Photo-enhanced salt-water splitting using orthorhombic Ag8SnS6 photoelectrodes in photoelectrochemical cells

•Ag8SnS6 samples were prepared using sulfurization of Ag–Sn metal precursors.•Orthorhombic Ag8SnS6 can be obtained using three-stage sulfurization process.•Sample with [Ag]/[Ag+Sn] ratio of 0.88 has the maximum PEC performance.•The maximum PEC performance of samples in salt-water is 2.5 mA cm−2.

Orthorhombic Ag8SnS6 photoelectrodes are prepared on various substrates via reactive sulfurization using the radio-frequency magnetron sputtering of silver-tin metal precursors. Evaluations of the photoelectrochemical performances of Ag8SnS6 photoelectrodes with various levels of silver content are carried out in various aqueous solutions. X-ray diffraction patterns and Hall measurements of samples after a three-stage sulfurization process show that all samples are the pure orthorhombic Ag8SnS6 phase with n-type conductivity. The energy band gaps, carrier concentrations, and mobilities of samples on glass substrates are 1.31–1.33 eV, 7.07 × 1011–8.52 × 1012 cm−3, and 74.9–368 cm2 V−1 s−1, respectively, depending on the [Ag]/[Ag+Sn] molar ratio in samples. The highest photoelectrochemical performances of orthorhombic Ag8SnS6 photoelectrodes in aqueous 0.35 M Na2S + 0.25 M K2SO3 and 0.5 M NaCl solutions are respectively 2.09 and 2.5 mA cm−2 at an applied voltages of 0.9 and 1.23 V vs. a reversible hydrogen electrode under light irradiation with a light intensity of 100 mW cm−2 from a 300-W Xe lamp.

Graphical abstractOrthorhombic Ag8SnS6 photoelectrodes were prepared using three-stage sulfurization of radio-frequency magnetron sputtering of Ag–Sn metal precursors. The highest photoelectrochemical performance of orthorhombic Ag8SnS6 photoelectrodes in the aqueous 0.5 M NaCl solutions was 2.5 mA cm−2 at an applied voltage of 1.23 V vs. an Ag/AgCl electrode under light irradiation from a 300 W Xe lamp.Figure optionsDownload full-size imageDownload as PowerPoint slide