Platinum-Supported Zirconia Nanotube Arrays Supported on Graphene Aerogels Modified with Metal–Organic Frameworks: Adsorption and Oxidation of Formaldehyde at Room Temperature

Article abstract of DOI:10.1002/chem.201904426

Precious-metal catalysts (e.g., Au, Rh, Ag, Ru, Pt, and Pd) supported on transition-metal oxides (e.g., Al₂O₃, Fe₂O₃, CeO₂, ZrO₂, Co₃O₄, MnO₂, TiO₂, and NiO) can effectively oxidize volatile organic compounds. In this study, porous platinum-supported zirconia materials have been prepared by a “surface-casting” method. The synthesized catalysts present an ordered nanotube structure and exhibited excellent performance toward the catalytic oxidation of formaldehyde. A facile method, utilizing a boiling water bath, was used to fabricate graphene aerogel (GA), and the macroscopic 3D Pt/ZrO₂-GA was modified by introducing an adjustable MOF coating by a surface step-by-step method. The unblocked mesoporous structure of the graphene aerogel facilitates the ingress and egress of reactants and product molecules. The selected 7 wt.% Pt/ZrO₂-GA-MOF-5 composite demonstrated excellent performance for HCHO adsorption. Additionally, this catalyst achieved around 90 % conversion when subjected to a reaction temperature of 70 °C (T_{90 %}=70 °C). The Pt/ZrO₂-GA-MOF-5 composite induces a catalytic cycle, increasing the conversion by simultaneously adsorbing and oxidizing HCHO. This work provides a simple approach to increasing reactant concentration on the catalyst to increase the rate of reaction.

Full text of DOI:10.1002/chem.201904426

A Journal of
Accepted Article
Title: Platinum-supported zirconia nanotube arrays supported on
graphene aerogels modified with metal-organic frameworks:
adsorption and oxidation of formaldehyde at room temperature
Authors: Haocun Tan, Dongyun Chen, Najun Li, Qingfeng Xu, Hua Li,
Jinghui He, and Jian-Mei Lu
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content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.201904426
Link to VoR: http://dx.doi.org/10.1002/chem.201904426
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Platinum-supported zirconia nanotube arrays supported on
graphene aerogels modified with metal-organic frameworks:
adsorption and oxidation of formaldehyde at room temperature
Haocun Tan, Dongyun Chen,* Najun Li, Qingfeng Xu, Hua Li, Jinghui He, and Jianmei Lu*
Abstract: The precious metal catalyst (such Au, Pd, Rh, Ag, Ru, Pt
degradation[13-15] and plasma treatment[16]
methods, the most promising is to completely degrade
formaldehyde into H O and CO by thermal catalytic oxidation
since higher removal rate is achieved with
concentration of secondary pollution by-products.[
.
Among these
and Pd) which was supported on transition metal oxide (for example,
Al
2
O
3
,
Fe
2
O
3
,
CeO
2
,
ZrO
2
,
Co
3
O
4
,
MnO
2
,
TiO
2
and NiO) can
2
2
effectively oxidize VOCs. In this study, porous platinum-supported
zirconia materials were prepared by a "surface-casting" method. The
synthesized catalyst presents an ordered nanotube structure and
exhibits excellent performance toward the catalytic oxidation of
formaldehyde. Herein, a facile method, utilizing a boiling water bath,
was used to fabricate graphene aerogels (GA), and a macroscopic
a
a
lower
The
17-22]
efficiency of noble metal-supported transition metal oxides to
[
19, 20,
remove formaldehyde at room temperature is considerable.
2
3, 24]
A series of noble metal-supported oxides have been used
to catalyze formaldehyde degradation such as Pt/TiO
[
25]
2
,
,
,[26] Pt/MnO
,[27] Pt/MnO ,[28] Pd-Mn/Al
-CeO O
.[32] Yazawa et al. studied
[29]
3
D Pt/ZrO
2
-GA was modified by introducing an adjustable MOF
surface step-by-step method. The unblocked
Pt/Fe
Au/TiO
the loading of platinum on a metal oxides (such as La
2
O
3
2 x 2 2
3
coating via
a
2
,[30] Ag/CeO ,[31] and Ag/Co
2
3
O
4
mesoporous structure of the graphene aerogel facilitates the ingress
and egress of reactants and product molecules. The selected MOF-5
composite demonstrates excellent performance for HCHO
2
O
3
, MgO,
.) to form
catalyst and catalytic oxidation of propane at low
temperatures. The results show that the stronger the acidity of
the platinum-loaded support has higher catalytic activity. Hence,
2
-
ZrO
2
, Al
2
O
3
, SiO
2
-Al
2
O
3
, SiO
2
, and SO -ZrO
2
a
4
[33]
adsorption. Additionally, the 7wt.% Pt/ZrO
achieved ~90% conversion when subjected to
temperature of 70°C (T90%=70°C). The Pt/ZrO -GA-MOF-5 composite
2
-GA-MOF-5 catalyst
a
reaction
2
2
ZrO is selected as the base material to support Pt. Additionally,
induces a catalytic cycle, that is, increasing the reaction rate by
simultaneously adsorbing and oxidizing HCHO. This work provides a
simple way to increase reactant concentration on the catalyst to
increase the reaction rate.
considering that the active phase of the catalyst should be highly
uniformly dispersed and the catalyst easily recycled, the
unblocked mesoporous structure of graphene aerogel (GA) has
a large specific surface area, which can disperse nanoparticles
well and provide excellent channels for gas molecules to enter
and exit. In the process of generating aerogel, the catalyst is
easily combined with graphene sheets, we construct the aerogel
using graphene sheets and add the catalyst thereto before the
aerogel is formed.
Introduction
Formaldehyde is generally considered to be a toxic indoor air
pollutant and one of the most concerned VOCs.[1, 2] Typically,
formaldehyde is derived from painting and decoration materials,
textiles and from smoking.[3] Even at lower concentrations
Recently, the combination of metal-organic framework
MOF) with other catalysts is a hot topic at this stage of research.
Many MOFs have excellent adsorption properties because of
their considerable pore volume and specific surface area, and its
(
(
<0.5ppm), HCHO species in the air will cause severe health
problems, such as irritating the respiratory system and skin,
causing coughs, headaches, cardiovascular disease, and
possibly even has some negative impacts on the central nervous
system and genetic material.[4-7] As people pay more and more
attention to the quality of their living environment and their own
health, formaldehyde has attracted more and more attention.
chemical stability.
excellent adsorption capacity for gases such as formaldehyde,
CH OH, hydrogen and CO . Therefore, it is feasible to modify
the surface of the catalyst with MOF to increase the catalytic
rate. Herein, MOF-5 is dispersed on a GA to improve the HCHO
adsorption properties.[34]
A great deal of MOF materials exhibit
3
2
Hitherto, numerous investigations have reported the
catalytic oxidation of HCHO, however, there have been few
reports on the modification of the catalyst surface with MOFs to
improve CO conversion. In view of this, we disperse MOF on the
surface of GO sheets by self-assembly and form aerogel by a
simple boiling water bath method (showed in Scheme 1). In this
Currently, typical methods of eliminating formaldehyde
include chemical and physical adsorption,[8-12] photocatalytic
[1]
H.C. Tan, Prof. D.Y. Chen, Prof. N.J. Li, Prof. Q.F. Xu, Prof. H. Li,
Prof. J.H. He, and Prof. J.M. Lu,
College of Chemistry, Chemical Engineering and Materials Science
Collaborative Innovation Center of Suzhou Nano Science and
Technology
2
work, Pt/ZrO -GA-MOF-5 can simultaneously adsorb and
catalyze the oxidation of HCHO, thereby increasing the HCHO
oxidation rate.
Soochow University
Suzhou 215123, P. R. China
dychen@suda.edu.cn, lujm@suda.edu.cn
Supporting information for this article is given via a link at the end of
the document.
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Figure 2b also demonstrates the successful synthesis of 7 wt%
Pt/ZrO . At the same time, it can be seen from Figure 2b that
2
the lattice spacing (white) is approximately 1.96 nm, which
corresponds to the (002) crystal plane of platinum.
2
Scheme 1. Schematic representation of the synthesis of Pt/ZrO -GA-MOF-5.
Results and Discussion
Preparation and characterization of SBA-15-OH and Pt/ZrO
2
SBA-15-OH, prepared according to a previously reported
method, was used as a silica hard template. Thereafter, porous
Pt/ZrO
method. The SBA-15-OH channels were immersed in the
PtCl ·6H and ZrOCl ·8H precursor solution by
2
materials were prepared by a so-called surface-casting
H
2
6
2
O
2
2
O
impregnation. The SBA-15-OH template was then leached out
using a hot sodium hydroxide solution. SEM and TEM were
used to characterized the surface morphologic structure and
structure of the prepared SBA-15-OH and Pt/ZrO
2
materials
Figure 2. HAADF-STEM images of: 7wt.% Pt/ZrO
spectroscopy mappings of: (d) Zr, (e) O, and (f) Pt; high-resolution TEM
micrograph of: 5 wt.% Pt/ZrO (b).
2
(a,c), and STEM EDX
(
Figure S1, Figure 1a and Figure 1b). Figures S1a and S1b
show a SEM and TEM micrograph, respectively, of the highly
ordered mesoporous silica SBA-15-OH. The key to the
2
successful synthesis of highly ordered mesoporous ZrO
2
is the
The crystal form and phase structure of the transition metal
oxide (ZrO ) in the catalyst can be further determined by
characterization of X-ray diffraction. Figure 3a and 3b clearly
ordered nanotube arrays and the silanol-rich surface of SBA-15-
OH. At the same time, it can be clearly observed that the size of
the synthesized nanotube arrays is ~10nm. Further observations
2
show the wide-angle and low-angle powder XRD patterns of the
show that the Pt/ZrO
SBA-15-OH (Figure S1b), indicating that Pt/ZrO
successfully synthesized by the surface-casting method.
Furthermore, it is evident that metallic platinum (black dots) is
successfully supported on the zirconia nanotube arrays (Figure
2
structure (Figure 1b) is similar to that of
catalyst. The position of the diffraction peak shown is the same
̅
was
as the standard card value of ZrO
entry 49-1642). For the cubic ZrO
2
(space group Fm3m, PDF2
2
2
structure, three peaks at
30.12°, 50.22° and 59.74° 2θ are attributed to the (111), (220)
and (311) planes, respectively.[35, 36] In the obtained diffraction
pattern (Figure 3a), the position of each diffraction peak was
accurately obtained and confirmed to belong to a cubic zirconia
structure (PDF 2 entry: 49-1642). However, at this calcination
temperature, zirconia typically forms a monoclinic or tetragonal
structure rather than a cubic structure. The reason for this
phenomenon may be that the residual silicon oxide after the
1
b) and are uniformly dispersed and uniform in size, having a
particle size distribution, estimated from the TEM image, to be
–5 nm.
3
2
leaching treatment of Pt/ZrO causes it to form a cubic structure.
The specific surface area and pore size distribution of Pt/ZrO
2
catalysts and SBA-15-OH were determined by BET and BJH
models (Figures 3c and 3d). The nitrogen adsorption desorption
isotherms indicate that both materials are mesoporous materials
because they are all type IV curves as shown in Figure 4c. The
unique capillary condensation phenomenon that occurs at
P/P
removal of the silicon dioxide template. In addition, hysteresis
loop appearing at higher pressures (P/P =0.75-0.99) indicate the
0
=0.60-0.80 coincides with an ordered mesopores formed by
2 2
Figure 1. (a)SEM images of Pt/ZrO ; (b)TEM images of Pt/ZrO ,
0
STEM EDX spectroscopy mapping confirmed the elemental
distribution and composition of Pt/ZrO and Figure 2a and 2b
presence of structural defects or channels between the
2
[35]
nanotubes.
Two peaks appear in the pore size distribution
displayed the typical HAADF-STEM image. Mapping images of
platinum, zirconium, and oxygen (Figure 2e, 2d and 2f) indicate
that Pt is uniformly distributed on zirconia. The HRTEM image of
displayed in Figure 3d. The tube wall thickness of SBA-15-OH
corresponds to a primary pore diameter centered in 3.5 nm, and
the other peak comes from the inner hollow tube.
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folding ability in a certain sense. In a word, the surface of
Pt/ZrO
2
-GA was modified with a KH550 and succinic anhydride.
Then, the Zn2 as a metal node is coordinated with the
+
2
carboxylate-terminated Pt/ZrO -GA, and finally, terephthalic acid
is added as an organic ligand for self-assembly, and the growth
process is repeated several times to obtain MOF-5. Herein,
2
modifying the Pt/ZrO -GA surface functional group is a critical
step because of the formation of strong chemical bonding.
Furthermore, by controlling the number of the self-assembly
processes, the MOF crystallite size and number can be tailored.
Figure 4c and 4d show the Pt/ZrO
there is an obvious MOF-5 growth on Pt/ZrO
assembly reaction between Zn(CH COO)
2
-GA-MOF-5 catalyst, and
-GA. The self-
·2H and
2
3
2
2
O
terephthalic acid resulted in MOF-5 crystals with an average size
of 0.5–1 μm (Figure 4d)
2
Figure 3. (a) Wide-angle powder XRD (WXRD) patterns of Pt/ZrO , compared
̅
with a standard ZrO
2
(space group Fm3m, PDF2 entry 49-1642). Pt loading
account is: 1, 3, 5, 7 and 9wt.%. (b) Low-angle powder XRD patterns of
Pt/ZrO nanotube arrays. (c) Nitrogen adsorption-desorption isotherms. (d)
Pore size distributions of Pt/ZrO and SBA-15-OH.
2
2
As shown in Figure S3, the chemical composition of the
prepared catalyst and its elemental valence state were analyzed
by XPS. The high-resolution XPS spectra of the 7%Pt/ZrO
d and Pt 4f binding energies are shown in Figure S3a and
Figure S3c, respectively. As the reported result, the Zr 3d5/2
binding energy of stoichiometric ZrO is in the scope of 182.2–
83.3 eV.[37-40] All Pt/ZrO
catalysts displayed Pt 4f5/2 peaks
2
Zr
3
2
1
2
centered on 73.3 eV, 75.1 eV and 78.3eV (Figure S3c), which
were corresponded to metallic Pt0 and ionic Pt2+ and Pt4+
species, respectively.[36, 40, 41] The XPS data also confirmed the
existence of the mixed valence states of Pt. As demonstrated in
Figure S3b, three typical peaks were clearly observed in the O
Figure 4. SEM images of: (a) Pt/ZrO
2
-GA and (c) Pt/ZrO
-GA-MOF-5.
2
-GA-MOF-5; TEM
images of: (b) Pt/ZrO -GA and (d) Pt/ZrO
2
2
2
To confirm that the surface of Pt/ZrO -GA was modified by
MOF-5, XPS investigations were conducted, and the results
shown in Figure S3d and Figure S2. The results confirmed the
presence of zinc. Thermogravimetric analysis method was used
to determine the thermostability of the catalyst and to quantify
the loading of MOF-5 or other compositions on the catalyst. TGA
1s XPS spectra of the Pt/ZrO
2
catalysts. The binding energies in
the range of 529.6–530.1eV and 531.7–532.1eV are attributed
to to lattice oxygen (Olatt
) and adsorbed oxygen (Oads),
respectively.[36]
measurements were performed under a N
2
flow across a
operation temperature from 25°C to 800°C and the results
shown in Figure 5a. For all synthetic catalysts, the initial mass
loss is typically associated with organic residues. The sharp
peak appearing at ~486 °C is attributed to the decomposition of
the MOF-5 organic ligand, indicating a complete collapse of the
skeleton.[42] Further, from the results of TGA, it was calculated
2 2
Preparation and characterization of Pt/ZrO -GA and Pt/ZrO -
GA-MOF-5
Pt/ZrO
2
-GA was prepared via a boiling water bath method,
and Pt/ZrO
2
-GA-MOF-5 was further prepared by a stepwise self-
assembly method. The morphology and structure of the
prepared Pt/ZrO -GA and Pt/ZrO -GA-MOF-5 were
characterized by SEM and TEM (Figure 4a~4d).
representative SEM micrograph (Figure 4a) of Pt/ZrO
2
2
that the MOF-5 on the surface of the modified Pt/ZrO
2
-GA was
A
～
5wt.%. Additionally, the IR spectra (Figure 5b) demonstrates
2
-GA
the existence of MOF-5 in the catalyst. The asymmetric
shows a continuous macroporous structure that will improve
ingress and egress of the catalyst and formaldehyde reactant.
The corresponding TEM micrograph (Figure 4b), clearly shows
stretching of carboxylate groups of BDC (from the terephthalic
acid) is shown in around 1501cm-1 and 1588cm ,
-1 [43,
44]
and
bands for the symmetric stretching of carboxylate groups were
that the Pt/ZrO
a size range of 400–600 nm. From the images of SEM and TEM,
it can be confirmed that MOF-5 is formed on the Pt/ZrO -GA
2
material is fixed on the graphene sheets having
shown at 1438cm-1 and 1379cm .
-1 [45]
The IR spectrum of
−1
2
Pt/ZrO -GA-MOF-5 showed several bands at 1300–660cm ,
2
which were derived from the out-of-plane vibrations of
terephthalic acid.[46, 47] In Figure 5b, all the characteristic bands
surface by self-assembly. At the same time, the ultra-thin
structure of the graphene sheet was observed, which proved its
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of Pt/ZrO
MOF-5 was incorporated into Pt/ZrO
2
-GA-MOF-5 were also observed, which confirmed that
-GA-MOF-5.
The SEM micrograph of the catalyst sample after being
subjected to continuous reaction for 24 hours at 150°C with a
HCHO flow rate of 20ml/min is shown in Figure 6d. The
morphology of the spent catalyst was not observed to change
significantly when compared with the morphology of the fresh
catalyst (Figure 6c). To further demonstrate the durability of the
catalyst, XRD analysis was performed. As shown in the Figure
2
6
b, the XRD pattern of the catalyst before and after the reaction
showed few change, indicating that it had good stability.[
Furthermore, the MOF-5 diffraction pattern indicates that MOF-5
is stable during the continuous completely oxidation of HCHO
and was successfully loaded onto the aerogel surface.
42]
Figure 5. (a) thermogravimetric analysis of MOF-5, 7wt.% Pt/ZrO
and 7wt.% Pt/ZrO -GA across a temperature range of 25–800°C; (b) IR
spectra of the catalyst and MOF-5 at 298 K.
2
-GA-MOF-5
2
Thus, GAs provides good support for the catalyst during the
catalytic reaction and provides excellent flow channels for the
ingress and egress of gas molecules. At the same time, MOF-5
adsorbing HCHO on the surface of GA accelerates the reaction
rate by enriching formaldehyde on the surface of the catalyst. A
simplistic schematic diagram of the catalytic HCHO oxidation
Catalytic performance of Pt/ZrO
Oxidation
2
-GA-MOF-5 toward HCHO
All samples showed high catalysis activity for HCHO
oxidation, even at reaction temperatures below 150°C, the
process on a Pt-supported ZrO catalyst, is shown in Figure 7.
2
conversion was still above 95%. 7wt.% Pt/ZrO
2
showed the
The catalytic reaction process is divided into the following steps:
First, Pt supported on zirconia adsorbs free oxygen and splits it
into active O atoms. The formation of a hydrogen bond between
the oxygen atom on the HCHO and the hydrogen atom in the
hydroxyl group on the surface of the zirconia causes the carbon
atom in the formaldehyde molecule to be positively charged,
forming an electrophilic carbon atom. The electrophilic carbon
atoms are then readily attacked by reactive oxygen atoms to
form a surface dioxymethylene group which is then further
oxidized to the formate salt. The formate formed on the surface
of the catalyst is easily decomposed into adsorbed carbon
highest activity due to the optimal Pt loading. At the same time,
too high a loading (9wt.% Pt) accounts to a decrease in catalytic
efficiency. One of the reasons is that excessive loading causes
agglomeration of Pt NPs, resulting in a decrease in specific
surface area, thereby reducing the catalytic effect. As can be
seen from Figure 6, the MOF supported catalyst increased the
reaction rate of HCHO. As shown in Figure S6, the stability of
2
7wt.% of Pt/ZrO -GA-MOF-5 was also investigated. Though
undergo 24 hours of continuous catalytic reaction at 100℃, its
catalytic efficiency remains above 99% and can not find any
significant change in SEM images and XRD patterns. This result
demonstrates the stability of the catalyst in this working
environment.
monoxide and H O. Therefore, the adsorbed carbon monoxide,
2
formate and diformaldehyde are the most important
intermediates in the catalytic reaction. Finally, CO is oxidized to
CO2 by O2 and the reaction process ends. Oxidation of formic
acid to carbon monoxide is the rate determining step of the
reaction.[41, 43] Finally, a virtuous cycle of HCHO adsorption and
catalytic oxidation is produced.
Figure 6. (a) Relationship between formaldehyde conversion rate and reaction
2
temperature; (b) XRD patterns of Pt/ZrO -GA-MOF-5 (before and after
2
reaction) and MOF-5; SEM micrographs of Pt/ZrO -GA-MOF-5 (before
reaction) (c) and (after reaction) (d).
Figure 7. Reaction scheme of the catalytic oxidation of HCHO on Pt-
2
supported ZrO catalysts.
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Conclusions
concentrated nitric acid (65 wt%) and 40 ml of H2O2 , refluxed at 80 ° C
for 3 hours, and filtered to give SBA-15-OH.[35]
Pt/ZrO
assembly method and was investigated as a catalyst toward the
catalytic oxidation of HCHO. The Pt/ZrO -GA surface was
modified with MOF-5, as the latter is known to adsorb
formaldehyde. At the same time, the GA network provides a
highly accessible tortuous channel system for the ingress and
2
-GA-MOF-5 was prepared via a one-step, self-
Preparation of Graphite Oxide (GO)
A certain amount of graphite sheet (1.5 g) was dispersed in a mixture of
H2SO4/H3PO4 (9:1 volume ratio), and then a strong oxidizing agent
KMnO4 (9.0 g) was slowly added to the above mixture under vigorous
stirring, and the whole reaction system was in ice-water bath and
ensured that the temperature is below 40°C. After the reaction was
completed, the mixture was allowed to stand overnight. Next, after
2
egress of reactant and product molecules. The 7wt.% Pt/ZrO
2
cooling to room temperature, the reaction mixture was poured into ice
sample exhibited excellent catalytic performance, which was
further improved after loading onto the aerogel by modification of
the aerogel surface. This catalyst sample achieves ~100%
formaldehyde conversion at low reaction temperatures (~100 °C).
At the same time, the composite material demonstrated
excellent stability during the catalytic oxidation of formaldehyde,
maintaining performance after 24 hours of continuous reaction.
As a result of the excellent catalytic performance and stability,
the catalyst demonstrates great potential for a wide-range of
applications.
3
(
~200cm ). Then, 30%H2O2 was slowly added until the color of the
solution turned bright yellow. After that, the mixture was allowed to stand
overnight. Then, the precipitate therein was separated and washed.
Subsequently, impurity ions in the product are removed by dialysis, and
the process continues for one week. Then, graphene oxide is obtained by
a freeze-drying method.
Preparation of Pt/ZrO2
Generally, a certain amount of chloroplatinic acid solution (H2PtCl6·6H2O,
1
g/100ml, 1.878 g of zirconium oxychloride was impregnated with a
certain amount of the above solution to adjust different Pt loadings. 1%,
.91ml; 3%, 5.72ml; 5%, 9.53ml ; 7%, 13.34 ml; 9%, 17.15 ml), 2.00 g of
1
SBA-15-OH, 3 ml of HCl (1.07 mol/L) were uniformly mixed and placed in
the reaction kettle. The temperature was kept at 50° C for 24 h, and then
heated to 90°C for 48 h. The obtained product was calcined in a tube
furnace, air atmosphere, heating rate 1°C/min, calcined at 450°C for 6 h,
and cooled down to ambient temperature naturally. In order to remove
the SBA-15-OH template, the obtained product was uniformly mixed with
a sodium hydroxide solution (2 mol/L), and refluxed at 70°C for 12 hours,
and the operation was repeated twice with 35 ml of a sodium hydroxide
solution each time. After the reaction, it was washed with ultrapure water
until neutral, and the product was dried under vacuum at 60°C for 8
hours.
Experimental Section
Materials and Reagents.
The reagents and chemicals listed below can be used directly without
any treatment. EO20PO70EO20 (P123) was purchased from Sigma-
Aldrich. Chloroplatinic acid hexahydrate (H2PtCl6·6H2O), tetraethyl
orthosilicate (TEOs), L-ascorbic acid, 1,4-dicarboxybenzene, succinic
anhydride, potassium permanganate was purchased from TOKYO
CHEMICAL INDUSTRY CO.,LTD. Zirconyl chloride octahydrate
(ZrOCl2·8H2O), KH550(3-aminopropyltriethoxysilane, APTES) was
purchased from Shanghai Macklin Biochemical C.,Ltd. Graphite flake,
sodium hydroxide, hydrochloric acid, nitric acid, hydrogen peroxide,
absolute ethyl alcohol, N,N-dimethylformamide (DMF), zinc acetate
Preparation of Pt/ZrO2-GA
Take 50mg GO, ultrasonically disperse it in 10ml H2O and add a certain
amount of catalyst (10mg, 20mg, 30mg), disperse evenly, then add
100mg L-ascorbic acid, dissolve completely, in 100°C water bath The
reaction was carried out for 30 minutes, and then directly frozen at -40 °C
for 1 hour. The water bath was again taken out at 100°C for 8 hours.
After the reaction was completed, the excess water in the container was
sucked out with a pipette, and finally freeze-dried.
(Zn(CH3COO)2·2H2O) was purchased from Sinopharm Chemical
ReagtenCo., Ltd. (China). Formaldehyde were purchased from Messer
Air Liquide, Ltd. (China).
Characterizations.
SEM and TEM images were received by Hitachi S-4700 and FEI Tecnai
G-20 microscopes, respectively. High resolution TEM images were
obtained by FEI Tecnai F-20. The crystal phase was analyzed by X-ray
diffraction (XRD) (X'Pert-Pro MPD) and high resolution TEM (HRTEM).
The elemental composition of Pt/ZrO2-GA-MOF-5 was determined by
XPS (ESCALAB 250Xi) and energy dispersive X-ray (EDX) spectroscopy,
which was obtained by FEI Tecnai F-20 microscope. The stability and
composition of Pt/ZrO2, Pt/ZrO2-GA, MOF-5 and Pt/ZrO2-GA-MOF-5
were analyzed by TGA (TG209 F1 Libra). The test for catalytic
degradation performance was carried out in a fixed bed reactor. The
concentration of HCHO was analyzed in real time by a formaldehyde
detector (formaldehyde meter, PPM-400 ST).
Preparation of Pt/ZrO2-GA-MOF-5
The surface of Pt/ZrO2/GA was modified with succinic anhydride and
KH550 (3-aminopropyltriethoxysilane). The carboxylation reaction of the
prepared Pt/ZrO2/GA is first carried out. The aerogel was immersed in 1
ml KH550 solution (KH550: ethanol =1:10, volume ratio) and placed on a
shaker for 8 hours. Then Pt/ZrO2/GA was immersed in 0.50 g of succinic
anhydride/10 ml of DMF and placed on a shaker for another 8 hours.
After the reaction is completed, it is rinsed several times with DMF. In
order to modify the MOF on the surface of the aerogel, we prepared two
solutions in advance for use. First, take 0.51g of terephthalic acid, 0.85ml
of triethylamine, 40ml of DMF, and mix the three to form a solution;
secondly, take 1.70g of zinc acetate (Zn(CH3COO)2·2H2O), 50ml of DMF
into a solution. Pt/ZrO2/GA was first soaked in 10 ml of zinc acetate
solution, placed on a shaker for 30 mins; washed several times with DMF,
then soaked in 10 ml of terephthalic acid solution, and placed on a
shaker for 2 hours. This process alternates 4 times. The DMF in the
aerogel was then replaced with absolute ethanol and finally lyophilized to
give the final product.
Preparation of SBA-15-OH
130 ml of ultrapure water and 20 ml of concentrated hydrochloric acid (37
wt.%) were mixed to make dilute hydrochloric acid, 4.00 g of P123 was
added and stirring was continued to completely dissolve in dilute
hydrochloric acid, and then 8.320 g of TEOS was slowly added dropwise.
And stirring at 38°C for 24 hours; then the mixture was hydrothermally
reacted at 110°C for 24 hours. After the reaction was completed, the
mixture was suction filtered to obtain a precipitate, which was dried at
Catalytic oxidation of HCHO
80°C. The dried precipitate was slowly added to a mixture of 120 ml of
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Chemistry - A European Journal
10.1002/chem.201904426
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A temperature controlled fixed bed reactor containing a U-shaped quartz
tube was used to catalyze the oxidation of HCHO. Typically, 50 mg of
catalyst (in terms of Pt/ZrO2) was placed in the reactor, then one end was
passed through HCHO (20 ml/min, 50 ppm, balanced in air) and the
other end was connected to an exhaust collection bag. The concentration
of HCHO was measured once every 10°C rise in temperature. The
concentration of HCHO was analyzed using a formaldehyde detector
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Chemistry - A European Journal
10.1002/chem.201904426
FULL PAPER
A Pt/ZrO
2
-GA was prepared
Haocun
Tan,[1]
Dongyun
as catalyst that can
a
Chen,*[1] Najun Li,[1] Qingfeng
Xu,[1] Hua Li,[1] Jinghui He,[1]
and Jianmei Lu* [1]
absorb and catalytically
oxidize HCHO at low
temperature. The MOF-5
was used to modify the
surface of the catalyst and
enhanced
adsorbability.In addition, the
pores of graphene aerogel
Page No. – Page No.
Platinum-supported
its
zirconia nanotube arrays
supported on graphene
aerogels modified with
metal-organic frameworks:
adsorption and oxidation of
(
GA)-supported
material
that facilitate diffusion of gas
molecules and increase
reaction rate.
formaldehyde
temperature
at
room
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