:Molybdenum disulfide

File:Molly Hill molybdenite.JPG{{chem2|MoS2}} is naturally found as either molybdenite, a crystalline mineral, or jordisite, a rare low temperature form of molybdenite.{{Cite web|url=https://www.mindat.org/min-2114.html|title=Jordisite|website=www.mindat.org}} Molybdenite ore is processed by flotation to give relatively pure {{chem2|MoS2}}. The main contaminant is carbon. {{chem2|MoS2}} also arises by thermal treatment of virtually all molybdenum compounds with hydrogen sulfide or elemental sulfur and can be produced by metathesis reactions from molybdenum pentachloride.{{cite book | author= Murphy, Donald W. |author2= Interrante, Leonard V. | year = 1995 | title = Inorganic Syntheses | volume = 30 | pages = 33–37 | doi = 10.1002/9780470132616.ch8 |last3= Kaner |last4= Mansuktto |chapter= Metathetical Precursor Route to Molybdenum Disulfide |isbn= 9780470132616}}

File:MoS2 antisites&vacancies.jpg of molybdenum disulfide. Scale bar: 1 nm.{{Cite journal | doi = 10.1038/ncomms7293| pmid = 25695374| pmc = 4346634| title = Exploring atomic defects in molybdenum disulphide monolayers| journal = Nature Communications| volume = 6| pages = 6293| year = 2015| last1 = Hong | first1 = J. | last2 = Hu | first2 = Z. | last3 = Probert | first3 = M. | last4 = Li | first4 = K. | last5 = Lv | first5 = D. | last6 = Yang | first6 = X. | last7 = Gu | first7 = L. | last8 = Mao | first8 = N. | last9 = Feng | first9 = Q. | last10 = Xie | first10 = L. | last11 = Zhang | first11 = J. | last12 = Wu | first12 = D. | last13 = Zhang | first13 = Z. | last14 = Jin | first14 = C. | last15 = Ji | first15 = W. | last16 = Zhang | first16 = X. | last17 = Yuan | first17 = J. | last18 = Zhang | first18 = Z. | bibcode = 2015NatCo...6.6293H}}]]

All forms of {{chem2|MoS2}} have a layered structure, in which a plane of molybdenum atoms is sandwiched by planes of sulfide ions. These three strata form a monolayer of {{chem2|MoS2}}. Bulk {{chem2|MoS2}} consists of stacked monolayers, which are held together by weak van der Waals interactions.

Crystalline {{chem2|MoS2}} exists in one of two phases, 2H-{{chem2|MoS2}} and 3R-{{chem2|MoS2}}, where the "H" and the "R" indicate hexagonal and rhombohedral symmetry, respectively. In both of these structures, each molybdenum atom exists at the center of a trigonal prismatic coordination sphere and is covalently bonded to six sulfide ions. Each sulfur atom has pyramidal coordination and is bonded to three molybdenum atoms. Both the 2H- and 3R-phases are semiconducting.{{Cite book|url=https://www.springer.com/series/562|title=Gmelin Handbook of Inorganic and Organometallic Chemistry - 8th edition|language=de}}

A third, metastable crystalline phase known as 1T-{{chem2|MoS2}} was discovered by intercalating 2H-{{chem2|MoS2}} with alkali metals.{{Cite journal|last1=Wypych|first1=Fernando|last2=Schöllhorn|first2=Robert|date=1992-01-01|title=1T-MoS2, a new metallic modification of molybdenum disulfide|url=http://pubs.rsc.org/is/content/articlehtml/1992/c3/c39920001386|journal=Journal of the Chemical Society, Chemical Communications|language=en|issue=19|pages=1386–1388|doi=10.1039/C39920001386|issn=0022-4936|url-access=subscription}} This phase has trigonal symmetry and is metallic. The 1T-phase can be stabilized through doping with electron donors such as rhenium,{{Cite journal|last1=Enyashin|first1=Andrey N.|last2=Yadgarov|first2=Lena|last3=Houben|first3=Lothar|last4=Popov|first4=Igor|last5=Weidenbach|first5=Marc|last6=Tenne|first6=Reshef|last7=Bar-Sadan|first7=Maya|last8=Seifert|first8=Gotthard|date=2011-12-22|title=New Route for Stabilization of 1T-WS2 and MoS2 Phases|journal=The Journal of Physical Chemistry C|volume=115|issue=50|pages=24586–24591|doi=10.1021/jp2076325|issn=1932-7447|arxiv=1110.3848|s2cid=95117205}} or converted back to the 2H-phase by microwave radiation.{{Cite journal|last1=Xu|first1=Danyun|last2=Zhu|first2=Yuanzhi|last3=Liu|first3=Jiapeng|last4=Li|first4=Yang|last5=Peng|first5=Wenchao|last6=Zhang|first6=Guoliang|last7=Zhang|first7=Fengbao|last8=Fan|first8=Xiaobin|date=2016|title=Microwave-assisted 1T to 2H phase reversion of MoS 2 in solution: a fast route to processable dispersions of 2H-MoS 2 nanosheets and nanocomposites|journal=Nanotechnology|language=en|volume=27|issue=38|pages=385604|doi=10.1088/0957-4484/27/38/385604|pmid=27528593|issn=0957-4484|bibcode=2016Nanot..27L5604X|s2cid=23849142}} The 2H/1T-phase transition can be controlled via the incorporation of sulfur (S) vacancies.{{Cite journal |last1=Gan |first1=Xiaorong |last2=Lee |first2=Lawrence Yoon Suk |last3=Wong |first3=Kwok-yin |last4=Lo |first4=Tsz Wing |last5=Ho |first5=Kwun Hei |last6=Lei |first6=Dang Yuan |last7=Zhao |first7=Huimin |date=2018-09-24 |title=2H/1T Phase Transition of Multilayer MoS 2 by Electrochemical Incorporation of S Vacancies |url=https://pubs.acs.org/doi/10.1021/acsaem.8b00875 |journal=ACS Applied Energy Materials |language=en |volume=1 |issue=9 |pages=4754–4765 |doi=10.1021/acsaem.8b00875 |s2cid=106014720 |issn=2574-0962|url-access=subscription }}

Nanotube-like and buckyball-like molecules composed of {{chem2|MoS2}} are known.{{Cite journal | doi = 10.1039/B901466G| pmid = 20419198| title = Recent progress in the research of inorganic fullerene-like nanoparticles and inorganic nanotubes| journal = Chemical Society Reviews| volume = 39| issue = 5| pages = 1423–34| year = 2010| last1 = Tenne | first1 = R. | last2 = Redlich | first2 = M.}}

While bulk {{chem2|MoS2}} in the 2H-phase is known to be an indirect-band gap semiconductor, monolayer {{chem2|MoS2}} has a direct band gap. The layer-dependent optoelectronic properties of {{chem2|MoS2}} have promoted much research in 2-dimensional {{chem2|MoS2}}-based devices. 2D {{chem2|MoS2}} can be produced by exfoliating bulk crystals to produce single-layer to few-layer flakes either through a dry, micromechanical process or through solution processing.

Micromechanical exfoliation, also pragmatically called "Scotch-tape exfoliation", involves using an adhesive material to repeatedly peel apart a layered crystal by overcoming the van der Waals forces. The crystal flakes can then be transferred from the adhesive film to a substrate. This facile method was first used by Konstantin Novoselov and Andre Geim to obtain graphene from graphite crystals. However, it can not be employed for a uniform 1-D layers because of weaker adhesion of {{chem2|MoS2}} to the substrate (either silicon, glass or quartz); the aforementioned scheme is good for graphene only.{{Cite journal|last1=Novoselov|first1=K. S.|last2=Geim|first2=A. K.|last3=Morozov|first3=S. V.|last4=Jiang|first4=D.|last5=Zhang|first5=Y.|last6=Dubonos|first6=S. V.|last7=Grigorieva|first7=I. V.|last8=Firsov|first8=A. A.|date=2004-10-22|title=Electric Field Effect in Atomically Thin Carbon Films|journal=Science|language=en|volume=306|issue=5696|pages=666–669|doi=10.1126/science.1102896|issn=0036-8075|pmid=15499015|bibcode=2004Sci...306..666N|arxiv=cond-mat/0410550|s2cid=5729649}} While Scotch tape is generally used as the adhesive tape, PDMS stamps can also satisfactorily cleave {{chem2|MoS2}} if it is important to avoid contaminating the flakes with residual adhesive.{{Cite journal|last1=Castellanos-Gomez|first1=Andres|last2=Poot|first2=Menno|last3=Steele|first3=Gary A.|last4=van der Zant|first4=Herre S. J.|last5=Agraït|first5=Nicolás|last6=Rubio-Bollinger|first6=Gabino|date=2012-02-07|title=Elastic Properties of Freely Suspended MoS2 Nanosheets|journal=Advanced Materials|language=en|volume=24|issue=6|pages=772–775|doi=10.1002/adma.201103965|pmid=22231284|issn=1521-4095|arxiv=1202.4439|bibcode=2012AdM....24..772C |s2cid=205243099}}

Liquid-phase exfoliation can also be used to produce monolayer to multi-layer {{chem2|MoS2}} in solution. A few methods include lithium intercalation{{Cite journal|last1=Wan|first1=Jiayu|last2=Lacey|first2=Steven D.|last3=Dai|first3=Jiaqi|last4=Bao|first4=Wenzhong|last5=Fuhrer|first5=Michael S.|last6=Hu|first6=Liangbing|date=2016-12-05|title=Tuning two-dimensional nanomaterials by intercalation: materials, properties and applications|journal=Chemical Society Reviews|language=en|volume=45|issue=24|pages=6742–6765|doi=10.1039/C5CS00758E|pmid=27704060|issn=1460-4744}} to delaminate the layers and sonication in a high-surface tension solvent.{{Cite journal|last1=Coleman|first1=Jonathan N.|last2=Lotya|first2=Mustafa|last3=O’Neill|first3=Arlene|last4=Bergin|first4=Shane D.|last5=King|first5=Paul J.|last6=Khan|first6=Umar|last7=Young|first7=Karen|last8=Gaucher|first8=Alexandre|last9=De|first9=Sukanta|date=2011-02-04|title=Two-Dimensional Nanosheets Produced by Liquid Exfoliation of Layered Materials|journal=Science|language=en|volume=331|issue=6017|pages=568–571|doi=10.1126/science.1194975|issn=0036-8075|pmid=21292974|bibcode=2011Sci...331..568C|hdl=2262/66458|s2cid=23576676 |hdl-access=free}}{{Cite journal|last1=Zhou|first1=Kai-Ge|last2=Mao|first2=Nan-Nan|last3=Wang|first3=Hang-Xing|last4=Peng|first4=Yong|last5=Zhang|first5=Hao-Li|date=2011-11-11|title=A Mixed-Solvent Strategy for Efficient Exfoliation of Inorganic Graphene Analogues|journal=Angewandte Chemie|language=en|volume=123|issue=46|pages=11031–11034|doi=10.1002/ange.201105364|bibcode=2011AngCh.12311031Z |issn=1521-3757}}

{{chem2|MoS2}} excels as a lubricating material (see below) due to its layered structure and low coefficient of friction. Interlayer sliding dissipates energy when a shear stress is applied to the material. Extensive work has been performed to characterize the coefficient of friction and shear strength of {{chem2|MoS2}} in various atmospheres.{{Cite journal|last1=Donnet|first1=C.|last2=Martin|first2=J. M.|last3=Le Mogne|first3=Th.|last4=Belin|first4=M.|date=1996-02-01|title=Super-low friction of MoS2 coatings in various environments|journal=Tribology International|volume=29|issue=2|pages=123–128|doi=10.1016/0301-679X(95)00094-K}} The shear strength of {{chem2|MoS2}} increases as the coefficient of friction increases. This property is called superlubricity. At ambient conditions, the coefficient of friction for {{chem2|MoS2}} was determined to be 0.150, with a corresponding estimated shear strength of 56.0 MPa. Direct methods of measuring the shear strength indicate that the value is closer to 25.3 MPa.{{Cite journal|last1=Oviedo|first1=Juan Pablo|last2=KC|first2=Santosh|last3=Lu|first3=Ning|last4=Wang|first4=Jinguo|last5=Cho|first5=Kyeongjae|last6=Wallace|first6=Robert M.|last7=Kim|first7=Moon J.|date=2015-02-24|title=In Situ TEM Characterization of Shear-Stress-Induced Interlayer Sliding in the Cross Section View of Molybdenum Disulfide|journal=ACS Nano|volume=9|issue=2|pages=1543–1551|doi=10.1021/nn506052d|pmid=25494557|issn=1936-0851}}

The wear resistance of {{chem2|MoS2}} in lubricating applications can be increased by doping {{chem2|MoS2}} with Cr. Microindentation experiments on nanopillars of Cr-doped {{chem2|MoS2}} found that the yield strength increased from an average of 821 MPa for pure {{chem2|MoS2}} (at 0% Cr) to 1017 MPa at 50% Cr.{{Cite journal|last1=Tedstone|first1=Aleksander A.|last2=Lewis|first2=David J.|last3=Hao|first3=Rui|last4=Mao|first4=Shi-Min|last5=Bellon|first5=Pascal|last6=Averback|first6=Robert S.|last7=Warrens|first7=Christopher P.|last8=West|first8=Kevin R.|last9=Howard|first9=Philip|date=2015-09-23|title=Mechanical Properties of Molybdenum Disulfide and the Effect of Doping: An in Situ TEM Study|journal=ACS Applied Materials & Interfaces|volume=7|issue=37|pages=20829–20834|doi=10.1021/acsami.5b06055|pmid=26322958|issn=1944-8244|doi-access=free}} The increase in yield strength is accompanied by a change in the failure mode of the material. While the pure {{chem2|MoS2}} nanopillar fails through a plastic bending mechanism, brittle fracture modes become apparent as the material is loaded with increasing amounts of dopant.

The widely used method of micromechanical exfoliation has been carefully studied in {{chem2|MoS2}} to understand the mechanism of delamination in few-layer to multi-layer flakes. The exact mechanism of cleavage was found to be layer dependent. Flakes thinner than 5 layers undergo homogenous bending and rippling, while flakes around 10 layers thick delaminated through interlayer sliding. Flakes with more than 20 layers exhibited a kinking mechanism during micromechanical cleavage. The cleavage of these flakes was also determined to be reversible due to the nature of van der Waals bonding.{{Cite journal|last1=Tang|first1=Dai-Ming|last2=Kvashnin|first2=Dmitry G.|last3=Najmaei|first3=Sina|last4=Bando|first4=Yoshio|last5=Kimoto|first5=Koji|last6=Koskinen|first6=Pekka|last7=Ajayan|first7=Pulickel M.|last8=Yakobson|first8=Boris I.|last9=Sorokin|first9=Pavel B.|date=2014-04-03|title=Nanomechanical cleavage of molybdenum disulphide atomic layers|journal=Nature Communications|language=en|volume=5|pages=3631|doi=10.1038/ncomms4631|pmid=24698887|bibcode=2014NatCo...5.3631T|doi-access=free}}

In recent years, {{chem2|MoS2}} has been utilized in flexible electronic applications, promoting more investigation into the elastic properties of this material. Nanoscopic bending tests using AFM cantilever tips were performed on micromechanically exfoliated {{chem2|MoS2}} flakes that were deposited on a holey substrate.{{Cite journal|last1=Bertolazzi|first1=Simone|last2=Brivio|first2=Jacopo|last3=Kis|first3=Andras|title=Stretching and Breaking of Ultrathin MoS2|journal=ACS Nano|language=en|volume=5|issue=12|pages=9703–9709|doi=10.1021/nn203879f|pmid=22087740|year=2011|url=http://infoscience.epfl.ch/record/170263}} The Young's modulus of monolayer flakes was 270 GPa, while the thicker flakes were stiffer, with a Young's modulus of 330 GPa. Molecular dynamic simulations found the in-plane Young's modulus of {{chem2|MoS2}} to be 229 GPa, which matches the experimental results within error.{{Cite journal|last1=Jiang|first1=Jin-Wu|last2=Park|first2=Harold S.|last3=Rabczuk|first3=Timon|date=2013-08-12|title=Molecular dynamics simulations of single-layer molybdenum disulphide (MoS2): Stillinger-Weber parametrization, mechanical properties, and thermal conductivity|journal=Journal of Applied Physics|volume=114|issue=6|pages=064307–064307–10|doi=10.1063/1.4818414|issn=0021-8979|bibcode=2013JAP...114f4307J|arxiv=1307.7072|s2cid=119304891}}

Bertolazzi and coworkers also characterized the failure modes of the suspended monolayer flakes. The strain at failure ranges from 6 to 11%. The average yield strength of monolayer {{chem2|MoS2}} is 23 GPa, which is close to the theoretical fracture strength for defect-free {{chem2|MoS2}}.

The band structure of {{chem2|MoS2}} is sensitive to strain.{{cite journal| first1=H. | last1=Li| first2= J. | last2=Wu| first3= Z. | last3=Yin | first4=H. | last4=Zhang| title=Preparation and Applications of Mechanically Exfoliated Single-Layer and Multilayer MoS₂ and WSe₂ Nanosheets| journal= Acc. Chem. Res.| year= 2014| volume= 47| issue=4| pages= 1067–75| doi=10.1021/ar4002312| pmid=24697842}}{{Cite journal|title=Novel effects of strains in graphene and other two dimensional materials|journal=Physics Reports|volume=1503|pages=1–54|doi= 10.1016/j.physrep.2015.12.006|year=2016|last1=Amorim|first1=B.|last2=Cortijo|first2=A.|last3=De Juan|first3=F.|last4=Grushin|first4=A.G.|last5=Guinea|first5=F.|last6=Gutiérrez-Rubio|first6=A.|last7=Ochoa|first7=H.|last8=Parente|first8=V.|last9=Roldán|first9=R.|last10=San-Jose|first10=P.|last11=Schiefele|first11=J.|last12=Sturla|first12=M.|last13=Vozmediano|first13=M.A.H.|bibcode=2016PhR...617....1A|arxiv=1503.00747|s2cid=118600177}}{{cite journal | last1 = Zhang | first1 = X. | last2 = Lai | first2 = Z. | last3 = Tan | first3 = C. | last4 = Zhang | first4 = H. | year = 2016 | title = Solution-Processed Two-Dimensional MoS₂ Nanosheets: Preparation, Hybridization, and Applications | journal = Angew. Chem. Int. Ed. | volume = 55 | issue = 31| pages = 8816–8838 | doi = 10.1002/anie.201509933 | pmid = 27329783}}

Molybdenum disulfide is stable in air and attacked only by aggressive reagents. It reacts with oxygen upon heating forming molybdenum trioxide:

:{{chem2|2 MoS2 + 7 O2 → 2 MoO3 + 4 SO2}}

Chlorine attacks molybdenum disulfide at elevated temperatures to form molybdenum pentachloride:

:{{chem2|2 MoS2 + 7 Cl2 → 2 MoCl5 + 2 S2Cl2}}

Molybdenum disulfide is a host for formation of intercalation compounds. This behavior is relevant to its use as a cathode material in batteries.{{cite journal | last1 = Stephenson | first1 = T. | last2 = Li | first2 = Z. | last3 = Olsen | first3 = B. | last4 = Mitlin | first4 = D. | year = 2014 | title = Lithium Ion Battery Applications of Molybdenum Disulfide (MoS₂) Nanocomposites | journal = Energy Environ. Sci. | volume = 7 | pages = 209–31 | doi = 10.1039/C3EE42591F}}{{cite journal | last1 = Benavente | first1 = E. | last2 = Santa Ana | first2 = M. A. | last3 = Mendizabal | first3 = F. | last4 = Gonzalez | first4 = G. | year = 2002 | title = Intercalation chemistry of molybdenum disulfide | journal = Coordination Chemistry Reviews | volume = 224 | issue = 1–2 | pages = 87–109 | doi = 10.1016/S0010-8545(01)00392-7 | hdl = 10533/173130 | hdl-access = free}} One example is a lithiated material, {{chem2|Li_{x}MoS2}}.{{cite book|title =Progress in intercalation research|author1=Müller-Warmuth, W. |author2=Schöllhorn, R. |name-list-style=amp | url={{Google books|id=IyB_rPo3osUC|page=50|plainurl=yes}} |publisher= Springer| year = 1994| isbn =978-0-7923-2357-0}} With butyl lithium, the product is {{chem2|LiMoS2}}.

File:Graphite moly.jpg

Due to weak van der Waals interactions between the sheets of sulfide atoms, {{chem2|MoS2}} has a low coefficient of friction. {{chem2|MoS2}} in particle sizes in the range of 1–100 μm is a common dry lubricant.{{citation| last=Claus| first= F. L. |year= 1972| title=Solid Lubricants and Self-Lubricating Solids| journal= New York: Academic Press | bibcode= 1972slsl.book.....C}} Few alternatives exist that confer high lubricity and stability at up to 350 °C in oxidizing environments. Sliding friction tests of {{chem2|MoS2}} using a pin on disc tester at low loads (0.1–2 N) give friction coefficient values of <0.1.{{cite book|first1=Gary L. |last1=Miessler|first2=Donald Arthur|last2= Tarr|title=Inorganic Chemistry|url={{google books |plainurl=y |id=oLQPAQAAMAAJ}}|year=2004|publisher=Pearson Education|isbn=978-0-13-035471-6}}{{cite book|first1=Duward |last1=Shriver|first2=Peter |last2=Atkins|title=Inorganic Chemistry|url={{google books |plainurl=y |id=so8oAQAAMAAJ}}|date=17 February 2006|publisher=W. H. Freeman|isbn=978-0-7167-4878-6| last3= Overton| first3= T. L.| last4= Rourke| first4= J. P.| last5= Weller| first5= M. T.| last6= Armstrong| first6= F. A.}}

{{chem2|MoS2}} is often a component of blends and composites that require low friction. For example, it is added to graphite to improve sticking. A variety of oils and greases are used, because they retain their lubricity even in cases of almost complete oil loss, thus finding a use in critical applications such as aircraft engines. When added to plastics, {{chem2|MoS2}} forms a composite with improved strength as well as reduced friction. Polymers that may be filled with {{chem2|MoS2}} include nylon (trade name Nylatron), Teflon and Vespel. Self-lubricating composite coatings for high-temperature applications consist of molybdenum disulfide and titanium nitride, using chemical vapor deposition.

Examples of applications of {{chem2|MoS2}}-based lubricants include two-stroke engines (such as motorcycle engines), bicycle coaster brakes, automotive CV and universal joints, ski waxes{{cite web| access-date = 2011-01-06| url = http://www.swixsport.com/dav/8dde5f4784.pdf| title = On dry lubricants in ski waxes| publisher = Swix Sport AX| url-status = dead| archive-url = https://web.archive.org/web/20110716174041/http://www.swixsport.com/dav/8dde5f4784.pdf| archive-date = 2011-07-16}} and bullets.{{cite web| access-date = 2009-06-06| url = http://www.norma.cc/en/Ammunition-Academy/Barrel-wear/| title = Barrels retain accuracy longer with Diamond Line| publisher=Norma}}

Other layered inorganic materials that exhibit lubricating properties (collectively known as solid lubricants (or dry lubricants)) includes graphite, which requires volatile additives and hexagonal boron nitride.{{cite book|title=Ullmann's Encyclopedia of Industrial Chemistry|last=Bartels|first=Thorsten|publisher=Wiley VCH|year=2002|location=Weinheim|chapter=Lubricants and Lubrication|doi=10.1002/14356007.a15_423|display-authors=etal|isbn=978-3527306732}}

File:Molybdenum disulfide - 17.jpg revealed by molybdenum disulfide]]

{{chem2|MoS2}} is employed as a cocatalyst for desulfurization in petrochemistry, for example, hydrodesulfurization. The effectiveness of the {{chem2|MoS2}} catalysts is enhanced by doping with small amounts of cobalt or nickel. The intimate mixture of these sulfides is supported on alumina. Such catalysts are generated in situ by treating molybdate/cobalt or nickel-impregnated alumina with {{chem|H|2|S}} or an equivalent reagent. Catalysis does not occur at the regular sheet-like regions of the crystallites, but instead at the edge of these planes.{{cite book| last1= Topsøe| first1= H.| last2= Clausen| first2= B. S.| last3= Massoth| first3= F. E. | title =Hydrotreating Catalysis, Science and Technology| publisher = Springer-Verlag| location= Berlin| year = 1996}}

{{chem2|MoS2}} finds use as a hydrogenation catalyst for organic synthesis.{{cite book|last1=Nishimura|first1=Shigeo|title=Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis|date=2001|publisher=Wiley-Interscience| location= New York| isbn= 9780471396987|pages=43–44 & 240–241|edition=1st|url={{google books |plainurl=y |id=RjZRAAAAMAAJ|page=43}}}} As it is derived from a common transition metal, rather than a group 10 metal, {{chem2|MoS2}} is chosen when price or resistance to sulfur poisoning are of primary concern. {{chem2|MoS2}} is effective for the hydrogenation of nitro compounds to amines and can be used to produce secondary amines via reductive amination.{{cite journal|last1=Dovell|first1=Frederick S.| last2= Greenfield| first2= Harold| title=Base-Metal Sulfides as Reductive Alkylation Catalysts|journal=The Journal of Organic Chemistry|date=1964|volume=29|issue=5|pages=1265–1267|doi=10.1021/jo01028a511}} The catalyst can also effect hydrogenolysis of organosulfur compounds, aldehydes, ketones, phenols and carboxylic acids to their respective alkanes. However, it suffers from low activity, often requiring hydrogen pressures above 96 MPa and temperatures above 185 °C.

{{chem2|MoS2}} plays an important role in condensed matter physics research.{{Cite web |last=Wood |first=Charlie |date=2022-08-16 |title=Physics Duo Finds Magic in Two Dimensions |url=https://www.quantamagazine.org/physics-duo-finds-magic-in-two-dimensions-20220816/ |access-date=2022-08-19 |website=Quanta Magazine |language=en}}

{{chem2|MoS2}} and related molybdenum sulfides are efficient catalysts for hydrogen evolution, including the electrolysis of water;{{cite journal| last1= Kibsgaard| first1= Jakob| last2=Jaramillo|first2=Thomas F.|last3=Besenbacher|first3=Flemming|title=Building an appropriate active-site motif into a hydrogen-evolution catalyst with thiomolybdate [Mo₃S₁₃]²⁻ clusters|journal=Nature Chemistry| volume= 6| issue= 3| year= 2014| pages= 248–253|doi=10.1038/nchem.1853|pmid=24557141|bibcode=2014NatCh...6..248K| url= https://zenodo.org/record/889641}}{{cite journal| first1=A. B. | last1= Laursen| first2= S. | last2= Kegnaes| first3=S. | last3= Dahl | first4= I. | last4= Chorkendorff| title= Molybdenum Sulfides – Efficient and Viable Materials for Electro- and Photoelectrocatalytic Hydrogen Evolution| journal=Energy Environ. Sci.| year= 2012| volume= 5| issue= 2| pages= 5577–91| doi=10.1039/c2ee02618j}} thus, are possibly useful to produce hydrogen for use in fuel cells.{{cite web|title=Superior hydrogen catalyst just grows that way|url=https://share-ng.sandia.gov/news/resources/news_releases/superior-catalyst/#.Wia84bbMw5s|website=share-ng.sandia.gov|publisher=Sandia Labs|access-date=December 5, 2017|format=news release|quote=a spray-printing process that uses molybdenum disulfide to create a “flowering” hydrogen catalyst far cheaper than platinum and reasonably close in efficiency.}}

{{chem2|MoS2}}@Fe-N-C core/shell{{Cite journal |last1=Yan |first1=Yan |last2=Liang |first2=Shuang |last3=Wang |first3=Xiang |last4=Zhang |first4=Mingyue |last5=Hao |first5=Shu-Meng |last6=Cui |first6=Xun |last7=Li |first7=Zhiwei |last8=Lin |first8=Zhiqun |date=2021-10-05 |title=Robust wrinkled MoS 2 /N-C bifunctional electrocatalysts interfaced with single Fe atoms for wearable zinc-air batteries |journal=Proceedings of the National Academy of Sciences |language=en |volume=118 |issue=40 |pages=e2110036118 |doi=10.1073/pnas.2110036118 |issn=0027-8424 |pmc=8501804 |pmid=34588309|bibcode=2021PNAS..11810036Y |doi-access=free}} nanosphere with atomic Fe-doped surface and interface ({{chem2|MoS2}}/Fe-N-C) can be used as a used an electrocatalyst for oxygen reduction and evolution reactions (ORR and OER) bifunctionally because of reduced energy barrier due to Fe-N₄ dopants and unique nature of {{chem2|MoS2}}/Fe-N-C interface.

As in graphene, the layered structures of {{chem2|MoS2}} and other transition metal dichalcogenides exhibit electronic and optical properties{{Cite journal | last1 = Wang | first1 = Q. H. | last2 = Kalantar-Zadeh | first2 = K. | last3 = Kis | first3 = A. | last4 = Coleman | first4 = J. N. | last5 = Strano | first5 = M. S. | title = Electronics and optoelectronics of two-dimensional transition metal dichalcogenides | doi = 10.1038/nnano.2012.193 | journal = Nature Nanotechnology | volume = 7 | issue = 11 | pages = 699–712 | year = 2012 | pmid = 23132225| bibcode = 2012NatNa...7..699W | s2cid = 6261931 | url = http://infoscience.epfl.ch/record/182177}} that can differ from those in bulk.{{cite journal| first1=R. |last1=Ganatra |first2= Q. |last2= Zhang| title= Few-Layer MoS₂: A Promising Layered Semiconductor| journal= ACS Nano| year= 2014| volume= 8|issue=5 | pages= 4074–99| doi=10.1021/nn405938z|pmid=24660756}} Bulk {{chem2|MoS2}} has an indirect band gap of 1.2 eV,{{cite journal|doi=10.1038/ncomms4087|pmid=24435154|title=Electronic transport and device prospects of monolayer molybdenum disulphide grown by chemical vapour deposition|journal=Nature Communications|volume=5|pages=3087|year=2014|last1=Zhu|first1=Wenjuan|last2=Low|first2=Tony|last3=Lee|first3=Yi-Hsien|last4=Wang|first4=Han|last5=Farmer|first5=Damon B.|last6=Kong|first6=Jing|last7=Xia|first7=Fengnian|last8=Avouris|first8=Phaedon|bibcode=2014NatCo...5.3087Z|arxiv=1401.4951|s2cid=6075401}}{{cite journal|doi=10.1038/ncomms7293|pmid=25695374|pmc=4346634|title=Exploring atomic defects in molybdenum disulphide monolayers|journal=Nature Communications|volume=6|pages=6293|year=2015|last1=Hong|first1=Jinhua|last2=Hu|first2=Zhixin|last3=Probert|first3=Matt|last4=Li|first4=Kun|last5=Lv|first5=Danhui|last6=Yang|first6=Xinan|last7=Gu|first7=Lin|last8=Mao|first8=Nannan|last9=Feng|first9=Qingliang|last10=Xie|first10=Liming|last11=Zhang|first11=Jin|last12=Wu|first12=Dianzhong|last13=Zhang|first13=Zhiyong|last14=Jin|first14=Chuanhong|last15=Ji|first15=Wei|last16=Zhang|first16=Xixiang|last17=Yuan|first17=Jun|last18=Zhang|first18=Ze|bibcode=2015NatCo...6.6293H}} while Transition metal dichalcogenide monolayers have a direct 1.8 eV electronic bandgap,{{cite journal|last1=Splendiani| first1=A.| last2= Sun| first2= L.| last3= Zhang| first3=Y.| last4= Li| first4= T.| last5= Kim| first5= J.|last6=Chim|first6=J.|last7=F.|year=2010|title=Emerging Photoluminescence in Monolayer MoS₂|journal=Nano Letters|volume=10|issue=4|pages=1271–1275| doi=10.1021/nl903868w| pmid=20229981|bibcode=2010NanoL..10.1271S|last8=Wang|first8=Feng}} supporting switchable transistors and photodetectors.{{cite journal | last1 = Lopez-Sanchez | first1 = O. | last2 = Lembke | first2 = D. | last3 = Kayci | first3 = M. | last4 = Radenovic | first4 = A. | last5 = Kis | first5 = A. | year = 2013 | title = Ultrasensitive photodetectors based on monolayer MoS₂ | journal = Nature Nanotechnology | volume = 8 | issue = 7| pages = 497–501 | doi = 10.1038/nnano.2013.100 | pmid = 23748194 | bibcode = 2013NatNa...8..497L | s2cid = 5435971 | url = http://infoscience.epfl.ch/record/183895}}{{cite journal| first1=C. N. R. |last1= Rao| first2= H. S. S. |last2=Ramakrishna Matte |first3=U. |last3=Maitra| title= Graphene Analogues of Inorganic Layered Materials| journal= Angew. Chem.| edition= International| year= 2013| volume= 52|issue= 50| pages= 13162–85|doi=10.1002/anie.201301548|pmid= 24127325}}

{{chem2|MoS2}} nanoflakes can be used for solution-processed fabrication of layered memristive and memcapacitive devices through engineering a {{chem2|MoO_{x}|}}/{{chem2|MoS2}} heterostructure sandwiched between silver electrodes.{{Cite journal | doi = 10.1038/nmat4135| pmid = 25384168| title = Layered memristive and memcapacitive switches for printable electronics| journal = Nature Materials| volume = 14| issue = 2| pages = 199–204| year = 2014| last1 = Bessonov | first1 = A. A. | last2 = Kirikova | first2 = M. N. | last3 = Petukhov | first3 = D. I. | last4 = Allen | first4 = M. | last5 = Ryhänen | first5 = T. | last6 = Bailey | first6 = M. J. A. | bibcode = 2015NatMa..14..199B}} {{chem2|MoS2}}-based memristors are mechanically flexible, optically transparent and can be produced at low cost.

The sensitivity of a graphene field-effect transistor (FET) biosensor is fundamentally restricted by the zero band gap of graphene, which results in increased leakage and reduced sensitivity. In digital electronics, transistors control current flow throughout an integrated circuit and allow for amplification and switching. In biosensing, the physical gate is removed and the binding between embedded receptor molecules and the charged target biomolecules to which they are exposed modulates the current.{{cite news |title=Ultrasensitive biosensor from molybdenite semiconductor outshines graphene |date= 4 September 2014 |url=http://www.rdmag.com/news/2014/09/ultrasensitive-biosensor-molybdenite-semiconductor-outshines-graphene?et_cid=4135513&et_rid=677699018&location=top |work=R&D Magazine}}

{{chem2|MoS2}} has been investigated as a component of flexible circuits.{{Cite journal|title = Two-dimensional flexible nanoelectronics|journal = Nature Communications|date = 2014-12-17|pages = 5678|volume = 5|doi = 10.1038/ncomms6678|first1 = Deji|last1 = Akinwande|first2 = Nicholas|last2 = Petrone|first3 = James|last3 = Hone|pmid=25517105|bibcode = 2014NatCo...5.5678A|doi-access = free}}{{Cite journal|title = Large-Area Monolayer MoS₂ for Flexible Low-Power RF Nanoelectronics in the GHz Regime|journal = Advanced Materials|date = 2015-12-01|pages = 1818–1823|doi = 10.1002/adma.201504309|pmid = 26707841|first1 = Hsiao-Yu|last1 = Chang|first2 = Maruthi Nagavalli|last2 = Yogeesh|first3 = Rudresh|last3 = Ghosh|first4 = Amritesh|last4 = Rai|first5 = Atresh|last5 = Sanne|first6 = Shixuan|last6 = Yang|first7 = Nanshu|last7 = Lu|first8 = Sanjay Kumar|last8 = Banerjee|first9 = Deji|last9 = Akinwande|volume=28|issue = 9| s2cid=205264837|doi-access = free}}

In 2017, a 115-transistor, 1-bit microprocessor implementation was fabricated using two-dimensional {{chem2|MoS2}}.{{Cite journal|last1=Wachter|first1=Stefan|last2=Polyushkin|first2=Dmitry K.|last3=Bethge|first3=Ole|last4=Mueller|first4=Thomas|date=2017-04-11|title=A microprocessor based on a two-dimensional semiconductor|journal=Nature Communications|language=en|volume=8|pages=14948|doi=10.1038/ncomms14948|pmid=28398336|pmc=5394242|issn=2041-1723|bibcode=2017NatCo...814948W|arxiv=1612.00965}}

{{chem2|MoS2}} has been used to create 2D 2-terminal memristors and 3-terminal memtransistors.{{Cite news|url=https://www.nextbigfuture.com/2018/02/memtransistors-advance-neuromorphic-computing.html|title=Memtransistors advance neuromorphic computing {{!}} NextBigFuture.com|date=2018-02-24|work=NextBigFuture.com|access-date=2018-02-27|language=en-US}}

Due to the lack of spatial inversion symmetry, odd-layer MoS2 is a promising material for valleytronics because both the CBM and VBM have two energy-degenerate valleys at the corners of the first Brillouin zone, providing an exciting opportunity to store the information of 0s and 1s at different discrete values of the crystal momentum. The Berry curvature is even under spatial inversion (P) and odd under time reversal (T), the valley Hall effect cannot survive when both P and T symmetries are present. To excite valley Hall effect in specific valleys, circularly polarized lights were used for breaking the T symmetry in atomically thin transition-metal dichalcogenides.{{Cite journal |last1=Mak |first1=Kin Fai |last2=He |first2=Keliang |last3=Shan |first3=Jie |last4=Heinz |first4=Tony F. |title=Control of valley polarization in monolayer MoS2 by optical helicity |url=https://www.nature.com/articles/nnano.2012.96 |journal=Nature Nanotechnology |year=2012 |language=en |volume=7 |issue=8 |pages=494–498 |doi=10.1038/nnano.2012.96|pmid=22706698 |arxiv=1205.1822 |bibcode=2012NatNa...7..494M |s2cid=23248686}} In monolayer {{chem2|MoS2}}, the T and mirror symmetries lock the spin and valley indices of the sub-bands split by the spin-orbit couplings, both of which are flipped under T; the spin conservation suppresses the inter-valley scattering. Therefore, monolayer MoS2 have been deemed an ideal platform for realizing intrinsic valley Hall effect without extrinsic symmetry breaking.{{Cite journal |last1=Wu |first1=Zefei |last2=Zhou |first2=Benjamin T. |last3=Cai |first3=Xiangbin |last4=Cheung |first4=Patrick |last5=Liu |first5=Gui-Bin |last6=Huang |first6=Meizhen |last7=Lin |first7=Jiangxiazi |last8=Han |first8=Tianyi |last9=An |first9=Liheng |last10=Wang |first10=Yuanwei |last11=Xu |first11=Shuigang |last12=Long |first12=Gen |last13=Cheng |first13=Chun |last14=Law |first14=Kam Tuen |last15=Zhang |first15=Fan |date=2019-02-05 |title=Intrinsic valley Hall transport in atomically thin MoS2 |journal=Nature Communications |volume=10 |issue=1 |pages=611 |doi=10.1038/s41467-019-08629-9|pmid=30723283 |pmc=6363770 |arxiv=1805.06686 |bibcode=2019NatCo..10..611W}}

{{chem2|MoS2}} also possesses mechanical strength, electrical conductivity, and can emit light, opening possible applications such as photodetectors.{{Cite web|url = http://www.gizmag.com/molybdenum-di-sulphide-metal-graphene/33980|title = Metal-based graphene alternative "shines" with promise|date = September 25, 2014|access-date = September 30, 2014|publisher = Gizmag|last = Coxworth|first = Ben}} {{chem2|MoS2}} has been investigated as a component of photoelectrochemical (e.g. for photocatalytic hydrogen production) applications and for microelectronics applications.{{cite journal|last1=Radisavljevic|first1=B.|last2=Radenovic|first2=A.|last3=Brivio|first3=J.|last4=Giacometti|first4=V.|last5=Kis|first5=A.|year=2011| title=Single-layer MoS₂ transistors| journal=Nature Nanotechnology| volume=6| issue=3| pages=147–150|doi=10.1038/nnano.2010.279| pmid=21278752|bibcode=2011NatNa...6..147R|url=http://infoscience.epfl.ch/record/164049}}

Under an electric field {{chem2|MoS2}} monolayers have been found to superconduct at temperatures below 9.4 K.{{Cite journal|url=https://aip.scitation.org/doi/abs/10.1063/1.4740268|title=Electric-field-induced superconductivity at 9.4 K in a layered transition metal disulphide MoS2|first1=Kouji|last1=Taniguchi|first2=Akiyo|last2=Matsumoto|first3=Hidekazu|last3=Shimotani|first4=Hidenori|last4=Takagi|date=July 23, 2012|journal=Applied Physics Letters|volume=101|issue=4|pages=042603|via=aip.scitation.org (Atypon)|doi=10.1063/1.4740268|bibcode=2012ApPhL.101d2603T|url-access=subscription}}

• Molybdenum diselenide

{{reflist|30em}}

• {{Cite web |last=Wood |first=Charlie |date=2022-08-16 |title=Physics Duo Finds Magic in Two Dimensions |url=https://www.quantamagazine.org/physics-duo-finds-magic-in-two-dimensions-20220816/ |access-date=2022-08-19 |website=Quanta Magazine |language=en}}

{{Commons category|Molybdenum disulfide}}

{{Molybdenum compounds}}

{{sulfides}}

Category:Molybdenum(IV) compounds

Category:Disulfides

Category:Non-petroleum based lubricants

Category:Dry lubricants

Category:Semiconductor materials

Category:Transition metal dichalcogenides

Category:Hydrogenation catalysts

Category:Monolayers