High-Performance Phase-Pure SnS Photocathodes for Photoelectrochemical Water Splitting Obtained via Molecular Ink-Derived Seed-Assisted Growth of Nanoplates.
2020
Although
tin monosulfide (SnS) is one of the promising earth-abundant
semiconducting materials for photoelectrochemical water splitting,
the performance of SnS photocathodes remains poor. Herein, we report
a stepwise approach for the fabrication of highly efficient photocathodes
based on SnS nanoplates via elaborate modulation of molecular solutions.
It is demonstrated that phase-pure SnS nanoplates without detrimental
secondary phases (such as SnS2 and Sn2S3) can be readily obtained by adjusting the amounts of Sn and
S in the precursor solution. Additionally, the orientation of SnS
nanoplates is controlled by implementing different types of SnS seed
layers. The orientations of the SnS seed layers are changed according
to the molecular shapes of the Sn–S bonds in the molecular
solutions, depending on the relative nucleophilicity of the molecular
moieties formed by specific thiol–amine reactions. The molecular
Sn–S sheets in the seed ink was obtained by the reaction in
a solvent mixture of thiogylcolic acid and ethanolamine. By contrast,
the short Sn–S molecular rods result from the reaction in a
solvent mixture of 2-mercaptoethanol and ethylenediamine. Interestingly,
the relatively short rodlike morphology of the SnS seed induces the
growth of SnS nanostructures faceted by preferred (111) and (101)
planes, leading to fast charge transport. With the formation of a
proper band alignment with n-type CdS and TiO2, the preferred
(111)- and (101)-oriented SnS nanoplate-based photocathode exhibited
a photocurrent density of −19 mA cm–2 at
0 V versus a reversible hydrogen electrode, establishing a new benchmark
for SnS photocathodes.
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