1

LiHMediatedNH3SynthesisUnderMildCondi6on

JPGuo,PKWang,FChang,WBGao,THe,GTWu,PCHEN

DivisionforHydrogenEnergyandAdvancedMaterialsDalianInsDtuteofChemicalPhysic(DICP)

ChineseAcademyofSciences(CAS)

Contents

2

3

Components Proper6es

EarlyTM •  Negligibleac6vity

•  Formingstablebulknitrides

LateTM •  Negligibleac6vity

•  PredominantlycoveredwithH

Ru,FeandCo •  Effec6veunderhightemperaturesandhighpressures

•  Promotersneeded

Electronic

Promoters Cs > K > Na >> Li

BondNtoostrongly

BondNtooweakly

Controversialinterpreta6ons

CatalystsforNH3synthesis

LogadoIrandNørskovetal.JCatal,2001,197,229

Nørskovetal.,Nat.Chem.,2009,1,37

Sautetetal.,Nat.Chem.,2015,7,403

CoMoN

4 OnsiteX

Conduc6nghydrogena6onelsewhere?

100 200 300 400 5002

4

6

8

10

12

14

16

18

Am

oun

t of

H2 d

esor

bed

(w

t%)

Temperature (°C) 5

LiNH2-LiH

Mg(NH2)2-2LiH 2LiNH2-CaH2

Ca(NH2BH3)2

Li2EDA

LiBH4-NH2NH2

LiNH2BH3

Mg(NH2BH3)2-NH3

Target

PChen*

NatureRev:Mater2016

AdvEnergyMater2017

EES2008,2010,2011,2012

AngewChem2009

NatureMater2008Nature2002

HydridesforNH3

Ac6va6on SiteA

•  H2(g)+2*⇋2Had*• 

•  N2(g)+*⇋N2ad*

•  N2ad*+*→2Nad*

•  Nad*+Had*⇋NHad*

•  NHad*+Had*⇋NH2ad*

•  NH2ad*+Had*⇋NH3ad*

•  NH3ad*⇋NH3(g)+*

Elementarysteps

6

Early and late transition metals are candidates for N2 activation

7

Hydrogena6on SiteB

Ac6va6on SiteA

•  H2(g)+2*⇋2Had*• 

•  N2(g)+*⇋N2ad*

•  N2ad*+*→2Nad*

•  Nad*+Had*⇋NHad*

•  NHad*+Had*⇋NH2ad*

•  NH2ad*+Had*⇋NH3ad*

•  NH3ad*⇋NH3(g)+*

Elementarysteps

8

9

Hydrogena6ontoNH3

ANH2+H2=AH+NH3

LiH

KH

CaH2

BaH2

LiNH2

KNH2

Ca(NH2)2

Ba(NH2)2

+ H2

NH3

+N2??

10 •  H.Yamamoto,H.Miyaoka,S.Hino,H.Nakanishi,T.Ichikawa,Y.Kojima.Int.J.HydrogenEnerg.,

2009,34,9760-9764.

Hydrogena6on SiteB

Ac6va6on SiteA

•  H2(g)+2*⇋2Had*

•  N2(g)+*⇋N2ad*

•  N2ad*+*→2Nad*

•  Nad*+Had*⇋NHad*

•  NHad*+Had*⇋NH2ad*

•  NH2ad*+Had*⇋NH3ad*

•  NH3ad*⇋NH3(g)+*

Elementarysteps

11

N Transfer from TMN to LiH

300 400 500 600 700

-60

-40

-20

0

20

Fe4N+3/2H2=4Fe+NH3

Fe4N+3/2LiH=4Fe+1/2LiNH2+1/2Li2NH

2Mn2N+3/2H2=Mn4N+NH3

2Mn2N+3/2LiH=Mn4N+1/2LiNH2+1/2Li2NH

ΔG

(kJ m

ol-1)

T (K)

TMN + LiH → TMN1-x + Li2NH

12

Strongreductant

•  Experimental results show that LiH can abstract N from CrN, Mn2N and

Fe4N, respectively, forming Li2NH, LiNH2 and N-deficient nitride or metal.

13 XRDpaLernsshowtheNtransferfromMn2N(a)toLiHformingMn4N(b).

30 40 50 60 70

¢

¢

¢

Mn4N

t t tt

t

t

¢

Mn2Nt

2theta (deg ree)

a

b

IRresultsdemonstratetheformaDonofLi2NHandLiNH2.

3000 3100 3200 3300 3400 3500

L iH

Mn-L iH

νNH 2-

νasNH

2

-

Wavenumber(cm -1)

νsNH

2

-

Mn2N+LiH=Mn4N+LiNHx

NH3fromthehydrogena6onofLiNH2

14

•  Li2NHandLiNH2undergoself-hydrogenatedtoNH3attemperaturerightabove

400K.LiHisregenerated.

NH3 signal

LiNHx+H2=LiH+NH3

TM

LiH Li H

TM + N2 → TMNx（1）

LiH + TMNx → TM + LiNH2（2）

LiNH2 + H2 → LiH + NH3（3） N

NH

TM

LiH Li

NN

H TM

LiH Li

1

2

3

ChemicalCycle

15 -  Wang,Chang,Gao,Guo,Chenetal.NatureChem(2017)

N NH

NH2

ENH,NH2≠a’EN+b’

ENH,NH2=aEN+b

BreakingScalingRela6ons

N

NH/NH2

16

NH3

NH3

Cataly6cac6vi6es

l  Universalac6vi6esof3dTM(N)–LiH

l  TheFe-LiHandCo-LiHshowac6vi6esofca.69and56μmolg-1h-1at150°C. 17

N2/H2=1/3

10bar

WHSV:60000mL/g-h

Ac6va6onenergy:

<65kJ/mol

18

l  NeatV,Cr,Mn,CoandNihavenegligiblecatalyDcacDviDes.UponcomposiDngwithLiH,upto4ordersofmagnitudehigherthanthecorrespondingtransiDonmetalsareachieved.

Highlandvs.volcano

573K

-  Wang,Chang,Gao,Guo,Chenetal.NatureChem(2017)

4orders

Otheralkalihydrides?

Inoxideform:Cs>Rb>K>Na>>Li

Inhydrideform:

LiH>KH(Rb)>>NaH

Fe

•  Unpublisheddata

L.D.Kuzniecov,L.M.Dmitrienko,P.D.Rabina,U.A.Sokolinski,Chimia[M],Moscow,1982.

Alkalineearthhydrides?

•  Synthesis:BaH2>CaH2>>MgH2

•  Decomposi6on:BaNH>CaNH>>Mg3N2

•  Unpublisheddata

•  Unpublished results

u Catal-X exhibits remarkably high activity & long-term stability for more than

340 hours.

400ºC,1MPa,N2/3H2,30000/h

Catalystofprac6calpoten6al

NH3decomposi6on NH3synthesis

0.1

1

10

100L i2NH-TMNc ompos ites

r/kg N

H3kg c

at-1h

-1

T iV C rMnF eC oNiC u

Neatmetals s upportedonC NT

•  Alterenerge6cs,“break”thescalingrela6ons;•  Chemicalstateofalkali/alkalineearthisdecisive!

22

•  Nature Chem 2017

•  ACS Catal 2017

•  Angew Chem 2017

•  Angew Chem 2015

•  ACS Catal 2015

3orders

4orders

Collaborators:•  AnanWu(XiamenUniv.)

•  JunhuWang(DICP)

•  LingJiang(DICP)

•  MingshuChen(XiamenUniv.)

Funding&Facili6es:•  NSFC

•  DICPDMTOfunding

•  MOST

•  SSRF

Acknowledgements

23

Colleaguesandstudents

A/PJianpingGuo

Prof.GuotaoWu

Prof.TengHe

A/PLinLiu

Ms.XiaohuaJU

PeikunWang,HanWang,FeiChang,

WenboGao,WeijinZhang,

QianruWang，XilunZhang

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Stability

25 •  Wang,Chang,Gao,Guo,Chenetal.NatureChem(2017)

Kine6cparameters

ReacDonordersofN2andH2weremeasuredat633K.Eawasmeasuredinthetemperaturerangeof593-673K.

Catalyst α(NH3) β(N2) γ(H2) Ea(kJmol-1)

Refs

Cr-LiH -1.2 0.43 0.62 63.6 thiswork

Mn-LiH -1.3 0.12 1.1 50.6 thiswork

Fe-LiH -1.3 0.37 0.88 46.5 thiswork

Co-LiH -1.2 0.48 0.65 52.1 thiswork

Cs-Ru/MgO 0.0 0.8 -0.9 109 Aikaetal.

KM1 -1.5 0.9 2.2 70 Chorkendorffetal.

Ba-Co/C -0.9 1.2 0.9 102 Chorkendorffetal.

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