High-Performance Phase-Pure SnS Photocathodes for Photoelectrochemical Water Splitting Obtained via Molecular Ink-Derived Seed-Assisted Growth of Nanoplates

Abstract

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 SnS 2 and Sn 2 S 3 ) 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 TiO 2 , the preferred (111)-and (101)-oriented SnS nanoplatebased 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.

Thiol‐Amine‐Based Solution Processing of Cu2S Thin Films for Photoelectrochemical Water Splitting

“…In addition, these alkyl polysulfides can react with metal cations, such as Sn 2+ , to form molecular clusters containing Sn−S bonds. [33] Thus, it is speculated that the thiolate anions in the Merc‐En mixture break some Cu‐S bonds in Cu 2 S bulk powder by nucleophilic attack, resulting in the formation of molecular Cu‐thiolates, which are soluble in the solvent. Murria et al.…”

“… [28] Upon spin‐coating of these inks onto a variety of substrates followed by a low‐temperature annealing procedure, the solid‐state crystalline phase can be recovered. This straightforward dissolution and recovery strategy has been successfully applied to prepare various phase‐pure high‐quality crystalline chalcogenide thin films, such as Sb 2 Se 3 ,[ 23 , 29 , 30 , 31 , 32 ] SnS,[ 25 , 33 ] and CIGS,[ 27 , 34 ] demonstrating the versatility of this cost‐effective and low‐energy consuming process.…”

Vapor Phase Synthesis of SnS Facilitated by Ligand-Driven “Launch Vehicle” Effect in Tin Precursors

“…The low dimensional platelets of SnS were found to be vertically oriented to the substrate surface, as clearly seen in Figure 8c. This morphological attribute offers a huge number of active sites of the layered SnS phase that consequently increases the catalytic behavior of as-deposit material potentially interesting for the application in photovoltaic systems [59]. To analyze the films further by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), parts of the film deposited on molybdenum substrate for 15 min at T = 350 • C were scratched off the substrate surface.…”

Engineering in SnS-Based Solar Cell for an Efficient Device with Nickel Oxide (NiO) as the Hole Transport Layer

“…Because with the increase in defect density, carrier recombination is increased. FF and PCE go on drastically downward which means that high defect density and series resistance [11,12].…”