Lithium imide synergy with 3d transition-metal nitrides leading to unprecedented catalytic activities for ammonia decomposition

Article abstract of DOI:10.1002/anie.201410773

Alkali metals have been widely employed as catalyst promoters; however, the promoting mechanism remains essentially unclear. Li, when in the imide form, is shown to synergize with 3d transition metals or their nitrides TM(N) spreading from Ti to Cu, leadi

Full text of DOI:10.1002/anie.201410773

Angewandte
Chemie
DOI: 10.1002/anie.201410773
Ammonia Decomposition Very Important Paper
Lithium Imide Synergy with 3d Transition-Metal Nitrides Leading to
Unprecedented Catalytic Activities for Ammonia Decomposition**
Jianping Guo, Peikun Wang, Guotao Wu, Anan Wu, Daqiang Hu, Zhitao Xiong, Junhu Wang,
Pei Yu, Fei Chang, Zheng Chen, and Ping Chen*
Abstract: Alkali metals have been widely employed as catalyst
promoters; however, the promoting mechanism remains essen-
tially unclear. Li, when in the imide form, is shown to synergize
with 3d transition metals or their nitrides TM(N) spreading
from Ti to Cu, leading to universal and unprecedentedly high
catalytic activities in NH3 decomposition, among which
including ammonia and Fischer–Tropsch syntheses, water-gas
shift, hydrocarbon dehydrogenation, and so on.[2] The diffi-
culties in elucidating the properties of electronic promoters
mainly lie in the facts that they are normally present in small
quantities and the lack of in situ structural information.[3] It is,
therefore, not a surprise to note that the continuous efforts in
identifying the chemical state of K and its interaction with Fe
or Ru in ammonia synthesis, as an example, has lasted for
decades.[2] In-depth surface science and theoretical investiga-
tions show that K may decrease the work function of
transition metals and enhance the dissociative adsorption of
N2 by electron donation to Fe or Ru,[4] and/or weaken the
chemisorption of NH3 by electrostatic interactions.[5] K2O,
KOH, and a K-O-Fe species have been proposed as the
chemical forms.[6] The unclear chemical nature is also true for
other alkali metals, although the promoting capability has
been found to be in the order Cs > K > Na > Li.[7] Herein we
employ NH3 decomposition, a chemical process that has been
extensively studied for understanding the fundamentals of
NH3 synthesis for over half a century and is attracting
increasing attentions to be a potential route providing COx-
free hydrogen for fuel cells in recent years,[8] as a reference
reaction, and choose Li, commonly regarded as the least
electron donating alkali, as a promoter to illustrate that the
elusive electronic-promoting effect can be elucidated when Li
is in imide form and the intermediate ternary nitride species
of Li and transition-metal is formed. More importantly, such
an understanding paves the way for catalytic materials design
and development for processes of chemical production and
clean energy harvesting.
Catalysts developed for NH3 decomposition are mainly
based on Group 8 transition metals, among which Ru has the
highest activity followed by Ir, Rh, Ni, and Fe.[9] Early 3d
transition metals, namely Ti, V, Cr, and Mn, form stable
nitrides under an NH3 atmosphere and are essentially inactive
towards NH3 decomposition under moderate conditions.[10]
Such a situation changes drastically when Li2NH takes part in.
It should be put forth here that, to focus on the neat
interaction between 3d transition metal and Li2NH and to
facilitate the related characterizations, a high content of
Li2NH was employed in this study.
Metallic Li reacts with NH3 to form LiNH2, which
decomposes to NH3 and Li2NH, a compound with cubic
structure and with high Li ion mobility and capability in
storing hydrogen,[11] at temperatures above 523 K under
a flow of argon. An incidental finding that led us to the
present study is the substantial amount of H2 and N2 co-
produced with NH3 when LiNH2 was tested in a stainless steel
rather than a quartz reactor (Supporting Information, Fig-
ꢀ
Li2NH MnN has an activity superior to that of the highly
active Ru/carbon nanotube catalyst. The catalysis is fulfilled
via the two-step cycle comprising: 1) the reaction of Li2NH and
3d TM(N) to form ternary nitride of LiTMN and H2, and
2) the ammoniation of LiTMN to Li2NH, TM(N) and N2
resulting in the neat reaction of 2NH3ÐN2 + 3H2. Li2NH, as
an NH3 transmitting agent, favors the formation of higher N-
content intermediate (LiTMN), where Li executes inductive
ꢀ
effect to stabilize the TM N bonding and thus alters the
reaction energetics.
W
ith more than a hundred years of research and develop-
ment, heterogeneous catalysis has accumulated enormous
experimental and theoretical data that allow the correlation,
in principle, of the electronic structure of a catalyst with the
rate of an elementary step involved in a catalytic process,
which lays the foundation of a catalyst genome.[1] The data
base, however, has a weak link in the concrete and systematic
description of the nature of electronic promoters, the
substances that play vital roles in enhancing activity, selec-
tivity, and/or stability of catalysts for numerous processes
[*] J. Guo, P. Wang, Prof. Dr. G. Wu, D. Hu, Prof. Dr. Z. Xiong,
Prof. Dr. J. Wang, P. Yu, F. Chang, Prof. Dr. P. Chen
Collaborative Innovation Center of Chemistry for Energy Materials,
State Key Laboratory of Catalysis
Dalian Institute of Chemical Physics
Chinese Academy of Sciences, Dalian 116023 (P. R. China)
E-mail: pchen@dicp.ac.cn
Homepage: http://www.imide.dicp.ac.cn
Prof. Dr. A. Wu, Z. Chen
State Key Laboratory of Physical Chemistry of Solid Surfaces and
College of Chemistry and Chemical Engineering
Xiamen University, Xiamen 361005 (P. R. China)
[**] This work was supported by the Project of National Natural Science
Funds for Distinguished Young Scholars (51225206), 973 Project
(2010CB631304), and the National Natural Science Foundation of
China (21133004 and 21273187). We thank D. H. Gregory (Uni-
versity of Glasgow) for the discussions on ternary nitrides of Li and
transition metals and H. Wu (NIST) and M. Yang (DICP) for sharing
the information on metal nitrides and oxynitrides, and also the
Shanghai Synchrotron Radiation Facility for providing the beam
time.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201410773.
Angew. Chem. Int. Ed. 2015, 54, 1 – 6
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1
These are not the final page numbers!

.
Angewandte
Communications
ure S1a,b). If purposely impregnating Fe on LiNH2, signifi-
cantly enhanced yields of H2 and N2 together with a large
depression of NH3 were observed showing considerable
conversion of NH3 to N2 and H2 (Supporting Information,
Figure S1c).
Under a flow of pure NH3, the LiNH2-Fe sample shows
catalytic activity at 623 K, which is about 100 K lower than
that of Fe2N or Fe/CNTs. Its activity is over one order of
magnitude greater than those of Fe2N and Fe/CNTs at
temperatures below 723 K (Figure 1), manifesting the prom-
inent promoting role of Li.
perature. The mixture decomposes to N2 and NH3 at ca.
350 K and 500 K, respectively, regenerating Fe2N and Li2NH
following the overall reaction R2 (Figure 2a and S3b). At
elevated temperatures (see 500 K or above), the ammoniation
of Li3FeN2 should give off N2, Fe2N and Li2NH simulta-
neously. Fe2N and Li2NH, again, go back to the R1
(Supporting Information, Figure S3c) creating a catalytic
cycle that leads to the neat reaction R3:
3 Li2NH þ Fe2N Ð 2 Li3FeN2 þ 3=2 H2
2 Li3FeN2 þ NH3 Ð 3 Li2NH þ Fe2N þ 1=2 N2
NH3 Ð 1=2 N2 þ 3=2 H2
ðR1Þ
ðR2Þ
ðR3Þ
With Li3FeN2 as the starting chemical, similar activity was
observed as that of Li2NH-Fe2N (Supporting Information,
Figure S4). The active phases are again Fe2N and Li2NH.
Third, ND3 and 15NH3 isotopic labeling characterizations on
the Li2NH-Fe2N and 5 wt% Ru/CNTs samples, respectively,
carried out by performing steady-state isotopic transient
kinetic analysis (SSITKA)[12] at 553 K, show that significantly
1
more H2 and 14N2 are observable in the Li2NH-Fe2N than in
the Ru/CNTs within the first 5 min of gas shifting, and these
Figure 1. Rates of ammonia decomposition catalyzed by the Li2NH
1
additional H2 and 14N2 should have higher chances to form
and Fe-based samples. Reaction conditions: 30 mg catalyst, NH3 flow
rate 30 mLminꢀ1
.
directly from the catalyst revealing the occurrences of the R1
and R2 under the reaction condition (indeed, both R1 and R2
can take place at lower or similar temperatures as compared
with that of NH3 decomposition over the Li2NH-Fe2N as
Fe2N and Li2NH were detected by XRD and XANES on
a sample collected at 723 K (Figure 2b, Supporting Informa-
tion, Figure S9). Neat Li2NH
has a limited activity at tem-
peratures
below
773 K
(Figure 1; Supporting Informa-
tion, Figure S2), as does Fe2N.
A synergy between these two
compounds may occur leading
to the abnormally high cata-
lytic activity, which can be
demonstrated, to some extent,
by the following experimental
facts. First, the TPD-MS,
XRD, and XANES measure-
ments show that Fe2N reacts
with Li2NH at temperatures
above 500 K, giving rise to H2
and Li3FeN2 according to the
reaction R1 (Figure 2a and b).
Removing NH3 from the
reacting system described in
Figure 1 leads the formation of
Li3FeN2 as well. Second,
Li3FeN2 can be easily ammo-
niated to a mixture containing
LiNH2 and an amorphous Fe-
containing compound (in
which Fe remains in a tetrahe-
dral coordination, Figure 2b
and Supporting Information,
Figure 2. Interactions of Li2NH and Fe2N. a) TPD-MS signals of H2, N2 and NH3 from the Li2NH-Fe2N and
post-ammoniated Li3FeN2 samples, respectively. b) Fe K-edge XANES spectra of the Fe-containing samples
collected under different conditions. c),d) SSITKA analyses of the Li2NH-Fe2N (c) and 5 wt% Ru/CNTs
(g) samples under a gas shift from NH3 to ND3 and 14NH3 to 15NH3 at 553 K, respectively. Gas shifting
Figure S3a) at ambient tem- was conducted at time=0 min, the flow rate of 5 vol.% NH3/Ar is 30 mLminꢀ1
.
2
www.angewandte.org
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 1 – 6
These are not the final page numbers!

Angewandte
Chemie
shown in Figure 1, Figure 2a; Supporting Information, Fig-
ure S3). HD and 14N15N overweigh D2 and 15N2 for a longer
period time and remain in the outlet gas stream in the testing
history of the Li2NH-Fe2N as compared to that of the Ru/
CNTs, reflecting continuous contributions of 1H and 14N from
the catalyst to the gaseous products (Figure 2c and d) and also
showing the likelihood of the involvement of bulk phase of
the catalyst in the catalysis. Fourth, DFT calculations on the
Fe-doped Li2NH system also indicate that the formation of H2
is through the H transfer from N to Li nearby, which is
“excited” by the interaction of Fe and N forming a Fe-N-Li
moiety, followed by H–H coupling between H(N) and H(Li)
(Supporting Information, Figure S5).
It should be pointed out that Li in Li2NH and Li3FeN2 are
highly mobile[11a,13] under the
Such an understanding leads us to establish a novel
catalyst system for NH3 decomposition, that is, 3d transition
metals have a variety of stable or unstable interstitial lower N-
content nitrides (TM(N) for short). They also have relatively
stable higher N-content ternary nitrides with Li (LiTMN,
except Zn).[16] Following the same catalytic cycle as that of
Li2NH-Fe2N, the Li2NH-3d TM(N) are expected to exhibit
catalytic activities overweighing the neat 3d TM(N) in NH3
decomposition.
The performances of Li2NH-TM(N) spreading from Ti to
Cu are shown in Figure 3a. The general catalytic features are
as follows: 1) Universal catalytic activity. All Li2NH-TM(N)
tested here exhibit catalytic activities towards NH3 decom-
position at temperatures above 623 K, marking the drastic
reaction condition applied
here; the reacting depth of
catalyst particles in this partic-
ular case, as indicated by the
SSITKA measurements, may
be significantly greater than
that of the conventional tran-
sition-metal-catalyzed process
where the related catalysis
occurs mainly on the top sur-
face.
Fe has a few nitride forms
FeNx (0 < x ꢁ 1), however, the
N-rich nitride (FeN) is ther-
mally unstable. The difficulty
in dehydrogenation of NH3 on
Fe (100) surface, as simulated
recently, increases with the
increase in the surface N con-
tent owing to the insufficient
Fe coordination to the NHx
(x = 0, 1, and 2) intermedi-
ates,[14] in agreement with the
low catalytic activity of neat Fe
nitrides observed previously[10]
Figure 3. Catalytic activities and thermodynamic analyses of the Li2NH-TM(N). a) Catalytic activities of the
Li2NH-TM(N) samples, reaction condition is the same as that mentioned in Figure 1. b) Hourly NH3
and in this study. Li2NH,
repeatedly consumed and
regenerated by R1 and R2, is
beyond the role of electronic
promoter. It is an NH3 trans-
mitting agent with activated
*
conversion at 773 K for the Li2NH-TM(N) ( ) vs. those of early 3d TMN and CNTs-supported Co, Ni, Cu
~
!
*
( ) and Ru ( ). Activity of 5 wt% Ru/Al2O3 ( ) is taken from Ref. [19]. c),d) Temperature dependence of
the Gibbs free energy changes of the reactions 1) TM(N)+Li2NH!LiTMN+H2 +(NH3) and
2) LiTMN+NH3!Li2NH+TM(N)+N2.
ꢀ
ꢀ
N H bonding (the N H
stretch at ca. 3160 cmꢀ1 for Li2NH vs. 3340 cmꢀ1 for NH3).
More importantly, Li, as the second cation to N, executes
changes of the inert or low active neat TM(N) especially for
the early 3d TM(N) and Cu[10,17] (Figure 3b; Supporting
Information, Figure S7). 2) Unprecedentedly high activity.
The hourly conversion of NH3 per kg of catalyst at 773 K are
ca. 1.9 kg for Ti-, 5.1 kg for V-, 15.7 kg for Cr-, 26.7 kg for Mn-,
16.1 kg for Fe-, 17.0 kg for Co-, 12.1 kg for Ni-, and 3.1 kg for
Cu-Li2NH catalysts. Except for the Li2NH-Ni (which is
comparable to the Ni/SBA-15[18]), others are, to the best of
our knowledge, the highest values achieved on the respective
TM-based catalysts reported to date. We would like also to
emphasize that, although the optimization to respective
catalyst has yet to be carried out, the CrN-, Fe2N-, MnN-,
a positive inductive effect[15] to enhance the covalent Fe N
ꢀ
bonding, resulting in the significantly stabilized N-rich
intermediate (that is, Li3FeN2, compositionally equivalent to
Li3N + FeN). Implied by the Brønsted–Evans–Polanyi (BEP)
relationship, a reduced kinetic barrier and faster rate of
reaction are expected, which is strongly supported by the
abnormally high catalytic activity and low apparent activation
energy of Li2NH-Fe2N compared with neat Fe2N (Figure 1;
Supporting Information, Figure S6).
Angew. Chem. Int. Ed. 2015, 54, 1 – 6
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
3
These are not the final page numbers!

.
Angewandte
Communications
and Co-Li2NH have activities significantly higher than that of
5 wt% Ru/Al2O3.[19] The Li2NH-MnN is even superior to the
highly active 5 wt% Ru/CNTs in the whole testing history.
The overall catalytic activities of the Li2NH-TM(N) exhibit
a volcano shape centered at Mn site, in contrast to the neat 3d
TM(N) where Ni was found to have the best performance
(Figure 3b), such an interesting phenomenon is worthy of
experimental and theoretical elucidation.[20] 3) Low operation
temperature. Ti-, V-, and Cu-Li2NH catalysts exhibit activities
at ca. 673 K, others at temperatures just above 623 K,
representing the lowest starting temperatures reported for
the respective metal-based catalysts. All these features
evidence the significantly reduced kinetic barriers with the
help of Li2NH.
The TM to Li2NH weight ratio is kept at about 0.9 to allow
the substantial formation of LiTMN to facilitate the charac-
terization. Noted that the content of Li2NH can be largely
reduced to a few weight percentage of TM(N) without causing
substantial decrease in catalytic activity. Detailed character-
izations and optimizations on the respective Li2NH-TM(N)
catalysts will be given in separated investigations. The general
observations are that the catalytic cycle described for the
Li2NH-Fe2N is essentially kept by other Li2NH-TM(N), that
Fischer–Tropsch synthesis[23] and water-gas shift reaction.[24]
In this context, a map linking the TM catalyst, the promoter A
in proper chemical form and the reactive species X of an
elementary reaction may be built up by searching combina-
tion of TM, A, and X that is relatively stable than [TM-X] by
experimental trials and/or high-throughput computational
materials design.[25] We would like to further emphasize that
the endeavor in elucidating the promoting effect of alkali
metals or alkaline earth metals on transition metal-based
heterogeneous catalysis would benefit the materials develop-
ment for energy harvesting, where the thermodynamic
stability, the electronic structure, and the reactivity of
respective material can be tuned by the involvement of
alkali or alkaline earth metals. As pointed out in Ref. [22a],
the forming compounds with alkali or alkaline earth metals
favors the formation of a number of new TMO and TMON,
the potential candidates for photocatalysis. In hydrogen
production from thermochemical cycle, on the other hand,
the important role of Na in tuning the thermodynamic
properties of the cycle via stabilizing the higher O-content
oxide of Mn has also been demonstrated.[26]
is, TM(N) reacts with Li2NH giving rise to H2 and LiTMN, Experimental Section
Li2NH-3d TM(N) and TM(N) species were prepared by ball-milling
namely Li5TiN3, Li7VN4, Li9CrN5, Li7MnN4, Li2.5Co0.5N,
LiNiN, and Li2.5Cu0.5N (NH3 is co-produced in some cases)
following the reaction of TM(N) + Li2NH!LiTMN + H2 +
(NH3), where the easiness of H2 release decreases essentially
from Ti to Cu (Supporting Information, Figure S8). LiTMN,
on the other hand, can be ammoniated to liberate N2
according to the reaction of LiTMN + NH3!Li2NH +
TM(N) + N2, where the rates of ammoniation, on the
contrary, are much slower for the early TMs (Supporting
Information, Figure S10). The active state of 3d TM under the
reaction condition is TiN, Li7VN4, CrN, MnN, Fe2N, Co, Ni, or
Cu, respectively (Supporting Information, Figure S9). The
presence of active phases depends on the thermodynamic
natures of the above two reactions. Based on the enthalpies of
formation of Li2NH, NH3, and those reported binary and
ternary nitrides,[21] and by counting the entropy of the gas only
(unknown entropies of some nitrides), the temperature
dependence of the Gibbs free energy changes per LiTMN
of the corresponding two reactions are plotted in Figure 3c
and d. The presence of TM(N) and Li2NH are thermodynami-
cally favored at lower temperatures or high NH3 partial
pressures for most 3d TM except V, while LiTMN is favored
at higher temperatures or under low H2 or NH3 partial
pressures, in agreement with the experimental findings.
Figure 3c and d also indicate that, within the accuracy of
thermodynamic data, both the R1 and R2 have chances to
take place under the reaction condition applied in this study.
The stabilization effect of alkali metals on the formation
of oxides, oxynitrides, nitrides, and hydrides of TM of
unusually high oxidation state is well known.[15,22] Coinciden-
tally, O, N, and H etc. are common surface-rich species in
many catalytic processes. It is, therefore, rational to extend
our understanding on Li in promoting NH3 decomposition to
other catalytic processes. Indeed, a few recent investigations
implied or proposed similar functionality of alkali metals in
the mixtures of transition-metal chlorides and LiNH2 at 323 K,
followed by washing and heating to 573 K in an argon flow. LiTMN
compounds were prepared by calcining Li3N and respective metals
under N2 pressure at 923 K. The ammoniation of ternary lithium
nitrides was performed in a homemade stainless steel reactor filled
with pressurized NH3. The structures of Li2NH-TM(N) and LiTMN
were characterized by XRD or XANES. Ammonia decomposition
reaction was performed in a continuous-flow fixed-bed quartz
reactor. The gas composition was analyzed using on-line gas
chromatograph (GC-2014C, Shimadzu) equipped with a Porapak N
column and TCD detector. Temperature-programmed reaction and
SSITKA were employed to investigate the interactions between
TM(N) and Li2NH. See the Supporting Information for more detailed
information.
Received: November 5, 2014
Published online: && &&, &&&&
Keywords: ammonia decomposition · electronic promoter ·
.
heterogeneous catalysis · lithium imide · nitrides
[1] J. K. Nørskov, T. Bligaard, Angew. Chem. Int. Ed. 2013, 52, 776 –
777; Angew. Chem. 2013, 125, 806 – 807.
[2] B. E. Koel, J. Kim in Handbook of Heterogeneous Catalysis
(Eds.: G. Ertl, H. Knçzinger, F. Schꢀth, J. Weitkamp), Wiley-
VCH, Weinheim, 2008, pp. 1593 – 1624.
[3] T. W. Hansen, J. B. Wagner, P. L. Hansen, S. Dahl, H. Topsøe,
C. J. H. Jacobsen, Science 2001, 294, 1508 – 1510.
[4] G. Ertl, M. Weiss, S. B. Lee, Chem. Phys. Lett. 1979, 60, 391 – 394.
[5] a) D. R. Strongin, G. A. Somorjai, J. Catal. 1988, 109, 51 – 60;
b) S. Dahl, A. Logadottir, C. J. H. Jacobsen, J. K. Nørskov, Appl.
Catal. A 2001, 222, 19 – 29.
[6] Z. Paꢁl, G. Ertl, S. B. Lee, Appl. Surf. Sci. 1981, 8, 231 – 249.
[7] K. Aika, T. Takano, S. Murata, J. Catal. 1992, 136, 126 – 140.
[8] a) R. Z. Sørensen, J. S. Hummelshøj, A. Klerke, J. B. Reves, T.
Vegge, J. K. Nørskov, C. H. Christensen, J. Am. Chem. Soc. 2008,
4
www.angewandte.org
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 1 – 6
These are not the final page numbers!

Angewandte
Chemie
130, 8660 – 8668; b) F. Schꢀth, R. Palkovits, R. Schlçgl, D. S. Su,
Energy Environ. Sci. 2012, 5, 6278 – 6289.
[17] A. Boisen, S. Dahl, J. K. Nørskov, C. H. Christensen, J. Catal.
2005, 230, 309 – 312.
[18] H. C. Liu, H. Wang, J. G. Shen, Y. Sun, Z. M. Liu, Appl. Catal. A
2008, 337, 138 – 147.
[19] S. F. Yin, B. Q. Xu, W. X. Zhu, C. F. Ng, X. P. Zhou, C. T. Au,
Catal. Today 2004, 93, 27 – 38.
[20] A. Logadottir, T. H. Rod, J. K. Nørskov, B. Hammer, S. Dahl,
C. J. H. Jacobsen, J. Catal. 2001, 197, 229 – 231.
[9] a) S. F. Yin, B. Q. Xu, X. P. Zhou, C. T. Au, Appl. Catal. A 2004,
277, 1 – 9; b) F. Hayashi, Y. Toda, Y. Kanie, M. Kitano, Y. Inoue,
T. Yokoyama, M. Hara, H. Hosono, Chem. Sci. 2013, 4, 3124 –
3130; c) A. H. Lu, J. J. Nitz, M. Comotti, C. Weidenthaler, K.
Schlichte, C. W. Lehmann, O. Terasaki, F. Schꢀth, J. Am. Chem.
Soc. 2010, 132, 14152 – 14162.
[21] J. F. Herbst, L. G. Hector, Jr., Phys. Rev. B 2012, 85, 195137.
[22] a) Y. B. Wu, P. Lazic, G. Hautier, K. Persson, G. Ceder, Energy
Environ. Sci. 2013, 6, 157 – 168; b) K. Miwa, S. Takagi, M.
Matsuo, S. Orimo, J. Phys. Chem. C 2013, 117, 8014 – 8019.
[23] a) J. Gaube, H. F. Klein, Appl. Catal. A 2008, 350, 126 – 132;
b) M. C. Ribeiro, G. Jacobs, B. H. Davis, D. C. Cronauer, A. J.
Kropf, C. L. Marshaw, J. Phys. Chem. C 2010, 114, 7895 – 7903.
[24] Y. P. Zhai, D. Pierre, R. Si, W. L. Deng, P. Ferrin, A. U. Nilekar,
G. W. Peng, J. A. Herron, D. C. Bell, H. Saltsburg, M. Mavrika-
kis, M. Flytzani-Stephanopoulos, Science 2010, 329, 1633 – 1636.
[25] S. Curtarolo, G. L. W. Hart, M. B. Nardelli, N. Mingo, S. Sanvito,
O. Levy, Nat. Mater. 2013, 12, 191 – 201.
[10] C. R. Lotz, F. Sebba, Trans. Faraday Soc. 1957, 53, 1246 – 1252.
[11] a) B. A. Boukamp, R. A. Huggins, Phys. Lett. A 1979, 72, 464 –
466; b) P. Chen, Z. T. Xiong, J. Z. Luo, J. Y. Lin, K. L. Tan,
Nature 2002, 420, 302 – 304.
[12] S. L. Shannon, J. G. Goodwin, Chem. Rev. 1995, 95, 677 – 695.
[13] M. Nishijima, Y. Takeda, N. Imanishi, O. Yamamoto, M. Takano,
J. Solid State Chem. 1994, 113, 205 – 210.
[14] S. C. Yeo, S. S. Han, H. M. Lee, J. Phys. Chem. C 2014, 118,
5309 – 5316.
[15] J. Etourneau, J. Portier, F. Menil, J. Alloys Compd. 1992, 188, 1 –
7.
[16] N. Tapia-Ruiz, M. Segales, D. H. Gregory, Coord. Chem. Rev.
2013, 257, 1978 – 2014.
[26] B. J. Xu, Y. Bhawe, M. E. Davis, Proc. Natl. Acad. Sci. USA 2012,
109, 9260 – 9264.
Angew. Chem. Int. Ed. 2015, 54, 1 – 6
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
5
These are not the final page numbers!

.
Angewandte
Communications
Communications
Ammonia Decomposition
Beyond an electronic promoter: A synergy
between Li2NH and 3d transition-metal
nitrides leads to unprecedented catalytic
activities for NH3 decomposition. Li2NH
acts as more than just an electronic
promoter: it is an NH3 transmitting agent
and favors the formation of a higher N-
content intermediate, thereby altering the
overall reaction energetics.
J. Guo, P. Wang, G. Wu, A. Wu, D. Hu,
Z. Xiong, J. Wang, P. Yu, F. Chang,
Z. Chen, P. Chen*
&&& — &&&
Lithium Imide Synergy with 3d Transition-
Metal Nitrides Leading to Unprecedented
Catalytic Activities for Ammonia
Decomposition
6
www.angewandte.org
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 1 – 6
These are not the final page numbers!