Methane Cracking over Cobalt Molybdenum Carbides

Article abstract of DOI:10.1007/s10562-018-2378-4

Abstract: The catalytic behaviour of Co₃Mo₃C, Co₆Mo₆C, Co₃Mo₃N and Co₆Mo₆N for methane cracking has been studied to determine the relationship between the methane crac

Full text of DOI:10.1007/s10562-018-2378-4

Catalysis Letters
https://doi.org/10.1007/s10562-018-2378-4
Methane Cracking over Cobalt Molybdenum Carbides
I. Alshibane1 · S. Laassiri1 · J. L. Rico2 · J. S. J. Hargreaves1
Received: 12 March 2018 / Accepted: 28 March 2018
© The Author(s) 2018
Abstract
The catalytic behaviour of Co3Mo3C, Co6Mo6C, Co3Mo3N and Co6Mo6N for methane cracking has been studied to determine
the relationship between the methane cracking activity and the chemical composition. The characterisation of post-reaction
samples showed a complex phase composition with the presence of Co3Mo3C, α-Co and β-Mo2C as catalytic phases and the
deposition of different forms of carbon during reaction.
Graphical Abstract
Keywords Methane cracking · Catalytic decomposition · Cobalt molybdenum carbide · Cobalt molybdenum nitride
1 Introduction
The design of novel and efficient materials for catalytic reac-
tions is of major interest. Although, many of the materials
studied in heterogeneous catalysis are metal and metal oxide
based, attention has been directed towards the development
of entirely novel catalyst families that could display modified
performance. Examples of the materials investigated include
carbides, nitrides and boron alloys [1–3]. Amongst these
materials, carbides have arguably received the most atten-
tion due to the perceived analogies between their behaviour
and that of precious metals, suggesting them to be potential
replacements. In this context, the presence of interstitial car-
bon species has been argued to modify the electronic proper-
ties of the parent metal in systems such as those based upon
molybdenum or tungsten, making them akin to precious met-
als such as platinum [4, 5].
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s10562-018-2378-4) contains
supplementary material, which is available to authorized users.
* J. S. J. Hargreaves
Justin.Hargreaves@glasgow.ac.uk
I. Alshibane
I.alshibane.1@research.gla.ac.uk
S. Laassiri
Said.Laassiri@glasgow.ac.uk
J. L. Rico
Jlceri@yahoo.com.mx
1
WestCHEM, School of Chemistry, University of Glasgow,
Joseph Black Building, Glasgow G12 8QQ, UK
2
Laboratorio de Catálisis, Facultad de Ingeniería Química,
Within the literature, metal carbides are known to pos-
sess activity for a wide range of applications including
Universidad Michoacana de San Nicolás de Hidalgo,
Edif. V1, C.U., 58060 Morelia, Michoacán, Mexico
Vol.:(0123456789)
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I. Alshibane et al.
Fischer–Tropsch processes [6–8], hydrogenation [9–11],
dehydroaromatisation [12], oxygen and hydrogen evolution
[13] and ammonia decomposition [14, 15]. In more recent
work, the reactivity of cobalt molybdenum carbide was stud-
ied for ammonia synthesis to gain an enhanced understand-
ing of the potential role of lattice composition (i.e. the influ-
ence of the presence of interstitial carbon versus interstitial
nitrogen) upon catalytic activity [16]. Although Co3Mo3C
was found to be active for ammonia synthesis, the material
was only active at higher temperature (500 °C) compared to
its nitride counterpart which is active at 400 °C, and such
activity was associated with the presence of some lattice
nitrogen residing in 16c Wyckoff sites as determined from
in-situ neutron diffraction studies.
2.2 Materials Characterization
X-ray diffraction patterns were collected on a Pana-
lytical X’Pert PRO instrument, using Cu Kα radiation
(λ = 0.154 nm) over a 2θ range of 5°–85°, a step size of
0.0167°, and a counting time of 1 s per step. Samples were
prepared by compaction into a Si sample holder. Phase
identification was obtained by comparison with JCPDS
database files. The surface areas of the samples were deter-
mined by application of the BET method to N2 physisorp-
tion isotherms collected at − 196 °C upon samples previ-
ously degassed at 110 °C under vacuum for 12 h. Scanning
electron microscopy was performed on Philips XLSEM and
FEI Quanta 200F Environmental instruments operating at
20 kV for the investigation of morphology. Samples were
coated with an Au/Pd alloy prior to imaging. CHN analysis
was undertaken by combustion using an Exeter Analytical
CE-440 Elemental Analyzer. Thermogravimetric analysis
(TGA) was carried out using a TA instruments QA instru-
ment with measurements being undertaken in temperature
range from room temperature to 1000 °C (ramp rate 10
degrees per minute) under a flow rate of 50 mL min−1 of
air. Raman spectra of the samples were recorded at room
temperature on a Horiba Jobin Yvon LabRam HR confocal
Raman microscope, using a laser excitation of 523 nm.
In the current manuscript, comparison is made between
the performance of Co3Mo3C and Co6Mo6C for methane
cracking to determine the role of stoichiometry and such
performance is contrasted with their isostructural nitride
counterparts. The methane cracking reaction is of poten-
tial interest as an environmentally friendly approach for
COx-free hydrogen production [17–19].
2 Experimental
2.1 Materials Preparation
2.3 Catalytic Activity Tests
The preparation of cobalt molybdenum related materials has
been documented in detail in our previous work [16, 20]. In
a typical synthesis, CoMoO4 was prepared by adding 5.59 g
of Co(NO3)2·6H2O (> 98%, Sigma-Aldrich) and 4.00 g of
(NH4)6Mo7O24·4H2O (99.98%, Sigma-Aldrich) dissolved in
200 mL of deionized water. The solution was then heated to
85 °C and held at this temperature for 5 h. The resulting pur-
ple precipitate was filtered and washed with deionized water
and ethanol. The precipitate was then calcined in static air
at 500 °C for 5 h to obtain dehydrated cobalt molybdate.
Co3Mo3N was prepared by ammonolysis of CoMoO4 under
NH3 (BOC, 99.98%) at a flow rate of 100 mL min−1 at
785 °C for 5 h. The temperature was increased from ambi-
ent to 357 °C at 5.6 °C min−1, then after to 447 °C min−1
at 0.2 °C min−1 before being finally increased to 785 °C at
2.1 °C min−1. Co3Mo3C was prepared by the carburization
of Co3Mo3N under 20 vol% CH4 in H2 (BOC, 99.98%) at a
flow rate of 12 mL min−1 at 700 °C for 2 h with a ramp rate
of 6 °C min−1 to reach 350 °C followed by 1 °C min−1 to
attain 700 °C. Co6Mo6C was prepared by reducing Co3Mo3C
at 900 °C for 5 h under 60 mL min−1 of a 75 vol% H2 in Ar
(BOC, 99.98%) gas mixture.
Methane cracking reactions were performed using 0.2 g of
material which was placed in a quartz tube reactor under a
gas feed of 12 mL min−1 of a mixture of 75 vol% CH4 in
N2 (BOC, 99.98%) at 800 °C for 8 h on stream. Hydrogen
production was monitored by online gas chromatography
(GC) using a TCD with Ar as carrier gas and employing
a Molecular Sieve 13× column. The gas exhaust was also
analysed in a periodic manner for the determination of COx
by off-line FTIR analyses employing a gas-phase FTIR cell
which could be isolated and by-passed for off-line analyses.
FTIR spectra were recorded using a FTIR-8400S, Shimadzu
apparatus. Each spectrum was collected at a spectral resolu-
tion of 2 cm−1, applying a scan range of 500–3500 cm−1.
3 Results
The structural and textural properties of the cobalt molyb-
denum based materials following the different nitridation
and carburisation processes were monitored using a range of
techniques. The results of the structural characterisation by
XRD have been reported previously [16]. Powder XRD and
neutron diffraction studies have confirmed the formation of
1 3

Methane Cracking over Cobalt Molybdenum Carbides
high quality pure phases of Co3Mo3C, Co6Mo6C, Co3Mo3N
and Co6Mo6N. These results can be found in the Supplemen-
tary Information (Figs. S1, S2).
be expected resulting from the presence of a surface pas-
sivation layer [22] for the carbide and nitride materials,
which are known to be air-sensitive. Importantly, no Raman
bands related to carbon deposition during the synthesis of
Co3Mo3C and Co6Mo6C samples were observed which is
consistent with the preparation of non-coked materials.
The SEM images presented in Fig. 2 demonstrate that
all the materials prepared are pseudomorphic and exhibit
a needle-like morphology as reported elsewhere [16]. The
surface areas of the materials were determined to be 7, 18,
4 and 13 m2 g−1 for CoMoO4, Co3Mo3N, Co6Mo6N and
Co3Mo3C respectively (Table 1). The lower surface area of
the Co6Mo6C phase (∼ 3 m2 g−1), can be attributed to the
higher reaction temperature applied in its preparation.
The role of the nature of the stoichiometry and also the
interstitial element present in the catalytic methane cracking
activity of cobalt molybdenum materials was investigated
by comparing the activity of the Co3Mo3C and Co6Mo6C
to Co3Mo3N and Co6Mo6N materials. The reaction profiles
illustrating the evolution of the mass normalised hydro-
gen formation rate as a function of time on stream is pre-
sented Fig. 3. Although, all materials displayed activity
Raman spectra of the pre-reaction cobalt molybdenum
materials are presented in Fig. 1. The Raman bands at 354,
806, 866, 930 and 941 cm−1 are consistent with the pres-
ence of a surface cobalt molybdate phase [21] as might
Fig. 1 Raman spectra of as prepared materials (a) CoMoO4, (b)
Co3Mo3N, (c) Co3Mo3C, (d) Co6Mo6N and (e) Co6Mo6C
Fig. 2 SEM images of as
prepared materials: a Co3Mo3N,
b Co3Mo3C, c Co6Mo6N and d
Co6Mo6C
1 3

I. Alshibane et al.
Table 1 Summary of the textural and structural characterisation of post-reaction catalysts
Post-reaction XRD phase
Nitrogen contenta/wt%
Carbon contenta/wt%
SBETb/m2 g−1
As-prepared Post-reaction As-prepared Post-reaction As prepared Post-reaction
CoMoO4 Graphite (003-0401), β-Mo2C (001-1188),
α-Co (01-089-7093)
Co3Mo3N Co3Mo3C (03-065-7128), graphite (003-
0401), β-Mo2C (001-1188), α-Co (01-089-
7093)
–
N.d.
–
–
71
85
1
3
7
31
63
3.0 0.1 N N.d.
18
Co3Mo3C Co3Mo3C (03-065-7128), graphite (003-
0401), β-Mo2C (001-1188), α-Co (01-089-
7093)
Co6Mo6N Co3Mo3C (03-065-7128), graphite (003-
0401), β-Mo2C (001-1188), α-Co (01-089-
7093)
–
N.d.
2.5 0.1
–
84
84
69
1
1
1
13
4
50
59
24
1.6 0.1 N N.d.
Co6Mo6C Co3Mo3C (03-065-7128), graphite (003-
–
N.d.
1.3 0.1
3
0401)
N.d. not detected
aNitrogen analysis undertaken using an Exeter Analytical CE-440 Elemental Analyser
bSBET is the specific surface area evaluated using the BET model
Fig. 4 FTIR analyses of gas-phase products from CoMoO4 reacted
with CH4/N2 (a) the feed gas, (b) 800 °C, (c) 800 °C 20 min, (d)
800 °C 50 min, and (e) 800 °C 60 min. Bands 1 and 3 are related to
gas-phase CO2 whereas band is 2 related to gas-phase CO
Fig. 3 Hydrogen formation rates as a function of time on stream for
methane cracking over (a) CoMoO4, (b) Co6Mo6C, (c) Co3Mo3N and
(d) Co6Mo6N at 800°C
for hydrogen production, clear differences in the hydrogen
formation rates are observed. Hydrogen production tended
to reach a plateau after 120 min on stream. However, in the
case of the Co3Mo3C sample, less reproducible behaviour
occurred, which was possibly related to carbon build-up
during the reaction resulting in reactor blockage. Similar
observations were witnessed upon repeating the experiment
and the structural and textural properties of the post-reaction
samples were all similar (Fig. S3). Due to the fact that the
performance of Co3Mo3C is less reproducible, its reaction
profile is not presented in Fig. 3 but is instead shown in Fig.
S2.
[16]. However, the reaction is thermodynamically unfavour-
able at high temperature and ammonia content at equilibrium
is ~ 0.001 mol% at ca. 800 °C. Thus, the consumption of
hydrogen to generate ammonia by reaction with the N2 inter-
nal standard within the methane feed under these conditions
can be safely ruled out.
In the case of cobalt molybdenum nitride and carbides,
off-line FTIR spectra recorded periodically during reaction
showed that the production of CO and CO2 during meth-
ane cracking was below the detection limit. However, as
might be expected, CO and CO2 were clearly observed when
CoMoO4 was used as a catalyst (Fig. 4). FTIR analysis of
gas products from this sample shows after 20 min of reac-
tion, bands at 660 and 2360 cm−1 which can be related to
In the presence of N2 and H2, as is the case in this study,
Co3Mo3N and Co3Mo3C have been reported to be active cat-
alytic systems for ammonia generation at ambient pressure
1 3

Methane Cracking over Cobalt Molybdenum Carbides
CO2 and at 2177 cm−1 which is assigned to CO. However,
the production of CO and CO2 ceased after 50 min of reac-
tion. It is noteworthy that the production of CO, even in
small concentrations, can be harmful in the case of some
downstream applications such as the use of H2 in PEM fuel
cells [23, 24]. The results presented herein suggest, beyond
the initial loss of the surface passivation layer upon reaction,
the use of cobalt molybdenum nitrides or carbides might
be suitable for the production of COx-free hydrogen from
methane cracking for such applications.
The characterisation of the post-reaction materials is
presented in Figs. 5, 6, 7, 8 and 9 and in Table 1. Figure 5
presents the post-reaction powder XRD patterns. The XRD
results are consistent with the formation of graphite as
expected. In addition, a number of significant phase transfor-
mations to the original materials have occurred upon reac-
tion (Fig. 5; Table 1). In most cases, Co3Mo3C appeared to
be the predominant phase, although the formation of some
β-Mo2C and α-Co is also apparent. However, interestingly,
in the case of CoMoO4, only β-Mo2C, α-Co and graphite
were evident after reaction with the ternary carbide phase
being absent.
Fig. 5 Powder X-ray diffraction patterns of the post-reaction:
(a) CoMoO4, (b) Co3Mo3N, (c) Co3Mo3C, (d) Co6Mo6N and (e)
Co6Mo6C materials. Diamond: Co3Mo3C (03-065-7128), asterisk:
graphite (003-0401), open circle: β-Mo2C (001-1188), open square:
α-Co (01-089-7093)
As shown in Fig. 6, morphological changes also
occurred upon reaction. The agglomerated needle-like
morphology was transformed to agglomerated block like
structures. In contrast, post-reaction Co6Mo6C appeared to
Fig. 6 SEM post-reaction
images of: a Co3Mo3N, b
Co3Mo3C, c Co6Mo6N and d
Co6Mo6C
1 3

I. Alshibane et al.
exhibit larger particle sizes compared to its post-reaction
Co3Mo3N, Co3Mo3C and Co6Mo6N counterparts within
the statistical limitations of the observations made. It
is also interesting to note that in general, post-reaction
catalyst displayed a higher surface area than pre-reaction
materials. Both the drastic change in morphology and the
enhanced surface area can be, at least partly, attributed to
the significant deposition of carbon as a result of reaction.
The comparatively lower surface area evident in the case
of Co6Mo6C is in accordance with the large particle size
observed for this sample by SEM.
The CoMoO4 and Co6Mo6C post-reaction samples were
found to contain ~70 wt% C (Table 1), with a higher post-
reaction carbon content (~84 wt% C) evident for Co3Mo3C,
Co3Mo3N and Co6Mo6N as would be anticipated from their
higher hydrogen formation rates. The nature of the carbona-
ceous species deposited was characterized by Raman spec-
troscopy. Post-reaction Raman spectra, presented in Fig. 7,
provide strong evidence of the presence of disordered and
graphitic carbon with Raman bands observed at 1350 and
1582 cm−1 labelled (D) and (G) respectively [25]. An addi-
tional band, of lower intensity, at 1620 cm−1 labelled as D′
was observed for the Co3Mo3N, Co3Mo3C and Co6Mo6N
samples. In the literature, several explanations exist and the
additional band can be correlated in principle to the pres-
ence of a high concentration of defects [26–28]. Additional
Raman bands related to cobalt molybdate were detected in
the post-reaction CoMoO4 and post-reaction Co3Mo3C.
To further characterise the nature of the carbon deposit
after reaction, TGA in air was carried out over the tem-
perature range 100–1000 °C (Fig. 8). It was observed that
the carbon oxidation started for all materials from 500 °C
and was complete by 700 °C. Beyond, this point no further
change in the weight of the material was observed. The total
weight loss was between 60 and 80 wt% which accords well
with the results of post-reaction elemental analysis (Table 1).
The first derivative profiles for the different post-reaction
materials are presented in Fig. 9. In all materials, two weight
loss regions have been observed. The first weight loss peak is
observed in the temperature range between 500 and 600 °C
while the second weight loss peak is observed at higher tem-
peratures (600–700 °C). The contribution of the first peak
was particularly significant in the post-reaction CoMoO4
material and to some extent in the Co3Mo3C. However, the
oxidation of carbon in Co3Mo3N, Co6Mo6N and Co6Mo6C
materials occurred mainly at temperature ranging between
600 and 700 °C. The contrast between the two oxidation
regions could suggest the presence of two forms of carbon.
However, the presence of the oxide phase, as evidenced in
their Raman spectra, in the case of post-reaction CoMoO4
and post-reaction Co3Mo3C as observed by Raman spectra
(Fig. 7) may have enhanced the oxidation of carbon at low
temperature.
Fig. 7 Raman spectra of the post-reaction materials (a) CoMoO4, (b)
Co3Mo3N, (c) Co3Mo3C, (d) Co6Mo6N and (e) Co6Mo6C
Fig. 8 TGA traces under air for post-reaction materials: (purple)
CoMoO4, (red) Co3Mo3N, (green) Co3Mo3C, (black) Co6Mo6N and
(blue) Co6Mo6C
Fig. 9 Derivative weight curves for post-reaction materials under
air (a) CoMoO4, (b) Co3Mo3N, (c) Co3Mo3C, (d) Co6Mo6N and (e)
Co6Mo6C
1 3

Methane Cracking over Cobalt Molybdenum Carbides
analysis revealed changes in the structural properties
upon reaction. As might be expected under the reaction
conditions applied, post-reaction powder XRD (Fig. 5),
showed the carburisation of all the materials studied when
reacted. However, the products of carburisation slightly
differ depending on the initial composition. In the post-
reaction CoMoO4, only β-Mo2C (001-1188) and α-Co (01-
089-7093) are observed as a result of the carburisation
of CoMoO4 as well as graphite generated from methane
cracking. However, a mixture of Co3Mo3C (03-065-7128),
α-Co (01-089-7093) and β-Mo2C (001-1188) is detected
upon reaction of Co3Mo3N, Co3Mo3C and Co6Mo6N with
methane. In the case of Co6Mo6C relocation of the carbon
located in the 8a (0 0 0) Wyckoff site to the 16c (1/8 1/8
1/8) site occurs associated with the formation of Co3Mo3C
without clear evidence of the formation of β-Mo2C and
α-Co [01-089-7093 (001-1188)] phases as observed in the
previous cases.
4 Discussion
The topotactic transformation pathways and pseudomor-
phic nature of the cobalt molybdenum carbide and nitride
families evident in this study offers, in principle, an ele-
gant route to study the effect of interstitial carbon/nitrogen
on the catalytic activity of cobalt molybdenum materials
for methane cracking. All the prepared materials possess
activity for hydrogen production at 800 °C. Interestingly,
the catalytic activity of these materials varied depending
upon initial composition with Co6Mo6N being the most
active (Fig. 3). The activity of the material was found to
−1
stabilise around 1.8 mmol H2 gcatalyst min−1, which is
high when compared against the activity of some other
−1
nitride systems (e.g. 180 µmol H2 gcatalyst min reported
for a silicon-vanadium nitride nanocomposite under
directly comparable conditions) [29]. In fact, the activ-
ity of the Co6Mo6N is directly comparable to the activity
−1
In summary, for the three most active catalysts, the phases
detected after reaction comprised a mixture of Co3Mo3C
(03-065-7128), α-Co (01-089-7093) and β-Mo2C (001-
1188). While, for the least active material CoMoO4, only
the β-Mo2C and α-Co (01-089-7093) were detected. Another
major aspect, where differences are potentially evident, is
the accessible surface area of the active phases. The surface
area measured in post-reaction Co3Mo3N, Co3Mo3C and
Co6Mo6N samples ranged between 50 and 63 m2 g−1 while
in the case of CoMoO4 and Co6Mo6C the surface area was
limited to ~30 m2 g−1. Despite the fact that no simple link
can be established between the catalytic activity to phase
composition and accessible surface area, it can be argued
that the presence of Co3Mo3C, α-Co and β-Mo2C and high
surface area leads to an enhanced activity for methane crack-
ing. In addition, the initial composition seems to play an
important role in the final activity of the catalysts. These dif-
ferences may indicate differences in the active surface com-
position resulting from the carburisation process of different
cobalt molybdenum precursors. Further characterisation of
the carburisation process of cobalt molybdenum materials by
in-situ neutron diffraction, in condition of relevance to this
study, are currently under investigation and will bring new
insight to the process. Elsewhere, cobalt-molybdenum oxy-
carbide surface phases have been proposed to be of impor-
tance for activity and lifetime [31].
of iron oxide (for which a rate of 1 mmol H2 gcatalyst
min−1 was previously reported for iron oxide under the
same reaction conditions) [30]. In general, the activity of
the carbides and nitrides presented a normalised hydrogen
−1
production rate ranging from 1.1 to 1.8 mmol H2 gcatalyst
−1
min−1. A slightly lower activity (0.8 mmol H2 gcatalyst
min−1) was found for the CoMoO4 system. In addition to
the relatively enhanced activity of the cobalt molybdenum
carbide and nitride systems when compared to the oxide
counterpart, the absence of significant production of COx,
beyond that which might be expected from conversion of
the surface passivation layer, during the methane crack-
ing reaction is of potential interest in relation to free of
COx-H2 production.
As expected, the production of H2 was accompanied by
carbon deposition. Due to the nature of the reaction, the
amount of carbon deposited on carbide and nitride systems
can be correlated directly to the activity of methane crack-
ing as expected. Elemental analysis showed significant
deposition of carbon ~ 85 wt% on Co3Mo3N, Co3Mo3C
and Co6Mo6N confirming the high activity of these materi-
als, in spite of the less reproducible hydrogen production
behaviour of Co3Mo3C. Thermogravimetric analyses con-
ducted under air confirmed that the weight loss associated
with carbon oxidation to be consistent with the elemental
analyses of post-reaction materials. The nature of the car-
bon present upon reaction has been investigated by Raman
spectroscopy (Fig. 7). The Raman futures were dominated
by the presence of two forms of carbon: disordered and
graphitic carbon. The existence of several forms of carbon
was also evident from the derivative weight curves for
post-reaction samples.
5 Conclusion
A range of cobalt molybdenum containg materials have
been prepared and tested as catalysts for the production of
hydrogen from methane at 800 °C. After a short induction
period, all samples were active and stable for the generation
of hydrogen over the period tested, with the exception of
While it is tempting to discuss the activity of the
catalysts against their initial composition, post-reaction
1 3

I. Alshibane et al.
7. Ordomsky VV, Legras B, Cheng K, Paul S, Khodakov AY (2015)
Catal Sci Technol 5(3):1433
Co3Mo3C. Amongst the evaluated materials, the Co6Mo6N
sample showed the highest activity of about 1.8 mmol H2
g−1 min−1, comparable to those observed for iron oxide sys-
tems under similar reaction conditions. The results revealed
that a significant phase transformation from metal nitrides
to Co3Mo3C and β-Mo2C occurred throughout the methane
cracking reaction. Interestingly, in the case of Co6Mo6C
relocation of the carbon located in the 0 0 0 (8a) site to 1/8
1/8 1/8 (16c) sites resulting in the formation of Co3Mo3C
was observed. Furthermore, results from Raman spectros-
copy and powder XRD show that at least two forms of
carbon are formed on the catalyst surface during methane
decomposition.
8. Vo D-VN, Adesina AA (2011) Chap. 7: evaluation of promoted
Mo carbide catalysts for Fischer-Tropsch synthesis: synthesis,
characterisation, and time-on-stream behaviour. In: de Klerk A,
King DL (eds) Synthetic liquids production and refining, vol 1084.
ACS, Washington, DC, pp 155–184
9. Ranhotra GS, Bell AT, Reimer JA (1987) J Catal 108(1):40
10. Kojima I, Miyazaki E, Inoue Y, Yasumori I (1982) J Catal
73(1):128
11. Lee JS, Yeom MH, Park KY, Nam I-S, Chung JS, Kim YG, Moon
SH (1991) J Catal 128(1):126
12. Perret N, Wang X, Delannoy L, Potvin C, Louis C, Keane MA
(2012) J Catal 286:172
13. Jiang J, Liu Q, Zeng C, Ai L (2017) J Mater Chem A 5(32):16929
14. Choi J-G (1999) J Catal 182(1):104
15. Pansare SS, Torres W, Goodwin JG (2007) Catal Commun
8(4):649
Acknowledgements We are grateful to Mr M. G. Reddy form the Uni-
versity of Glasgow for conducting elemental analyses. JSJH wishes to
acknowledge the Engineering and Physical Sciences Research Council
for support through grant EP/L02537X/1. JLR is grateful to Cona-
cyt for funding a sabbatical stay at the University of Glasgow and to
LINAN-IPICYT for electron microscope facilities.
16. AlShibane I, Daisley A, Hargreaves JSJ, Hector AL, Laassiri S,
Rico JL, Smith RI (2017) ACS Sustain Chem Eng 5(10):9214
17. Abbas HF, Wan Daud WMA (2010) Int J Hydrogen Energy
35(3):1160
18. Li Y, Li D, Wang G (2011) Catal Today 162(1):1
19. Amin AM, Croiset E, Epling W (2011) Int J Hydrogen Energy
36(4):2904
Compliance with Ethical Standards
20. Hunter SM, McKay D, Smith RI, Hargreaves JSJ, Gregory DH
(2010) Chem Mater 22(9):2898
21. Xu K, Chao J, Li W, Liu Q, Wang Z, Liu X, Zou R, Hu J (2014)
RSC Adv 4(65):34307
Conflict of interest The authors declare no conflict of interest.
22. Alconchel S, Sapina F, Martinez E (2004) Dalton Trans (16:):2463
23. Schmittinger W, Vahidi A (2008) J Power Sources 180(1):1
24. Choudhary TV, Aksoylu E, Goodman DW (2003) Nonoxidative
activation of methane. Catal Rev 45(1):151
Open Access This article is distributed under the terms of the Crea-
tive Commons Attribution 4.0 International License (http://creativeco
mmons.org/licenses/by/4.0/), which permits unrestricted use, distribu-
tion, and reproduction in any medium, provided you give appropriate
credit to the original author(s) and the source, provide a link to the
Creative Commons license, and indicate if changes were made.
25. Gupta A, Chen G, Joshi P, Tadigadapa S, Eklund (2006) Nano Lett
6(12):2667
26. Cançado LG, Pimenta MA, Neves BRA, Dantas MSS, Jorio A
(2004) Phy Rev Lett 93(24):247401
27. Kudin KN, Ozbas B, Schniepp HC, Prud’homme RK, Aksay IA,
Car R (2008) Nano Lett 8(1):36
References
28. Livneh T, Haslett TL, Moskovits M (2002) Phy Rev B
66(19):195110
1. Alexander AM, Hargreaves JSJ (2010) Chem Soc Rev 39(11):4388
2. Hargreaves JSJ (2013) Coord Chem Rev 257:(13–14) 2015
3. Hargreaves JSJ, McFarlane AR, Laassiri S (eds) (2018) Alterna-
tive catalytic materials: carbides, nitrides, phosphides and amor-
phous boron alloys. RSC, London
29. AlShibane I, Hargreaves JSJ, Hector AL, Levason W, McFarlane
A (2017) Dalton Trans 46(27):8782
30. Alharthi A, Blackley RA, Flowers TH, Hargreaves JSJ, Pul-
ford ID, Wigzell J, Zhou W (2014) J Chem Technol Biotechnol
89(9):1317
4. Levy RB, Boudart M (1973) Science 181:547
5. Oyama ST (1992) Catal Today 15:179
31. Izhar S, Kanesugi H, Tominaga H, Nagai M (2007) Appl Catal A:
Gen 317:82
6. Weller S, Hofer LJE, Anderson RB (1948) J Am Chem Soc
70(2):799
1 3