Hydrodechlorination of p-Chlorophenol on Pd-Coated Fe3O4@polypyrrole Catalyst with Ammonia Borane as Hydrogen Donor

Article abstract of DOI:10.1007/s10562-019-02664-3

Ammonia borane (AB) (hydrogen donor), was used for the hydrodechlorination of p-chlorophenol on Fe₃O₄@PPY@Pd at room temperature and pressure. Fe₃O₄@PPY@Pd was characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The high-performance liquid chromatography and carbon balance results showed that p-chlorophenol was efficiently and quantitatively transformed into phenol. At the AB and catalyst contents of 2.5?mmol and 60?mg, respectively, the dechlorination of p-chlorophenol (100?mg/L) followed pseudo-first-order kinetics (rate constant = 0.023?min^?1), and removal efficiency up to 92.5% was obtained in 120?min. The apparent activation energy was 31.6?kJ/mol. The Fe₃O₄@PPY@Pd composite catalyst could be reused without a significant loss in activity. This confirms the good stability of the catalyst. Here, a reductive approach for the dechlorination of organic compounds in water is provided. It is also useful for the fabrication of Pd-based nanocatalysts with easy accessibility, superior activity, and convenient recovery. Graphical Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-019-02664-3

Catalysis Letters
https://doi.org/10.1007/s10562-019-02664-3
Hydrodechlorination of p-Chlorophenol on Pd-Coated Fe3O4@
polypyrrole Catalyst with Ammonia Borane as Hydrogen Donor
Xuefeng Wei1 · Xiaoyang Wan1 · Juan Miao1 · Ruichang Zhang1 · Jun Zhang1 · Qingshan Jason Niu1
Received: 29 August 2018 / Accepted: 13 January 2019
© Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract
Ammonia borane (AB) (hydrogen donor), was used for the hydrodechlorination of p-chlorophenol on Fe3O4@PPY@Pd at
room temperature and pressure. Fe3O4@PPY@Pd was characterized by scanning electron microscopy, X-ray diffraction,
and X-ray photoelectron spectroscopy. The high-performance liquid chromatography and carbon balance results showed
that p-chlorophenol was efficiently and quantitatively transformed into phenol. At the AB and catalyst contents of 2.5 mmol
and 60 mg, respectively, the dechlorination of p-chlorophenol (100 mg/L) followed pseudo-first-order kinetics (rate con-
stant = 0.023 min−1), and removal efficiency up to 92.5% was obtained in 120 min. The apparent activation energy was
31.6 kJ/mol. The Fe3O4@PPY@Pd composite catalyst could be reused without a significant loss in activity. This confirms the
good stability of the catalyst. Here, a reductive approach for the dechlorination of organic compounds in water is provided. It
is also useful for the fabrication of Pd-based nanocatalysts with easy accessibility, superior activity, and convenient recovery.
Graphical Abstract
Keywords Hydrodechlorination · Chlorophenol · Ammonia borane · Polypyrrole · Pd nanoparticles · Fe3O4
1 Introduction
Chlorophenols (CPs), one type of halogenated persistent
organic pollutants, are identified as priority contaminants
in water and wastewater due to their high toxicity on human
health fluents adverse environmental impacts, and persis-
tence in the environment [1, 2]. Many traditional methods
are employed for treating chlorinated aromatic organic com-
pounds, such as physical methods (e.g., ion exchange and
adsorption) [3, 4], biochemical methods [5, 6] and chemical
oxidation (e.g. Fenton/H2O2 oxidation, and photocatalytic
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s10562-019-02664-3) contains
supplementary material, which is available to authorized users.
* Xuefeng Wei
xfwei@haust.edu.cn
1
College of Chemical Engineering & Pharmaceutics, Henan
University of Science and Technology, Luoyang 471023,
People’s Republic of China
Vol.:(0123456789)
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X. Wei et al.
degradation) [7–10]. However, the CPs are usually highly
resistant to environmental degradation, and also difficult
to mineralize by common disposal technologies owing
to the high stability of the Cl–C bonds in CPs which are
responsible for their toxicity and persistence [11]. Reductive
dechlorination, such as electrocatalytic hydrodechlorination
[12–16] and Fe0/Pd bimetal reduction [17–19], are alterna-
tive and efficient strategies to convert them into chlorine-free
phenols, reducing the toxicity of CPs, and making further
treatment of CPs conveniently and economically.
Hence, many highly efficient catalysts have been reported
such as non-noble nano-metal catalysts [45, 46] or alloy
catalysts [47] and noble metal (Rh, Pd, Ru, and Pt) cata-
lysts. Among these catalysts, Pd-based catalysts are the
most investigated catalysts for hydrogen generation and have
extensive industrial applications [48].
Pd-based composite catalyst have been employed for the
hydrolysis of AB [48] and HDH of 2,4-dichlorophenol [49].
The AB has the advantages of solid-state hydrogen storage,
high hydrogen content, in-situ production of H2, good water
solubility and controlled catalytic hydrogen release. There-
fore, it is a predictable hydrogen donor for the HDH of CPs.
However, to the best of our knowledge, there has been no
report on AB-assisted HDH in aqueous solutions.
Hydrodehalogenation (HDH) has become an effective
approach to degrade CPs. Therefore, exploring various
methods for catalytic HDH has persistently attracted many
researchers in this field. Pd shows good adsorption and
absorption to hydrogen [20]. It can intercalate hydrogen in
its lattice, and hence can hold large hydrogen concentrations
[21]. Hence, Pd has become the most studied catalyst for the
HDH of CPs.
One drawback of the Fe3O4-supported nanocomposites
catalysts is that the metal nanoparticles anchored on the
support surface are easily corroded and fall off, resulting
in the poor stability and reusability of the catalysts [50].
Therefore, it remains a challenge to improve the stability of
catalysts without sacrificing catalytic activity. Polypyrrole
(PPy), which is an electrically conducting polymers, is used
as a host matrix to obtain highly dispersed metallic particles
owing to its high electrical conductivity, chemical stability,
and satisfactory processability [51]. Metal microparticles
dispersed on polymer-modified electrodes have been used
in the electro-catalysis applications. In our previous studies
[13–15, 52, 53], we prepared Pd-coated on the PPy-modified
electrodes for the dechlorination of chlorophenols. These
electrodes showed good dechlorination performance.
Zhang et al. [54] prepared core–shell Fe3O4/Pd@PPy
composites by a one-step synthesis method. These compos-
ites showed superior catalytic activity and reusability for
the reduction of 4-nitrophenol in a NaBH4 solution. In this
study, we prepared core–shell Pd-coated Fe3O4@PPY com-
posite catalysts (Fe3O4@PPY@Pd) for the HDH of p-chlo-
rophenol (4-CP). The catalysts were prepared by a two-step
in order to exposure the surface of the composites to Pd.
AB was used as hydrogen donor. The dechlorination per-
formance of the Fe3O4@PPY@Pd composite catalysts and
the HDH kinetics of p-chlorophenol were also investigated.
Various Pd-based catalysts such as commercialized Pd/C
[22–24], Pd/SiO2 [25, 26], Pd/Fe/C [27], and Pt/Pd/Fe [28]
have been developed. The Pd/SiO2 catalysts prepared in
alkaline 2-propanol, which exhibited much more efficient
dechlorination of p-chloroanisole than a conventional Pd/C
catalyst [25] and completely debrominated debromination
of hexabromocyclododecane [26] in an alkaline 2-propanol/
methanol solution. The Pd/Fe/C nanomaterial with a mag-
netic core and C capping layer demonstrated significantly
higher catalytic activity than the Fe/C nanoparticle by
removal of a model halogenated organic pollutant on eosin
Y [27]. From the viewpoint of practical applications, a cata-
lyst should be recyclable and reusable. By using magnetic
catalysts such magnetic nanospheres, traditional separation
methods such as centrifugation and filtration techniques,
which are inefficiency and time-wasting, can be avoided
[29, 30]. Ferro ferric oxide (Fe3O4) nanoparticles, which
are magnetic in nature, can be easily recovered, and hence
are used as a catalyst carrier. Pd/Fe3O4, Au/Fe3O4 and PdAu/
Fe3O4 nano composites are prepared by direct reduction of
the corresponding metal salts [31, 32].
Hydrogen (H2) gas injection is normally used in previous
applications of Pd-catalytic HDH processes [33–37], How-
ever, transportation and storage of compressed H2 presents
safety issues, and expeditiously dissolving H2 into water
involves engineering problems [4, 38, 39]. As an alterna-
tive, in-situ production of H2 has been proposed.
2 Experimental Section
2.1 Experimental Chemicals and Materials
Ammonia borane (AB, NH3BH3) is a promising material
for solid-state hydrogen storage. It is regarded as a potential
hydrogen reservoir owing to its low molecular weight and
high hydrogen content. It is soluble in aqueous solutions and
stable towards hydrolysis in aqueous solutions [40, 41]. The
hydrogen gas can be released from the catalytic hydrolysis
of AB (Eq. R1) under mild conditions [42–44].
Experimental chemicals including Pd(II) chloride (PdCl2,
> 95%) powder, ferric sulfate [Fe2(SO4)3], ferrous sulfate
(FeSO4·7H2O), ferric trichloride (FeCl3), sodium boro-
hydride (NaBH4), ammonium hydroxide, methyl alcohol,
sodium dodecyl benzene sulfonate (SDBS), pyrrole and
p-chlorophenol (>99%) were of analytical grade and were
supplied by Sinopharm chemical reagent Co. AB was from
H3NBH3 + 2H2O → NH4BO2 + 3H2
(R1)
1 3

Hydrodechlorination of p-Chlorophenol on Pd-Coated Fe3O4@polypyrrole Catalyst with Am…
Zhengzhou boron energy materials Co. Ltd., China. All the
solutions were prepared in deionized (DI) water obtained
using a Millipore-Q system.
2.3 Characterization
The morphology, composition, and crystal structure of the
catalyst were investigated. Morphology of the catalysts was
examined using a scanning electron microscope (SEM,
Hitachi SU8010, Japan). The XPS spectra were acquired
using an ESCA Lab 250xi (Thermo VG Scientific, USA)
with Al Ka radiation. The loading level of Pd particles was
analyzed by inductively coupled plasma-atomic emission
spectrometry (ICP-AES, RIS Intrepid ER/S, Thermo Ele-
mental, USA). The crystal structure of the electrodeposit
was analyzed using a Bruker/AXS model D8 Advance
X-ray diffractometer (XRD) using Co Ka radiation with
k=1.7902 Å.
2.2 Experimental Methods
2.2.1 Synthesis of the Fe3O4@PPY Core–Shell Composite
Fe3O4 powder was prepared by the co-precipitation method.
In a typical procedure, 5.0 g FeSO4·7H2O and 7.0 g
Fe2(SO4)3 were dissolved in DI water. To this solution,
ammonium hydroxide was added to under stirring for 2 h
under 273 K to adjust the pH to 11. The black precipitate so
obtained was washed with DI water and ethyl alcohol until
the pH of the washings became neutral. Finally, the precipi-
tate was dried in the air.
The concentrations of p-chlorophenol and its dechlorina-
tion product were analyzed by high performance liquid chro-
matography (HPLC, Waters, USA) using a separation col-
umn (Waters Atlantis T3) (4.6 mm×250 mm, 5 µm) and an
ultraviolet/visible detector (Waters 2489). The mobile phase
was 30% water (containing 2% acetic acid) and 70% metha-
nol at a flow rate of 0.8 mL/min and a working wavelength
of 280 nm. The dechlorination product was identified by
gas chromatography–mass spectrometry system (GC–MS,
Trace GC Ultra-ISQ, Thermo Fisher, USA) equipped with
a TG-5MS (0.25 µm, 30 m×0.25 mm) capillary column.
The Fe3O4@PPY composites were synthesized using a
chemical oxidation method. In a typical procedure, 0.1 g
of Fe3O4 powder prepared in the previous step and 10 mL
SDBS (5 mM) were added to 30 mL of DI water. To this
mixture, 0.3 mL freshly distilled pyrrole was added under
stirring. Then, 25 mL of a 0.05 g/mL FeCl3 solution was
added while stirring. The resulting mixture was stirred for
another 1 h. Finally, the composites were washed with DI
water three times and dried in an air oven.
2.2.2 Synthesis of Fe3O4@PPY@Pd Catalyst
3 Results and Discussion
3.1 Characterization of the As‑Prepared Catalyst
3.1.1 SEM
PdCl2 and NaCl (in a molar ratio of 1:3) were dissolved in DI
water assisted by ultrasonic waves to obtain a Pd(II) aque-
ous solution. Pd-coated Fe3O4@PPY was prepared by the
reduction of NaBH4. A certain amount of Fe3O4@PPY com-
posite was dissolved in DI water followed by the addition
of a Pd(II) solution under stirring for 30 min. This reaction
mixture was then added to a newly prepared NaBH4 solution
under vigorous stirring for 1 h. The precipitate was filtered
and washed with water several times. The finally obtained
slurry was dried at 373 K for 12 h. Finally, the Fe3O4@
PPY@Pd catalyst was obtained.
Figure 1 shows the surface morphology of the Fe3O4@
PPY@Pd composite catalyst. The composite showed a uni-
form spherical shape with an average diameter of 0.5 µm
and formed three-dimensional porous clusters (Fig. 1a).
The magnified SEM image in Fig. 1b shows that the cata-
lyst showed many pores and cracks, in spite of the particle
agglomeration.
2.2.3 HDH of p-Chlorophenol
3.1.2 XRD
The HDH of p-chlorophenol was carried out in a 250 mL
three-necked round-bottomed flask provided with a mechan-
ical stirrer. The Fe3O4@PPY@Pd composite was used as the
catalyst and AB solution was injected as a hydrogen donor
at ambient temperature. The volume of the aqueous solution
containing AB and p-chlorophenol was 50 mL. The initial
concentration of p-chlorophenol was 100 mg/L. The reac-
tion was carried out at ambient temperature (293 1 K) and
in a hot water bath when effect of temperature on the HDH
performance of the catalysts was investigated.
Figure 2 shows the XRD pattern of the as-prepared Fe3O4@
PPY@Pd composite catalyst. The catalyst showed six dif-
fraction peaks at 2θ = 21.5, 35.4, 41.8, 50.9, 63.6, 67.9
and 74.9° corresponding to the (111), (220), (311), (400),
(422), (511), and (440) planes of face-centered cubic
Fe3O4 (JCPDS no. 75-0449) [55]. Besides these charac-
teristic peaks of Fe3O4 nanospheres, additional peaks were
observed at 2θ=47.1 and 54.9°, corresponding to the (111)
and (200) crystalline planes of face-centered Pd nanoparti-
cles (JCPDS no. 87-0639) [56]. The average diameter of the
1 3

X. Wei et al.
Fig. 1 SEM images of the Fe3O4@PPY@Pd composite catalyst. a ×5000; b ×50,000
and Fe3+. Figure 3c shows the N 1s XPS spectrum of the
catalyst. The three peaks with binding energies of 398.5,
399.6 and 400.2 eV can be attributed to the imine (=N–),
amine (–NH–), and positively charged nitrogen (N+) species
in PPY [60]. The binding energies of 284.6 and 529.8 eV
can be indexed to C 1s and O 1s, respectively. The peak for
C 1s can be attributed to the use of SDBS for the synthesis
of Fe3O4@PPY.
3.1.4 ICP-AES
The Pd content of the catalyst was determined by ICP. It was
found that the Fe3O4@PPY@Pd composite catalyst had a Pd
loading of 6.45% .
3.2 HDH of p‑Chlorophenol in Aqueous Solution
Fig. 2 XRD patterns of the Fe3O4@PPY@Pd composite catalyst
3.2.1 Dosage of Fe3O4@PPY@Pd Composite Catalyst
Figure 4 shows the AB-assisted HDH of p-chlorophenol
on the Fe3O4@PPY@Pd composite catalyst in an aque-
ous solution. The initial concentrations of p-chlorophenol
was 100 mg/L. The addition of AB was 1.5 mmol. The
catalyst dosages of 5, 20, 40, 50, 60, 70, 80, and 100 mg
were used. When a catalyst loading of 5 mg and a dechlo-
rination time of 160 min were used, the conversion effi-
ciency of p-chlorophenol was very low (23.6%), which
was probably because the low dosage of catalyst could not
offer enough active hydrogen (H*) for HDH reaction. At a
constant dechlorination time, the conversion efficiency of
p-chlorophenol on the Fe3O4@PPY@Pd composite cata-
lyst increased significantly with an increase in the catalyst
dosage from 5 to 60 mg. At the catalyst dosage of 60 mg, a
conversion efficiency of 80.5% was obtained (dechlorina-
tion time was 160 min). However, at higher catalyst dos-
ages (80 and 100 mg), the conversion efficiency decreased
Pd nanoparticles was estimated using the Scherrer equation
(6.7 nm).
3.1.3 XPS
XPS measurements were carried out to investigate the chem-
ical composition of the Fe3O4@PPY@Pd catalyst. The Pd
3d, Fe 2p, and N 1s region spectra and full XPS spectrum of
the catalyst are shown in Fig. 3.
Figure 3a shows the Pd 3d peaks at 335.3 and 340.7 eV,
corresponding to Pd0 which was the dominant component of
,
the catalyst. The other pair of peaks at 337.8 and 342.8 eV
correspond to the Pd(II) from the residual Pd halides [57,
58]. Figure 3b shows the Fe 2p peaks. The peak at 710.9 eV
corresponds to Fe 2p3/2. Since the binding energy of Fe 2p3/2
is about 709 eV for Fe2+ and 711 eV for Fe3+ [59], the Fe
2p3/2 peak at 710.9 eV indicates the coexistence of Fe2+
1 3

Hydrodechlorination of p-Chlorophenol on Pd-Coated Fe3O4@polypyrrole Catalyst with Am…
Fig. 3 XPS spectra of the Fe3O4@PPY@Pd composite catalyst, a Pd 3d, b Fe 2p, c N 1s, and d full spectrum
Fig. 4 Dechlorination of p-chlorophenol with different dosages of the
Fig. 5 Conversion of p-chlorophenol with different dosages of AB.
C(p-chlorophenol)0 = 100 mg/L, m=60 mg
Fe3O4@PPY@Pd composite catalyst. C(p-chlorophenol)0 = 100 mg/L,
n(AB)0 = 1.5 mmol
1 3

X. Wei et al.
slightly. High catalyst dosages might accelerate the hydro-
gen evolution reaction (HER).
3.2.3 Apparent Reaction Kinetics
The effect of temperature on the HDH of p-chlorophenol
by the Fe3O4@PPY@Pd composite catalyst was investi-
gated. Figure 6 shows the correlation between the p-chlo-
rophenol concentration and the dechlorination time at
various temperatures. HDH of p-chlorophenol followed
pseudo first-order kinetics (shown in Fig. S2). The appar-
ent reaction rate constant k at 283, 293, 303, and 313 K
was approximately equal to 0.0112, 0.0230, 0.0349, and
0.0402 min−1, respectively. The rate constant for the trans-
formation of p-chlorophenol normalized by the Pd concen-
tration (0.0027 g/0.050 L=0.054 g/L) was 0.43 L/gPd min
at 293 K. This value is in the same level as that reported by
Liu et al. for the HDH of p-chlorophenol in NaBH4 using a
Pd/Fe3O4@SiO2@m–SiO2 [61, 62]. The initial turnover fre-
quency values (TOF0) of HDH of p-chlorophenol at 293 K
was calculated as 0.109 min−1, according to the literature
[63]. The TOF0 value was lower than that of HDH of p-chlo-
rophenol by hydrogen gas on the palladium-resin compos-
ites, about 0.5~1.1 min−1 in neutral condition, reported in
the literature [63]. The aggregation of Pd nanoparticles in
our work might be one of the reasons for the lower TOF0.
In future work, we wish to extend this study by increasing
the surface area of the Pd catalyst to improve the catalytic
activity.
3.2.2 Dosage of AB
Figure 5 shows the effect of the AB dosage on the HDH
of p-chlorophenol by Fe3O4@PPY@Pd composite catalyst
when the catalyst dosage was 60 mg and the dechlorina-
tion time was 120 min. Various AB dosage were used: 1.5,
2.0, 2.5, and 3.0 mmol. When the AB dosage and other
HDH conditions were kept constant, the conversion effi-
ciency of p-chlorophenol improved with an increase in
the dechlorination time. The conversion of p-chlorophenol
increased with an increase of AB dosage from 1.5 to 2.5.
The conversion of p-chlorophenol decreased significantly
when the AB dosage was increased to 3.0 mmol during
120 min reaction time. Hydrolysis of AB on the 60 mg
Fe3O4@PPY@Pd catalyst were conducted to investigate
the amount of hydrogen released by AB without p-chlo-
rophenol (shown in Fig. S1). Production of H2 conforms
to the hydrogen release equation (Eq. R1), i.e., hydrolysis
of 1 mol of AB yields 3 moles of H2 gas. Hydrolysis of
2.5 mmol AB have been almost completed in 90 min on the
Fe3O4@PPY@Pd composite catalysts. Compared to the
amount of p-chlorophenol, the hydrogen released from AB
was excessive. It is speculated that the HDH still proceed
after 90 min because the rate of hydrogen release slowed
down when p-chlorophenol exited. The lower conversion
of p-chlorophenol in first hour with addition of 3.0 mmol
AB might be caused by the rapid hydrogen release rate.
The effect of temperature on the HDH of p-chlorophe-
nol could be expressed by the Arrhenius theorem equa-
tion: k = A exp(− Ea/RT). The apparent reaction rate
constant k and 1/T are related by the following formula:
ln k=9.052–3.797×103/T (R2 =0.9313). The correspond-
ing fitted line is shown in Fig. 7. The apparent activation
energy for the HDH of p-chlorophenol on Fe3O4@PPY@
Fig. 6 Effect of temperature on the dechlorination of p-chlorophe-
Fig. 7 Arrhenius plot of ln k and 1/T for the dechlorination p-chloro-
nol on the Fe3O4@PPY@Pd composite catalysts. C(p-chlorophenol)0
100 mg/L, m=60 mg, n(AB)0 = 2.5 mmol
=
phenol on the Fe3O4@PPY@Pd composite catalyst. C(p-chlorophenol)0
100 mg/L, m=60 mg, n(AB)0 = 2.5 mmol
=
1 3

Hydrodechlorination of p-Chlorophenol on Pd-Coated Fe3O4@polypyrrole Catalyst with Am…
Fig. 8 Variations in the concentration of phenol and the sum of the
Fig. 9 Repeated HDH of p-chlorophenol by the Fe3O4@PPY@Pd
p-chlorophenol and phenol concentrations during the HDH process.
C(p-chlorophenol)0 = 100 mg/L, m=60 mg, n(AB)0 = 2.5 mmol
composite catalyst recycled five times
Pd composite catalyst was calculated to be 31.6 kJ/mol. The
apparent activation energy was less than 40 kJ/mol, indicat-
ing that the reaction was controlled by the diffusion process.
In this experiment, the amount of AB was much greater than
that of p-chlorophenol and the bubble overflow was observed
in the HDH reactions which were conducted in semi-opened
system. The insufficient utilization of evolved H2 might be
responsible for the diffusion step.
removal efficiency of about 92.5%. The removal efficiency
after four cycles was 91.1%. This indicates that the Fe3O4@
PPY@Pd composite catalyst showed good stability and reus-
ability in the HDH of p-chlorophenol. The separation of the
Fe3O4@PPY@Pd composite using a magnet is shown in
Fig. S4.
SEM was employed to investigate the surface morphol-
ogy of the catalyst recovered after the fifth cycle of HDH.
The morphology of this catalysts (Fig. S5) was found to
be similar to that of the as-prepared catalysts (Fig. 1). The
XRD pattern and XPS spectrum of the used Fe3O4@PPY@
Pd composite catalyst are shown in Figs. S6 and S7. The
results obtained from Figs. S6 and S7 were comparable to
those obtained from Figs. 2 and 3, respectively. Hence, it
can be stated that the Fe3O4@PPY@Pd composite catalyst
had good stability.
3.2.4 Carbon Balance
Figure 8 shows the concentration of phenol during the decay
of p-chlorophenol as function of time, along with the sum
of the concentrations of p-chlorophenol and phenol. With
the HDH of p-chlorophenol, the concentration of phenol
increased gradually. The sum concentrations of the p-chloro-
phenol and phenol during the HDH reaction was maintained
as the initial amount of p-chlorophenol, implying that phenol
was the only dechlorination product, which was not reduced
further. According to the literatures [15, 64], a small fraction
of dechlorination product phenol would be reduced further
to form cyclohexanone or cyclohexanol. We investigated
the dechlorination products of p-chlorophenol by GC–MS
system. The GC–MS spectra were shown in Fig. S3. Neither
cyclohexanone nor cyclohexanol was observed. The results
were consistent with those of HPLC.
4 Conclusions
We prepared a Fe3O4@PPY@Pd core–shell composite cata-
lyst and investigated its catalytic activity towards the HDH
of p-chlorophenol in presence of AB as a hydrogen donor.
The magnetism of Fe3O4@PPY facilitated the recycling of
the catalyst. The Fe3O4@PPY@Pd nano catalyst showed
good catalytic activity towards the HDH of p-chlorophe-
nol with a reaction rate constant (per unit mass) of 0.43 L/
gPd·min. The Fe3O4@PPY@Pd nano catalyst could be recy-
cled at least five times without significant degradation in
its catalytic activity. AB acted as a reducing agent in the
HDH of p-chlorophenol. It proposes a new idea and refer-
ence for HDH of chlorophenols and also provids a promis-
ing candidate for various Pd based catalytic applications.
In this study, the decomposition product of AB and their
3.2.5 Catalytic Durability of the Fe3O4@PPY@Pd Composite
A five-cycle recycle/HDH study was carried out to evaluate
the reusability of Fe3O4@PPY@Pd composite catalyst. The
results showed that the removal efficiency hardly changed
during all the five cycles of dechlorination (Fig. 9). In the
first cycle, the virgin catalyst showed a p-chlorophenol
1 3

X. Wei et al.
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Acknowledgements This work was supported by National Natural
Science Foundation of China (21403058, 21576073, and 41601520),
the Scientific and Technological Project in Henan Province of China
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