanorods were successfully synthesized and applied for photoelectrochemical salt-water splitting with high activity and stability, achieving a maximum photocurrent density of 0.79 mA/cm(-2) at 1.5 V bias vs. Ag/AgCl electrode in 0.5 M NaCl solution, with the ability to maintain activity for at least 2000 seconds. The crystal phases and energy band gap values of the samples varied with the [Ag]/[Ag + Sn] molar ratio in the reaction solution.