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

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.