Surface engineering of earth-abundant Fe catalysts for selective hydrodeoxygenation of phenolics in liquid phase

Article abstract of DOI:10.1039/d0sc00983k

Development of inexpensive sulfur-free catalysts for selective hydrogenolysis of the C-O bond in phenolics (i.e., selective removal of oxygen without aromatic ring saturation) under liquid-phase conditions is highly challenging. Here, we report an efficient approach to engineer earth-abundant Fe catalysts with a graphene overlayer and alkali metal (i.e., Cs), which produces arenes with 100% selectivity from liquid-phase hydrodeoxygenation (HDO) of phenolics with high durability. In particular, we report that a thin (a few layers) surface graphene overlayer can be engineered on metallic Fe particles (G?Fe) by a controlled surface reaction of a carbonaceous compound, which prevents the iron surface from oxidation by hydroxyls or water produced during HDO reaction. More importantly, further tailoring the surface electronic properties of G?Fe with the addition of cesium, creating a Cs-G?Fe composite catalyst in contrast to a deactivated Cs?Fe one, promotes the selective C-O bond cleavage by inhibiting the tautomerization, a pathway that is very facile under liquid-phase conditions. The current study could open a general approach to rational design of highly efficient catalysts for HDO of phenolics.

Full text of DOI:10.1039/d0sc00983k

View Article Online
View Journal
Chemical
Science
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: J. Zhang, J. Sun,
L. Kovarik, M. H. Engelhard, L. Du, B. Sudduth, H. Li and Y. Wang, Chem. Sci., 2020, DOI:
1
0.1039/D0SC00983K.
Volume
Number
9
1
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
7
January 2018
Pages 1-268
Chemical
Science
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
rsc.li/chemical-science
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 2041-6539
EDGE ARTICLE
Xinjing Tang et al.
Caged circular siRNAs for photomodulation of gene
expression in cells and mice
rsc.li/chemical-science

Page 1 of 8
PleaseC dh oe mn oi ct a al dS cj ui es nt cme argins
View Article Online
DOI: 10.1039/D0SC00983K
ARTICLE
Received 00th January 20xx,
Surface Engineering of Earth-abundant Fe Catalysts for Selective
Hydrodeoxygenation of Phenolics in Liquid Phase
a
a
b
b
c
a
Jianghao Zhang, Junming Sun,* Libor Kovarik, Mark H. Engelhard, Lei Du, Berlin Sudduth,
a
a,b
Houqian Li, Yong Wang*
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Development of inexpensive sulfur-free catalysts for selective hydrogenolysis of the C-O bond in phenolics (i.e., selective
removal of oxygen without aromatic ring saturation) under liquid-phase conditions is highly challenging. Here, we report an
efficient approach to engineer the earth-abundant Fe catalysts with graphene overlayer and alkali metal (i.e., Cs), which
produces arenes with 100% selectivity from liquid-phase hydrodeoxygenation (HDO) of phenolics with high durability. In
particular, we report that a thin (a few layers) surface graphene overlayer can be engineered on metallic Fe particles (G@Fe)
by a controlled surface reaction of carbonaceous compound, which prevents the iron surface from oxidation by hydroxyls
or water produced during HDO reaction. More importantly, further tailoring the surface electronic properties of G@Fe with
the addition of cesium, creating a Cs-G@Fe composite catalyst in contrast to a deactivated Cs@Fe one, promotes the
selective C-O bond cleavage by inhibiting the tautomerization, a pathway that is very facile under liquid-phase conditions.
The current study could open a general approach to rational design of highly efficient catalysts for HDO of phenolics.
dominant when similar catalysts were used in liquid-phase
Introduction
Since its discovery , 2D graphene has been attracting increased
attention due to its potential applications in a variety of areas
such as catalysis . Recently, new surface band structures
caused by the electron transfer between metal substrate and
graphene overlayers have been demonstrated to affect the
HDO, a preferred process in biomass conversion which avoids
the energy consumption associated with vaporization8
, 10-13
. We
1
have recently developed a Pd-Fe bimetallic catalyst for selective
9
oxygen removal in gas-phase HDO of phenolics . Over the Pd-Fe
2
14
catalyst, oxophilic Fe is responsible for direct C-O bond
cleavage whereas Pd facilitates hydrogen dissociation,
improving hydrogen coverage on Fe and facilitating the removal
of the hydroxyls generated, which mitigates the oxidation and
adsorption/activation
of
adsorbed
molecules
in
3
, 4
electrocatalysis . Graphene coating has also been reported to
8
, 15
deactivation of surface Fe . When the same Pd-Fe catalyst
was applied in liquid-phase reaction conditions, it exhibited low
selectivity to arenes due to the facile aromatic ring saturation
5
be capable of protecting metal surfaces from oxidation .
Hydrodeoxygenation (HDO) plays pivotal roles in biomass
conversion, i.e., removing oxygen-containing functional groups
from bio-oil. During the HDO of phenolics, selective removal of
the oxygen without saturation of the aromatic ring not only
minimizes the consumption of valuable hydrogen, but also
produces a gasoline blending stock with high octane number,
which is critical to the efficient upgrading of bio-oil . While
sulfide-based catalysts have been shown to be promising for
selective production of arenes, sulfur contamination is
16
via tautomerization . To our best knowledge, it is still highly
challenging to develop an inexpensive sulfur-free catalyst for
selective HDO of phenolics under liquid-phase reaction
1
7
conditions .
Motivated by the protection of transition metals by graphene
6
3
, 5, 18
overlayer
and improved C-O bond hydrogenolysis by alkali
19, 20
metals in homogeneous catalysis
, herein we report a facile
approach by which a heterogeneous and highly stable Fe-based
catalyst can be engineered to produce arenes from phenolics
with 100% selectivity under liquid-phase conditions. Compared
to other alkali metals, Cs has been reported to show higher
7
inevitable in the products . Among the precedent efforts on
8
, 9
exploring sulfur-free catalysts , several catalysts have been
demonstrated to exhibit high selectivity to arenes in gas-phase
HDO. However, the ring saturation products were found to be
21
charge transfer to Fe . Therefore, Cs was employed in this
study to tailor catalyst surface properties. A suite of
complementary characterization techniques including scanning
transmission electron microscopy (STEM) coupled with electron
energy loss spectroscopy (EELS), Raman spectroscopy,
a.The Gene & Linda Voiland School of Chemical Engineering and Bioengineering,
Washington State University, Pullman, WA 99164, USA. Email:
junming.sun@wsu.edu
b.
Institute for Integrated Catalysis and Environmental Molecular Sciences
Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
2 2
temperature programmed surface reaction with H (H -TPSR),
Email: yong.wang@pnnl.gov
School of Chemistry and Chemical Engineering, Harbin Institute of Technology,
Harbin 150001, CN.
c.
in situ X-ray photoelectron spectroscopy (XPS), and in situ
attenuated total reflectance Fourier-transform infrared
spectroscopy (ATR-FTIR) reveal that the thin graphene
†
Footnotes relating to the title and/or authors should appear here.
Electronic Supplementary Information (ESI) available: [details of any supplementary
information available should be included here]. See DOI: 10.1039/x0xx00000x
Please do not adjust margins

PleaseC dh oe mn oi ct a al dS cj ui es nt cme argins
Page 2 of 8
ARTICLE
Journal Name
overlayer prevents the Fe surface from oxidation, making the
graphene/Fe composite (G@Fe) a durable Fe-based catalyst
resistant to oxidation in HDO of phenol. More importantly,
upon modification of this graphene/Fe composite with an alkali
metal (i.e., Cs, denoted as Cs-G@Fe), the graphene overlayers
could also regulate the Fe-alkali metal interactions. As such,
rather than a poison of Fe surface on Cs@Fe, tailored surface
electronic properties were observed on the Cs-G@Fe
composite, leading to exclusive arene production in HDO of
phenolics in liquid phase via inhibiting tautomerization and
aromatic ring saturation of phenolics.
Results and discussion
Structure of the catalysts
View Article Online
DOI: 10.1039/D0SC00983K
The G@Fe catalyst was synthesized with a chemical vapor
2
2
deposition method reported elsewhere , and details are
described in Fig. S1. Continuous graphene overlayers (1-3
layers) on the Fe surface can be clearly discerned by the high
resolution TEM and the corresponding EELS elemental mapping
analysis (Fig. 1a-c and Fig. S2). The presence of the graphene
overlayer is further confirmed by the I2D/I
G
ratio and the width
of Raman spectrum (Fig. 1d and Fig. S3). The D
band in the spectrum reveals that the graphene layer has a
2
2, 23
of 2D band
2
4
certain amount of the defects which may act as the anchoring
25
sites of metal dopants . In the EELS spectra of G@Fe (Fig. 1e),
Fig. 1 Characterization of the catalysts. STEM (a) and elemental mapping (b) images of G@Fe. Blue: Fe, Green: C, red: O. (c) High
resolution TEM image of the edge of G@Fe particle in white square of (a). (d) Raman spectra of G@Fe. (e) EELS spectra by
scanning the regions of A and B in (b). (f) H
2
-TPSR profiles of Fe and G@Fe. Cs 3d (g) and C 1s (h) region of high energy resolution
pseudo-in situ XPS of catalysts. (i) Proposed structure of Cs-G@Fe catalyst, the number of graphene layers could be 1-3.
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 8
PleaseC dh oe mn oi ct a al dS cj ui es nt cme argins
Journal Name
the peak structure in the carbon K-edge region indicates sp
bonding . Note that, before being exposed to air for under the liquid-phase conditions. Herein, using phenol as a
microscopy, as-synthesized sample was passivated by exposure probe molecule, we evaluated the bare Fe (BET surface area: 9.2
ARTICLE
2
cyclohexanol in HDO of phenol) dominate on these catalysts
View Article Online
26
DOI: 10.1039/D0SC00983K
2
2
2
to 1%O /N
2
.
If the Fe surface is not fully covered by the m /g), G@Fe (BET surface area: 4.5 m /g) and Cs-G@Fe (BET
2
graphene overlayers, oxidation of Fe by O
2
would be inevitable. surface area: 4.5 m /g) in liquid-phase HDO. As shown in Fig. 2a
From Fig. 1b, majority of the surface Fe on G@Fe is protected and 2b, the bare Fe catalyst showed both low activity and poor
from oxygen oxidation by the graphene overlayers as evidenced selectivity to benzene in a 4-hour reaction. G@Fe exhibited 4
by absence of oxygen (further confirmed by EELS spectrum b in times higher activity than the bare Fe. Separate time-on-stream
Fig. 1e), except a few minor oxygen patches such as spot a in tests showed drastic deactivation of the bare Fe catalyst,
Fig. 1b which is also confirmed by EELS spectrum a in Fig. 1e. whereas the deactivation was significantly mitigated on the
The nearly full coverage and protection of Fe surface by G@Fe catalyst (Fig. S6). This observation, in alignment with the
graphene overlayers were further confirmed by examining the aforementioned characterization, suggests that graphene
Raman spectra and H
samples after oxygen exposure (i.e., air for Raman and 2% stabilized activities on the metallic Fe and thus the higher
/He for H -TPSR). For the Fe sample, formation of surface iron apparent activity. Despite the improved apparent activity of
oxides after exposure to oxygen was confirmed by both Raman G@Fe catalyst, benzene selectivity remained constantly low at
Fig. S4) and H -TPSR (water formation peak at 309 °C in Fig. 1f ~30%, suggesting that the nature of the active sites on G@Fe is
due to the reduction of Fe oxides by H ). In contrast, both same as that of bare Fe. In homogeneous catalysis, alkali metal
2
-TPSR profiles of the Fe and G@Fe overlayers indeed protect the Fe from oxidation, leading to the
O
2
2
(
2
2
Raman (Fig. S4) and H
2
-TPSR (Fig. 1f) characterization shows the additives have been used in the selective C-O bond cleavage of
absence of iron oxides after the G@Fe sample was exposed to aromatic ethers with Ni-based complex catalysts1 . In this
oxygen. These results strongly suggest that graphene is able to study, doping Cs on G@Fe significantly increased the benzene
protect the surface Fe from oxidation. The G@Fe sample can be selectivity to 100% (Fig 2a and 2b), likely due to the inhibited
further modified with alkali metal (i.e. Cs) for the selective C-O tautomerization. Note that alkali metals have been used as
bond cleavage, as suggested by homogeneous catalysis for the additives on other catalysts for selective hydrogenation of
9, 20
19, 20
36
37
selective hydrogenolysis of aromatic ethers
discussed in the following sections.
, which will be nitroarenes or promotion to aromatic ring saturation .
Different from those reported ones, directly doping alkali metal
The surface electronic properties were further studied with XPS on the Fe without graphene overlayers is not able to enhance
after a pseudo in situ pretreatment with H at 300 °C (simulating the selectivity, instead the catalyst was almost completely
2
the surface under HDO reaction). Over G@Fe, C 1s spectrum deactivated. It suggests that the graphene overlayers, other
displays a peak at 284.8 eV (Fig. S5), characteristic of the sp2 than prevent Fe oxidation, must play another pivotal role to
2
2
carbon of graphene on Fe . The C in iron carbide was reported prevent the poison of surface Fe via a mediated Fe-alkali metal
27
to be located at ~283.4 eV that may overlap with the signal of interaction, the reason of which remains unclear and subjects
graphene. The highly symmetric peak shape, however, suggests to further studies. Regardless, we first applied a similar
the amount of carbide, if any, is minimal on the catalyst surface. approach used in homogeneous catalysis to the heterogeneous
The C1s peak is also used as a reference for the charge analogues and achieved the selective C-O bond cleavage of
correction of other species. Fig. 1g shows the Cs 3d region of phenolics in HDO. It should be mentioned that the addition of
G@Fe and Cs-G@Fe. Upon adding Cs on G@Fe, the Cs 3d alkali metal resulted in the decrease of apparent rate for
spectrum shows the binding energy of 724.5 eV for Cs 3d5/2 and benzene production as shown in Fig 2a. This decrease can be
28, 29
7
38.5 eV for 3d3/2
. In Fe 2p spectrum of G@Fe (Fig. 1h), two expected since tautomerization reaction pathway also
peaks centered at 706.8 eV for 2p3/2 and 720.0 eV for 2p1/2 are contributed to benzene formation (Fig. S7), and the Cs addition
30
observed, characteristic of metallic Fe . Notably, doping Cs on completely shut down the tautomerization pathway. The
the surface shifts the Fe peaks to lower binding energy by 0.6 stability of the representative Cs-G@Fe was also studied and
3
1
eV, suggesting that the Fe becomes more electron rich due to results are shown in Fig. 2c. Although a slight decrease in
st
electron donation from Cs to Fe through the graphene reactivity was observed after the 1 cycle, the catalyst remained
overlayers. This charge transfer via electron tunneling has been relatively stable afterwards for 4 additional testing cycles. More
widely demonstrated on metal covered with conductive importantly, the benzene selectivity remained at 100% in all the
3
2
33, 34
graphene layers or even a thin layer of oxide insulator
.
tested cycles. It should also be mentioned that, due to the
Based on these results, the surface structure of Cs-G@Fe magnetic nature of the catalyst, the catalysts can be readily
catalyst can be inferred as shown in Fig. 1i. Briefly, the graphene separated from the liquid phase by applying a magnetic field as
27, 35
layer is deposited on Fe substrate
, while the Cs species is demonstrated in the cyclic stability tests (Fig. S8). The spent Cs-
anchored on graphene, which further modifies the electronic G@Fe after the HDO reaction was characterized with Raman
properties of Fe.
Catalytic performances
spectroscopy and TEM (Fig. S9). The 2D peak in Raman
spectrum indicated the structure of carbon is still graphitic. TEM
As previously mentioned, although several catalysts, including image showed the graphene overlayer was still intact and
Fe-based ones, have been reported to selectively produce
arenes in the gas-phase HDO of phenolics, aromatic ring-
saturation reactions (e.g. producing cyclohexane and
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

PleaseC dh oe mn oi ct a al dS cj ui es nt cme argins
Page 4 of 8
ARTICLE
Journal Name
View Article Online
DOI: 10.1039/D0SC00983K
Fig. 2 Catalytic performances in HDO of phenol. (a-b) Apparent benzene formation rate (a) and product selectivity (b) over
different catalysts in a 4-h reaction. Reacting condition: 300 °C, 50 mL hexadecane as solvent, 1.6 MPa H , 0.15 g catalyst, 0.6 g
phenol, 4h. (c) stability test of Cs-G@Fe in HDO of phenol under same reacting condition, each cycle took 4 h. (d) Arrhenius plot
2
for G@Fe and Cs-G@Fe. Reacting condition: 50 mL hexadecane, 1.6 MPa H
obtained at conversions below 15%.
2
, 0.15 g catalyst, 0.6 g phenol. Apparent activity was
attached to the catalyst surface. These results indicate the has been shown to influence the activation energy (E
a
) of a
catalyst surface structure remained the same as the one shown reaction . Therefore, separate kinetic analysis was done to
in Fig. 1i after the HDO reaction. compare the apparent E of the reactions on the G@Fe and Cs-
It has been well known, Fe single atom could be formed and G@Fe (Fig. 2d). The reaction pathways are categorized into two
43
a
38
stabilized on either defect sites of graphene or N doped types: direct deoxygenation (DDO) producing benzene and
graphene39, 40. This Fe species may serve as the active sites for hydrogenation followed by deoxygenation (HYD) producing
DDO. From Raman spectra (Fig. 1d), however, the defect sites ring-saturated compounds (Fig. S11). Over G@Fe, both
on G@Fe is minimum. In addition, although N
2 a
gas was used pathways exist. The apparent E of HYD (89 kJ/mol) is much
during the synthesis of G@Fe, no N signal can be detected at lower than that of DDO (143 kJ/mol). This is consistent with the
4
4, 45
~
400 eV in the EELS (Fig. 1e) and XPS (Fig. S10). It suggests that higher bond dissociation energy of Caromatic-O
and the results
4
6
Fe single atom, if any, should be negligible on the G@Fe from previously reported kinetic studies . Over the Cs-G@Fe,
catalyst. Here, we postulate that the actives sites are likely Fe the ring saturation was inhibited (i.e. Cs significantly increased
covered with several graphene overlayers through which
a a
E for ring saturation) and the apparent E of direct C-O bond
3
2
electron tunneling takes place . A similar observation has been cleavage is 141 kJ/mol which is comparable with that of DDO on
reported in electrocatalysis where graphene covered Ni-Co G@Fe (143 kJ/mol). This implies that Cs may not be directly
3
41
alloy and Fe
3
C
allow electrons moving through these involved in C-O bond cleavage, but instead, is primarily
graphene overlayers while protecting Ni-Co and Fe
electrolytes.
3
C in acid responsible for inhibition of the ring-saturation pathway.
Possible reaction mechanisms
16
The binding energy of Fe is lowered by 0.6 eV after adding Cs, Previous results have shown that, while direct C-O bond
as shown in Fig 1h. This implies that the addition of Cs leads to cleavage selectively produces arenes, tautomerization mainly
the charge transfer and, consequently, the tuned surface contributes to the ring saturation on the Fe-based catalysts in
electronic properties of the graphene-protected Fe and the liquid-phase reactions (Fig. S7 and notation). Based on the fact
42
catalyst functionalities . The change of electronic properties that the E
a
for DDO remains the same after Cs addition, it is
4
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 8
PleaseC dh oe mn oi ct a al dS cj ui es nt cme argins
Journal Name
ARTICLE
View Article Online
DOI: 10.1039/D0SC00983K
Fig. 3 Spectroscopic studies of reaction mechanisms. (a-b) In situ ATR-FTIR spectra at different regions for phenol adsorption on
G@Fe and Cs-G@Fe. The bond vibration attributed to each specific peak is highlighted in red. (c) Proposed reaction mechanisms for
the selective HDO over Cs-G@Fe.
hypothesized that the addition of Cs largely inhibits the G@Fe confirms that surface Cs species is indeed able to inhibit
tautomerization reaction pathway but has a minimal effect on tautomerization and thus leads to selective C-O bond cleavage
the C-O bond cleavage. To further verify this hypothesis, in situ of phenol, as elucidated in Fig. 3c. One possible interpretation
ATR-FTIR was employed to investigate the phenol adsorption for this selective catalysis is there may be two types of active
over G@Fe and Cs-G@Fe. As shown in Fig. 3a, both spectra of sites on G@Fe (i.e., one for tautomerization and another for
-
1
G@Fe and Cs-G@Fe display peaks at 1579, 1468 cm
selective C-O bond cleavage), and depositing Cs may selectively
block the one for tautomerization with the other one being
47
-1
(
stretching vibrations of the aromatic ring) and 1256 cm
4
8
(
stretching vibration of the C-O bond) , an indication of surface exposed to phenol for C-O cleavage. To test this hypothesis, we
adsorbed phenol species. Most importantly, in contrast to the further compared the performances of other alkali metal doped
Cs-doped surface, G@Fe exhibits other peaks or shoulder at catalysts with same molar loading (Fig. S12). Given the slight
-
1
54
1
726, 1620, 1374, 1301 cm , which can be assigned to difference of ionic sizes between K and Na , if the alkali metals
4
9
stretching vibration of C=O bond , stretching of aliphatic C=C serve as the block site, a similar catalytic performance in terms
bond , wagging and twisting vibrations of CH
49
48
2
of surface of benzene selectivity can be expected over K-G@Fe and Na-
cyclohexadienone, respectively. This observation suggests that G@Fe. The fact that a significant different benzene selectivity
cyclohexadienone intermediate is indeed formed from the was observed on K-G@Fe (95%) and on Na-G@Fe (44%) suggest
50
tautomerization of phenol in the absence of Cs, which is that the alkali metal may not be a site blocker. In contrast, the
further supported by C-H stretching region as shown in Fig. 3b. inhibition of tautomerization (i.e., benzene selectivity) is well
-1
Both spectra display peaks at ~3052 and ~3013 cm , which are correlated with the capability of electron donation of alkali
5
1, 52
21
attributed to C-H vibrations in the aromatic ring
. The metal to the Fe (Fig. S12). Therefore, though the electronic
-
1
spectrum of G@Fe also shows other peaks in 2944-2877 cm , structure and the specific roles of Cs-G@Fe remain unclear, we
characteristic of stretching of Csp3-H in cyclohexadienone propose the charge transfer from Cs to the active site (i.e.
species . The above results are aligned with other infrared graphene-covered Fe) may play pivotal roles to inhibit the
spectroscopic studies that also observed the keto intermediates functionality for catalyzing tautomerization of phenol. While
from tautomerization in the HDO of phenol50, 53. The fact that allowing the electron tunneling, graphene overlayers may
no tautomerization intermediates were observed on Cs doped
50
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

PleaseC dh oe mn oi ct a al dS cj ui es nt cme argins
Page 6 of 8
ARTICLE
Journal Name
mediate the interaction between Fe and alkali metal/substrate 7.
oxygen to prevent Fe from deactivation.
M. Grilc, B. Likozar and J. Levec, Appl. Catal.ViBew, 2A0rt1ic4le,O1n5lin0e-
51, 275-287.
Y. Hong, H. Zhang, J. Sun, K. M. Ayman, A. J. R. Hensley, M.
1
DOI: 10.1039/D0SC00983K
8.
Gu, M. H. Engelhard, J.-S. McEwen and Y. Wang, ACS Catal.,
2
014, 4, 3335-3345.
Conclusions
9.
J. Sun, A. M. Karim, H. Zhang, L. Kovarik, X. S. Li, A. J.
Hensley, J.-S. McEwen and Y. Wang, J. Catal., 2013, 306, 47-
57.
Our results present an approach to protect Fe with graphene
and further tune the G@Fe catalyst with alkali metal for
selective hydrogenolysis of C-O bond in HDO of phenol. 10.
Graphene overlayers on Fe protect Fe from oxidation while, at
P. M. Mortensen, J.-D. Grunwaldt, P. A. Jensen and A. D.
Jensen, ACS Catal., 2013, 3, 1774-1785.
F. Yang, D. Liu, Y. Zhao, H. Wang, J. Han, Q. Ge and X. Zhu,
ACS Catal., 2018, 8, 1672-1682.
11.
the same time, maintaining the nature of Fe as confirmed by its
catalytic activity resembling that of bare Fe. More importantly,
analogous with homogeneous catalysis, alkali metals such as Cs
could be added to tailor the surface electronic properties of
G@Fe, leading to the selective inhibition of tautomerization and
thus exclusive C-O bond cleavage in the heterogeneously
catalyzed HDO of phenolics (i.e., phenol). To our best
knowledge, this is the first sulfur-free inexpensive catalyst
1
2.
H. Y. Zhao, D. Li, P. Bui and S. T. Oyama, Appl. Catal. A,
2
011, 391, 305-310.
1
1
3.
4.
J.-S. Moon and Y.-K. Lee, Top. Catal., 2015, 58, 211-218.
Q. Tan, G. Wang, A. Long, A. Dinse, C. Buda, J. Shabaker and
D. E. Resasco, J. Catal., 2017, 347, 102-115.
15.
Y. Hong, S. Zhang, F. F. Tao and Y. Wang, ACS Catal., 2017,
7
, 3639-3643.
reported for exclusive hydrogenolysis of the C-O bond in 16.
phenolics under liquid-phase conditions. Moreover, the
catalyst also offers other beneficial properties, i.e. magnetic 17.
J. Zhang, J. Sun, B. Sudduth, X. Pereira Hernandez and Y.
Wang, Catal. Today, 2020, 339, 305-311.
J. Zhang, J. Sun and Y. Wang, Green Chem., 2020, 22, 1072-
1098.
material for a facile separation from reaction slurry, making it a
18.
Y. Yao, Q. Fu, Y. Y. Zhang, X. Weng, H. Li, M. Chen, L. Jin, A.
Dong, R. Mu, P. Jiang, L. Liu, H. Bluhm, Z. Liu, S. B. Zhang
and X. Bao, Proc. Natl. Acad. Sci. U.S.A, 2014, 111, 17023-
promising catalyst for liquid-phase reactions. This work could
also lead to a general methodology for rational design of
heterogeneous catalysts for selective HDO of oxygenates.
1
7028.
A. G. Sergeev and J. F. Hartwig, Science, 2011, 332, 439-
43.
19.
20.
21.
22.
23.
4
Conflicts of interest
There are no conflicts to declare.
N. I. Saper and J. F. Hartwig, J. Am. Chem. Soc., 2017, 139,
17667-17676.
T. Yang, X.-D. Wen, Y.-W. Li, J. Wang and H. Jiao, Surf. Sci.,
2
009, 603, 78-83.
Y. Xue, B. Wu, Y. Guo, L. Huang, L. Jiang, J. Chen, D. Geng,
Y. Liu, W. Hu and G. Yu, Nano Res., 2011, 4, 1208-1214.
A. C. Ferrari, J. C. Meyer, V. Scardaci, C. Casiraghi, M.
Lazzeri, F. Mauri, S. Piscanec, D. Jiang, K. S. Novoselov, S.
Roth and A. K. Geim, Phys. Rev. Lett., 2006, 97, 187401.
Z. H. Ni, W. Chen, X. F. Fan, J. L. Kuo, T. Yu, A. T. S. Wee and
Z. X. Shen, Phys. Rev. B, 2008, 77.
Acknowledgements
This work was supported by the U.S. Department of Energy
(
DOE), Office of Science, Basic Energy Sciences (BES) and
Division of Chemical Sciences, Biosciences and Geosciences
grant DE-FG02-05ER15712; DE-AC05-RL01830, FWP-47319). 24.
(
The authors thank the Franceschi Microscopy and Imaging
Center (FMIC) in Washington State University for the access to
TEM. We would also like to acknowledge Prof. Hongfei Lin in
Washington State University for the GC-MS analysis of the
products.
2
5.
O. Cretu, A. V. Krasheninnikov, J. A. Rodriguez-Manzo, L.
Sun, R. M. Nieminen and F. Banhart, Phys. Rev. Lett., 2010,
105, 196102.
26.
Y. Zhu, S. Murali, M. D. Stoller, K. J. Ganesh, W. Cai, P. J.
Ferreira, A. Pirkle, R. M. Wallace, K. A. Cychosz, M.
Thommes, D. Su, E. A. Stach and R. S. Ruoff, Science, 2011,
3
32, 1537-1541.
References
27.
N. A. Vinogradov, A. A. Zakharov, V. Kocevski, J. Rusz, K. A.
Simonov, O. Eriksson, A. Mikkelsen, E. Lundgren, A. S.
Vinogradov, N. Martensson and A. B. Preobrajenski, Phys.
Rev. Lett., 2012, 109, 026101.
1.
K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y.
Zhang, S. V. Dubonos, I. V. Grigorieva and A. A. Firsov,
Science, 2004, 306, 666-669.
2.
3.
4.
5.
D. Deng, K. S. Novoselov, Q. Fu, N. Zheng, Z. Tian and X. 28.
Bao, Nat. Nanotechnol., 2016, 11, 218-230.
J. Deng, P. Ren, D. Deng and X. Bao, Angew. Chem. Int. Ed., 29.
J. Campbell, J. Nakamura and C. T. Campbell, J. Catal., 1992,
136, 24-42.
A. F. Carley, P. R. Davies, K. R. Harikumar, R. V. Jones and
M. W. Roberts, J Phys. Chem. B, 2004, 108, 14518-14526.
A. K. Opitz, A. Nenning, C. Rameshan, R. Rameshan, R.
Blume, M. Havecker, A. Knop-Gericke, G. Rupprechter, J.
Fleig and B. Klotzer, Angew. Chem. Int. Ed., 2015, 54, 2628-
2632.
2
015, 54, 2100-2104.
D. Deng, L. Yu, X. Chen, G. Wang, L. Jin, X. Pan, J. Deng, G. 30.
Sun and X. Bao, Angew. Chem. Int. Ed., 2013, 52, 371-375.
M. Tavakkoli, T. Kallio, O. Reynaud, A. G. Nasibulin, C.
Johans, J. Sainio, H. Jiang, E. I. Kauppinen and K. Laasonen,
Angew. Chem. Int. Ed., 2015, 54, 4535-4538.
C. Li, X. Zhao, A. Wang, G. W. Huber and T. Zhang, Chem.
Rev., 2015, 115, 11559-11624.
31.
M. Ding, B. H. W. S. de Jong, S. J. Roosendaal and A.
Vredenberg, Geochim. Cosmochim. Acta., 2000, 64, 1209-
1219.
6.
6
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 8
PleaseC dh oe mn oi ct a al dS cj ui es nt cme argins
Journal Name
ARTICLE
32.
33.
34.
E. Cobas, A. L. Friedman, O. M. Van't Erve, J. T. Robinson
View Article Online
DOI: 10.1039/D0SC00983K
and B. T. Jonker, Nano Lett., 2012, 12, 3000-3004.
D. Ricci, A. Bongiorno, G. Pacchioni and U. Landman, Phys.
Rev. Lett., 2006, 97, 036106.
M. Sterrer, T. Risse, M. Heyde, H. P. Rust and H. J. Freund,
Phys. Rev. Lett., 2007, 98, 206103.
3
3
5.
6.
P. Restuccia and M. C. Righi, Carbon, 2016, 106, 118-124.
H. Wei, Y. Ren, A. Wang, X. Liu, X. Liu, L. Zhang, S. Miao, L.
Li, J. Liu, J. Wang, G. Wang, D. Su and T. Zhang, Chem. Sci.,
2
017, 8, 5126-5131.
3
7.
8.
I. D. Mora-Vergara, L. Hernández Moscoso, E. M.
Gaigneaux, S. A. Giraldo and V. G. Baldovino-Medrano,
Catal. Today, 2018, 302, 125-135.
A. W. Robertson, B. Montanari, K. He, J. Kim, C. S. Allen, Y.
A. Wu, J. Olivier, J. Neethling, N. Harrison, A. I. Kirkland and
J. H. Warner, Nano Lett., 2013, 13, 1468-1475.
3
3
9.
0.
H. T. Chung, D. A. Cullen, D. Higgins, B. T. Sneed, E. F. Holby,
K. L. More and P. Zelenay, Science, 2017, 357, 479-484.
W. Liu, L. Zhang, X. Liu, X. Liu, X. Yang, S. Miao, W. Wang,
A. Wang and T. Zhang, J. Am. Chem. Soc., 2017, 139, 10790-
4
10798.
41.
Y. Hu, J. O. Jensen, W. Zhang, L. N. Cleemann, W. Xing, N. J.
Bjerrum and Q. Li, Angew. Chem. Int. Ed., 2014, 53, 3675-
3679.
4
4
2.
3.
C. T. Campbell, Nat. Chem., 2012, 4, 597-598.
L. Wang, H. Li, W. Zhang, X. Zhao, J. Qiu, A. Li, X. Zheng, Z.
Hu, R. Si and J. Zeng, Angew. Chem. Int. Ed., 2017, 56, 4712-
4718.
44.
Y.-R. Lu, Comprehensive Handbook of Chemical Bond
Energies, Taylor & Francis Group, Boca Raton, Florida,
United States., 1st edn., 2007.
45.
46.
47.
48.
X. Wang and R. Rinaldi, Angew. Chem. Int. Ed., 2013, 52,
1
1499-11503.
H. Wang, S. Liu and K. J. Smith, Energ. Fuel, 2016, 30, 6039-
049.
T. Lai, C. Lee, K. Wu, Y. Shu and C. Wang, Appl. Catal. B,
006, 68, 147-153.
6
2
E. Wiercigroch, E. Szafraniec, K. Czamara, M. Z. Pacia, K.
Majzner, K. Kochan, A. Kaczor, M. Baranska and K. Malek,
Spectrochim. Acta. A Mol. Biomol. Spectrosc., 2017, 185,
317-335.
49.
50.
51.
N. Vlachos, Y. Skopelitis, M. Psaroudaki, V. Konstantinidou,
A. Chatzilazarou and E. Tegou, Anal. Chim. Acta, 2006, 573-
574, 459-465.
P. M. de Souza, R. C. Rabelo-Neto, L. E. P. Borges, G. Jacobs,
B. H. Davis, T. Sooknoi, D. E. Resasco and F. B. Noronha, ACS
Catal., 2015, 5, 1318-1329.
A. Popov, E. Kondratieva, J. M. Goupil, L. Mariey, P. Bazin,
J.-P. Gilson, A. Travert and F. Maugꢀ, J Phys. Chem. C, 2010,
114, 15661-15670.
5
2.
3.
L. Mino, A. Zecchina, G. Martra, A. M. Rossi and G. Spoto,
Appl. Catal. B, 2016, 196, 135-141.
P. M. de Souza, R. C. Rabelo-Neto, L. E. P. Borges, G. Jacobs,
B. H. Davis, D. E. Resasco and F. B. Noronha, ACS Catal.,
5
2
017, 7, 2058-2073.
R. D. Shannon, Acta Crystallographica Section A, 1976, 32,
51-767.
54.
7
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Chemical Science
Page 8 of 8
View Article Online
DOI: 10.1039/D0SC00983K
For Table of Contents Only
Tailoring the graphene-covered Fe with Cs modifies the surface electronic properties of the
composite Cs-G@Fe catalysts such that selective C-O bond cleavage of phenol is achieved in
liquid phase by inhibiting the facile tautomerization followed by ring saturation.