Enhanced N2affinity of 1T-MoS2with a unique pseudo-six-membered ring consisting of N-Li-S-Mo-S-Mo for high ambient ammonia electrosynthesis performance

Article abstract of DOI:10.1039/d0ta10696h

The Haber-Bosch process is widely used to convert atmospheric nitrogen (N2) into ammonia (NH3). However, the extreme reaction conditions and abundant carbon released by this process make it important to develop a greener NH3 production method. The electrochemical nitrogen reduction reaction (NRR) is an attractive alternative to the Haber-Bosch process. Herein, we demonstrated that molybdenum sulfide on nickel foil (1T-MoS2-Ni) with low crystallinity was an active NRR electrocatalyst. 1T-MoS2-Ni achieved a high faradaic efficiency of 27.66% for the NRR at -0.3 V (vs. RHE) in a LiClO4 electrolyte. In situ X-ray diffraction and ex situ X-ray photoemission analyses showed that lithium ions were intercalated into the 1T-MoS2 layers during the NRR. Moreover, theoretical calculations revealed the differences between six membered rings formed in the 1T-MoS2 and 2H-MoS2 systems with Li intercalation. The bond distances of d(Mo-N) and d(N-Li) of in Li-1T-MoS2 were found to be shorter than those in Li-2H-MoS2, resulting in a lower energy barrier of N2 fixation and higher NRR activity. Therefore, 1T-MoS2-Ni is promising as a scalable and low-cost NRR electrocatalyst with lower power consumption and carbon emission than the Haber-Bosch process.

Full text of DOI:10.1039/d0ta10696h

View Article Online
View Journal
Journal of
Materials Chemistry A
Materials for energy and sustainability
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: S. Patil, H. Chou,
Y. Chen, S. Hsieh, C. Chen, C. Chang, S. Li, Y. Lee, Y. Lin, H. Li, Y. J. Chang, Y. Lai and D. Wang, J. Mater.
Chem. A, 2020, DOI: 10.1039/D0TA10696H.
Volume
Number 12
28 March 2018
Pages 4883-5230
6
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Journal of
Materials Chemistry A
Materials for energy and sustainability
rsc.li/materials-a
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 2050-7488
COMMUNICATION
Zhenhai Wen et al.
An electrochemically neutralized energy-assisted low-cost
acid-alkaline electrolyzer for energy-saving electrolysis
hydrogen generation
rsc.li/materials-a

Page 1 of 23
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA10696H
Enhanced N2 Affinity of 1T-MoS2 with Unique Pseudo Six-membered Ring Consisting of N—Li—
S—Mo—S—Mo for High Ambient Ammonia Electrosynthesis Performance
Shivaraj B. Patil,1# Hung-Lung Chou,2# Yu-Mei Chen,1 Shang-Hsien Hsieh,3 Chia-Hao Chen,3 Chia-Che
Chang,1 Shin-Ren Li,1 Yi-Cheng Lee,1 Ying-Sheng Lin,1 Hsin Li,1 Yuan Jay Chang,1 Ying-Huang Lai,1
Di-Yan Wang1*
1 Department of Chemistry, Tunghai University, Taichung 40704, Taiwan
2
Graduate Institute of Applied Science and Technology, National Taiwan University of Science and
Technology, Taipei 10607, Taiwan
3 National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
#Shivaraj B. Patil and Hung-Lung Chou contributed equally to this work
Corresponding author: diyanwang@thu.edu.tw
Abstract
The Haber–Bosch process is widely used to convert atmospheric nitrogen (N2) into ammonia (NH3).
However, the extreme reaction conditions and abundant carbon released by this process make it important
to develop a greener NH3 production method. The electrochemical nitrogen reduction reaction (NRR) is
an attractive alternative to the Haber–Bosch process. Herein, we demonstrated that molybdenum sulfide
on nickel foil (1T-MoS2-Ni) with low crystallinity was an active NRR electrocatalyst. 1T-MoS2-Ni
achieved a high faradaic efficiency of 27.66% for the NRR at −0.3 V (vs. RHE) in LiClO4 electrolyte. In-
situ X-ray diffraction and ex-situ X-ray photoemission analyses showed that lithium ions intercalated into
the 1T-MoS2 layers during the NRR. Moreover, theoretical calculations revealed the differences between
six membered rings formed in the 1T-MoS2 and 2H-MoS2 systems with Li intercalation. The bond
distances of d(Mo—N) and d(N—Li) of in Li-1T-MoS2 were found to be shorter than those in Li-2H-
MoS2, resulting in a lower energy barrier of N2 fixation and higher NRR activity. Therefore, 1T-MoS2-Ni
is promising as a scalable and low-cost NRR electrocatalyst with lower power consumption and carbon
emission than the Haber–Bosch process.
Keywords: 1T-MoS2, Nitrogen Reduction Reaction, Pseudo Six-member Ring, in-situ X-ray diffraction,
Lithium Interactions

Journal of Materials Chemistry A
Page 2 of 23
View Article Online
DOI: 10.1039/D0TA10696H
Introduction
Ammonia (NH3) has attracted extensive interest for over a century because of its wide range of
applications, including as a green fertilizer and non-carbon fuel for vehicles.1-3 Although nitrogen (N2) is
the most abundant gas in the Earth’s atmosphere, it is metabolically useless unless nitrogen fixation is
carried out. The electrocatalytic nitrogen reduction reaction (NRR) is a promising process that breaks the
triple bond of N2 with suitable catalysts to form NH3 (N2 + 6H+ + 6e– → 2NH3).4-7 There are three main
factors that need to be considered to optimize electrocatalysts for the NRR: (1) the adsorption ability of
N2 on the catalyst surface, (2) reaction selectivity to suppress the hydrogen evolution reaction (HER), and
(3) the compatibility and stability of materials.8, 9 It is important to develop new catalysts that acceptably
address these factors to realize highly efficient electrochemical N2 reduction to NH3.
12
Recently, many metal sulfides such as 2H-MoS2,10 FeS2,11 and SnS2 have been investigated as
catalysts for the NRR. However, metal sulfides show low faradaic efficiency (FE) in the NRR,13-15 which
has been attributed to poor N2 adsorption on their surface and the inability to effectively suppress the
HER. Understanding the detailed reaction mechanism of these catalysts could provide direction to design
more active NRR catalysts. The electrochemical properties and reaction pathway of FeS2 in the NRR
were studied experimentally and by density functional theory (DFT) simulations.11 The results showed
that Fe atoms acted as NRR active centres and greatly lowered the energy barrier for the NRR. Sun et al.16
revealed that Mo atoms were the NRR active centres of 2H-MoS2, which displayed an FE of 1.2%. MoS2
was decorated with Ru clusters to provide extra binding sites for N2 activation for the NRR, resulting in
an FE of 18%.17
Increasing catalyst surface activity through atomic manipulation is a promising direction to raise
the FE of the electrochemical NRR. The preparation of metal oxides or sulfides with high metallic surface
exposure to increase NRR activity has been proposed.18 For example, Xin and co-workers achieved an FE
of 14.6% (3.6 µg/h/mgcat) for atomically dispersed Mo atoms on N-doped porous carbon.19 The high FE
and NH3 yield of this catalyst were attributed to its high metal exposure, which facilitated N2 adsorption.
It has also been found that low crystalline (amorphous) materials show enhanced NRR activity
over their crystalline counterparts, which is attributed to the dangling bonds of low crystalline materials
acting as unsaturated coordination sites for N2 adsorption.20 For example, Yan et al.21 found that low
crystalline Au on CexO2-reduced graphene oxide exhibited an FE of 10.10%, which was much higher than
that of its crystalline counterpart (3.67%). The improved NRR activity was ascribed to the low crystalline
structure providing more active sites for N2 adsorption than the corresponding crystalline structure.

Page 3 of 23
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA10696H
Recently, 1T-MoS2 has emerged as a promising material for a wide range of electrochemical
applications because of its metallic properties and highly active surface, which is composed of a single
layer of S-Mo-S structure in which Mo is linked to six S atoms to form an octahedral lattice.22-24 This
structure endows 1T-MoS2 with abundant active sites and high electronic conductivity (six orders of
magnitude higher than that of 2H-MoS2).22 These characteristics facilitate the exclusive interactions of
ions/molecules dissolved in an electrolyte with a 1T-MoS2 catalyst and the rapid diffusion of ions.25 The
dense active sites of 1T-MoS2 promote catalytic activity and its high electronic conductivity affords fast
electron transfer.24 Indeed, 1T-MoS2 has been used as an active catalyst for the HER.22, 23 To design an
active 1T-MoS2 NRR electrocatalyst, its HER activity needs to be suppressed and N2 adsorption ability
needs to be increased.
The NRR efficiency of 1T-MoS2 might be increased by forming new intermolecular interactions
in the MoS2 structure to facilitate N2 adsorption. For example, the FE of 2H-MoS2 was increased by the
formation of an additional Li-S bond in its crystal structure during Li+ intercalation.25 The FE of this
structure was 9.8%, which still has room for improvement. Because 1T-MoS2 has a different crystal
structure from that of 2H-MoS2, it could form different intermolecular interactions with Li+, which could
modify its NRR catalytic activity. In this work, to further improve the NRR catalytic performance of 1T-
MoS2, low crystalline 1T-MoS2 grown on nickel foil (denoted as 1T-MoS2-Ni) is designed as a robust
electrocatalyst for the NRR. The performance of 1T-MoS2-Ni as an NRR electrocatalyst in LiClO4
electrolyte is investigated. In-situ X-ray diffraction (XRD) and ex-situ X-ray photoelectron spectroscopy
(XPS) measurements are carried out to examine the intercalation of Li into 1T-MoS2. A detailed reaction
pathway for Li-intercalated 1T-MoS2 (Li-1T-MoS2) in the NRR is also elucidated.
Results and Discussion
To study the differences between the catalytic mechanisms of N2 reduction on the surface of Li-
1T-MoS2 and Li-intercalated 2H-MoS2 (Li-2H-MoS2), model optimization was performed in 14×14×20
Å3 systems by DFT calculations, as shown in Figure 1(a) and (b), respectively. The calculated N2
adsorption energies at the Mo and S sites of the intrinsic 1T-MoS2 and Mo sites of Li-1T-MoS2 and Li-
2H-MoS2 are listed in Table 1. The active site for N2 adsorption on 1T-MoS2 is Mo because the Mo site
possesses a negative N2 adsorption energy (−0.28 eV). The N2 adsorption energies on Li-1T-MoS2 and Li-
2H-MoS2 were −0.72 and −0.70 eV, respectively, indicating their much stronger ability to adsorb N2 than
that of intrinsic 1T-MoS2. These results indicated that N2 adsorption on the 1T-MoS2 or 2H-MoS2 surface
was strongly affected by the specific interactions of Li and S atoms, which is consistent with the findings
of a previous report.26 To study the suppression of hydrogen adsorption on S site in Li-1T-MoS2, DFT
calculation was also performed in Table S1. The results indicated that the hydrogen (H*) adsorption free

Journal of Materials Chemistry A
Page 4 of 23
View Article Online
DOI: 10.1039/D0TA10696H
energies (ΔGH*) of 0.03 eV was obtained on S-edge sites of pristine MoS2 system. In contrast, with Li–S
interactions, the ΔGH* increased dramatically to 0.49 eV on S-edge sites of Li-MoS2 system. The result
represented that S-edge sites in pristine MoS2 system were more favorable for HER than that of Li-MoS2
thermodynamically. Therefore, the Li-S bond can efficiently suppress the HER on the S atoms of MoS2,
which are believed to behave as the active sites for the HER.16, 26-29
After geometry relaxation, the optimized calculated distance of N2 in Li-1T-MoS2 and Li-2H-
MoS2 (Figure 1 (a) and (b), respectively) showed that a pseudo six-membered ring containing the
interaction N…Li…S—Mo—S—Mo formed. The N…Li interaction in the six-membered ring is believed
to enhance the N2 adsorption ability on the surface of MoS2 and possibly weaken the N≡N bond to
improve the conversion efficiency of the NRR. Comparison of the Li-1T-MoS2 and Li-2H-MoS2 systems
revealed that the bond distances of d(Mo—N) of ~1.797 Å and d(N—Li) of ~2.119 Å in Li-1T-MoS2
were shorter than d(Mo—N) of ~2.010 Å and d(N—Li) of ~2.639 Å in Li-2H-MoS2, respectively. These
results indicate that the N2 adsorption ability of Li-1T-MoS2 is stronger than that of Li-2H-MoS2. In other
words, the Li-1T-MoS2 system should facilitate the formation of N-H bonds. Directed by these results, we
fabricated and characterized Li-1T-MoS2 as an NRR electrocatalyst.
Thiourea has been widely used as a sulfur source in the conventional synthesis of
organic/inorganic compounds because of its high sulfur content, easy release of sulfur, and low cost, even
though it is recognized as a toxic chemical. To make our catalyst fabrication as green and eco-friendly as
possible, herein, 1T-MoS2-Ni was fabricated by immersing pre-treated (acid-washed) Ni foil in a solution
containing molybdic acid and a minimal amount of thiourea through a facile hydrothermal process.
Figure 2(a) shows the XRD pattern of 1T-MoS2-Ni, which indicates that 1T-MoS2-Ni has low
crystallinity with two peaks at 9.0° and 18.72° corresponding to the (002) and (004) planes of 1T-MoS2,
respectively, in agreement with the literature.30 These results were attributed to the formation of low
crystalline 1T-MoS2 on Ni foil. In contrast, 1T-MoS2 grown on carbon fiber paper (1T-MoS2-CFP) and
1T-MoS2 grown on Ti foil (1T-MoS2-Ti) displayed higher crystalline structures with peaks from the same
planes observed in their XRD patterns (see the supporting information). Figure S1(d-e) show the Raman
spectra of 1T-MoS2 grown on different substrates and confirm the formation of 1T-MoS2 with low
crystallinity over Ni foil.23, 31, 32 A scanning electron microscopy (SEM) image of 1T-MoS2-Ni is shown in
Figure 2(b). It reveals that the 1T-MoS2-Ni consists of particles with rough surfaces. In contrast, 1T-
MoS2-CFP consisted of sheet structure with high crystallinity (Figure S2). To analyze the element
distribution of 1T-MoS2-Ni, energy-dispersive X-ray spectroscopy (EDX) elemental mapping analysis
was carried out. Figure 2(c) shows a cross-sectional SEM image of 1T-MoS2-Ni, which clearly illustrates
that the 1T-MoS2 is attached to the Ni foil. Figure 2(d)–(g) show related EDX mapping of 1T-MoS2-Ni,

Page 5 of 23
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA10696H
which confirmed the uniform distributions of Mo and S on Ni. The few signals from oxygen (Figure 1(h))
could originate from the chemisorption of atmospheric oxygen.
To investigate the catalytic activity of 1T-MoS2-Ni in the NRR, electrochemical experiments
were conducted in N2-saturated 0.25 M LiClO4. The electrochemical reactions were carried out in an H-
type cell in which the counter and working electrodes were separated by a Nafion membrane. Platinum
wire (Pt) and a saturated calomel electrode (SCE) were used as counter and reference electrodes,
respectively. All potentials are referenced to the reversible hydrogen electrode (RHE). Figure 3(a)
presents the results of linear sweep voltammetry (LSV) performed at a scan rate of 10 mV/s to determine
the possible electrochemical window for the NRR over 1T-MoS2-Ni. A current density of 10 mA/cm2 was
obtained at an applied voltage of −0.6 V (vs. RHE). To investigate the dependence of the electrochemical
NRR by the 1T-MoS2-Ni electrocatalyst on potential, constant-current curves were measured at different
voltages of −0.2 to −0.6 V for 40 min, as shown in Figure 3(b). The current density increased from 2.0 to
10.0 mA/cm2 as the applied voltage changed from −0.2 to −0.6 V. Interestingly, no bubbles were
observed in the range from −0.2 V to −0.6 V, meaning that hydrogen evolution on the surface of catalysts
was suppressed substantially.
To detect and quantify the NH3 formed during the electrocatalytic NRR over 1T-MoS2-Ni at
different potentials, indophenol was added as an indicator and measured by ultraviolet–visible (UV–Vis)
absorption spectroscopy. Figure 3(c) shows UV–Vis absorption spectra of the electrolytes colored with
indophenol. The results showed that the highest absorption intensity was around 0.40 a.u. at −0.3 V and
the lowest was ~0.03 a.u. at −0.2 V. To further confirm the generation of NH3 over the 1T-MoS2-Ni
electrocatalyst, 1H nuclear magnetic resonance (NMR) spectra were obtained, as presented in Figure 3(d).
14
15
The sample for NMR measurements was produced using a mixture of N2 and N2 as the gas source in
1
+
+
0.25 M LiClO4 at −0.3 V (vs. RHE) for 4 h. The H NMR spectrum clearly showed 14NH4 and 15NH4
signals, illustrating that NH3 was produced by electrolysis over the 1T-MoS2-Ni catalyst.
The NH3 yields and related FE of 1T-MoS2-Ni at given voltages are plotted in Figure 3(e). At
−0.2 V, the catalyst exhibited an FE of 11.57% and produced NH3 at a rate of 0.11 µg/min, whereas it
achieved its highest FE of 27.66% with an NH3 yield rate of 1.05 µg/min/cm2 at −0.3 V. Beyond −0.3 V,
FE decreased at more negative potential (8.02% at −0.4 V, 4.32% at −0.5 V, and 0.70% at −0.6 V). This
phenomenon may be ascribed to the domination of the HER over the NRR at more negative potential. The
formation of hydrazine during the reaction was not detected (Figure S3). Griess test of electrolyte and gas
chromatography of N2 gas were also performed to check the NOx contamination and no contamination
was found. (Figure S3, S4). Furthermore, controlled experiments were performed to show no effect of
counter electrodes, anions of the salt and Ni foil on NRR as shown in Figure S5.

Journal of Materials Chemistry A
Page 6 of 23
View Article Online
DOI: 10.1039/D0TA10696H
To validate the effects of the 1T phase of 1T-MoS2-Ni with low crystallite nature on its
performance as an NRR electrocatalyst, 1T-MoS2-CFP and 1T-MoS2-Ti with highly crystalline structures
were fabricated (Figure S1 and S2). In addition, 2H-MoS2-CFP was also prepared by annealing 1T-
MoS2-CFP at high temperature in sulfur vapor. The structure characterization of 1T-MoS2-CFP, 1T-
MoS2-Ti, and 2H-MoS2-CFP is provided in the Supporting Information. All electrochemical tests were
carried out in 0.25 M LiClO4 electrolyte at −0.3 V. Figure 3(f) shows that 1T-MoS2-CFP, 1T-MoS2-Ti,
and 2H-MoS2-CFP with high crystallinity only achieved FEs of 12.24%, 10.5%, and 8.06%, respectively,
in the NRR. These results confirm that the low crystallite nature of 1T-MoS2-Ni leads to its high FE in the
NRR by providing abundant active sites. Table S2 compares the performance of 1T-MoS2-Ni with that of
other reported metal sulfide NRR electrocatalysts.
To validate the stability of 1T-MoS2-Ni, long term measurements and multiple cycles of the NRR
were conducted. Long-term electrocatalytic NRR was carried out for 13 h at −0.3 V. Figure 4(a) shows
the time-dependent current curve of 1T-MoS2-Ni at -0.3 V for 13 h. The corresponding absorption
spectrum (inset of Figure 3(a)) reveals that the absorption intensity of indophenol was 1.99 a.u. after 13 h.
After 13 h of electrocatalysis, the FE of 1T-MoS2-Ni was still 26.47%. Figure 4(b) displays the data
obtained from consecutive electrochemical cycling tests. The NRR was conducted at −0.3 V for 40 min
five times using the same 1T-MoS2-Ni sample. Both FE and NH3 yield rate remained similar over the five
cycles (corresponding time-dependent current curves and UV–Vis spectra are provided in Figure S6).
Overall, these results indicated that 1T-MoS2-Ni demonstrated remarkably stable catalytic activity in the
NRR.
The intercalation/interaction of Li+ with MoS2/S2ˉ has been recognized as another factor that can
raise the NRR activity of 2H-MoS2.26 To investigate the Li+ intercalation of 1T-MoS2 during the
electrochemical NRR in LiClO4 electrolyte, XPS and in-situ XRD measurements were performed (see
Figure S7 for the in-situ XRD setup). Intrinsic 1T-MoS2 and 2H-MoS2 with no Li intercalation were used
as reference samples for comparison. Figure 5(a), (b), and (c) show Mo 3d, S 2p, and Li 1s spectra,
respectively, for the samples. Two characteristic peaks from Mo 3d5/2 and Mo 3d3/2 were clearly identified
in the Mo 3d spectrum of MoS2. These peaks of intrinsic 1T-MoS2 were shifted to lower binding energy
compared with those of 2H-MoS2 (Figure 5(a)). Similarly, the peaks ascribed to 2P1/2 and 2P3/2 in the S
2p spectrum of intrinsic 1T-MoS2 were also shifted to lower binding energy compared with those of 2H-
MoS2 (Figure 5(b)). The lower binding energies of Mo and S for intrinsic 1T-MoS2 than for 2H-MoS2
can be attributed to the increased electron density of the Mo and S atoms of 1T-MoS2 compared with the
case for 2H-MoS2.22, 24, 25, 30, 33, 34 After electrolysis at −0.3 V for 40 min, the Mo 3d and S 2p peaks of 1T-
MoS2-Ni slightly shifted to lower and higher energy, respectively, indicating that the oxidation state of S

Page 7 of 23
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA10696H
atoms of 1T-MoS2-Ni was higher than that of intrinsic 1T-MoS2. This result was attributed to the
intercalation of Li+ into 1T-MoS2-Ni to form Li-1T-MoS2-Ni, resulting in the formation of Li-S bonds.26,
34 Figure 5(c) shows the rise of the Li 1s peak of Li-1T-MoS2-Ni, further substantiating the intercalation
of Li+ into 1T-MoS2.
Figure 5(d) displays selected XRD patterns of 1T-MoS2-CFP collected during the NRR in
LiClO4 electrolyte with a linear scan from 0 to −0.6 V. We chose 1T-MoS2-CFP for in-situ XRD studies
because its higher crystallinity than that of 1T-MoS2-Ni facilitated observation of its structural
transformation. The corresponding linear scan is shown in Figure 5(e). The results reveal that the peak
observed at 9.5° for 1T-MoS2 shifted to 7° at more negative potential, confirming that Li+ was
intercalated into the 1T-MoS2 layers.35 To further study the role of Li+ in the NRR activity of Li-1T-
MoS2-Ni, Na2SO4 was used as the electrolyte in the NRR. Figure 5(f) shows the FE of Li-1T-MoS2-Ni,
intrinsic 1T-MoS2, and 2H-MoS2 electrocatalysts operated in 0.25 M NaSO4 electrolyte at −0.3 V for 40
min. The corresponding current-dependent curves and UV–Vis spectra are provided in Figure S8.
Interestingly, Li-1T-MoS2-Ni exhibited a higher FE compared with those of intrinsic 1T-MoS2 and 2H-
MoS2. Further, post catalytic characterizations including XRD and SEM of 1T-MoS2-Ni (Figure S9)
revealed that 1T phase with low crystallite nature remains unchanged. Owing to Li intercalation into
MoS2 matrix, shift of dominant peak in XRD from 9⁰ to 7⁰ was also observed. Overall, these results
confirmed the influence of Li+ on the NRR activity of MoS2. The role of Li+ in increasing the FE of MoS2
was further examined by DFT simulations.
To investigate the catalytic mechanism of Li-1T-MoS2 in the NRR compared with those of intrinsic
1T-MoS2 and Li-intercalated 2H-MoS2 (Li-2H-MoS2), DFT calculations were performed to determine
their molecular structures and map potential energy diagrams of the NRR. In the models, N2 was adsorbed
on three kinds of MoS2 slab surfaces consisting of one Li atom, 25 Mo atoms, and 46 S atoms, as shown
in Figure 6(a). The charge transfer between Mo, S, and Li atoms in Li-1T-MoS2 was believed to be an
important index that affects the adsorption ability of N2 molecules and thus NRR activity. Figure 6(b)
presents the representative electron contour map of Li-1T-MoS2 and the calculated charge transfer values
are listed in Table 2. The formation of Li-S bonds was predicted in this model. Our results clearly
showed that charge transfer occurred from Li to S in the Li-1T-MoS2 system. The charge on S increased
from 6.73e for intrinsic 1T-MoS2 to 6.96e for Li-1T-MoS2 and the charge on Li decreased from 3.61e for
bare Li to 2.16e for Li-1T-MoS2. Therefore, the charge of an N atom of N2 increased from 6.87e to 6.98e
upon adsorption by Li-1T-MoS2, which could affect the bond strength of N2 and facilitate the NRR.
Figure 7 shows that the activation energy of the potential determining step for the NRR on intrinsic
1T-MoS2, Li-1T-MoS2, and Li-2H-MoS2. For intrinsic 1T-MoS2, an energy barrier of +0.79 eV was found

Journal of Materials Chemistry A
Page 8 of 23
View Article Online
DOI: 10.1039/D0TA10696H
for the reductive protonation of adsorbed N2 (*NNH formation) without external potential. The energy
barriers of the reductive protonation step for Li-intercalated 1T- and 2H-MoS2 were much smaller than
that for intrinsic 1T-MoS2. In addition, the potentials of *NN adsorption (−0.72 eV) and *NNH formation
(−0.23 eV) for Li-1T-MoS2 were slightly lower than those for Li-2H-MoS2 (−0.68 and −0.19 eV,
respectively). In this step for the Li-1T-MoS2 system, the N-N bond length increased from 1.18 Å in *N2
to 1.23 Å *NNH. Therefore, the deformation charge density (Figure 6(b)) clearly illustrated the charge
transfer from N2 to a positively charged Mo atom, resulting in the formation of an N-Mo bond and
notable weakening of the N≡N triple bond and facilitating the intermediate protonation reaction to form
*NNH. Indeed, the opening of the inert triple bond of N2 was the most energetically demanding step of
the NRR, which is logical. Overall, our results indicated that the Li-1T-MoS2 catalyst demonstrated a
relatively low energy barrier for the NRR, making it a promising electrocatalyst for this challenging but
important reaction.
Conclusion
We fabricated a high-performance 1T-MoS2-Ni electrocatalyst for NRR with advantages including high
exposure of metal active sites and high conductivity. The 1T-MoS2-Ni electrocatalyst achieved an FE of
27.66% and generated NH3 at a rate of 1.05 µg/min/cm2 at −0.3 V in 0.25 M LiClO4 electrolyte. DFT
calculations indicated the formation of a pseudo six-membered ring with N2 in the presence of Li+, which
not only lowered the energy barrier for N2 fixation but also effectively suppressed the HER through
strong Li—S interactions. This work provides fundamental insights on electrocatalyst fabrication and
interfacial chemistry between the electrode and electrolyte, which may act as a blueprint for developing
advanced NRR electrocatalysts in the future.
Materials:
Molybdic acid (H2MoO4; ACS 85% min) and lithium perchlorate (LiClO4; Analysis 99+%) were
procured from Acros organics. Thiourea (CH4N2S; ACS 99+%), phenol (C6H5OH; ACS 100%), super P;
(ACS 99+%), Nafion (5 wt%) and titanium (Ti; 99.99%) foil were procured from Sigma-Aldrich. Sodium
hydroxide (NaOH; ACS 97+%) was procured from Shimakyu’s pure chemicals. Sodium hypochlorite
(NaClO; 6-14% active Cl basis) and sodium sulfate (Na2SO4; ACS 99+%) were procured from
Honeywell-Fluka. Sodium pentacyanonitrosylferrate (III) dihydrate (Na2[Fe(CN)5NO].2H2O; ACS 99+%)
and lithium sulfate (Li2SO4; ACS 99.7%) were procured from Alfa Aesar. Nickel (Ni; 99.99%) foil was
procured from MTI corporation whereas carbon fiber paper (CFP) was procured from CeTech Co., Ltd.
14N2 (5N) and 15N2 (98 atom % 15N) gases were procured from Toyo gas Co., Ltd., and Sigma-Aldrich,
respectively. Distilled water and absolute ethanol were used throughout the experiments.

Page 9 of 23
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA10696H
Fabrication of 1T-MoS2 Nano-flowers:
1T-MoS2 nano-flowers were fabricated by adopting simple hydrothermal method. Typically, 2.5 mM of
H2MoO4 and 6.25 mM of CH4N2S were dissolved in 40 mL of distilled water and stirred vigorously for
30 min to form a homogeneous solution. The solution was then transferred to Teflon-lined stainless-steel
autoclave and sealed it. The autoclave was heated to 180 ⁰C for 24 h and then cooled to room temperature.
The obtained product was washed for several times with DI-water and ethanol. The resulting sample was
dried at 60 ⁰C to obtain shiny black powder. The black powder was further characterized.
Fabrication of 1T-MoS2 on CFP, Ni and Ti foils:
Similarly, 1T-MoS2 on CFP, Ni and Ti foil were synthesized by placing CFP, Ni and Ti foil into the
autoclave, respectively, and maintaining all procedure unchanged. Finally, the samples were dried at 60
⁰C and stored in a desiccator.
Fabrication of 1T-MoS2 electrode catalyst:
Whereas, 1T-MoS2 on Ni foil, CFP and Ti foil were used as it is by downsizing to 1 x 2 cm2 area. During
the electrochemical measurements, it was immersed into the electrolyte with an area of 1 x 1 cm2.
Characterization:
XRD patterns were recorded by XRD instrument (Rigaku Miniflex 600). JEOL JSM-7800F and JEOL
2100F were used to capture FESEM and HRTEM images, respectively. X-ray photoemission
spectroscopy (XPS) measurements were perform at the SPEM end station (BL09A) of the National
Synchrotron Radiation Research Center (NSRRC).36 The photon energy used to obtain Mo 3d, S 2p and
Li 1s XPS spectra was 320 eV. The in-situ XRD measurement was taken with electrochemical cell under
linear scan voltammetry method at a scan rate of 1 mV/s. The schematic setup is provided in the
supporting information. In-situ XRD analysis was performed at the beamline of BL23A small/wide angle
X-ray scattering (SWAXS) at Taiwan Light Source (TLS) and the beamline of 09A at the Taiwan Photon
Source (TPS) in National Synchrotron Radiation Research Center.
Pretreatment prior to electrochemical measurements: Before each electrochemical measurement, all
the units of electrochemical cell were boiled and rinsed several times in DI water and dried at 100 °C.
Nafion membrane was used as received (no additional acid treatment). New membrane was used for each
measurement to avoid contamination. Furthermore, all the labware including vials, pipet etc., were also
rinsed DI water for several times. The 15N2 and 14N2 gases were passed through saturator (0.05 M H2SO4)
for high purity. Ar was purged for 30 min prior to 15N2 flow to expel inherent 14N2.37, 38

Journal of Materials Chemistry A
Page 10 of 23
View Article Online
DOI: 10.1039/D0TA10696H
Electrochemical setup and measurements: The nitrogen reduction reactions were performed in a H-cell
at ambient conditions. It consists of two cells separated by a Nafion 211 membrane. Reference and
working electrodes were placed in single cell whereas counter electrode was placed in another cell. CHI-
660 electrochemical analyzer with typical three electrode system was used to carry out all the
electrochemical measurements. Herein, 1T-MoS2-Ni was devised as working electrode whereas platinum
rod (Pt) and saturated calomel electrode (SCE) were implemented as counter and reference electrodes,
respectively. The potentials reported in this work were changed to RHE scale with the following equation:
E (vs. RHE) = E (vs. SCE) + 0.245 + 0.059 × pH. Subsequently, the current density was recorded with
respect to geometric surface area of the working electrode. N2-saturated 0.25 M LiClO4 was used as an
electrolyte in this work. All experiments were carried out at room temperature.
Ammonia (NH3) detection:
Indophenol method with UV-vis spectroscopy was used to detect and quantify the yield amount of NH3 in
the solution. Briefly, 1 mL of electrolyte was collected from the cathodic cell and reacted with 100 µL of
oxidizing solution containing NaClO (pCl=6-14) in 1 M NaOH. It was followed by the addition of 100
µL of 0.5 M phenol and 50 µL of catalyst solution containing 0.002 M Sodium nitropusside as the
catalyst solution in turn. The solution mixture was mixed well gently for 30 s and kept still for 30 min in
dark conditions. The absorbance measurements were recorded at λ = 640 nm. NH3 concentration was
+
quantified by concentration-absorbance calibration curve. Standard NH4Cl solution with NH4
concentrations 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15 µg/mL in 0.25 M LiClO4 were used to
calibrate concentration-absorbance curve. The fitting curve (y = 0.2952x + 0.008, R2 = 0.9979) found to
be in linear coherence with the concentration of NH3 (Figure S10). Similarly, it was done for Na2SO4
electrolyte also. NMR method was also carried out to support Indophenol test results (Figure S10). NMR
14
+
15
+
calibration curve was obtained using equimolar concentration of NH4 and NH4 as shown in Figure
S11.
NH3 yield rate (YNH3) calculation:
Yield ratemass (NH3) = (c(NH3) × V) / (t × A)
Where c(NH3) is the measured the concentration of NH3, V is the volume of electrolyte, t is the duration
time of the reduction reaction, and A is the geometric area of the cathode (1×1 cm2).
Faradic efficiency (FE) calculation:
FE calculation in 0.25 M LiClO4 electrolyte was carried out assuming that one NH3 molecule is produced
with 3 electrons. It can be represented as follows:

Page 11 of 23
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA10696H
FE = (3F x CNH3 x V) / (17 x Q)
Eq. 2
Where, F stands for Faradaic constant (96485 C/mol) and Q stands for total quantity of supplied coulomb.
Hydrazine (N2H4) detection:
The Watt and Chrisp method was adopted to quantify the N2H4 in the electrolyte after the reaction.39 The
coloring agent was prepared by mixing 5.99 g of para-(dimethylamino) benzaldehyde (ρ-C9H11NO) with
30 mL of hydrochloric acid (HCl) and 300 mL of ethanol (C2H5OH). Briefly, 9 mL of 1.0 M HCl was
added to 1 mL of electrolyte (after the reaction) and was followed by the addition of 5 mL of coloring
agent. The absorbance measurements were recorded at λ = 455 nm after incubating for 30 min.
15N2 Isotope labeling studies:
Using 15N2 and 14N2 as feeding gases, the 15N and 14N isotopic labeling studies were carried out,
respectively. 99% enrichment of 15N in 15N2 was supplied by Sigma-Aldrich. The 15N2 and 14N2 gases
were passed through saturator (0.05 M H2SO4) for high purity. Briefly, electrocatalysis was carried out at
0.3 V for 4 h with continuously purging saturated a 15N2 gas in the electrolyte (0.25 M LiClO4). After the
o
reaction, the reaction solution was concentrated to 2.0 mL at 80 C for 3 hr. The pH of the concentrated
solution was adjusted to ~3 with adding few 0.01 M HCl. Then, 1 mL of the concentrated solution mixed
with 0.2 mL of d6-DMSO was used for 1H NMR spectroscopy measurement.
Theoretical calculations:
41
In DFT calculations, we employed projector-augmented waves (PAW)40,
generalized gradient
approximation (GGA).42-44 In the plane wave calculations, cutoff energy of 500 eV was applied, which
was automatically set by the total energy convergence calculation for 1T-MoS2 slab systems. DFT
simulations were performed based on the unit cell of 1T-MoS2 system shown in Figure S12-15.45The
dimension of unit cell of a = b =3.19 Å, c = 5.945 Å3 , and  =  = 90o, =120o. Initially, the 1T-MoS2
was constructed to consist of 1T-MoS2 unit cell structure containing one Mo atoms with one S atoms; the
system was then allowed to reach its lowest energy configuration by a relaxation procedure. For these
calculations, a 3 × 3 × 1 k-Point mesh was used in the super cell. The atoms in the cell were allowed to
relax until the forces on unconstrained atoms are less than 0.01 eV/Å. The adsorption energy in N2-1T-
MoS2 system, Ead, is defined as the sum of interactions between the capping molecule and slab system,
Ead  Etotal  E


EN 2

E
, where Etotal,
MoS2
EN2
are the total energy of the
and it is given as
and
MoS2
system, 1T-MoS2 system energy, and the single N2 molecule energy. The negative sign of Ead corresponds
to the energy gain of the system due to molecular adsorption.

Journal of Materials Chemistry A
Page 12 of 23
View Article Online
DOI: 10.1039/D0TA10696H
Supporting Information.
Additional XRD patterns, SEM images, time dependent curves, UV spectra, calibration graphs, in-situ
XRD set-up and theoretical considerations.
Notes:
The authors declare no conflict of interest.
Author Contributions
S. Patil and D. Wang conceived the project and designed the experiments. S. Patil, Y. Chen, C.
Chang, S. Li, Y. Lee and Y. Lai performed material preparation, structural characterization and
electrochemical measurements. S. Hsieh, and C. Chen helped to perform the X-ray
photoemission measurement in the NSRRC. H. Chou helped to perform DFT simulation. Y. Lin,
Hsin Li and Y. Chang helped to do NMR measurement. S. Patil and D. Wang co-wrote the paper.
All authors discussed the results and commented on the manuscript.
Acknowledgements
This work has been financially supported by the Ministry of Science and Technology of Taiwan (MOST
106-2113-M-029-006-MY2, MOST 106-2632-M-029-001 and MOST 107-2622-M-029-001-CC2) and
Tunghai University. We thank Dr. U-Ser Jeng for assistance at beamline BL23A at Taiwan Light Source
(TLS) and Dr. Hwo-Shuenn Sheu, Dr. Yu-Chun Chuang for assistance at beamline 09A at the Taiwan
Photon Source (TPS).
References:
1.
T. Oshikiri, K. Ueno and H. Misawa, Angewandte Chemie International Edition, 2016, 55, 3942-
3946.
2.
3.
4.
5.
6.
7.
V. Rosca, M. Duca, M. T. de Groot and M. T. Koper, Chemical Reviews, 2009, 109, 2209-2244.
R. F. Service, Science (New York, NY), 2014, 345, 610.
C. Guo, J. Ran, A. Vasileff and S.-Z. Qiao, Energy & Environmental Science, 2018, 11, 45-56.
X. Cui, C. Tang and Q. Zhang, Advanced Energy Materials, 2018, 8, 1800369.
Z. Yan, M. Ji, J. Xia and H. Zhu, Advanced Energy Materials, 2019, 1902020.
Y.-C. Hao, Y. Guo, L.-W. Chen, M. Shu, X.-Y. Wang, T.-A. Bu, W.-Y. Gao, N. Zhang, X. Su and X.
Feng, Nature Catalysis, 2019, 2, 448-456.
8.
9.
S. Dou, X. Wang and S. Wang, Small Methods, 2019, 3, 1800211.
G. F. Chen, S. Ren, L. Zhang, H. Cheng, Y. Luo, K. Zhu, L. X. Ding and H. Wang, Small Methods,
2019, 3, 1800337.
10.
11.
J. Zhang, X. Tian, M. Liu, H. Guo, J. Zhou, Q. Fang, Z. Liu, Q. Wu and J. Lou, Journal of the
American Chemical Society, 2019, 141, 19269-19275.
C. C. Chang, S. R. Li, H. L. Chou, Y. C. Lee, S. Patil, Y. S. Lin, C. C. Chang, Y. J. Chang and D. Y. Wang,
Small, 2019, 15, 1904723.

Page 13 of 23
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA10696H
12.
P. Li, W. Fu, P. Zhuang, Y. Cao, C. Tang, A. B. Watson, P. Dong, J. Shen and M. Ye, Small, 2019, 15,
1902535.
13.
14.
15.
16.
K. C. MacLeod and P. L. Holland, Nature chemistry, 2013, 5, 559.
X. Guo, H. Du, F. Qu and J. Li, Journal of Materials Chemistry A, 2019, 7, 3531-3543.
S. B. Patil and D. Y. Wang, Small, 2020, 2002885.
L. Zhang, X. Ji, X. Ren, Y. Ma, X. Shi, Z. Tian, A. M. Asiri, L. Chen, B. Tang and X. Sun, Advanced
Materials, 2018, 30, 1800191.
17.
18.
19.
20.
21.
22.
23.
B. H. Suryanto, D. Wang, L. M. Azofra, M. Harb, L. Cavallo, R. Jalili, D. R. Mitchell, M. Chatti and D.
R. MacFarlane, ACS Energy Letters, 2018, 4, 430-435.
Y. Qiu, X. Peng, F. Lü, Y. Mi, L. Zhuo, J. Ren, X. Liu and J. Luo, Chemistry–An Asian Journal, 2019,
14, 2770-2779.
L. Han, X. Liu, J. Chen, R. Lin, H. Liu, F. Lü, S. Bak, Z. Liang, S. Zhao and E. Stavitski, Angewandte
Chemie, 2019, 131, 2343-2347.
M. M. Shi, D. Bao, S. J. Li, B. R. Wulan, J. M. Yan and Q. Jiang, Advanced Energy Materials, 2018,
8, 1800124.
S. J. Li, D. Bao, M. M. Shi, B. R. Wulan, J. M. Yan and Q. Jiang, Advanced materials, 2017, 29,
1700001.
X. Geng, W. Sun, W. Wu, B. Chen, A. Al-Hilo, M. Benamara, H. Zhu, F. Watanabe, J. Cui and T.-p.
Chen, Nature communications, 2016, 7, 1-7.
M. A. Lukowski, A. S. Daniel, F. Meng, A. Forticaux, L. Li and S. Jin, Journal of the American
Chemical Society, 2013, 135, 10274-10277.
24.
25.
M. Acerce, D. Voiry and M. Chhowalla, Nature nanotechnology, 2015, 10, 313.
J. He, G. Hartmann, M. Lee, G. S. Hwang, Y. Chen and A. Manthiram, Energy & Environmental
Science, 2019, 12, 344-350.
26.
27.
Y. Liu, M. Han, Q. Xiong, S. Zhang, C. Zhao, W. Gong, G. Wang, H. Zhang and H. Zhao, Advanced
Energy Materials, 2019, 9, 1803935.
C. Tsai, H. Li, S. Park, J. Park, H. S. Han, J. K. Nørskov, X. Zheng and F. Abild-Pedersen, Nature
communications, 2017, 8, 1-8.
28.
29.
B. Seo and S. H. Joo, Nano Convergence, 2017, 4, 1-11.
C.-H. Lee, S. Lee, Y.-K. Lee, Y. C. Jung, Y.-I. Ko, D. C. Lee and H.-I. Joh, ACS Catalysis, 2018, 8,
5221-5227.
30.
31.
T. Xiang, Q. Fang, H. Xie, C. Wu, C. Wang, Y. Zhou, D. Liu, S. Chen, A. Khalil and S. Tao, Nanoscale,
2017, 9, 6975-6983.
N. H. Attanayake, A. C. Thenuwara, A. Patra, Y. V. Aulin, T. M. Tran, H. Chakraborty, E. Borguet,
M. L. Klein, J. P. Perdew and D. R. Strongin, ACS Energy Letters, 2017, 3, 7-13.
D. Yang, S. J. Sandoval, W. Divigalpitiya, J. Irwin and R. Frindt, Physical Review B, 1991, 43, 12053.
Y. Li, H. Wang, L. Xie, Y. Liang, G. Hong and H. Dai, Journal of the American Chemical Society,
2011, 133, 7296-7299.
32.
33.
34.
35.
36.
37.
38.
L. Wu, N. Y. Dzade, M. Yu, B. Mezari, A. J. van Hoof, H. Friedrich, N. H. de Leeuw, E. J. Hensen
and J. P. Hofmann, ACS energy letters, 2019, 4, 1733-1740.
C. D. Quilty, L. M. Housel, D. C. Bock, M. R. Dunkin, L. Wang, D. M. Lutz, A. Abraham, A. M. Bruck,
E. S. Takeuchi and K. J. Takeuchi, ACS Applied Energy Materials, 2019, 2, 7635-7646.
H.-J. Liao, Y.-M. Chen, Y.-T. Kao, J.-Y. An, Y.-H. Lai and D.-Y. Wang, The Journal of Physical
Chemistry C, 2017, 121, 24463-24469.
S. Z. Andersen, V. Čolić, S. Yang, J. A. Schwalbe, A. C. Nielander, J. M. McEnaney, K. Enemark-
Rasmussen, J. G. Baker, A. R. Singh and B. A. Rohr, Nature, 2019, 570, 504-508.
C. Li, S. Mou, X. Zhu, F. Wang, Y. Wang, Y. Qiao, X. Shi, Y. Luo, B. Zheng and Q. Li, Chemical
Communications, 2019, 55, 14474-14477.

Journal of Materials Chemistry A
Page 14 of 23
View Article Online
DOI: 10.1039/D0TA10696H
39.
40.
41.
G. W. Watt and J. D. Chrisp, Analytical Chemistry, 1952, 24, 2006-2008.
D. Vanderbilt, Physical review B, 1990, 41, 7892.
M. C. Payne, M. P. Teter, D. C. Allan, T. Arias and a. J. Joannopoulos, Reviews of modern physics,
1992, 64, 1045.
42.
J. P. Perdew, J. A. Chevary, S. H. Vosko, K. A. Jackson, M. R. Pederson, D. J. Singh and C. Fiolhais,
Physical review B, 1992, 46, 6671.
43.
44.
45.
G. Kresse and J. Hafner, Phys. Rev. B, 1996, 54, 11169.
G. Kresse and D. Joubert, Physical review b, 1999, 59, 1758.
T. Hu, R. Li and J. Dong, The Journal of chemical physics, 2013, 139, 174702.

Page 15 of 23
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA10696H
Figures:
Figure 1. The optimized configuration of pseudo six-member ring on (a) 1T-MoS2 and (b) 2H-MoS2 with
Li-S interactions which consisted of the link of N…Li…S—Mo—S—Mo, respectively. The
corresponding bond distances were provided on the right part of figures.

Journal of Materials Chemistry A
Page 16 of 23
View Article Online
DOI: 10.1039/D0TA10696H
Figure 2. (a) The XRD pattern of 1T-MoS2-Ni. (b) The SEM image of 1T-MoS2-Ni. The amplification
image was shown in the inset. (c) Cross section SEM image and (d) related EDX spectrum of 1T-MoS2-
Ni. Elemental mapping of (e) S atom, (f) Mo atom, (g) Ni atom and (h) O atom of 1T-MoS2-Ni.

Page 17 of 23
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA10696H
Figure 3. (a) Linear sweep voltammetry of 1T-MoS2-Ni operated in N2-saturated 0.25 M LiClO4
electrolyte. (b) Time dependent current curves of 1T-MoS2-Ni at different potential (-0.2 to -0.6 V v.s.
RHE) in N2-saturated 0.25M LiClO4. (c) UV-vis absorption spectra of the electrolytes colored with
+
indophenol indicator at a series of potentials for 40 min. (d) 1H NMR spectrum of the yielded 15NH4 and
+
14NH4 after NRR electrolysis at -0.3V using 15N2 and 14N2 as feeding gases, respectively. (e) Faradaic
efficiency and respective NH3 yield rate of 1T-MoS2-Ni at different potentials. (f) Faradaic efficiency of
different materials tested at -0.3 V in 0.25 M LiClO4 electrolyte.

Journal of Materials Chemistry A
Page 18 of 23
View Article Online
DOI: 10.1039/D0TA10696H
Figure 4. (a) Time dependent current curves of 1T-MoS2-Ni over 13h (inset: UV-vis absorption spectra
of the electrolyte stained with indophenol indicator after NRR electrolysis for 13h). (b) Faradaic
efficiency and respective NH3 yield rate of 1T-MoS2-Ni for consecutive 5 cycles (40 min each).

Page 19 of 23
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA10696H
Figure 5. (a) Mo-3d, (b) S-2p and (c) Li-1s XPS spectra of Li-1T-MoS2-Ni, intrinsic 1T-MoS2 and 2H-
MoS2, respectively. (d) In-situ XRD patterns of representative 1T-MoS2-CFP collected during operation
of NRR in the LiClO4 electrolyte with a scan rate of 0.5 mV from 0 to -0.6 V. (e) The corresponding
linear scan voltammetry of 1T-MoS2-CFP for in-situ XRD measurement. The XRD spectra were collected
from each voltage (red dashed line), as shown in Figure 3 (d). (f) Faradaic efficiency of different catalysts
at -0.3V in 0.5 M Na2SO4 electrolyte.

Journal of Materials Chemistry A
Page 20 of 23
View Article Online
DOI: 10.1039/D0TA10696H
Figure 6. (a) The models of side-view of Li-1T-MoS2 slab surface with a formation of Li-S bond. (b) The
representative electron contour map of intermediates N2 adsorbed on Mo atom of Li-1T-MoS2.

Page 21 of 23
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA10696H
Figure 7. Potential energy diagram for NRR at intrinsic 1T-MoS2, Li-1T-MoS2 and Li-2H-MoS2. An
asterisk (*) denoted as the adsorption site.
Table 1. Adsorption energies and optimized geometries calculation of N in Li-1T-MoS and Li-2H-
2
2
MoS systems
2
System
Ead
(eV)
Distance
(Mo-N)
(Å)
Distance (N-
Distance
(Li-S)
(Å)
Distance
(Li-N)
(Å)
Distance
(Mo-S)
(Å)
N)
(Å)
Mo site of
1T-MoS2
S site of 1T-
MoS2
-0.28
+3.2
1.801
1.174
2.412;
2.424
Mo site of
Li-1T-MoS2
Mo site of
Li-2H-MoS2
-0.72
-0.70
1.797
2.010
1.181
1.172
2.444;
2.389
2.413;
2.238
2.119
2.639
2.413;
2.425
2.413;
2.425

Journal of Materials Chemistry A
Page 22 of 23
View Article Online
DOI: 10.1039/D0TA10696H
Table 2. Bader Charge Analysis of N adsorption on 1T-MoS with Li-S interactions
2
2
Species
MoS2
Charge (e)
Charge difference (e)
Mo: 4.70
S1: 6.80
S1: 6.80
N2
Li
N: 6.87
L: 3.61
1T-MoS2 with Li
Mo (edge): 4.38
S1 (edge): 6.90
S2 (edge): 6.96
Li: 2.16
Mo (edge): 4.38 - 4.70 = -0.32
S1 (edge): 6.90 - 6.80 = +0.10
S2 (edge): 6.96 - 3.73 = +0.23
Li: 2.16 - 3.61 = -1.45
N: 6.98
N: 6.98 - 6.87 = +0.11

Page 23 of 23
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA10696H
232x168mm (149 x 149 DPI)