Photoelectrochemical salt water splitting using ternary silver–tin–selenide photoelectrodes

Abstract

Ternary AgSnSe2 and Ag8SnSe6 semiconductor photoelectrodes are prepared on various substrates via the selenization of thermally evaporation of silver–tin metal precursors. The structural, optical and electrical properties of ternary AgSnSe2 and Ag8SnSe6 samples are investigated as a function of the [Ag]/[Ag + Sn] molar ratio in the metal precursors. X-ray diffraction patterns of samples show that the phases of samples change from cubic AgSnSe2 to cubic Ag8SnSe6 phase at a selenization temperature of 410 °C when the molar ratio of [Ag]/[Ag + Sn] in silver–tin metal precursors increase from 0.51 to 0.68. The images obtained from a field-emission scanning electron microscopy show that the surface microstructures of samples change from plate-like microstructures with some pinholes to polygonal microstructures with increasing [Ag]/[Ag + Sn] molar ratios in samples. The energy bang gaps, carrier concentrations and mobilities of the samples are in the ranges of 0.86–1.19 eV, 1.27 × 1011–2.39 × 1012 cm−3 and 238–655 cm2 V−1 s−1, respectively. The highest photo-enhanced current densities of the samples in aqueous Na2S + K2SO3 and NaCl solutions are 3.34 and 0.61 mA cm−2 at an applied voltage of 0 and + 0.4 V vs. an Ag/AgCl electrode under 100 mW cm−2 light illumination from a Xe lamp source, respectively.