Photoanode/Electrolyte Interface Modification for Efficient Hydrogen Evolution in CuSnS Dots-Sensitized Solar PEC Cells.

It is proven through transmission electron microscope (TEM) analysis that solar sensitizer CuSnS (CTS) dots prepared via the hot-injection route are nonspherical, polyhedral nanocrystals with the size of ∼11 nm. CTS dots were deposited into a porous TiO layer to form CTS/TiO, an effective type II heterojunction in photoanodes. The electronic and energy band structures of TiO and CTS were studied by the plane-wave ultrasoft pseudopotential method based on density functional theory (DFT) and verified by ultraviolet-visible (UV-vis) spectroscopy. UV-vis and Photoluminescence (PL) spectra show that the CTS/TiO photoanode exhibits wider visible-light absorption as well as lower charge recombination. ZnS quantum dots (QDs) deposited on the CTS/TiO photoanode through the in situ successive ion layer adsorption and reaction (SILAR) method as the passivation layer can inhibit the reverse carrier transfer and increase the photocurrent density by building a potential barrier on the CTS/TiO photoanode and electrolyte interface. When 2-layer ZnS QDs are deposited, the maximum photocurrent density of the photoelectrochemical (PEC) cell composed of a ZnS/CTS/TiO photoanode, a Pt counter electrode, and NaSO solution electrolyte is 8.43 mA/cm and the maximum applied bias photon-to-current efficiency (ABPE) is 7.79%. Under 1 sun (AM 1.5, 100 mW/cm) with 0.6 V bias, its hydrogen yield reached 125.7 μmol·cm after 4 h with the rate of 31.4 μmol·cm·h in contrast to the yield of 107.86 μmol·cm with the rate of 21.3 μmol·cm·h for the CTS/TiO photoanode.