Supplementary Information

Full text

Supporting Information
Unlocking the potential of SnS2: Transition metal catalyzed
utilization of reversible conversion and alloying reactions
Zhi Xiang Huang,1,2 Ye Wang,1 Bo Liu,1 Dezhi Kong,1 Jun Zhang,3 Tupei Chen,3 Hui Ying
Yang1
1. Pillar of Engineering Product Development, Singapore University of Technology and
Design, 8 Somapah Road, Singapore 487372, Singapore
2. Airbus Group Innovations Singapore, 110 Seletar Aerospace View, Singapore 797562
3. School of Electrical and Electronic Engineering, Nanyang Technological University,
Singapore 639798, Singapore
1 Corresponding author. Tel.: +65 6303 6663; Fax: +65 6779 5161.
E-mail address: yanghuiying@sutd.edu.sg (H. Y. Yang)

Figure S1 SEM images of SnS2/3DG synthesized with and without surfactants (SDS or
CTAB). (a) no surfactant, CTAB:SnCl4 in ratios of (b) 1:10, (c) 1:100, and SDS:SnCl4 in
ratios of (d) 1:10, (e) 1:30, (f) 1:100. SEM images of the different samples indicating the
height of the SnS2 nanosheets, (g) no surfactant, (h) CTAB:SnCl4 = 1:10, (i) SDS:SnCl4 =
1:100.
Effects of Surfactant on SnS2 growth on 3DG
In a previous work, we reported the synthesis of SnS2/3DG which was prepared via
solvothermal of SnCl4 and TAA on 3DG (Figure S1a). In an effort to improve the mass
loading of SnS2 on 3DG prior to growth of catalyst (MoS2), surfactants which are known to
affect the size and morphology of the synthesized product, were used to refine SnS2/3DG.
Two surfactants, namely cationic Cetyltrimethylammonium bromide (CTAB) and anionic
sodium dodecyl sulfate (SDS), were attempted. The effects of the surfactants were observed
by varying the molar ratio of surfactant to tin precursor (SnCl4). Figure S1b and c shows the
effects of CTAB:SnCl4 in molar ratios of 1:10 and 1:100. At high concentrations of CTAB,
there was a significant size reduction of SnS2 nanosheet (~300 nm) (Figure S1b). However,
during the synthesis of SnS2 on 3DG, a competing reaction was occurring which can be
observed by the severe agglomeration of SnS2 (inset of Figure S1b). At lower concentrations
of CTAB, size reduction of SnS2 nanosheet was less significant (~600-800 nm) (Figure S1b).
On the other hand, at high concentrations of SDS, greater size reduction of SnS2 nanosheet

(~200-250 nm) was observed (Figure S1d). Furthermore, an increased density of SnS2
nanosheet can also be clearly seen. However, similar to the case of CTAB, severe
agglomeration of SnS2 was also observed (inset of Figure S1d). At lower concentrations of
SDS, agglomeration of SnS2 was still present albeit less severe (Figure S1e). The reduced
agglomeration was accompanied by a further size reduction of SnS2 nanosheet (~100-150
nm). This could be attributed to the improved utilization of surfactants towards size reduction
of SnS2 and growth on 3DG. At low concentrations of SDS, SnS2 nanosheets were about
~200nm. In terms of nanosheet height, the surfactants capped the growth to 250 nm and 200
nm when CTAB and SDS was added, respectively. The width of the nanosheets remained
fairly constant at 10 – 20 nm. Amongst the different surfactants and concentrations, SDS at
low concentrations (SDS:SnCl4, 1:100) was selected as only a small amount was required to
successfully reduce the size of SnS2 nanosheets. Furthermore, the improved packing density
of SnS2 left sufficient gap between each nanosheet to facilitate the subsequent growth of
MoS2. Owing to the increased density of SnS2 on 3DG, active mass loading of SnS2 was
increase by ~20%.

Figure S2 Photograph and low magnification SEM image of as-prepared materials, top:
pristine 3DG after Ni-etch, middle: SnS2/3DG, bottom: SnS2/MoS2/3DG. The etched 3DG are
precut into regular 1.2mm diameter discs to facilitate the direct use of the final products in
coin-cell as electrodes.
3DG
SnS2/3DG
SnS2/MoS2/3DG

Figure S3 TGA curves of SnS2/MoS2/3DG, SnS2/3DG, and as-prepared 3DG.
Calculation of SnS2/MoS2/3DG composition
As described in the main text and shown in Figure 3C, TGA is used to derive the composition
of the as-synthesized SnS2/MoS2/3DG. In order to obtain accurate mass loading of MoS2 and
SnS2 on 3DG, a batch of 3DG with identical mass was used to synthesize SnS2/3DG. This
process was repeated for the growth of MoS2 on SnS2/3DG. Thereafter, the as-synthesized
SnS2/MoS2/3DG and SnS2/3DG was crushed into powder form and used directly for TGA
analysis. In this manner, the weight difference between SnS2/MoS2/3DG and SnS2/3DG arises
solely from MoS2. As SnS2 and MoS2 oxidizes in air at the same temperature range 200 to
500 oC, it is reasonable to assume that any additional weight loss is due to the oxidation of
MoS2. After accounting for the loss of weight due to moisture (~5 %), the weight loss due to
oxidation of SnS2 in SnS2/3DG and SnS2 and MoS2 in SnS2/MoS2/3DG was ~12 % and ~15
% respectively. This indicates that the weight loss due to MoS2 is ~3 %. In both samples,
weight loss due to the combustion of 3DG is ~ 33 %. Therefore, the mass composition of
SnS2/3DG is SnS2 : 3DG = 0.67 : 0.33 while that of SnS2/MoS2/3DG is SnS2 : MoS2 : 3DG =
0.65 : 0.03 : 0. 32.

Figure S4 High resolution XPS spectra of C 1s

Figure S5 CV curve of SnS2/3DG electrode in the first 3 cycles at a scan rate of 0.1 mV s-1 in
a potential range of 0.01 – 3.0 V vs. Li/Li+.

Figure S6 SEM images of as-synthesized control samples (a) SnS2 and (b) SnS2/MoS2 with
inset showing high magnification. Electrochemical performance of control samples SnS2 and
SnS2/MoS2. CV curve of (c) SnS2/MoS2 and (d) SnS2 electrode in the first 3 cycles at a scan
rate of 0.1 mV s-1 in a potential range of 0.01 – 3.0 V vs. Li/Li+. (e) Galvanostatic
discharge/charge curves of SnS2/MoS2 and SnS2 electrode for the first cycle at current density
of 50 mA g-1. (f) Rate capabilities of the SnS2/MoS2 and SnS2 electrode.

Table S1
Fitting results of the EIS curves in Fig 6 using the equivalent circuit
Sample Re(Ω) R(sf+ct)(Ω)
SnS2/MoS2/3DG 1.29 33.65
SnS2/3DG 2.85 64.67

Figure S7 HRTEM image of post cycled SnS2/MoS2/3DG electrode in full discharge (0.01 V)
state.