Graphdiyne-based Pd single-Atom catalyst for semihydrogenation of alkynes to alkenes with high selectivity and conversion under mild conditions

Article abstract of DOI:10.1039/d0ta07705d

The development of efficient heterogeneous catalysts for alkyne hydrogenation with high activity and selectivity is highly desirable and yet remains a great challenge. Herein, a Pd single-Atom catalyst (Pds-GDY) is prepared using graphdiyne as support, and used in the semihydrogenation of alkynes. As a proof of concept, the Pds-GDY exhibits a high activity for the semihydrogenation of phenylacetylene under mild reaction conditions, with a TOF of 6290 h-1, and a selectivity of 99.3% at 100% conversion, both much higher than those of the counterparts comprising Pd nanoparticles (NPs), namely, PdNP1-GDY (with 2 nm Pd NPs) and PdNP2-GDY (with 12 nm Pd NPs). In addition, after the full conversion of phenylacetylene, Pds-GDY could still maintain a selectivity as high as 98.9% towards styrene, with almost no phenylethane produced even with a prolonged reaction time; in contrast, for PdNP1-GDY and PdNP2-GDY, within the same reaction time, the selectivity decreases dramatically to 66.6% and 8.5%, respectively. Infrared spectroscopy reveals that Pds-GDY features the weakest adsorption to styrene, which is responsible for its high performance. This work provides an effective strategy to rationally design Pd catalysts for semihydrogenation of alkynes to alkenes with desirable activity and selectivity. This journal is

Full text of DOI:10.1039/d0ta07705d

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DOI: 10.1039/D0TA07705D
ARTICLE
Graphdiyne-Based
Pd
Single-Atom
Catalyst
for
Semihydrogenation of Alkynes to Alkenes with High Selectivity
and Conversion under Mild Conditions
Received 00th January 20xx,
Accepted 00th January 20xx
Xue-Peng Yin, Shang-Feng Tang, Chao Zhang, Hong-Juan Wang,* Rui Si,* Xiu-Li Lu,* and Tong-Bu
Lu*
DOI: 10.1039/x0xx00000x
The development of efficient heterogeneous catalysts for alkyne hydrogenation with high activity and selectivity is highly
desirable and yet remains a great challenge. Herein, a Pd single-atom catalyst (Pds-GDY) is prepared using graphdiyne as
support, and used in the semihydrogenation of alkynes. As a proof of concept, the Pds-GDY exhibits a high activity for the
semihydrogenation of phenylacetylene under mild reaction conditions, with a TOF of 6290 h-1, and a selectivity of 99.3% at
100% conversion, both much higher than those of the counterparts comprising Pd nanoparticles (NPs), namely, PdNP1-GDY
(with 2 nm Pd NPs) and PdNP2-GDY (with 12 nm Pd NPs). In addition, after the full conversion of phenylacetylene, Pds-GDY
could still maintain a selectivity as high as 98.9% towards styrene, with almost no phenylethane produced even with a
prolonged reaction time; in contrast, for PdNP1-GDY and PdNP2-GDY, within the same reaction time, the selectivity decreases
dramatically to 66.6% and 8.5%, respectively. Infrared spectroscopy reveals that Pds-GDY features the weakest adsorption
to styrene, which is responsible for its high performance. This work provides an effective strategy to rationally design Pd
catalysts for semihydrogenation of alkynes to alkenes with desirable activity and selectivity.
fabricating bimetallic catalysts through alloying Pd with metals such
as In, Ag, Pb, and Cu, also known as the “site-isolating” structural
modification.17-20 For example, Feng et al. reported that PdIn(110)
Introduction
Semihydrogenation of alkynes to alkenes is of great importance on
account of the extensive applications of alkenes in chemical
industry, such as agrochemicals, vitamins, polymers, and olefin
metathesis.1-5 Up to now, palladium(Pd)-based catalysts are most
used in this area because of their outstanding hydrogenation
activities; however, they typically suffer from low selectivities due
to further hydrogenation of alkenes (a phenomenon also known as
over-hydrogenation).6-9 In order to restrain the over-hydrogenation,
many methods have been developed;10-16 for example, Pd metal
could be modified by lead or quinoline (e.g., Lindlar catalyst) to
suppress the hydrogenation of alkenes and thus to improve the
selectivity in semihydrogenation of alkynes. However, these Pd-
based catalysts are often toxic and not environment-friendly.
Another efficient strategy to achieve desirable selectivity is
surface with atomic Pd sites has a high catalytic selectivity for
semihydrogenation of acetylene, with 92% selectivity for ethylene
at 90 °C, much higher than that of Pd3In(111) surface with Pd trimer
sites.17 However, the “site-isolating” structural modification of Pd-
based catalysts could not enable the high exposure of active sites
(which only reside on the surface of alloys), thus leading to low
utilization of Pd atoms and a poor atom economy. In either case
above, Pd-based heterogeneous catalysts can hardly achieve high
activity simultaneously with outstanding selectivity under mild
reaction conditions. Therefore, it is highly desirable to develop Pd-
based catalysts with high TOF, high conversion, excellent selectivity,
and good stability for semihydrogenation of alkynes.
Recently, as a new emerging class of heterogeneous catalysts,
single-atom catalysts (SACs) featuring isolated metal atoms
anchored on solid supports have shown great advantages in water
splitting, oxygen reduction, CO2 reduction, and organic synthesis, by
virtue of their maximized atomic utilization as well as unique
structures.21-29 In particular, for noble-metal-based catalysts, the
utmost atomic utilization can dramatically decrease the material
cost. In addition, benefiting from the relatively uniform structure of
metal atoms with low coordination numbers therein, many SACs
show high selectivities and activities in the catalytic process.30 It has
been shown that Pd SACs fabricated on various supports give higher
activities for hydrogenation of alkynes to alkenes, compared with
Pd nanoparticle counterparts.31-35 However, a high conversion and a
high selectivity could not be simultaneously achieved for these Pd
X. Yin, S. Tang, C. Zhang, H. Wang, X. Lu, Prof. T. Lu
MOE International Joint Research Laboratory of Materials Microstructure,
Institute for New Energy Materials and Low Carbon Technologies, School of
Material Science & Engineering, Tianjin University of Technology, Tianjin 300384,
People’s Republic of China.
Prof. R. Si
Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics,
Chinese Academy of Sciences Shanghai 201204 (China)
E-mail: hongjuanwang@tjut.edu.cn
sirui@sinap.ac.cn,
luxiuli@email.tjut.edu.cn,
lutongbu@tjut.edu.cn.
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
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SACs, unless (in a few cases) under an extremely high H2 pressure. reaction solvent and temperature, Pds-GDY, PdNP1-GDY, and PdNP2
-
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s
DOI: 10.1039/D0TA07705D
For example, isolated Pd species anchored on TiO2 support (Pd- GDY were obtained. Specifically, for the preparation of Pd -GDY,
TiO2) show a high selectivity (>90%) and high conversion (99%) for GDY powder (10 mg) was dispersed in DMF (5 mL) to obtain a
semihydrogenation of phenylacetylene to styrene at a high H2 dispersion of GDY. Then K2PdCl4 (470 L, 10 mM) was added into
pressure of 1.0 MPa, and yet the conversion decreases dramatically the above dispersion, and the mixture was stirred for 2 h at 0 C to
to 16% at 0.4 MPa H2 pressure owing to the limited catalytic activity obtain Pds-GDY. In contrast, PdNP1-GDY and PdNP2-GDY were
of Pd SACs.35 Thus, it remains a challenge to achieve both high prepared by replacing the DMF with deionized water and regulating
selectivity and high activity for semihydrogenation of alkyne under the reaction temperatures (0 C for PdNP1-GDY and 60 C for PdNP2
mild conditions. GDY). The prepared GDY was characterized by Raman and X-ray
-
As a new carbon material, graphdiyne (GDY) features the unique photoelectron spectroscopy (XPS). As shown in Figure S1a, the
butadiyne linkages between benzene rings, which could serve as Raman spectrum shows four distinct peaks at 1420 cm-1 (D band),
the sites to stabilize isolated metal atoms of low valence, and thus 1578 cm-1 (G band), 1924 cm-1, and 2163 cm-1, respectively, in
enable high catalytic activities.36-38 Herein, on the basis of the which the peaks at 1924 cm-1 and 2163 cm-1 can be attributed to
unique structure of GDY, we prepared three types of Pd-GDY the vibration of conjugated diyne linkers, in good accordance with
catalysts, comprising Pd single atoms (denoted as Pds-GDY ) and those reported in the literatures.39-40 In addition, the high-
two types of Pd nanoparticles with sizes around 2 nm (PdNP1-GDY) resolution XPS of C 1s of GDY in Figure S1b could be deconvoluted
and 12 nm (PdNP2-GDY). The catalytic performances of these Pd-GDY into four subpeaks, in which the peak at 285.1 eV was assigned to
catalysts in semihydrogenation of alkynes show an evident the C≡C (sp).40 And the atomic ratio of sp/sp2 is approximately 2,
dependence on the size of Pd species under room temperature and which is consistent with the chemical composition of GDY. The
0.2 MPa H2 pressure. Remarkably, Pds-GDY displays an outstanding microstructure and composition of Pd-GDY catalysts were further
catalytic activity, with TOF up to 6290 h-1 at 100% conversion with investigated by transmission electron microscopy (TEM), high-
99.3% selectivity in hydrogenation of phenylacetylene to styrene. resolution transmission electron microscopy (HR-TEM), and high-
Moreover, Pds-GDY shows almost no activity for the further angle annular dark-field scanning transmission electron microscopy
hydrogenation of styrene, even when the reaction is kept going on (HAADF-STEM). As shown in Figure 1a, no Pd clusters or
after the full conversion of phenylacetylene. By contrast, for PdNP1
-
nanoparticles were observed in the TEM image of Pds-GDY; in
GDY and PdNP2-GDY, they both display the unwanted abilities to contrast, the average sizes of Pd nanoparticles in PdNP1-GDY and
further hydrogenate styrene, and show much lower activities for PdNP2-GDY were about 2 and 12 nm, respectively (Figure 1b and 1c).
styrene production. And their selectivities for styrene drop to 66.6% As shown in Figure 1d and 1e of Pds-GDY, abundant isolated Pd
and 8.5% after 3 h hydrogenation. The experimental results atoms can be observed in GDY because of the different Z contrast of
indicated that the higher catalytic performance of Pds-GDY
originates from the weaker adsorption of styrene on Pd single
atoms compared with the cases on Pd nanoparticles in PdNP1-GDY
and PdNP2-GDY. In addition, Pds-GDY also shows high performances
for the semihydrogenation of some other alkynes, including 1-
octyne, 3-octyne, and diphenylacetylene.
Results and discussion
Figure 1. (a-c) TEM images of Pds-GDY (a), PdNP1-GDY (b), and PdNP2-GDY (c). (d, e)
Scheme 1. Illustration for the preparation of Pds-GDY, PdNP1-GDY, and PdNP2-GDY.
HAADF-STEM image (d) and the enlarged HAADF-STEM image (e) of (d) of Pds-
GDY. (f) EDS spectrum for Pds-GDY. (g-j) EDS mapping images of Pds-GDY.
In this study, the Pd-GDY catalysts were prepared by simple wet-
chemistry routes as shown in Scheme 1. First, GDY powder was
synthesized from hexaethynylbenzene by a modified Hay–Glaser
coupling reaction. The sp-hybridized alkynyl carbon atoms in GDY
provide the sites for anchoring Pd atoms. Through controlling the
Pd and C. The energy dispersive spectroscopy (EDS) (Figure 1f)
shows that the C, Pd, and Cl elements coexist in the sample of Pds-
GDY (the other elements come from the Cu grid). Moreover, the
elemental mapping images for Pds-GDY reveal the uniform spatial
2 | J. Name., 2012, 00, 1-3
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distributions of C, Pd, and Cl over the entire structure (Figure 1g-j). nanoparticles.41 In addition, as shown in Figure S8, the Raman
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s
Furthermore, the X-Ray Diffractometer (XRD) pattern in Figure S2 peaks attributed to the vibration of conjugDaOteI:d10d.i1y0n3e9/lDin0kTsA0in77P0d5D-
confirms that no crystalline Pd species is formed in Pds-GDY. For GDY, PdNP1-GDY, and PdNP2-GDY were not as prominent as those for
PdNP1-GDY and PdNP2-GDY, the XRD patterns (Figure S2) display GDY, indicating the interaction between Pd species and -C≡C-C≡C-
peaks at 2 = 40.1, which could be assigned to the (111) plane of moieties.36 Furthermore, more detailed structural information for
metallic Pd, indicating the formation of Pd nanoparticles. In Pds-GDY was obtained from the Pd K-edge X-ray absorption near-
addition, the HR-TEM images in Figure S3 and S5 show clear fringes edge structure (XANES) spectra and extended X-ray absorption fine
of 0.22 nm, which can be ascribed to the (111) lattice plane of structure (EXAFS) spectra. As shown in Figure 2b, the near-edge
cubic-phase Pd, in good accordance with the XRD results. feature of Pds-GDY is between those of Pd foil and PdO, confirming
Moreover, the HR-TEM images and corresponding elemental the slightly positively charged Pd species, in good consistency with
mapping images of PdNP1-GDY and PdNP2-GDY confirm the the XPS results. Moreover, as shown by the FT-EXAFS spectra in
distribution of Pd nanoparticles on the support of GDY (Figure S4 Figure 2c, the Pd foil displays a distinct peak at about 2.8 Å, which is
and S6). The surface area, pore volume, and pore size distribution attributed to the Pd-Pd bond. In the FT-EXAFS of Pds-GDY, only the
of Pds-GDY, PdNP1-GDY, and PdNP2-GDY were analyzed by measuring peak centered at the distance of ca. 2.0 Å was observed and no Pd-
the N2 adsorption−desorption isotherms at 77 K (Figure S7), the Pd contribution was found, further confirming that Pd atoms are
specific surface area of Pds-GDY, PdNP1-GDY, and PdNP2-GDY were atomically dispersed on the surface of GDY. In order to unveil the
25.0, 21.5, and 21.0 m2/g, respectively. In addition, the average coordination environment around Pd in Pds-GDY, its FT-EXAFS curve
pore sizes and pore volume for PdNP1-GDY are almost the same as was fitted in R space. The fitting results shown in Table S2
those of Pds-GDY (Table S1). However, the average pore sizes and demonstrate that on average each Pd atom coordinates with two C
pore volume of PdNP2-GDY have obvious decrease compared with and two Cl atoms.
those of Pds-GDY and PdNP1-GDY. This phenomenon could be
attributed to much larger size of Pd nanoparticles (12 nm) in PdNP2
-
GDY than those in PdNP1-GDY(2 nm) and Pds-GDY (atomic Pd sites),
bringing to the coverage of some mesopores in GDY supports.
Figure 2. (a) Core-level Pd 3d XPS of Pds-GDY, PdNP1-GDY, PdNP2-GDY, and K2PdCl4.
(b, c) Pd K-edge XANES (b) and FT-EXAFS spectra (c) of Pds-GDY, with Pd foil and
PdO as reference.
Further insights into the electronic and structural information on
these Pd-GDY catalysts were obtained from XPS and X-ray
absorption fine structure (XAFS) spectroscopy. As demonstrated in
Figure 2a, for Pd 3d, the two main peaks located at 338.3 and 343.6
eV could be attributed to Pd 3d5/2 and Pd 3d3/2 in K2PdCl4. These
two peaks in Pds-GDY shift to lower binding energy at 337.7 and
342.8 eV, which are higher than that of Pd0 (336.0 and 341.3 eV)
and lower than that of Pd2+ (338.3 and 343.6 eV), demonstrating
that Pd atoms are positively charged Pd+ (0 <  < 2), indicating the
strong interaction between Pd atoms and GDY. For PdNP1-GDY and
PdNP2-GDY, the two peaks could be divided into four peaks at 336.0,
337.7, 341.3, and 342.8 eV, which could be ascribed to the
coexistence of Pd0 and Pd+, further confirming the formation of Pd
Figure 3. (a) Illustration showing different hydrogenation processes of
phenylacetylene over different Pd-GDY catalysts. (b-d) The conversion of
phenylacetylene and the selectivity toward styrene and phenylethane as a
function of reaction time over PdNP2-GDY (b), PdNP1-GDY (c), and Pds-GDY (d). (e)
The comparison of catalytic performances for Pds-GDY, PdNP1-GDY, and PdNP2-GDY
catalysts. Reaction conditions: 2 mg catalyst, 1.0 mmol phenylacetylene, 2 mL
ethanol, 25 °C, 0.2 MPa H2.
Semihydrogenation of alkynes to alkenes is of great importance
in the chemical industry.41 As a proof of concept, the catalytic
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performances of Pds-GDY, PdNP1-GDY, and PdNP2-GDY in 1/9 (phenylacetylene/styrene), Pds-GDY still displays VaiehwigArhticalecOtinvliintye
DOI: 10.1039/D0TA07705D
phenylacetylene hydrogenation was tested in an autoclave in for the semihydrogenation of phenylacetylene to styrene with 100%
ethanol solvent under 0.2 MPa pressure hydrogen at 25 °C. As conversion and 99.9% selectivity, and only trace phenylethane was
shown in Figure 3a, the Pd-GDY catalysts exhibit distinct size- detected. Moreover, as shown in Figure S18, when the reaction
dependent performances on the hydrogenation of phenylacetylene. system was scaled up by elevating the amount of phenylacetylene,
The conversion of phenylacetylene and the selectivity for styrene Pds-GDY maintains a high catalytic performance. Furthermore, Pds-
and phenylethane as a function of reaction time over the prepared GDY could also be used as the catalyst for semihydrogenation of
catalysts are shown in Figure 3b-d. As shown in Figure 3b, the other alkynes (such as 1-octyne, 3-octyne, and diphenylacetylene)
highest selectivity toward styrene for PdNP2-GDY is only 59.7% with with high performances (Table S6). These results further confirm
86.4% conversion, and the selectivity is reduced to 8.5% at 100% the unique advantages of Pds-GDY in selective hydrogenation.
conversion of phenylacetylene after reaction for 3 h. For PdNP1-GDY,
The strong size-dependent activity of the Pd-GDY catalysts for the
as shown in Figure 3c, it achieves 95.8% selectivity with 100% hydrogenation of alkynes may originate from the different
conversion after reaction for 2h; however, PdNP1-GDY subsequently adsorption ability for alkenes.44 To understand the adsorption
catalyzes the hydrogenation of styrene to phenylethane and properties of Pds-GDY, we recorded the FT-IR spectra of all Pd-GDY
displays only 66.6% selectivity to styrene after 3 h reaction. By stark catalysts after exposure to styrene and subsequent removal of free
contrast, for Pds-GDY, the selectivity toward styrene could reach at styrene. As shown in Figure S19, the peaks of vibrational signals
99.3% with 100% conversion of phenylacetylene at 2 h (Figure 3d), attributed to -C=C- shift to lower wavenumber because of the
and even with prolonged reaction time, the further hydrogenation interaction with Pd species in the Pd-GDY catalysts, and the
of styrene is effectively suppressed, which is beneficial for the intensities of the vibrational signals increase in the order of Pds-GDY
styrene separation. In brief, the hydrogenation properties on PdNP2
-
< PdNP1-GDY < PdNP2-GDY, indicating the weakest binding capability
GDY, PdNP1-GDY, and Pds-GDY are quite different (Figure 3a and 3e) of Pd single atoms in Pds-GDY to styrene molecules. As a result, Pds-
and show a prominent size-dependence. After the 100% conversion GDY shows the best performance for semihydrogenation of
of phenylacetylene, Pds-GDY shows the best catalytic performance, phenylacetylene to styrene and demonstrates almost no ability for
including a highest TOF of 6290 h-1 for styrene production with the further hydrogenation of styrene to phenylethane.
99.3% selectivity; in contrast, the TOF values (and selectivity) were
4551 h-1 (95.8%) for PdNP1-GDY and 1270 h-1 (38.8%) for PdNP2-GDY
(Table S4). Durability and recyclability of catalysts are critical for
practical applications. To test the durability of Pds-GDY, the catalyst
Conclusions
In conclusion, we developed facile strategies to prepare Pd-
GDY catalysts, including Pds-GDY, PdNP1-GDY, and PdNP2-GDY.
The HAADF-STEM and XAFS analyses of the Pds-GDY confirmed
after
a test run was collected and washed for subsequent
recycling.42 As shown in Figure S9, the selectivity and activity were
still high with negligible changes after five recycling tests. In
addition, we have measured the semihydrogenation performance
of Pds-GDY at 50 C. As shown in Figure S10, the reaction rate for
the hydrogenation of phenylacetylene at 50 C was greatly
improved compared with that at 25 C. In addition, Pds-GDY still
shows high selectivity (>99%) to styrene at 100% conversion of
phenylacetylene. In addition, the TEM image, Pd 3d XPS spectra,
HAADF-STEM images and Raman spectra after the catalytic test
were shown in Figure S11-S14, indicating that Pds-GDY has a high
stability in semihydrogenation of phenylacetylene. Besides, As
shown in Figure S15 the Cl 2p XPS spectra of Pds-GDY was analyzed
showing the corresponding binding energies at 198.5 eV (Cl-Pd) and
200.3 eV (Cl-C).43 In addition, the amounts of chlorine showed no
obvious decrease after the catalytic test, further indicating the
stability of Pds-GDY (Table S5).
the isolated Pd atoms anchored on GDY support. The PdNP1
-
GDY and PdNP2-GDY samples contain Pd nanoparticles with size
about 2 and 12 nm, respectively. The prepared Pd-GDY
catalysts exhibit strong size-dependent activities for the
hydrogenation of alkynes. Benefiting from the weak
adsorption ability to styrene, Pds-GDY shows a superior activity
and selectivity in semihydrogenation of phenylacetylene to
styrene, compared with PdNP1-GDY, PdNP2-GDY and commercial
Pd/C catalyst. This work not only designs a highly efficient Pd
single-atom catalyst for selective hydrogenation reaction
under mild reaction conditions but also provides the
understanding of the correlation between the size of Pd
species and hydrogenation performance.
To further investigate the performance of Pds-GDY in
semihydrogenation of alkynes to alkenes, a series of additional
experiments were conducted. As shown in Table S6, GDY gives no
activity for hydrogenation of phenylacetylene, demonstrating that
the active sites derived from the Pd species in Pds-GDY, PdNP1-GDY,
Experimental section
Materials.
Potassium chloropalladite (K2PdCl4), phenylacetylene (536-74-3),
1-octyne (629-05-0), 3-octyne (15232-76-5) and diphenylacetylene
(501-65-5) purchased from energy-chemical (Shanghai, China).
Ethanol and DMF purchased from Sinopharm Chemical Reagent Co.,
Ltd (Shanghai, China). All reagents were of analytical grade and
used without further purification. The GDY powder was synthesized
according to Li’s work.45 Ultra-pure water with a resistivity of 18.2
MΩ was used in all synthesis.
and PdNP2-GDY. As
a
comparison, hydrogenations of
phenylacetylene were also performed on Pd/C-D (Pd nanoparticles
prepared on mesoporous carbon in DMF solution) and commercial
Pd/C under the same conditions (Figure S17 and Table S6). It is
shown that Pd/C-D and Pd/C converts phenylacetylene completely
to phenylethane after reacting for 2h, demonstrating no selectivity
toward styrene. Notably, even in a reactant with a molar ratio of
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Catalyst preparation.
nm. The actual Pd loadings were analyzed by the inductively
coupled plasma-mass spectrometry (ICP-MS, iCAP RQ). The X-
View Article Online
DOI: 10.1039/D0TA07705D
Pds-GDY: In a typical synthesis of Pds-GDY, 10 mg GDY powder
was uniformly dispersed in 5 mL DMF solution to obtain a
dispersion of GDY. Then 470 L 10 mM K2PdCl4 was put into the
above dispersion and stirred for 2 h at 0 C. The resulting product
was washed several times with DMF and ethanol and dried under
vacuum at 50 °C.
ray absorption fine structure (XAFS) spectra at Pd K-edge (E0 =
24350 eV) was performed at BL14W1 beamline of Shanghai
Synchrotron Radiation Facility (SSRF) operated at 3.5 GeV
under “top-up” mode with a constant current of 250 mA. The
XAFS data were recorded under fluorescence mode with a
Lytle-type ion chamber. The energy was calibrated accordingly
to the absorption edge of pure Pd foil. Athena and Artemis
codes were used to extract the data and fit the profiles. For
the X-ray absorption near edge structure (XANES) part, the
experimental absorption coefficients as function of energies
μ(E) were processed by background subtraction and
normalization procedures, and reported as “normalized
absorption” with E0 = 24350 eV for all the tested samples and
Pd foil/PdO standard. For the extended X-ray absorption fine
structure (EXAFS) part, the Fourier transformed (FT) data in R
space were analyzed by applying first-shell approximate model
for Pd-C and Pd-Cl contributions. The passive electron factors,
PdNP1-GDY and PdNP2-GDY: The preparation methods of PdNP1
-
GDY and PdNP2-GDY were similar to those of Pds-GDY. 10 mg GDY
was uniformly dispersed in 5 mL H2O to obtain a dispersion of GDY.
Then 470 L 10 mM K2PdCl4 was put into the above dispersion and
stirred for 2 h at 0 C and 60 C, respectively. The PdNP1-GDY and
PdNP2-GDY were finally obtained after washing several times with
H2O and ethanol and dried under vacuum at 50 °C.
Pd/C-D: In detail, 10 mg mesoporous carbon powder was
uniformly dispersed in 5 mL DMF solution to obtain a dispersion of
mesoporous carbon. Then 470 L K2PdCl4 (10 mM) and 200 mL
NaBH4 (4 mg/mL) was put into the above dispersion and stirred for
2 h at 0 °C. The resulting product was washed several times with
DMF and ethanol and dried under vacuum at 50 °C.
2
S0 , were determined by fitting the experimental data on Pd
foils and fixing the coordination number (CN) of Pd-Pd to be
12, and then fixed for further analysis of the measured
samples. The parameters describing the electronic properties
(e.g., correction to the photoelectron energy origin, E0) and
local structure environment including CN, bond distance (R)
and Debye-Waller factor around the absorbing atoms (2)
were allowed to vary during the fit process. The fitted ranges
for k and R spaces were selected to be k =311 Å−1 or 312 Å−1
with R = 13 Å (k2 weighted).
Catalyst testing.
Liquid-phase hydrogenation of phenylacetylene (536-74-3),
1-octyne
(629-05-0),
3-octyne
(15232-76-5),
and
diphenylacetylene (501-65-5) were performed in a 50 mL
stainless steel autoclave. 2.0 mg of catalyst was placed into the
autoclave with 2.0 mL of ethanol (as a solvent) and 1.0 mmol
alkyne under magnetic stirring at 25 °C. After the system was
purged with hydrogen gas for three times, 0.2 MPa of H2
pressure remained. When the reaction time was reached,
products were tested by Thermo Trace1300 gas
chromatography equipped with a flame ionization detector.
The signals of alkyne, alkene, and alkane (as the reactant,
desirable product, and byproduct respectively in
semihydrogenation of alkyne) were recorded. Catalytic activity
and selectivity were calculated as follows:
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was supported by the National Key R&D Program of
China (2017YFA0700104), the National Natural Science
Foundation of China (21790052 and 21805207), 111 Project of
China (D17003) and the Science & Technology Development
Fund of Tianjin Education Commission for Higher
Education(2018KJ129).
Characterization.
X-ray diffraction (XRD) patterns were obtained on SmartLab
9KW equipped with Cu Kα radiation (
=
1.5147 Å). Notes and references
Transmission electron microscopy (TEM) characterization was
recorded using a Tecnai G2 Spirit TWIN at an acceleration
voltage of 120 KV. Aberration-corrected scanning transmission
electron microscope (STEM) images were performed using a
Titan Cubed Themis G2 300 equipped with a Probe Corrector.
X-ray photoelectron spectra (XPS) data were collected on an
ESCALAB250Xi with the Al Kα radiation as the X-ray source. All
binding energies were calibrated based on the C 1s peak at
284.8 eV. Raman spectra were obtained on high resolution
laser confocal fiber Raman spectrometer (HORIBA EVOLVTION,
HORIBA Jobinyvon, France) at the excitation wavelength of 532
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Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/D0TA07705D
ARTICLE
ToC
Graphdiyne-Based Pd Single-Atom Catalyst for Semihydrogenation of Alkynes to
Alkenes with High Selectivity and Conversion under Mild Conditions
Xue-Peng Yin, Shang-Feng Tang, Chao Zhang, Hong-Juan Wang, Xiu-Li Lu,* Rui Si,* and Tong-Bu Lu*
Keywords: graphdiyne, semihydrogenation, Pd single-atom catalyst
SYNOPSIS
The prepared Pd-GDY catalysts show an evident dependence on the size of Pd species in hydrogenation reaction under mild
conditions. Specifically, Pds-GDY shows superior activity and selectivity in semihydrogenation of phenylacetylene with much higher
TOF of 6290 h-1, and higher selectivity of 99.3% at 100% conversion under mild reaction conditions.
ToC figure
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