Synergistic effect of atomic layer deposition-assisted cocatalyst and crystal facet engineering in SnS₂ nanosheet for solar water oxidation

The severe bulk recombination and sluggish oxygen evolution reaction (OER) dynamics of photoanodes severely restrict the application of photoelectrochemical (PEC) devices. To solve these two problems, crystallographic facet orientation and cocatalyst emergence with a high-quality photoanode/cocatalyst interface were realized through an air annealing-assisted strategy to treat atomic layer deposition (ALD)-modified SnS₂ nanosheet arrays. Based on experimental observations and theoretical calculations, the reduced (001) crystal facet of SnS₂ decreases the recombination of photogenerated carriers in the bulk and improves the carrier separation of the photoanode. Moreover, the unexpectedly formed ZnTiO_xS_y film decreases the overpotential of the surface OER, reduces interface recombination, and extends the carrier lifetime. These synergistic effects lead to significantly enhanced PEC performance, with a high photocurrent density of 1.97 mA cm^-2 at 1.23 V vs. reversible hydrogen electrode (RHE) and a low onset potential of 0.21 V vs. RHE, which are superior to reported mostly SnS₂-based photoanodes.