Vertically Aligned 2D SnS₂/FTO Photoanode with Robust Light Trapping and Photoelectric Conversion Capacities for Photoelectrochemical Water Splitting

Two-dimensional (2D) materials with strong light absorption and high charge carrier transfer kinetics have drawn much attention in photoelectrochemical (PEC) water splitting. However, the efficient photoelectric conversion performances of monomer 2D materials are a crucial basis for developing novel designs of composite photoelectrodes. Herein, high-quality vertically aligned 2D SnS₂/FTO photoelectrodes were synthesized via a modified chemical vapor deposition (CVD) method, where the FTO substrates were slantedly placed downstream. Particularly, a 2D SnS₂/FTO photoanode synthesized at <i>d</i> = 8 cm and <i>f</i> = 70 sccm exhibits excellent transient photocurrent densities of about 4.6 (full spectrum) and 3.6 (λ ≥ 420 nm) mA cm^-2 at 1.23 V versus RHE under light illumination (AM 1.5G, 100 mW cm^-2) conditions. Besides, the optimal η_IPCE, η_APCE, and η_sep efficiencies are approximately 20.64, 21.41, and 77.1%, respectively, which are also significantly improved compared to those of other 2D SnS₂/FTO photoelectrodes. In the 2D SnS₂/FTO PEC water splitting system, the maximal theoretical evolution rates of hydrogen and oxygen are approximately 5.83 and 2.91 μmol cm^-2 h^-1, respectively, according to photocurrent density. The effective photoelectric properties of the 2D SnS₂/FTO photoanode are mainly attributed to the light trapping structure and high crystallinity of 2D SnS₂ nanosheets, which greatly promote incident photon harvesting, provide abundant reflecting pathways, and cooperate with rapid charge carrier transfer kinetics, thereby obviously enhancing photoelectric conversion capacity and oxidation dynamics rates for PEC water splitting. This work supplies the important basis and values for designing and constructing highly efficient SnS₂-based heterojunction photoelectrodes, which are conducive to developing more practical applications, such as optoelectronic devices, water splitting, wastewater treatment, pollutant degradation, and so on.