Ultradispersed Nickel Phosphide on Phosphorus-Doped Carbon with Tailored d-Band Center for Efficient and Chemoselective Hydrogenation of Nitroarenes

Article abstract of DOI:10.1021/acscatal.8b02091

Nickel phosphide is a promising catalyst for hydrogenation of nitroarenes but suffers from sluggish H desorption and low chemoselectivity. Herein, we overcome these problems through reducing the Ni₂P into subnanosized clusters, tailoring the d-band center of Ni, and coupling them with P-doped carbon. Using density functional theory (DFT) calculations, we predicted that electron transfer from P-doped carbon to Ni₂P cluster results in downshift of d-band center of Ni that promotes H desorption on highly charged antibonding orbital of Ni-H, and reactant is preferentially adsorbed on P-doped carbon surface through nitro group due to the geometrical hindrance on Ni₂P clusters that leads to good selectivity. Then we developed a chemical anchoring method to fabricate Ni₂P supported on P-doped carbon with high dispersion of 81.3%. The synthesized catalyst delivers high activity and selectivity chemoselective hydrogenation of nitroarenes, and outperforms various noble- and transition-metal catalysts. Moreover, we revealed the origins of the superior performance of catalyst by characterizations, and confirmed the conclusion of DFT calculation. Such concept of tailoring d-band center and improving dispersion of active phase can provide insight for design of catalysts for hydrogenation and beyond.

Full text of DOI:10.1021/acscatal.8b02091

Subscriber access provided by READING UNIV
Article
Ultradispersed nickel phosphide on phosphorus-doped carbon with tailored
d-band center for efficient and chemoselective hydrogenation of nitroarenes
Gao Ruijie, Lun Pan, Huiwen Wang, Xiangwen Zhang, Li Wang, and Ji-Jun Zou
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.8b02091 • Publication Date (Web): 01 Aug 2018
Downloaded from http://pubs.acs.org on August 1, 2018
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a service to the research community to expedite the dissemination
of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in
full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully
peer reviewed, but should not be considered the official version of record. They are citable by the
Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore,
the “Just Accepted” Web site may not include all articles that will be published in the journal. After
a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web
site and published as an ASAP article. Note that technical editing may introduce minor changes
to the manuscript text and/or graphics which could affect content, and all legal disclaimers and
ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or
consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W.,
Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 23
ACS Catalysis
1
2
3
4
5
6
7
8
9
Ultradispersed nickel phosphide on phosphorusꢀdoped carbon with
tailored d-band center for efficient and chemoselective hydrogenation
of nitroarenes
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Ruijie Gao,a,b Lun Pan,a,b Huiwen Wanga, Xiangwen Zhang,a,b Li Wang,a,b JiꢀJun
Zoua,b*
aKey Laboratory for Green Chemical Technology of the Ministry of Education, School of
Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
bCollaborative Innovative Center of Chemical Science and Engineering (Tianjin), Tianjin 300072,
China
*Eꢀmail: jj_zou@tju.edu.cn
Abstract: Nickel phosphide is a promising catalyst for hydrogenation of nitroarenes but suffers
from sluggish H desorption and low chemoselectivity. Herein, we overcome these problems
through reducing the Ni2P into subꢀnanosized clusters, tailoring the dꢀband center of Ni, and
coupling them with Pꢀdoped carbon. Using DFT calculations, we predicted that electron transfer
from Pꢀdoped carbon to Ni2P cluster results in downshift of dꢀband center of Ni that promotes H
desorption on highly charged antibonding orbital of NiꢀH, and reactant is preferentially adsorbed
on Pꢀdoped carbon surface through nitro group due to the geometrical hindrance on Ni2P clusters
that leads to good selectivity. Then we developed a chemical anchoring method to fabricate Ni2P
supported on Pꢀdoped carbon with high dispersion of 81.3%. The synthesized catalyst delivers
high activity and selectivity chemoselective hydrogenation of nitroarenes, and outperforms
various nobleꢀ and transitionꢀmetal catalysts. Moreover, we revealed the origins of the superior
performance of catalyst by characterizations, and confirmed the conclusion of DFT calculation.
Such concept of tailoring dꢀband center and improving dispersion of active phase can provide
insight for design of catalysts for hydrogenation and beyond.
Keywords: Ni2P, d band center, ultraꢀdispersion, synergistic effect, selective hydrogenation
ACS Paragon Plus Environment

ACS Catalysis
Page 2 of 23
1
2
3
4
5
1. Introduction
6
7
8
9
Substituted aromatic amines are important industrial intermediates for pharmaceuticals,
agrochemicals, fineꢀchemicals, dyes and polymers, and most of them are synthesized by
chemoselective hydrogenation of corresponding substituted nitro aromatics1ꢀ6. However, in most
cases the hydrogenation of reducible functional groups (e.g. –C=O, ꢀCl and –C=C) also occur with
the formation of ineluctable byproducts. Although some nobleꢀmetal based catalysts, for example,
Pt7ꢀ8, Pd9ꢀ10 and Au11 can achieve good selectivity via regulating particle sizes and morphology,
alloying with other metals, and coupling with support materials, the expensive price and rare
storage limit their applications. Therefore, the development of more lowꢀcost catalyst with high
activity and chemoselectivity is very necessary.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Recently intensity research studies have been devoted to designing heteroatomꢀdoped
carbonꢀbased catalysts12ꢀ17, e.g. N/Pꢀdoped carbon, for chemoselective hydrogenation of
nitroarenes18ꢀ19. Doping highly electronegative heteroatoms into the carbon matrix can effectively
improve the electronic density of nearby carbon atoms, and provides activated sites that can
exclusively adsorb nitro group and achieves a selectivity of nearly 100%. However, carbonꢀbased
catalysts suffer from medium capability in hydrogen activation, so they generally require high
o
reaction temperature, for example, Pꢀdoped carbon requires a temperature of 120 C to reach
considerable activity19. Transitionꢀmetal phosphides (TMPs) have also attracted much attention as
promising candidates for hydrogen activation due to their Ptꢀlike electronic structure20ꢀ24
.
Particularly, nickel phosphide has shown strong ability in hydrogen activation25ꢀ26 and efficiently
catalyze the hydrogenation of nitro or carbonyl group27ꢀ28 under relatively mild conditions. But it
still suffers from two shortcomings: one is poor chemoselectivity in the hydrogenation of
nitroarenes due to the nonꢀselective adsorption of various functional groups; the other is the
difficulty in release of atomic H for subsequent hydrogenation due to strong affinity. To improve
the selectivity, it is necessary to avoid the adsorption of reactants and intermediates on nickel
phosphide, so the particle size should be controlled in nano or subnano scale (to get geometrical
hindrance7,10ꢀ11) by means of fixing them on supports and thus nitro groups can be selectively
adsorbed on support materials. To facilitate the desorption of atomic H, it is necessary to weaken
the interaction between Ni and H, and a feasible way is to tune the dꢀband state of Ni to reach low
ACS Paragon Plus Environment

Page 3 of 23
ACS Catalysis
1
2
3
4
energy level of H desorption29ꢀ30, which may be achieved by interaction of doped carbon31ꢀ32
.
5
6
7
8
Based on the above considerations, combining nickel phosphide nanoclusters with Pꢀdoped carbon
may be a promising way to improve the selectivity and activity of Ni2P for hydrogenation of
nitroarenes.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
In this work, first by means of DFT calculation, we confirmed that Ni2P nanoclusters anchored
on Pꢀdoped carbon (Ni2P/PC) exhibit a downshifted dꢀband of Ni and exclusive adsorption of
reactant on PC, which contribute to facilitated H desorption and spillover for high activity and
adsorption of –NO2 groups for high selectivity. Then we developed a chemical anchoring method
to fabricate this catalyst with controllable dispersion of Ni2P clusters. With the dispersion of Ni2P
reaching 81.3%, the optimal Ni2P/PCꢀ2 catalyst shows a selectivity of >99.9% toward
4ꢀaminobenzaldehyde in hydrogenation of 4ꢀnitrobenzaldehyde, and a large turnover frequency
(TOF) of ~147.5 hꢀ1 based on the molar of Ni. Also experimental results reveal the excellent
performance is originated from the synergistic effect of Ni2P nanoclusters for H2 activation and
Pꢀdoped carbon support for preferential adsorption of nitro group.
2. Experimental section
Density Functional Theory Calculations. All density functional theory calculations were
carried out with Vienna Abꢀinitio Simulation Package33ꢀ34 (VASP). The exchange correlation
functional employed was the PerdewꢀBurkeꢀErnzerhof (PBE) functional of generalized gradient
approximation35ꢀ36. To locate transition states (TS), the Climbing Images Nudged Elastic Band
(CIꢀNEB) algorithm37 was used. Each transition state was confirmed by vibrational frequency
analysis. Oneꢀlayer slab of graphite was used for modeling carbon materials. The vacuum region
was 20 Å. The kinetic energy cutoff of 500 eV was employed. The kꢀpoint was set to 2 × 2 × 1 and
that of static method was 6 × 6 × 1. The formation energy is defined as the energy difference per
unit cell between the nanocrystal and isolated atoms38. The adsorption energies, Eads, are
calculated by using the following equation:
Eads = Eadsorbate+surface – (Eadsorbate + Esurface
)
where Eads is the adsorption energy, Eadsorbate+surface is total energy of surface covered with
adsorbates, Esurface is the energy of clean surface, Eadsorbate is the energy of adsorbate. The dꢀband
center, ξd is calculated39 by using the following equation:
ξd = ∑Ed/∑Nd
ACS Paragon Plus Environment

ACS Catalysis
Page 4 of 23
1
2
3
4
5
where Ed represents total dꢀelectron energy and Nd represents total dꢀelectron number. And Atomic
information of DFT models are given in the Supporting Information.
6
7
Synthesis of catalysts. Pꢀdoped carbon (PC) was synthesized according to our previously
8
9
o
reported method19. Simply, phytic acid aqueous solution was polymerized under 180 C and then
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
o
carbonized at 900 C under Ar flow. The Ni2P nanoclusters anchored on Pꢀdoped carbon were
synthesized by chemical anchoring method. Briefly, nickel nitrate (Ni(NO3)2 6H2O) and required
amounts of citric acid (CA) were dissolved in purified water and mixed, then kept stirring under
ambient condition for 12 h to allow the formation of NiꢀCA complex. After that, the aqueous
solution was mixed with PC and kept stirring for another 12 h to form NiꢀCA/PC composite. The
sample was then dried under freezing temperature for 12 h in vacuum and further at 60 oC for 1 h,
mixed with sodium hypophosphite, and calcined at 400 oC for 1 h under Ar atmosphere to realize
phosphorization of nickel. After that, the powders were washed for 3 times using deionized water
o
to remove unconverted sodium hypophosphite, and then dried under 60 C. The obtained catalyst
was referred as Ni2P/PCꢀx, where x represents the molar ratio of CA to Ni. As reference, activated
carbon (Ni2P/C) was employed as support by aforementioned synthesis route, in which carbon
support was first hydroxylation according to literature (detail in Supporting Information, SI). Bulk
Ni2P catalyst was also synthesized according to the reported procedure (detail in SI).
Characterization. Surface morphologies of catalysts were examined by SEM using a Hitachi
Sꢀ4800 instrument. TEM images were obtained using a Tecnai G2 F20 transmission electron
microscope at 200 kV, with elemental compositions being analyzed by energy dispersive Xꢀray
spectrometer (EDXS). The size distributions of Ni2P clusters were obtained by statistical analyses
carried out for at least 5 images of ~50 Ni2P clusters from different regions of each catalyst. The
crystal structures were recorded using a RigaKu D/maxꢀ2500 Xꢀray diffractometer (XRD)
equipped with a Cu Kα irradiation source. The element analysis was determined by Vario EL
CUBE equipped with METTLER x86 instrument. Elemental composition and bonding
information were analyzed using an Xꢀray photoelectron spectroscopy operated at a pass energy of
187.85 eV (Physical Electronics PHI 1600 ESCA XPS system using a monochromated Al Kα
Xꢀray source) and the C 1s peak at 284.6 eV was taken as internal standard. Raman spectra were
recorded using a Raman spectrometer (DXR Microscope) and a green semiconductor laser (532
nm) as excitation source. Nitrogen adsorptionꢀdesorption isotherms were analyzed with ASAP
ACS Paragon Plus Environment

Page 5 of 23
ACS Catalysis
1
2
3
4
5
6
7
8
9
2020 physisorption Analyzer at 77 K. FTꢀIR spectra were recorded on a BioRad FTS 6000
spectrometer. All of the samples were mixed with KBr and pressed into a thin plate for
measurement. The Ni content was determined by inductively coupled plasma optical emission
spectroscopy (ICPꢀOES) analysis.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Catalytic Hydrogenation. The hydrogenation was conducted in 50 mL autoclave equipped
with a PTFE lining, using 0.5 mmol nitroarenes, 5 mL solvent and 10 mg catalyst. The autoclave
was purged with N2 and H2 (15 bar) respectively for three times, pressurized to 10 bar, and heated
o
to 80 C for defined time. After the reaction, the autoclave was cooled to room temperature,
followed by centrifugation and analysis of a sample by GCꢀMS (Agilent 5975 equipped with HPꢀ5
capillary column) and GC (Agilent 7820 equipped with FID detector and ATꢀSEꢀ54 capillary
column). TOF was calculated from the reaction rate at 1 h reaction derived by the number of Ni
atoms exposed to the catalyst surface (eqs 1 and 2):
TOF = n0C/tncat
cat = mcatwDisNi/MNi
(1)
(2)
n
where n0 is the initial molar of substrate, C is the conversion of substrates at the reaction of t, ncat
is the molar of exposed Ni atom, w is the mass fraction of Ni in catalysts, MNi is molar mass of Ni,
and DisNi is the dispersion of Ni for catalysts.
3. Results and discussion
3.1 DFT design of catalyst. First, we used DFT calculation to confirm our hypothesis for
catalyst design by considering Ni2P cluster anchored on PC support (Ni2P/PC) and bulk Ni2P (111)
as a reference, with the slab models constructed in Figure S1 (SI). Notably, the adsorption energy
of Ni2P on PC is ꢀ1.23 eV, signifying that Ni2P nanoclusters on PC is very stable. Bader charge
analysis (Figure S2, Table S1, SI) shows the valence charge of Ni atom (9.94 |e|) in Ni2P/PC is
more than that of bulk Ni2P (9.77 |e|), indicating Ni atoms accept electrons from carbon. And the
isosurface value shows higher charge density around Ni atom of Ni2P/PC (Figure 1a, Figure S3,
SI), which further confirms the electronꢀtransfer from PC to Ni2P nanoclusters. Such electronꢀrich
effect is expected to tailor the dꢀband of Ni atom. In Figure 1b, the density of state (DOS) near the
Fermi level (Ef) shows the dꢀband center of Ni in Ni2P/PC (ꢀ1.88 eV) is more far away from Ef
than that in Ni2P (ꢀ1.42 eV), indicating a downshift in dꢀband when Ni2P nanoclusters are
anchored on PC. Correspondingly, as shown in Figure 1c, the desorption energy of H on Ni2P/PC
ACS Paragon Plus Environment

ACS Catalysis
Page 6 of 23
1
2
3
4
5
6
7
8
9
(ꢀ0.56 eV) is much lower than that on Ni2P (ꢀ1.12 eV), indicative of more feasible H desorption.
Moreover, the length of NiꢀH bond on Ni2P/PC is 1.90 Å, quite longer than intrinsic value of NiH
(1.57 Å) and that on Ni2P (1.65 Å), which further predicts an easier desorption of H from Ni2P/PC
(Figure S4, SI). Generally, the HꢀNi interaction can be considered as the coupling between the
valence states of H and the d states of Ni, which may form bonding and antibonding states. The
HꢀNi binding is governed by antibonding states, and the filling of antibonding states depend on
their energy levels. As the dꢀband center is intervenient between antibonding and bonding, it can
be used to describe the strength of HꢀNi binding. As illustrated in Figure 1d, when dꢀband center
of Ni downshifts, the energy level of antibonding states is lowered and easy to be filled, which
results in a low desorption energy of H.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 1. (a) Differential charge density in bulk Ni2P and Ni2P/PC (Yellow and cyan isosurfaces
represent electron accumulation and depletion, respectively; the isosurface value is 0.008 e Åꢀ3);
(b) Density of states (DOS) of plots of Ni ions in Ni2P and Ni2P/PC (dꢀband center of Ni is
highlighted in the DOS curve); (c) Desorption energies of dissociated H atoms on bulk Ni2P and
Ni2P/PC; (d) Schematic illustration of function of downshifted dꢀband on H desorption; (e)
Summary of adsorption models of 4ꢀnitrobenzaldehyde on Ni2P (111) and PC surface of Ni2P/PC.
Then we considered the selectivity of Ni2P/PC using 4ꢀnitrobenzaldehyde as a model
ACS Paragon Plus Environment

Page 7 of 23
ACS Catalysis
1
2
3
4
5
6
7
8
9
molecule as shown in Figure 1e. On Ni2P (111), the adsorption energies of 4ꢀnitrobenzaldehyde
via –NO2 and –CHO are calculated as ꢀ0.16 and ꢀ0.20 eV, respectively, suggesting an equal
adsorption of nitro and carbonyl group. Moreover, 4ꢀnitrobenzaldehyde lies parallelly on the
catalyst surface with an adsorption energy of ꢀ0.41 eV, which is more stable than perpendicular
adsorption models, in consistent with reported result that bulk Ni2P catalyst is low selective for the
hydrogenation of 4ꢀnitrobenzaldehyde27ꢀ28. In addition, the adsorption of 4ꢀnitrobenzaldehyde on
other Ni2P facets, e.g. Ni2P (100) and Ni2P (110) were also considered, but all of them show lower
adsorption energies, as shown in Figure S5 (SI). For Ni2P/PC, 4ꢀnitrobenzaldehyde molecule may
bind with Ni2P cluster or PC support. When binding with Ni2P, 4ꢀnitrobenzaldehyde
perpendicularly adsorbs via –NO2 and –CHO with adsorption energies of ꢀ0.06 and ꢀ0.09 eV
respectively, which is less stable than the case of Ni2P (111) (Figure S6, SI). Meanwhile, parallel
adsorption of 4ꢀnitrobenzaldehyde is not stable owing to the size limit of small Ni2P cluster and
steric hindrance. Alternatively, 4ꢀnitrobenzaldehyde is absorbed on PC via nitro group (with a
large adsorption energy of ꢀ0.63 eV), more stable than adsorption via carbonyl group (only ꢀ0.15
eV) and parallel adsorption (+0.32 eV) as shown in Figure S7 (SI), suggesting an excellent
selectivity of Ni2P/PC.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
3.2 Controllable synthesis of Ni2P/PC. Since DFT calculation predict Ni2P/PC as a promising
candidate for selective hydrogenation, we then synthesized this catalyst via a chemical anchoring
method. As shown in Figure S8 (SI), the synthesized Pꢀdoped carbon shows a typical carbon
matrix from the HRꢀTEM image and broad XRD peak at 24o indexed to graphitic carbon, in
agreement with our previous work19. Then the key to synthesize the subꢀnanometer Ni2P clusters
tightly anchored on PC is employing citric acid to fix Ni ions on PC surface, through the
interaction between carboxyl groups of CA and acidic hydroxyl groups of PC, as illustrated in
Scheme 1. As shown in Figure S9 (SI), a decreased signal at ca. 1700 cmꢀ1 assigned to C=O in
timeꢀdependent IR spectra indicates the NiꢀCA complexes are decomposed during the
phosphorization process, and the residual Ni ions bonding with the hydroxyl groups are then
phosphated, which can be confirmed by reduced acidic sites on Ni2P/PC (74 ꢁmol/g) compared
with PC (108 ꢁmol/g), as witnessed by NH3ꢀTPD (Figure S10, SI). So this chemical bonding
avoids the excessive aggregation of Ni ions and helps to get highly dispersed Ni2P nanoclusters.
ACS Paragon Plus Environment

ACS Catalysis
Page 8 of 23
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 1. Schematic illustration for chemical anchoring of Ni ions on Pꢀdoped carbon surface via
controlled decomposition of NiꢀCA.
Importantly, the size of Ni2P clusters can be regulated by the dosage of CA ligand47ꢀ48. With the
absence of CA, the Ni2P particles is ca. 7 nm (Figure 2a), and the faint lattice fringe of d = 0.221
nm indexed to plane (111) of Ni2P25 is observed from HRꢀTEM image (Figure S11, SI). With
increased dosage of CA, the particle size becomes smaller, and no obvious Ni2P particles can be
observed on PC surface with CA/Ni ratio of 2 (Figure 2bꢀd). The energyꢀdispersive Xꢀray (EDX)
spectrum and mapping evidences the presence of C, P, and Ni elements in Ni2P/PCꢀ2 (Figure S12,
S13, SI). Moreover, electronꢀenergy loss spectroscopy mapping shows the uniformly dispersed Ni
element on PC surface (Figure 2e), further confirming the formation of ultrafine Ni2P
nanoclusters. According to the particle size distributions (Figure 2f, Figure S14, SI), the particle
size of Ni2P decreases in the order of Ni2P/PCꢀ0 (7.6 nm) > Ni2P/PCꢀ0.5 (4.5 nm) > Ni2P/PCꢀ1
(2.8 nm) > Ni2P/PCꢀ2 (ultrafine). Since the chemisorption of CO over Ni2P can be approximate
regarded as monomolecularꢀlayer adsorption, the dispersion of Ni2P nanoclusters was further
calculated by CO chemisorption method (Figure 2f, Table S2, SI). Obviously, the dispersion of
Ni2P nanoclusters increases in the order of Ni2P/PCꢀ0 (38.5%) < Ni2P/PCꢀ0.5 (43.4%) <
Ni2P/PCꢀ1 (66.2%) < Ni2P/PCꢀ2 (81.3%), in consistent with the particle size distribution, which
confirms that CA ligand can reduce the size of Ni2P clusters. Using the same synthesis procedure,
Ni2P nanoclusters were also loaded on commercial carbon support (Ni2P/Cꢀ2), similarly no
obvious nanoparticles were found from TEM image (Figure S15, SI). The dispersion of Ni2P in
Ni2P/Cꢀ2 is 82.1%, similar with that of Ni2P/PCꢀ2, which further confirms the key role of CA for
synthesizing highly dispersed Ni2P nanoclusters. Nitrogen adsorptionꢀdesorption analysis shows
that Ni2P/PCꢀx catalysts give nearly unchanged BET area (around 700 cm2/g) compared with
~726.83 cm2/g of pristine PC (Figure S16, SI), suggesting a low loading amount of Ni2P. The
ACS Paragon Plus Environment

Page 9 of 23
ACS Catalysis
1
2
3
4
5
6
7
8
9
inductively coupled plasma optical emission spectroscopy (ICPꢀOES) analysis shows the loading
amounts of Ni for Ni2P/PCꢀx catalysts are around 0.5 wt.%, very close to the theoretical value in
the synthesis (Table S3, SI). The calculated molar ratio of Ni/P is lower than stoichiometry (2)
with the increasing dispersion of Ni2P nanoclusters, maybe due to unsaturated sites contained in
the nanostructure of Ni2P. Moreover, both Ni and P concentration in bulk are lower than those on
surface determined by XPS, suggesting anchored Ni2P nanoclusters mostly disperse the surface of
PC.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 2. HRꢀTEM images of (a) Ni2P/PCꢀ0, (b) Ni2P/PCꢀ0.5, (c) Ni2P/PCꢀ1 and (d) Ni2P/PCꢀ2
(scale bar 10 nm); (e) TEM image of Ni2P/PCꢀ2 (scale bar 50 nm) and corresponding EELS
mapping (C, P, Ni elements); (f) Distribution of particle size and dispersion of Ni2P nanoclusters
for Ni2P/PC; (g) XRD patterns of synthesized catalysts.
ACS Paragon Plus Environment

ACS Catalysis
Page 10 of 23
1
2
3
4
5
6
7
8
9
In XRD spectra (Figure 2g), synthesized catalysts show two peaks at 24° and 44o indexed to
graphitic carbon, without any other characteristic peaks of nickel phosphide phase due to the low
loading content. To further confirm the formation of Ni2P, we synthesized Ni2P/PC with 2.0 wt.%
loading of Ni (referred as HꢀNi2P/PC). As shown in Figure S17, XRD pattern of HꢀNi2P/PC
matches well with that of hexagonal Ni2P (PDF No.03ꢀ0953). Two distinct peaks at 1350 and 1590
cmꢀ1 appear in the Raman spectra (Figure S18, SI), attributed to the defective sp3 hybridized
carbon (D band) and the crystallized graphitic sp2 carbon (G band), respectively.40ꢀ42 Synthesized
Ni2P/PCꢀx catalysts show higher ID/IG values than pristine PC, suggesting that anchored Ni2P
nanoclusters break the order degree of carbon, revealing the interaction between Ni2P and PC
support.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
To study the chemical states of Ni2P/PCꢀ2, Xꢀray photoelectron spectroscopy (XPS)
measurements were conducted. The Ni 2p3/2 and 2p1/2 XPS spectra for Ni2P/PCꢀ2 (Figure 3a, b,
Table S4, SI) show three couples of subpeaks at about 852.98 and 856.84 eV, 862.05 and 870.20
eV, 875.19 and 881.59 eV, assigned to Niδ+, oxidized Ni species and the corresponding satellite
peaks22, respectively, quite similar with that of bulk Ni2P. The P 2p spectra of Ni2P/PCꢀ2 (Figure
3c) can be deconvoluted into four components at binding energies of 129.05, 129.89, 133.21 and
134.46 eV, attributed to P 2p3/2 and P 2p1/2 of metal phosphides (Pδꢀ), PꢀC bond and PꢀO bond in
Pꢀdoped carbon19,22, respectively. The presence of Niδ+ and Pδꢀ components strongly confirms the
formation of nickel phosphide nanoclusters. The fitted C 1s spectra show that Ni2P/PCꢀ2 contain
two carbon components (CꢀC, CꢀP) centered at 284.6 and 285.5 eV similar with PC (Figure S19,
SI). Specifically, the binding energies of Ni 2p3/2 and 2p1/2 peaks for Ni2P/PCꢀ2 are both shifted
negatively compared with those of bulk Ni2P catalyst (~0.12 eV shift for Ni 2p3/2 and ~0.18 eV
shift for Ni 2p1/2). The binding energies of P 2p3/2 and 2p1/2 for Ni2P/PCꢀ2 also negatively shift in
comparison to bulk Ni2P (~0.26 eV shift for P 2p3/2 and ~0.21 eV shift for P 2p1/2) as shown in
Figure S20 (SI). Reversely, the binding energy of P 2p of Ni2P/PCꢀ2 (Figure 3c) is shifted
positively compared with that of PC (~0.43 and 0.19 eV shifts for PꢀC and PꢀO respectively).
These results strongly suggest that Ni2P clusters have negative charge while PC support shows
positive charge, in agreement with DFT calculation.
To further probe the local environment of Ni2P nanoclusters, COꢀprobe infrared (IR)
spectroscopy was carried out (Figure 3d). Ni2P/PCꢀ0 shows a strong band at 2095 cmꢀ1, assigned
ACS Paragon Plus Environment

Page 11 of 23
ACS Catalysis
1
2
3
4
5
6
7
8
9
to CO adsorbed on unsaturated Niδ+ in Ni2P clusters43. Whereas the CO adsorption band blue
shifts gradually from Ni2P/PCꢀ0.5 to Ni2P/PCꢀ2, and Ni2P/PCꢀ2 exhibits the most shift of ~9 cmꢀ1,
suggesting a stronger CO adsorption44. This indicates that Ni ions in Ni2P/PCꢀ2 possess higher
dꢀband electron density that can form πꢀback bonding with CO43. Moreover, Ni2P/PCꢀx catalysts
show decreased intensity of CO adsorption band, which is reasonably assigned to the decreased
partial cover caused by the decreased size of Ni2P clusters, in good agreement with distribution of
particle size.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 3. XPS spectra of (a) Ni 2p3/2 and (b) Ni 2p1/2 of Ni2P/PCꢀ2 and Ni2P; (c) P 2p spectra of
Ni2P/PCꢀ2 and PC; (d) COꢀprobe molecule IR of Ni2P/PCꢀx and Ni2P/Cꢀ2.
3.3 Catalytic selective hydrogenation of nitroarenes using Ni2P/PC. We evaluated the
catalytic hydrogenation performance over the Ni2P/PC catalysts using 4ꢀnitrobenzaldehyde as a
model reactant under mild conditions (T=80 °C and P=10 bar). The catalytic behavior of Pꢀdoped
carbon, Ni2P, Ni2P/PCꢀ2 and Ni2P/Cꢀ2 catalysts was shown in Figure 4. When Pꢀdoped carbon is
used as the catalyst, no catalytic hydrogenation product is observed even in 20 h, indicating
Pꢀdoped carbon cannot activate hydrogen unless the reaction temperature is increased to 120 °C,
as we mentioned aforehand17. When bulk Ni2P is used as the catalyst, 100% conversion is
ACS Paragon Plus Environment

ACS Catalysis
Page 12 of 23
1
2
3
4
5
6
7
8
9
observed in 20 h. However, the chemoselectivity to aminobenzaldehyde is only 56.5% with a large
amount byproduct of carbonyl group reduction. When Ni2P nanoclusters are anchored onto PC
(Ni2P/PCꢀ2), it exhibits the best activity with a full conversion in 5 h and TOF (calculated at 1 h
reaction) reaching ~147.5 hꢀ1. More importantly, the chemoselectivity of 4ꢀaminobenzaldehyde
can approach >99.9%, and the amount of byproducts is below the detection limitations of gas
chromatographyꢀmass spectrometry (GCꢀMS) as shown in Figure S21, SI. In addition, Ni2P/Cꢀ2
shows very low activity because neither Ni2P nanoclusters nor carbon support can adsorb the
reactant. On the other side, PC is capable of adsorbing reactant due to improved electronic density
of carbon atoms nearby the dopants.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 4. Catalytic activity and chemoselectivity of synthesized catalysts for hydrogenation of
4ꢀnitrobenzaldehyde. (a) Time course of conversion of 4ꢀnitrobenzaldehyde; (b) Chemoselectivity
and TOF of 4ꢀaminobenzaldehyde. Reaction condition: 0.5 mmol 4ꢀnitrobenzaldehyde, 10 mg of
catalysts (1.5 mol% Ni), 4 mL of ethanol, 80 oC and 10 bar H2.
The kinetic profile in hydrogenation over Ni2P/PCꢀ2 reveals the conversion of
4ꢀnitrobenzaldehyde changes linearly with the reaction time, suggesting the hydrogenation
reaction follows pseudoꢀzeroꢀorder kinetics. Several additional experiments at different
concentration of 4ꢀnitrobenzaldehyde (0.05 M, 0.15 M and 0.20 M) were performed (Table S5,
entries 16ꢀ18, SI), and the TOF is 64.1, 63.0 and 63.5 hꢀ1 respectively, suggesting the reaction
conversion is independent on the concentration of reactant. The dependence profile of reaction
rate on 4ꢀnitrobenzaldehyde concentration and hydrogen pressure was further considered (Figure
S22, SI). The correlation coefficients of 4ꢀnitrobenzaldehyde concentration (α) and hydrogen
pressure (β) are 0.01 and 0.87, suggesting hydrogen activation is the rateꢀdetermining step in this
ACS Paragon Plus Environment

Page 13 of 23
ACS Catalysis
1
2
3
4
5
6
7
8
9
reaction. The Arrhenius plot gives an activation energy of 24.5 kJ·molꢀ1 over Ni2P/PCꢀ2 (Figure
S23, SI), lower than noble metal catalysts, such as AuꢀPt45 (31 kJ·molꢀ1), Ni46 (54.5 kJ·molꢀ1) and
Cu30 (61.4 kJ·molꢀ1), and much lower than the bulk Ni2P (79.2 kJ·molꢀ1). The activation energy is
significantly lowered over Ni2P/PCꢀ2, which clearly demonstrates that hydrogen desorption is
promoted by downshifted dꢀband of Ni as DFT calculation predicted. Furthermore, the Ni2P/PCꢀ2
performs higher activity than previously reported nobleꢀmetal (Table S6, SI) and transitionꢀmetal
catalysts (Table S7, S8, SI) under similar reaction conditions. In order to demonstrate the stability
and recyclability of Ni2P/PCꢀ2, we reused the catalyst in the reaction up to 10 times. The
selectivity of aniline keeps almost constant in all runs, although the conversion goes down a little
(Figure S24, SI). TEM and XPS characterizations confirm the morphology and structure of the
catalyst are well retained after the recycling tests (Figure S25, S26, SI), further demonstrating the
excellent catalytic stability.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Furthermore, we explored the hydrogenation of 14 other industrially interesting nitroarenes
using Ni2P/PCꢀ2 as catalyst and obtained the corresponding anilines in excellent yield and
selectivity (Table 1). Interestingly, halogen substituted nitrobenzenes were reduced to the
corresponding chloroanilines soothly without any dehalogenation (Table 1, entries 5ꢀ6). This
catalyst is able to selectively hydrogenate nitroꢀgroup to corresponding aminoꢀgroup with full
conversion and remains other unsaturated functional groups such as ꢀOH, ꢀCOOH, ꢀCN, ꢀC≡C and
–C=C unchanged (Table 1, entries 1ꢀ4, 10, 13ꢀ16). Especially for the hydrogenation of
3ꢀnitrostyrene, it gives a conversion of ~96.1% with a high selectivity toward 3ꢀaminostyrene
around 4 h mark. Even reaction time is prolonged to 8 h with the selectivity maintained constant.
Moreover, DFT calculation can also demonstrate high selectivity as shown in Figure S27, SI.
Ni2P/PCꢀ2 is active and selective for substrates with either electronꢀwithdrawing or
electronꢀdonating groups, suggesting it serves as a versatile catalyst for the selective
hydrogenation of substituted nitroarenes.
Table 1. Hydrogenation of Functionalized Nitroarenes Using
Ni2P/PCꢀ2 as Catalyst.
Entry
Substrate
Product
Time (h) Con./Sel. (%)
ACS Paragon Plus Environment

ACS Catalysis
Page 14 of 23
1
2
3
4
5
6
7
1
2
5
5
99.2/>99.9
98.2/>99.9
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
3
4
5
5
5
9
93.5/>99.9
94.6/>99.9
97.4/>99.9
6
7
4.5
10
99.0/>99.9
95.0/>99.9
8
10
89.6/>99.9
9
10
6
98.3/>99.9
98.4/>99.9
83.6/>99.9
10
11
9
12
13
14
4
8.5
5
90.5/>99.9
>99.9/>99.9
>99.9/>99.9
15
16
4
8
96.1/>99.0
100/>99.0
ACS Paragon Plus Environment

Page 15 of 23
ACS Catalysis
1
2
3
4
5
6
Reaction conditions: 0.5 mmol substrate, 10 mg Ni2P/PCꢀ2, 5 mL ethanol,
10 bar H2, 80 °C.
7
8
9
3.4 Origins of high activity and chemoselectivity for Ni2P/PC. To understand how the
dispersion of Ni2P clusters affect the selective hydrogenation of 4ꢀnitrobenzaldehyde, Ni2P/PCꢀx
were tested under the same reaction condition (Figure 5a). Ni2P/PCꢀ2 delivers the best catalytic
activity (taking 5 h for full conversion), and other catalysts with lower Ni2P dispersion exhibit
relatively lower catalytic performance (taking 5.5, 6.5 and 10 h to reach full conversion for
Ni2P/PCꢀ1, Ni2P/PCꢀ0.5 and Ni2P/PCꢀ0 respectively). Correspondingly, their reaction rates are in
order of 20.41 mol·Lꢀ1·hꢀ1 (Ni2P/PCꢀ2) > 18.54 mol·Lꢀ1·hꢀ1 (Ni2P/PCꢀ1) > 15.50 mol·Lꢀ1·hꢀ1
(Ni2P/PCꢀ0.5) > 10.13 mol·Lꢀ1·hꢀ1 (Ni2P/PCꢀ0) as revealed in Figure 5b and S28, SI. The catalytic
activity is further characterized by TOF as the function of Ni2P dispersion (size). As shown in
Figure 5c, although higher dispersion of Ni2P shows a relatively lower TOF value, Ni2P
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
dispersion shows
a significant effect on chemoselectivity of 4ꢀnitrobenzaldehyde to
4ꢀaminobenzaldehyde (Figure 5d). When the Ni2P dispersion is low, 4ꢀnitrobenzaldehyde can be
adsorbed in parallel on Ni2P, so both –CHO and –NO2 can be reduced, resulting in poor
chemoselectivity. Therefore, Ni2P/PCꢀ0 with lowest Ni2P dispersion (38.5%) delivers the lowest
chemoselectivity of ~60.1%. With the increasing of Ni2P dispersion, the adsorption of reactant on
Ni2P nanoclusters can be repressed due to geometric hindrance, which benefits the preferential
adsorption of 4ꢀnitrobenzaldehyde via nitro group on PC support, and thus delivers the superior
chemoselectivity.
ACS Paragon Plus Environment

ACS Catalysis
Page 16 of 23
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 5. Effects of particle size on the catalytic performance of 4ꢀnitrobenzaldehyde
hydrogenation. (a) Catalytic profiles of various catalysts with different particle size/dispersion of
Ni2P nanoclusters as a function of time and (b) corresponding reaction rate constants; (c) plot of
the particle size/dispersion and their TOFs, (d) plot of the particle size/dispersion and their
selectivity.
To better understand the underlying factors that afford the selective hydrogenation of
4ꢀnitrobenzaldehyde, attenuated total reflection infrared spectra (ARTꢀIR) was carried out to
understand the adsorbed behaviors of –NO2 and –CHO over Ni2P/PCꢀ2, Ni2P and Pꢀdoped carbon
(Figure 6aꢀc). For Ni2P/PCꢀ2, when nitrobenzene is used as the substrate, the asymmetric and
symmetric IR vibration frequencies of –NO2 at 1520 and 1343 cmꢀ1 appear23. When
4ꢀnitrobenzaldehyde is applied as the probe molecule, also only these two peaks attributed to
–NO2 obviously appear while no vibrations of –CHO present. For the adsorption of benzaldehyde,
no vibrations of –C=O (ca. 1700 cmꢀ1) 11 present, suggesting that Ni2P/PCꢀ2 can easily absorb
nitro group but does not absorb aldehyde group. In contrast, there are several characteristic peaks
ACS Paragon Plus Environment

Page 17 of 23
ACS Catalysis
1
2
3
4
5
6
7
8
9
attributed to –NO2 and –CHO for bulk Ni2P catalyst, which indicates Ni2P adsorbs both –NO2 and
–CHO nonꢀselectively, quite different from the case of Ni2P/PCꢀ2. Moreover, Pꢀdoped carbon
shows similar signals with Ni2P/PCꢀ2, suggesting a preferential adsorption of 4ꢀnitrobenzaldehyde
on PC via nitro group. These results also confirm that over Ni2P/PCꢀ2 the reactant is adsorbed on
PC support rather than on Ni2P.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 6. ATRꢀIR spectra of absorbed species on (a) Ni2P/PCꢀ2, (b) bulk Ni2P and (c) PC; (d) In
situ FTꢀIR spectra of PC and Ni2P/PCꢀ2 after being exposed under H2 at 80 oC for 30 min.
We then conducted inꢀsitu FTꢀIR measurements to investigate the activation behavior of H2 on
o
Ni2P nanoclusters and PC support (Figure 6d). This spectrum of PC exposed in the H2 at 80 C
exhibits no obvious peaks, confirming H2 molecule cannot be activated on PC under the reaction
temperature. It has been reported that H2 is able to dissociate into H atoms separately binding with
Ni and P atoms24. Actually, when Ni2P/PCꢀ2 exposed in the H2 atmosphere, a weak signal at 2350
cmꢀ1 corresponding to the stretching vibration of PꢀH47 appears, which indicates H2 molecule is
activated and dissociated on Ni2P rather than on PC support.
ACS Paragon Plus Environment

ACS Catalysis
Page 18 of 23
1
2
3
4
4. Conclusion
5
6
7
8
In summary, we have reported an outstanding catalyst for selective hydrogenation of
nitroarenes by reducing the Ni2P into subꢀnanosized clusters, tailoring the dꢀband center of Ni, and
coupling them with Pꢀdoped carbon. A chemical anchoring method was developed to fabricate
Ni2P with controllable dispersion of 81.3% on Pꢀdoped carbon. The electronꢀtransfer from
Pꢀdoped carbon to Ni2P clusters results in downshift of dꢀband center of Ni, which promotes H
desorption on highly charged antibonding orbital of NiꢀH, resulting in outstanding activity. The
adsorption of reactant is preferentially adsorbed on Pꢀdoped carbon surface through nitro group,
and the adsorption on Ni2P nanoclusters is suppressed due to the geometrical hindrance, leading to
excellent selectivity. Therefore, the optimized catalyst (Ni2P/PCꢀ2) shows excellent activity,
selectivity and stability in the hydrogenation of nitroarenes, much better than many reported
nobleꢀ and transitionꢀmetal catalysts.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Supporting Information
Supplementary experimental procedure, DFT calculation results, supplemental figures and
tables (Figure S1ꢀS28 and Table S1ꢀS8) and MS spectra of products.
Acknowledgements
This work was supported from the National Natural Science Foundation of China (U1462119)
and the Tianjin Municipal Natural Science Foundation (16JCQNJC05200).
References
1. Hartwig, J. F. CarbonꢀHeteroatom Bond Formation Catalysed by Organometallic Complexes.
Nature 2008, 455, 314ꢀ322.
2. Müller, T. E.; Hultzsch, K. C.; Yus, M.; Foubelo, F.; Tada, M. Hydroamination: Direct
Addition of Amines to Alkenes and Alkynes. Chem. Rev., 2008, 108, 3795ꢀ3892.
3. Song, J.; Huang, Z.ꢀF.; Pan, L.; Li, K.; Zhang, X.; Wang, L.; Zou, J.ꢀJ. Review on Selective
Hydrogenation of Nitroarene by Catalytic, Photocatalytic and Electrocatalytic Reactions. Appl.
Catal. B 2018, 227, 386ꢀ408.
4. Song, J.; Huang, Z.ꢀF.; Pan, L.; Zou, J.ꢀJ.; Zhang, X.; Wang, L. OxygenꢀDeficient Tungsten
Oxide as Versatile and Efficient Hydrogenation Catalyst. ACS Catal. 2015, 5, 6594ꢀ6599.
5. Tian, M.; Cui, X.; Yuan, M.; Yang, J.; Ma, J.; Dong, Z. Efficient Chemoselective
Hydrogenation of Halogenated Nitrobenzenes over an Easily Prepared γꢀFe2O3ꢀModified
ACS Paragon Plus Environment

Page 19 of 23
ACS Catalysis
1
2
3
4
Mesoporous Carbon Catalyst. Green Chem. 2017, 19, 1548ꢀ1554.
5
6
7
8
6. Dong, Z.; Le, X.; Dong, C.; Zhang, W.; Li, X.; Ma, J. Ni@Pd CoreꢀShell Nanoparticles
Modified Fibrous Silica Nanospheres as Highly Efficient and Recoverable Catalyst for
Reduction of 4ꢀNitrophenol and Hydrodechlorination of 4ꢀChlorophenol. Appl. Catal. B 2015,
162, 372ꢀ380.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
7. Wei, H.; Liu, X.; Wang, A.; Zhang, L.; Qiao, B.; Yang, X.; Huang, Y.; Miao, S.; Liu, J.; Zhang,
T. FeOxꢀSupported Platinum SingleꢀAtom and PseudoꢀSingleꢀAtom Catalysts for
Chemoselective Hydrogenation of Functionalized Nitroarenes. Nat. Commun., 2014, 5, 5634.
8. Gu, J.; Zhang, Z.; Hu, P.; Ding, L.; Xue, N.; Peng, L.; Guo, X.; Lin, M.; Ding, W. Platinum
Nanoparticles Encapsulated in MFI Zeolite Crystals by a TwoꢀStep Dry Gel Conversion
Method as a Highly Selective Hydrogenation Catalyst. ACS Catal., 2015, 5, 6893ꢀ6901.
9. Liu, P.; Zhao, Y.; Qin, R.; Mo, S.; Chen, G.; Gu, L.; Chevrier, D. M.; Zhang, P.; Guo, Q,;
Zhang, D.; Wu, B.; Fu, G.; Zheng, N. Photochemical Route for Synthesizing Atomically
Dispersed Palladium Catalysts. Science 2016, 352, 797ꢀ800.
10. Zhang, S.; Chang, C. R.; Huang, Z. Q.; Li, J.; Wu, Z.; Ma, Y.; Zhang, Z.; Wang, Y.; Qu, Y.
High Catalytic Activity and Chemoselectivity of Subꢀnanometric Pd Clusters on Porous
Nanorods of CeO2 for Hydrogenation of Nitroarenes. J. Am. Chem. Soc. 2016, 138,
2629ꢀ2637.
11. Tan, Y.; Liu, X.; Zhang, L.; Wang, A.; Li, L.; Pan, X.; Miao, S.; Haruta, M.; Wei, H.; Wang, H.;
Wang, F.; Wang, X.; Zhang, T. ZnAlꢀHydrotalciteꢀSupported Au25 Nanoclusters as
Precatalysts for Chemoselective Hydrogenation of 3ꢀNitrostyrene. Angew. Chem. Int. Ed.
2017, 56, 2709ꢀ2713.
12. Gong, K.; Du, F.; Xia, Z.; Durstock, M.; Dai, L. NitrogenꢀDoped Carbon Nanotube Arrays
with High Electrocatalytic Activity for Oxygen Reduction. Science 2009, 323, 760ꢀ764.
13. Liang, J.; Jiao, Y.; Jaroniec, M.; Qiao, S. Z. Sulfur and Nitrogen DualꢀDoped Mesoporous
Graphene Electrocatalyst for Oxygen Reduction with Synergistically Enhanced Performance.
Angew. Chem. Int. Ed. 2012, 51, 11496ꢀ11500.
14. Ni, S.; Li, Z.; Yang, J. Oxygen Molecule Dissociation on Carbon Nanostructures with
Different Types of Nitrogen Doping. Nanoscale 2012, 4, 1184ꢀ1189.
15. Yang, L.; Jiang, S.; Zhao, Y.; Zhu, L.; Chen, S.; Wang, X.; Wu, Q.; Ma, J.; Ma, Y.
ACS Paragon Plus Environment

ACS Catalysis
Page 20 of 23
1
2
3
4
5
BoronꢀDoped Carbon Nanotubes as MetalꢀFree Electrocatalysts for the Oxygen Reduction
Reaction. Angew. Chem. Int. Ed. 2011, 50, 7132ꢀ7135.
6
7
8
9
16. Wei, D.; Liu, Y.; Wang, Y.; Zhang, H.; Huang, L.; Yu, G. Synthesis of NꢀDoped Graphene by
Chemical Vapor Deposition and Its Electrical Properties. Nano Lett. 2009, 9, 1752ꢀ1758.
17. Li, Z.; Yu, H.; Bian, T.; Zhao, Y.; Zhou, C.; Shang, L.; Liu, Y.; Wu, L. Z.; Tung, C. H.; Zhang,
T. Highly Luminescent NitrogenꢀDoped Carbon Quantum Dots as Effective Fluorescent
Probes for Mercuric and Iodide Ions. J. Mater. Chem. C, 2015, 3, 1922ꢀ1928.
18. Kong, X.; Sun, Z.; Chen, M.; Chen, C. L.; Chen, Q. W. MetalꢀFree Catalytic Reduction of
4ꢀNitrophenol to 4ꢀAminophenol by NꢀDoped Graphene. Energy Environ. Sci. 2013, 6,
3260ꢀ3266.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
19. Gao, R.; Pan, L.; Lu, J.; Xu, J.; Zhang, X.; Wang, L.; Zou, J.ꢀJ. PhosphorusꢀDoped and
LatticeꢀDefective Carbon as Metalꢀlike Catalyst for the Selective Hydrogenation of
Nitroarenes. ChemCatChem 2017, 9, 4287ꢀ4294.
20. Popczun, E. J.; Mckone, J. R.; Read, C. G.; Biacchi, A. J.; Wiltrout, A. M.; Lewis, N. S.;
Schaak, R. E. Nanostructured Nickel Phosphide as an Electrocatalyst for the Hydrogen
Evolution Reaction. J. Am. Chem. Soc. 2013, 135, 9267ꢀ9270.
21. You, B.; Jiang, N.; Sheng, M.; Bhushan, M. W.; Sun, Y. Hierarchically Porous UrchinꢀLike
Ni2P Superstructures Supported on Nickel Foam as Efficient Bifunctional Electrocatalysts for
Overall Water Splitting. ACS Catal. 2016, 6, 714ꢀ721.
22. Peng, C.; Kang, L.; Cao, S.; Chen, Y.; Lin, Z.; Fu, W. Nanostructured Ni2P as a Robust
Catalyst for the Hydrolytic Dehydrogenation of AmmoniaꢀBorane. Angew. Chem. Int. Ed.
2015, 54, 15725ꢀ15729.
23. Chang, J.; Feng, L.; Liu, C.; Xing, W.; Hu, X. Ni2P Enhances the Activity and Durability of
the Pt Anode Catalyst in Direct Methanol Fuel Cells. Energy Environ. Sci. 2014, 7,
1628ꢀ1632.
24. Li, R.; Guan, Q.; Wei, R.; Yang, S.; Shu, Z.; Dong, Y.; Chen, J.; Li, W. A Potential Regularity
for Enhancing the Hydrogenation Properties of Ni2P. J. Phys. Chem. C 2015, 119, 2557ꢀ2565.
25. Zhang, L.; Fu, W.; Yu, Q.; Tang, T.; Zhao, Y.; Li, Y. Effect of Citric Acid Addition on the
Morphology and Activity of Ni2P Supported on Mesoporous Zeolite ZSMꢀ5 for the
Hydrogenation of 4,6ꢀDMDBT and Phenanthrene. J. Catal. 2017, 345, 295ꢀ307.
ACS Paragon Plus Environment

Page 21 of 23
ACS Catalysis
1
2
3
4
5
6
26. Carenco, S.; LeyvaꢀPérez, A.; Concepción, P.; Boissière, C. Mézailles, N.; Sanchez, C.;
Corma, A. Nickel Phosphide Nanocatalysts for the Chemoselective Hydrogenation of Alkynes.
Nano Today, 2012, 7, 21ꢀ28.
7
8
9
27. Liu, K.; Wang, Y.; Chen, P.; Zhong, W.; Liu, Q.; Li, M.; Wang, Y.; Wang, W.; Lu, Z.; Wang, D.
Noncrystalline Nickel Phosphide Decorated Poly(vinyl alcoholꢀcoꢀethylene) Nanofibrous
Membrane for Catalytic Hydrogenation of pꢀNitrophenol. Appl. Catal. B 2016, 196, 223ꢀ231.
28. Wang, H.; Shu, Y.; Zheng, M.; Zhang, T. Selective Hydrogenation of Cinnamaldehyde to
Hydrocinnamaldehyde over SiO2 Supported Nickel Phosphide Catalysts. Catal. Lett. 2008,
124, 219ꢀ225.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
29. Chen, Z.; Song, Y.; Cai, J.; Zheng, X.; Han, D.; Wu, Y.; Zang, Y.; Niu, S.; Liu, Y.; Zhu, J.;
Wang, G. Tailoring the dꢀBand Centers Enables Co4N Nanosheets to Be Highly Active for
Hydrogen Evolution Catalysis. Angew. Chem. Int. Ed. 2018, 57, 5076ꢀ5080.
30. Ye, T.ꢀN.; Lu, Y.; Li, J.; Nakao, T.; Yang, H.; Tada, T.; Kitano, M.; Hosono, H. CopperꢀBased
Intermetallic Electride Catalyst for Chemoselective Hydrogenation Reactions. J. Am. Chem.
Soc. 2017, 139, 17089ꢀ17097.
31. Wang, R.; Dong, X.; Du, J.; Zhao, J.; Zang, S. MOFꢀDerived Bifunctional Cu3P Nanoparticles
Coated by a N, PꢀCodoped Carbon Shell for Hydrogen Evolution and Oxygen Reduction. Adv.
Mater. 2018, 30, 1703711.
32. Su, H.; Zhang, K.; Zhang, B.; Wang, H.; Yu, Q.; Li, X.; Antonietti, M.; Chen, J. Activating
Cobalt Nanoparticles via the MottꢀSchottky Effect in NitrogenꢀRich Carbon Shells for
BaseꢀFree Aerobic Oxidation of Alcohols to Esters. J. Am. Chem. Soc. 2017, 139, 811ꢀ818.
33. Kresse, G.; Furthmuüller, J. Efficiency of AbꢀInitio Total Energy Calculations for Metals and
Semiconductors Using a PlaneꢀWave Basis Set. Comput. Mater. Sci. 1996, 6, 15ꢀ50.
34. Kresse, G.; Hafner, J. Ab Initio Molecular Dynamics for Liquid Metals. Phys. Rev. B:
Condens. Matter Mater. Phys. 1993, 47, 558ꢀ561.
35. Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple.
Phys. Rev. Lett. 1996, 77, 3865ꢀ3868.
36. Perdew, J. P.; Wang, Y. Accurate and Simple Analytic Representation of the ElectronꢀGas
Correlation Energy. Phys. Rev. B 1992, 45, 13244ꢀ13249.
37. Henkelman, G.; Uberuaga, B. P.; Jónsson, H. A Climbing Image Nudged Elastic Band Method
ACS Paragon Plus Environment

ACS Catalysis
Page 22 of 23
1
2
3
4
5
6
7
8
9
for Finding Saddle Points and Minimum Energy Paths. J. Chem. Phys. 2000, 113, 9901ꢀ9904.
38. Wang, F.; Han, Y.; Lim, C. S.; Lu, Y.; Wang, J.; Xu, J.; Chen, H.; Zhang, C.; Hong, M.; Liu, X.
Simultaneous Phase and Size Control of Upconversion Nanocrystals through Lanthanide
Doping. Nature 2010, 463, 1061ꢀ1065.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
39. Kitchin, J. R.; Nørskov, J. K.; Barteau, M. A.; Chen, J. G. Modification of the Surface
Electronic and Chemical Properties of Pt (111) by Subsurface 3d Transition Metals. J. Chem.
Phys. 2004, 120, 10240ꢀ10246.
40. Yu, H.; Shang, L.; Bian, T.; Shi, R.; Waterhouse, G. I. N.; Zhao, Y.; Zhou, C.; Wu, L. Z.; Tung,
C. H.; Zhang, T. NitrogenꢀDoped Porous Carbon Nanosheets Templated from gꢀC3N4 as
MetalꢀFree Electrocatalysts for Efficient Oxygen Reduction Reaction. Adv. Mater. 2016, 28,
5080ꢀ5086.
41. Zhang, C.; Mahmood, N.; Yin, H.; Liu, F.; Hou, Y. Synthesis of PhosphorusꢀDoped Graphene
and its Multifunctional Applications for Oxygen Reduction Reaction and Lithium Ion
Batteries. Adv. Mater. 2013, 25, 4932ꢀ4937.
42. Choi, C. H.; Park, S. H.; Woo, S. I. Binary and Ternary Doping of Nitrogen, Boron, and
Phosphorus into Carbon for Enhancing Electrochemical Oxygen Reduction Activity. ACS
Nano 2012, 6, 7084ꢀ7091.
43. Lee, Y.ꢀK.; Oyama, T. Bifunctional Nature of a SiO2ꢀSupported Ni2P Catalyst for
Hydrotreating: EXAFS and FTIR Studies. J. Catal. 2006, 239, 376ꢀ389.
44. Wang, L.; Zhang, J.; Zhu, Y.; Xu, S.; Wang, C.; Bian, C.; Meng, X.; Xiao, F.ꢀS. Strong
MetalꢀSupport Interactions by HydroxideꢀtoꢀOxide Support Transformation for Preparation of
SinterꢀResistant Gold Nanoparticles Catalysts. ACS Catal. 2017, 7, 7461ꢀ7465.
45. Serna, P.; Concepción, P.; Corma, A. Design of Highly Active and Chemoselective Bimetallic
GoldꢀPlatinum Hydrogenation Catalysts through Kinetic and Isotopic Studies. J. Catal. 2009,
265, 19ꢀ25.
46. Wang, J.; Yuan, Z.; Nie, R.; Hou, Z.; Zheng, X. Hydrogenation of Nitrobenzene to Aniline
over Silica Gel Supported Nickel Catalysts. Ind. Eng. Chem. Res. 2010, 49, 4664ꢀ4669.
47. Peng, H.; Yang, C. Q.; Wang, X.; Wang, S. The Combination of Itaconic Acid and Sodium
Hypophosphite as a New CrossꢀLinking System for Cotton. Ind. Eng. Chem. Res. 2012, 51,
11301ꢀ11311.
ACS Paragon Plus Environment

Page 23 of 23
ACS Catalysis
1
2
3
4
TOC
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
c
ACS Paragon Plus Environment