Electrochemically Deposited Sb and In Doped Tin Sulfide (SnS) Photoelectrodes

Abstract

Semiconducting tin sulfide (SnS) was deposited electrochemically from electrolytes containing Sn and S precursors and conditions optimized to maximize its performance as a photoelectrode. Films composed of primarily orthorhombic SnS were electrodeposited on titanium substrates from electrolyte containing 20 mM SnSO 4 and 100 mM Na 2 S 2 O 3 at pH 2.5. For deposition a cathodic pulse of −1.25 V vs Ag/AgCl was applied for 2.75 s followed by a 0.25 s pulse of +0.25 V vs Ag/AgCl repeated for 30−45 min. The films were annealed in argon at 300°C for 3 h. The addition of SbCl 3 (<5%) to the electrolyte gave rise to doping of the SnS film with Sb which resulted in an increase in the photocurrent as well as a switch from p-to n-type semiconducting behavior in an acidified Na 2 S 2 O 3 electrolyte. Incorporation of p-type In into the films from addition of In(NO 3 ) 3 had a smaller effect on the measured photocurrent, and at higher precursor concentration (>5%) the dopants resulted in the formation of secondary phases of Sb and In oxides with reduction in the measured photocurrent. This doped SnS material could potentially be used in systems for the photoelectrochemical production of hydrogen and oxidation of organic wastewater. Density functional theory calculations supported the experimentally observed conductivity increase for photoelectrons as an Sb dopant induced curvature of the valence band. These calculations also provided an explanation to the previous experimental work where Sb doping was used to decrease the resistivity of SnS films. The combination of an automated electrodeposition of an earth abundant metal sulfide with the theoretical calculations to guide the synthesis is an exemplar of how to improve the efficiency of SnS-based solar energy conversion materials. ■ INTRODUCTIONThe economical capture and conversion of solar photons requires materials and structures that are inexpensive and efficient at converting solar photons to electricity or solar fuels. 1,2 A wide range of semiconducting materials, including metal oxides, phosphides, selenides, sulfides, tellurides, and amorphous and crystalline silicon, have been investigated with varying degrees of success. 3 When considering semiconductor materials for a direct solar energy harvesting, two important criteria are (1) the potential for high solar-to-electrical or solar-to-hydrogen conversion efficiency and (2) earth abundance and cost in bulk quantities of the corresponding material components. 3 In addition, it is desired to synthesize these materials using inexpensive and scalable techniques, such as electrodeposition.Certain metal sulfides satisfy both criteria as they have high theoretical solar energy conversion efficiencies (∼24%) and are present in large numbers of minerals. 4 Sulfide-based compound semiconductors have long been the subject of investigation for electronic and optical applications, including FeS 2 , Cu 2 S, Cu 2 ZnSnS 4 (CZTS), RuS 2 , and CuInS 2 . 5−7 Several of these, such as FeS 2 , Cu 2 S, Co, and Cu 2 ZnSnS 4 (CZTS), are comp...

Simple eco-friendly synthesis of the surfactant free SnS nanocrystal toward the photoelectrochemical cell application

“…It can be noticed that at −0.2 V vs. RHE the spikes flatten out, suggesting that the kinetic barriers have been solved 39 . High photocurrent of the cells is obtained that is comparable with other previously reported SnS systems 30 , 32 , 36 , 37 , 40 – 46 in the literature listed in Table 1 .

Figure 4 ( a ) Linear sweep voltammogram of the SnS nanocrystal under chopped illumination; ( b ) Linear sweep voltammogram of the bulk SnS under chopped illumination.

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“…Therefore, the processability of SnS makes it a perfect system in exploring new 2D feature 24 . Up to date, SnS nano sheets have been synthesized using various methods, for example: chemical bath deposition 25 , chemical vapor transport 26 , chemical vapor deposition (CVD) 27 , colloidal nanoparticle synthesis 28 – 31 , electrochemical deposition 32 , vacuum evaporation 33 , spray pyrolysis 34 , and dip deposition 35 . Among these SnS layers, the mono-layer nanostructured SnS photoanode has exhibited the high photocurrent density of 7 mA cm −2 , which was synthesized by chemical spray pyrolysis 36 .…”

Electrodeposition and Characterization of a Tin Sulfide‐Electrochemically Reduced Graphene Oxide Heterojunction

“…In fact, Figure shows that at a potential of −0.624 V (corresponding to a 0 V respect to the Reversible Hydrogen Electrode, RHE) the SnS photolelectrode exhibited a photocurrent of 37 μA cm −2 , whereas the SnS/ERGO heterojunction exhibited a photocurrent of 66 μA cm −2 , representing a significantly enhancement in its photoactivity (about 78 %). Photocurrent values that are similar or even better to those previously reported in the literature for different SnS architectures, i. e: 70 μA cm −2 (porous structure,), 10 μA cm −2 (thin films,) and 0.02 μA cm −2 (nanorods arrays,). Moreover, a stability test has been performed for the SnS/ERGO heterojunction photoelectrode, (see inset of Figure (b)).…”

Electronic structures of SnS and SnS2

“…As anode material for Li‐ion batteries, SnS exhibits a lower irreversible capacity loss at the first cycle than SnS 2 and interesting performances . Other applications of SnS concern photocatalytic and photoelectrochemical properties , hydrogen storage , supercapacitors , electronic devices and thermoelectricity .…”