Close Space Sublimation Synthesis and Photoelectrochemical Efficiency of Vertical Tin Disulfide (SnS₂) Nanoflake Photoanodes

Tin disulfide (SnS₂) is a 2-dimensional material similar to MoS₂ and WS₂, with layers held together by weak Van der Waals forces. It has excellent optical and electronic properties that are suitable for a number of applications. Because of its high optical absorption coefficient, moderate band gap, and conduction and valence band edges that straddle the reduction and oxidation potentials of water, SnS₂ is a promising material for photoelectrochemical (PEC) water splitting. Several reports describing fundamental properties and synthesis methods have been published, however very few have successfully realized SnS₂-based photoanodes.
In this work, vertically aligned 2D SnS₂ nanoflakes were grown directly on FTO-glass substrates using a scalable close space sublimation (CSS) method. Scanning electron microscopy revealed that our nanoflakes contain vertical tapered structures with high aspect ratios and high density of exposed edges. They exhibit an indirect bandgap of 2.28eV and are excellent photoabsorbers. Photoanodes consisting of these nanoflakes were synthesized and measured in aqueous pH7 buffer containing Na₂SO₃ as hole-scavenger. Photocurrents up to 4.5mAcm^-2 were obtained at 1.23 V vs. RHE under simulated sunlight.