One-step fabrication of CuO-doped TiO2nanotubes enhanced the catalytic activity of Pt nanoparticles towards the methanol oxidation reaction in acid media

Article abstract of DOI:10.1039/d1nj00095k

To meet the requirements for the potential applications of fuel cells, it is of vital importance to search for advanced electrocatalysts toward the methanol oxidation reaction (MOR) that have both high electrocatalytic activity and great CO resistance. In this work, we herein report the fabrication of a novel class of Pt-CuO-TiO₂/C catalyst and discover that the as-obtained nanocatalyst exhibited excellent electrocatalytic properties for the MOR. Remarkably, the mass activity is as high as 1537.3 mA mg_Pt^?1, showing 6.0- and 2.75-fold enhancements compared with the reference Pt-C-H and Pt-TiO₂/C catalysts, respectively. Except the superb electrocatalytic activity, it is also demonstrated that such Pt-CuO-TiO₂/C has outstanding electrochemical stability and great tolerance to CO poisoning, representing an advanced electrocatalyst for use in fuel cells.

Full text of DOI:10.1039/d1nj00095k

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One-step fabrication of CuO-doped TiO2
nanotubes enhanced the catalytic activity of Pt
nanoparticles towards the methanol oxidation
reaction in acid media†
Cite this: New J. Chem., 2021,
45, 5872
Qinglan Fu, Mengyu Gan,* Li Ma, * Shuang Wei, Taichun Wu, Yanling Yang,
Tingting Li, Wang Zhan, Fei Xie and Xiujuan Zhong
To meet the requirements for the potential applications of fuel cells, it is of vital importance to search
for advanced electrocatalysts toward the methanol oxidation reaction (MOR) that have both high
electrocatalytic activity and great CO resistance. In this work, we herein report the fabrication of a novel
class of Pt–CuO–TiO2/C catalyst and discover that the as-obtained nanocatalyst exhibited excellent
À1
electrocatalytic properties for the MOR. Remarkably, the mass activity is as high as 1537.3 mA mgPt
,
Received 7th January 2021,
Accepted 4th March 2021
showing 6.0- and 2.75-fold enhancements compared with the reference Pt–C–H and Pt–TiO2/C
catalysts, respectively. Except the superb electrocatalytic activity, it is also demonstrated that such
Pt–CuO–TiO2/C has outstanding electrochemical stability and great tolerance to CO poisoning,
representing an advanced electrocatalyst for use in fuel cells.
DOI: 10.1039/d1nj00095k
rsc.li/njc
of effective strategies have been successfully developed.11–13
One of the most promising approaches is to introduce appropriate
1. Introduction
Direct methanol fuel cells (DMFCs) are small, lightweight, and catalyst supports, in which the introduced catalyst supports could
long-lasting portable power sources that show great promise not only help to uniformly disperse the catalyst nanoparticles to
for competing with current battery technology. However, the avoid the sintering and aggregation during the electrochemical
development of DMFCs and their practical applications are reactions, but also significantly enhance the electrical conductivity
significantly hindered by the lack of effective electrocatalysts of the catalysts to accelerate the charge transfer.14–16 Moreover,
for the methanol oxidation reaction (MOR) that occurs at the some interesting catalyst supports have also been demonstrated
anode.1–4 Therefore, developing robust electrocatalysts for the to be active toward the MOR, which could thus synergistically
anodic MOR is essential for the fabrication of commercially promote the electrocatalytic performance.17,18 In consideration of
viable DMFCs. Regarding anodic electrocatalytic reactions, Pt these favorable terms, many materials, including carbon
and Pd have been extensively considered as promising electro- materials,19,20 transition metal compounds,21,22 MXene,23–25 and
catalysts owing to their inherently high intrinsic activity; conductive polymers,26 have been employed as promising
however, their high cost and vulnerability to CO poisoning supports to greatly boost the electrochemical reactions. To date,
greatly diminish their wide practical application.5–7 Besides, carbon materials have been the typical supports for electro-
another main factor that limits the commercial application of chemical reactions owing to their high specific surface area, rich
DMFCs is their unsatisfactory life span, originating from the anchoring sites for stabilizing catalyst nanoparticles, and
corrosion of carbon materials in harsh environments, which high electrical conductivity.27–29 Despite these beneficial factors,
would inevitably lead to the agglomeration and sintering of the carbon supports still undergo the corrosion phenomenon in
Pt or Pd catalyst nanoparticles.8–10 To overcome this drawback, harsh environments, which may greatly decrease the electro-
numerous endeavors have been made, aiming to improve the catalytic performance of the catalyst nanoparticles.
electrochemical durability of electrode materials. With the
Recently, metal oxides have been utilized as promoters of Pt
intensive efforts that have been devoted to this area, a series catalysts toward fuel cell-related electrochemical reactions by
using them as the ideal supports. For one thing, metal oxides
can also uniformly disperse the catalyst nanoparticles to expose
College of Chemistry & Chemical Engineering, Chongqing University,
more surface active sites.30,31 For another, metal oxides can
Chongqing 400044, P. R. China. E-mail: mlsys404@126.com, mlsys607@126.com
provide rich hydroxyl groups and oxygen-species release for
electrochemical reactions, consequently alleviating the influence
† Electronic supplementary information (ESI) available. See DOI: 10.1039/
d1nj00095k
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of CO-like poisoning. Among various metal oxides, titanium dispersed into 20 mL of H2O, followed by ultrasonication for
dioxide (TiO2) has been widely regarded as a promising support 30 min to form a homogeneous CuO–TiO2/C slurry; 25 mg of
for Pt electrocatalysts for fuel cells because of its excellent trisodium citrate dehydrate was dissolved into 6 mL of distilled
stability in both acidic and basic solution.32,33 More importantly, water with magnetic stirring for 15 min to form a uniform
the TiO2 with hypo-d-electron character can also induce a strong solution. After that, 0.525 mL of 48.803 mM H2PtCl6–ethylene
metal–support interaction, which is beneficial for improving the glycol was injected into the above solution dropwise to obtain
electrochemical stability of the catalysts.34,35 Nevertheless, the an aqueous H2PtCl6 solution; 3.5 mg of NaBH4 was added into
lower electrical conductivity compared to conventional carbon 8 mL of H2O to form an NaBH4 water solution. Secondly,
supports limits their commercial applications in fuel cells. the H2PtCl6 mixed solution was injected dropwise into the
Therefore, exploring effective routes to ameliorate these CuO–TiO2/C suspension, and then sodium borohydride
weaknesses is highly imperative and meaningful for the future aqueous solution was mixed with the above solution, followed
development of DMFCs.36,37 Generally, doping TiO2 with by constant stirring for 24 h. The collected precipitate was dried
metal elements or introducing another metal oxide has been at 60 1C for 4 h to obtain Pt–CuO–TiO2/C. Furthermore, the
demonstrated to be an effective strategy for shortening the identical procedure was also employed to obtain Pt–TiO2/C and
bandgap of TiO2 and positively affecting the electrocatalytic Pt–C–H (home-made).
performance of catalysts.38–41
2.3. Electrochemical measurements
Guided by the above rules, we herein developed a facile
method for the fabrication of a novel class of Pt–CuO–TiO2/C
nanotubes with modified electronic structure, which could
function as promising catalyst supports for boosting the electro-
catalytic performance of Pt–C–H. Consequently, a mass activity
as high as 1537.3 mA mgPtÀ1 could be achieved at peak potential,
being correspondingly 6.0 and 2.75 times higher than those of
Pt–C–H (256.2 mA mgPtÀ1) and Pt–TiO2/C (558.7 mA mgPtÀ1).
More importantly, such a Pt–CuO–TiO2/C catalyst also displayed
excellent electrochemical stability, with good tolerance to CO
poisoning and resistance to agglomeration for long-duration
electrochemical operations.
Electrochemical measurements were carried out using a CHI
760E electrochemical instrument equipped with a classic three-
electrode system. The catalytic inks were prepared as follows: 2
mg of the catalyst was poured into 1 mL of solution (VH O
:
2
VC H OH = 1 : 1), and then 50 mL of 5 wt% Nafion solution was
2
5
dripped into the solution. After sonicating to obtain a uniform
ink, 5 mL of the catalyst ink was carefully dripped onto the
working electrode. All electrolytes were purified for at least
15 min in high-purity N2 before measurement.
2.4. Physical characterization
A scanning electron microscope (FE-SEM, JEOL JSM-7800F) and
a field emission transmission electron microscope (FE-TEM,
Talos F200S) were utilized to explore the morphological and
structural features. The surface element compositions and
chemical states of the samples were detected by X-ray photo-
electron spectroscopy (XPS, ESCALAB 250Xi) measurement
using a monochromatic Al-Ka X-ray source. Powder X-ray
diffraction (XRD) patterns were obtained using an XRD instrument
(RINT2000, Rigaku) with Cu-Ka radiation.
2. Experimental
2.1. Chemicals and materials
Vulcan XC-72R carbon black, trisodium citrate dehydrate,
sulfuric acid (Z95%), methanol, TiO2 nanopowder, ethanol
(C2H5OH, 99.7%), sodium borohydride, copper nitrate trihydrate
(Cu(NO3)2Á3H2O) and other chemical agents were all brought
from Kelong Chemical Reagent Company (Chengdu, China).
Hexachloroplatinic acid (H2PtCl6Á6H2O, 99.9%) was provided
by the First Reagent Factory (Shanghai, China). Nafion solution
was purchased from Chongqing Ruixing Co. Ltd. All Chemicals
are analytical reagent grade.
3. Results and discussion
Pt–CuO–TiO2/C was synthesized through a facile two-step wet
chemical method, in which the CuO–TiO2 was firstly synthesized
through a simple hydrothermal method. Subsequently, the
2.2. Material preparations
2.2.1. Preparation of CuO–TiO2 nanotubes. 6 g of NaOH Pt–CuO–TiO2/C was prepared by reducing the Pt precursor
was dissolved in 20 mL of ultrapure water, followed by the employing NaBH4 as the reductant. A series of advanced
addition of 0.5 g of TiO2 and 2.265 g of Cu(NO3)2Á3H2O. characterizations, including SEM, TEM, elemental EDS mapping,
The above suspension was ultrasonicated for 40 min. After that, XRD, and XPS, was conducted to systematically analyze the
the slurry was transferred to a 100 mL Teflon-lined autoclave and morphological and structural features. From Fig. S1 (ESI†), it
maintained at 150 1C for 24 h. Subsequently, the as-prepared can be clearly seen that the as-obtained TiO2 treated by NaOH
brown product was collected by centrifugation and washed with features the typical nanotube-like structure. After the deposition
ethanol and ultrapure water. The obtained product was dried at of the carbon and Pt nanoparticles, the SEM images show many
55 1C overnight. Similar procedures were employed for the unique clusters, suggesting the successful formation of Pt–CuO–
synthesis of Pt–TiO2@C, but in the absence of Cu(NO3)2Á3H2O.
TiO2/C (Fig. S2, ESI†). In addition to the SEM images, TEM images
2.2.2. Preparation of Pt–CuO–TiO2/C hybrid material. 20 mg were also obtained. As shown in Fig. 1A and B, the as-prepared
of the mixture of CuO–TiO2 and carbon black was uniformly samples were composed of the distinctive nanotubes and carbon
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(200), TiO2(111), Pt(111) and Pt(200) planes, respectively. The
HAADF-STEM image also shows the TiO2 nanotube-supported
Pt nanocatalyst, which was consistent with the TEM and SEM
results. In order to further confirm the formation of the Pt–CuO–
TiO2/C composite, we also conducted TEM-EDS characterization.
As shown in Fig. 1D, the elemental EDS mapping suggested that
Cu (blue), O (green), Ti (purple) and Pt (yellow) elements were
uniformly scattered throughout the whole sample. The TEM-EDS
spectrum of the Pt–CuO–TiO2/C composite is shown in Fig. 2A. As
illustrated in Fig. 2A, the typical peaks for C, O, Pt, Ti, and Cu
atoms could be clearly observed, being consistent with the
TEM-EDS elemental mapping results. Besides, the crystal phase
of the Pt–CuO–TiO2/C composite was characterized by XRD
(Fig. 2B), showing many strong XRD diffraction peaks, which
could be assigned to the TiO2 (JCPDS no. 82-0514), CuO (PDF#80-
1916), and Pt (JCPDS no. 87-0647).42 The crystal phase results
from the XRD analysis are consistent with the SAED results
(Fig. S3, ESI†). For comparison, the XRD pattern of the CuO–TiO2
nanotubes was also obtained. From Fig. S4 (ESI†), it can be clearly
seen that the XRD peaks of the sample could be assigned to the
CuO (PDF#80-1916) and TiO2 (PDF#82-0514), further indicating
the successful fabrication of the CuO–TiO2 nanotubes.
As is well known, the surface composition as well as the
chemical state are crucial for determining the ultimate electro-
catalytic properties.43,44 Therefore, gaining insight into the
surface composition and chemical oxidation state of the
Pt–CuO–TiO2/C is essential for understanding their influence on
the electrocatalytic properties. In this case, we used XPS technol-
ogy to detect the surface composition and oxidation state. Fig. 3A
shows the XPS survey spectrum of the Pt–CuO–TiO2/C. As can be
seen in Fig. 3A, the typical XPS peaks at the binding energies
around 70, 460, 530, and 940 eV are assigned to the Pt 4f, Ti 2p,
O 1s, and Cu 2p, respectively, which also indicated the formation
of the Pt–CuO–TiO2/C composite. Besides the survey spectrum,
the high-resolution XPS spectra of Pt 4f, Cu 2p, Ti 2p, and O 1s are
also shown in Fig. 3. As can be seen in Fig. 3B, the XPS spectrum
of Pt 4f can be deconvoluted into two strong peaks and four weak
peaks, in which the two strong peaks at the binding energies of
71.3 and 74.7 can be assigned to the metallic Pt of Pt 4f7/2 and Pt
4f5/2, while the other weak peaks are associated with the oxidative
Pt.45,46 Fig. 3C shows the Pt 4f XPS spectra of Pt–TiO2/C and
Pt–CuO–TiO2/C. As observed, the Pt 4f spectrum of Pt–CuO–TiO2/
C is positively shifted to higher binding energy as compared to the
Fig. 1 Morphology and chemical composition characterizations of
the Pt–CuO–TiO2/C catalyst. (A–C) Representative TEM images of the
Pt–CuO–TiO2/C catalyst. (D) HAADF-STEM and TEM-EDS elemental
mapping images of the Cu (blue), O (green), Ti (purple),and Pt (yellow)
atoms in the Pt–CuO–TiO2/C composite.
black that were loaded with the uniform nanoparticles, suggesting
that the Pt nanoparticles were uniformly dispersed on the surface
of carbon black to not only expose rich surface active centers, but
also greatly stabilize the Pt nanoparticles. The HRTEM image is
displayed in Fig. 1C; the measured lattice spacings of 0.2254 nm,
0.2195 nm, 0.2239 nm and 0.1939 nm originated from the TiO2
Fig. 2 Composition and structure characterization of the Pt–CuO–TiO2/C.
(A) TEM-EDS spectrum of the Pt–CuO–TiO2/C. (B) XRD pattern of the
Pt–CuO–TiO2/C.
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Fig. 4 (A) CV curves of the Pt–C–H, Pt–CuO–TiO2/C, and Pt–TiO2/C
catalysts in 0.5
values per catalyst. (C) MOR curves of the Pt–C–H, Pt–CuO–TiO2/C,
and Pt–TiO2/C catalysts in 0.5 H2SO4 CH3OH solution.
M H2SO4 solution. (B) The corresponding ECSA
M
+ 1 M
(D) Histogram of the mass activities of the Pt–C–H, Pt–CuO–TiO2/C,
and Pt–TiO2/C for the MOR.
specific activity can be calculated and the results are shown
in Table 1. Obviously, Pt–CuO–TiO2/C possessed the best
specific activity, which is 1.96 times and 3.4 times higher than
those of the Pt–TiO2/C and Pt–C–H catalysts, respectively. This
enhancement in ECSA and specific activity can be ascribed to
the optimization of the electronic structure after the CuO
doping, and the synergistic contributions of the TiO2 nanotubes
and carbon black. The anodic MOR was also employed as the
model reaction to evaluate the electrocatalytic performances of
different catalysts. Fig. 4C shows the MOR curves of the Pt–C–H,
Pt–CuO–TiO2/C, and Pt–TiO2/C catalysts in 0.5 M H2SO4 solution
containing 1 M CH3OH. As shown in Fig. 4C, the MOR curves
included two typical oxidation peaks, in which the peak that
appeared at the potential of around 0.7 V (versus SCE) was
assigned to the oxidation of methanol, while the other one at
the potential of around 0.4 V is associated with the further
oxidation of intermediates. Pt–CuO–TiO2/C clearly shows much
higher oxidation peaks as compared to the benchmarked
Pt–C–H and Pt–TiO2/C. For comparison, the mass activities of
these three electrocatalysts are summarized in Fig. 4D. As shown
in Fig. 4D, Pt–CuO–TiO2/C could deliver a high mass activity of
Fig. 3 Surface composition and oxidation state characterizations. (A)
Survey XPS spectrum of the Pt–CuO–TiO2/C. (B) High-resolution XPS
spectra of the Pt 4f in Pt–CuO–TiO2/C. (C) Pt 4f comparison of Pt–TiO2/C
and Pt–CuO–TiO2/C. High-resolution XPS spectra for (D) Cu 2p, (E) Ti 2p,
and (F) O 1s in Pt–CuO–TiO2/C composition.
Pt–TiO2/C, suggesting that the introduction of Cu could greatly
optimize the electronic structure of Pt. Fig. 3D shows the Cu 2p
XPS spectrum, which can be divided into two strong peaks
presented at the binding energies of 932.6 and 952.6 eV, corres-
ponding to the Cu 2p3/2 and Cu 2p1/2, and one oscillating satellite
peak (942.5 eV), suggesting the successful doping of Cu into
TiO2.47 Furthermore, the high-resolution XPS spectrum of Ti 2p
was also obtained and is shown in Fig. 3E. The two peaks at the
binding energies of 458.6 and 464.3 eV are assigned to the Ti 2p3/2
and Ti 2p1/2, respectively.48–50 The high-resolution XPS spectrum
of O 1s is displayed in Fig. 3F, showing that the O 1s XPS peaks are
associated with the TiO2. The XPS analyses further demonstrated
the successful fabrication of Pt–CuO–TiO2/C and suggested that
the doping of Cu could effectively modify the electronic structure
of TiO2 and thus boost the electrocatalytic performance.
1537.3 mA mgPtÀ1, giving 6.0- and 2.75-fold enhancements
À1
compared to Pt–C–H (256.2 mA mgPt
) and Pt–TiO2/C
(558.7 mA mgPtÀ1), suggesting the outstanding electrocatalytic
performance of the Pt–CuO–TiO2/C catalyst. Table 2 lists the
mass activity from other relevant research in methanol electro-
oxidation for comparison. The high electrocatalytic activity of
The electrochemical properties of the resulting Pt–CuO–
TiO2/C catalyst were systematically investigated and bench-
marked against the Pt–TiO2/C and Pt–C–H catalysts. The cyclic
voltammogram (CV) measurements for the Pt–CuO–TiO2/C,
Pt–TiO2/C, and Pt–C–H catalysts were firstly conducted in
0.5
M H2SO4 solution at a .
scan rate of 50 mV sÀ1
Table 1 Summary of the ECSA and specific activity of Pt–CuO–TiO2/C,
Pt–TiO2/C and Pt–C–H catalysts
The electrochemical active surface areas (ECSAs) of these
electrocatalysts were calculated according to the hydrogen
adsorption/desorption peaks in the CV curves.19,51,52 As shown
in Fig. 4B, Pt–CuO–TiO2/C possessed the highest ECSA of up to
103.2 m2 gPtÀ1, relatively larger than those of Pt–TiO2/C
(73.3 m2 gPtÀ1) and Pt–C–H (59.7 m2 gPtÀ1). Therefore, the
À2
Sample
ECSA (m2 gÀ1
)
Specific activity (mA cmPt
)
Pt–TiO2–CuO/C
Pt–TiO2/C
Pt–C–H
103.2
73.3
59.7
1.49
0.76
0.43
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Table 2 Summary of the mass activity for Pt–TiO2–CuO/C and Pt–TiO2/C catalysts and other correlative work reported recently in methanol
electrooxidation
À1
Catalyst
Mass activity (mA mgPt
)
Conditions
Ref.
Pt–TiO2–CuO/C
Pt–TiO2/C
Pt–NRCeO2/GNs
Pt/CeO2/PANI
Pt/TiO2@NC-NCNTs
Pt/Co@NCNTs-MC
Pt/DSCT
Pt/LP-TiO2/CFP
Pt/TiC NWs
PtNi CNCs
1537.3
558.7
498
400
577
700.3
462
1182.8
360
696
688
0.5 M H2SO4 + 1 M CH3OH
0.5 M H2SO4 + 1 M CH3OH
0.5 M H2SO4 + 0.5 M CH3OH
0.5 M H2SO4 + 0.5 M CH3OH
0.5 M H2SO4 + 1 M CH3OH
1 M H2SO4 + 1 M CH3OH
0.5 M H2SO4 + 1 M CH3OH
0.5 M H2SO4 + 1 M CH3OH
0.5 M H2SO4 + 1 M CH3OH
0.5 M H2SO4 + 1 M CH3OH
0.5 M H2SO4 + 1 M CH3OH
1 M H2SO4 + 1 M CH3OH
This work
This work
53
54
55
56
57
58
59
60
61
62
Pt-HPCS@CoP/NC
Pt/WN/CNT-rGO
702.4
Pt–CuO–TiO2/C is ascribed to the exposure of rich surface active Fig. 7A–C, Pt–CuO–TiO2/C showed no obvious changes or
sites, optimization of the electronic structure after the Cu serious Pt NP aggregation. In conclusion, the introduction of
doping, and the synergistic contributions of the TiO2 nanotubes CuO–TiO2 can enhance the interaction between the catalytic
and carbon black.
species and the carrier, and thus alleviate catalytic aggregation.
Furthermore, the origin of the promoted MOR stability for
In addition to the MOR activity, the electrochemical
durability is also another crucial factor determining the future Pt–CuO–TiO2/C was studied in detail. Normally, the durability
prospects of the developed catalyst in fuel cells.63 To this end, of the anode electrocatalysts toward MOR is easily destroyed
we herein conducted chronoamperometric (CA) tests to by some poisonous intermediates, such as CO and HCHO.
evaluate its electrochemical stability by utilizing the Pt–C–H Therefore, we conducted CO stripping experiments to evaluate
and Pt–TiO2/C catalysts as benchmarks. Fig. 5A shows the CA the antipoisoning capability of the electrocatalyst.64–66 As seen
curves of the different catalysts in 0.5 M H2SO4 + 1 M CH3OH in Fig. 8, the Pt–CuO–TiO2/C exhibited a peak potential of CO
solution. As can be seen, the Pt–CuO–TiO2/C showed much oxidation at 633 mV, which was much lower than those for
higher current density as compared to the Pt–C–H and Pt–TiO2/C Pt–C–H (659 mV) and Pt–TiO2/C (649 mV), suggesting the great
catalysts over time, indicating the high electrochemical stability. tolerance of CO by Pt–CuO–TiO2/C. More importantly, we found
For easy comparison, the retained current densities of these that the onset potential of CO oxidation on Pt–CuO–TiO2/C was
electrocatalysts after a continuous 3600 s CA test are also 575 mV, which was more negative than those for Pt–C–H
summarized in Fig. 5B. As shown in Fig. 5B,Àt1he Pt–CuO–TiO2/ (611 mV) and Pt–TiO2/C (599 mV), further demonstrating the
C retained a current density of 70.6 mA mgPt after the 360À01s strong antipoisoning ability of Pt–CuO–TiO2/C for CO.
test, being much higher than those of Pt–C–H (9.8 mA mgPt
)
The improvement of CO tolerance mainly depends on the
and Pt–TiO2/C (16.5 mA mgPtÀ1), revealing the enhanced electro- synergistic mechanism of the catalyst. The feasible reaction
chemical stability of the Pt–CuO–TiO2/C catalyst. Meanwhile, the mechanism of methanol oxidation on Pt–CuO–TiO2/C can be
catalytic durability of the Pt–CuO–TiO2/C and Pt–C–H catalysts described via the following reaction equations:
was researched using the accelerated durability test (ADT), as
Pt + CH3OH - Pt–(CO)ads + 4H+ + 4eÀ
TiO2 + H2O - TiO2–OH + H+ + eÀ
(1)
shown in Fig. 6A and B. Fig. 6C shows that the Pt–CuO–TiO2/C
catalyst exhibits a lower ECSA loss ratio compared to the Pt–C–H
catalyst after the 1000 cycles CV test, which further verified the
better durability of the Pt–CuO–TiO2/C.
(2)
TiO2–OH + Pt–(CO)ads - Pt + TiO2 + CO2 + H+ + eÀ
(3)
TEM was used to probe the morphology and structure of the
Pt–CuO–TiO2/C catalyst after the ADT. As can be seen in
Primarily, methanol dehydrogenates mainly on Pt active sites,
producing many intermediate products CO and chemisorbing
Fig. 6 CVs of the (A) Pt–CuO–TiO2/C and (B) Pt–C–H catalysts before
and after 1000 cycles in 0.5 M H2SO4 solution. (C) Comparison of ECSA
remaining and loss ratio for the Pt–CuO–TiO2/C and Pt–C–H catalysts
after 1000 cycles CV test.
Fig. 5 (A) CA curves of Pt–C–H, Pt–CuO–TiO2/C, and Pt–TiO2/C in
0.5 M H2SO4 + 1 M CH3OH solution. (B) Magnified CA curves of Pt–C–H,
Pt–CuO–TiO2/C, and Pt–TiO2/C.
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that these results can boost the study of metal oxide-supported
catalysts for fuel cell reactions and accelerate the rapid
development of fuel cells.
Conflicts of interest
Fig. 7 TEM images of Pt–CuO–TiO2/C (A–C) after 1000 cycles CV test.
There are no conflicts to declare.
Acknowledgements
This work was financially supported by the National Natural
Science Foundation of China (Grant No. 21676034).
References
Fig. 8 CO stripping experiments for (A) Pt–C–H, (B) Pt–TiO2/C, and (C)
Pt–CuO–TiO2/C in 0.5 M H2SO4 solution.
1 X. Luo, C. Liu, X. Wang, Q. Shao, Y. Pi, T. Zhu, Y. Li and
X. Huang, Nano Lett., 2020, 20, 1967–1973.
2 T.-J. Wang, F.-M. Li, H. Huang, S.-W. Yin, P. Chen, P.-J. Jin
and Y. Chen, Adv. Funct. Mater., 2020, 2000534.
3 H. Xu, H. Shang, C. Wang, L. Jin, C. Chen and Y. Du,
Nanoscale, 2020, 12, 2126–2132.
4 H. Shang, H. Xu, C. Wang, L. Jin, C. Chen, G. Zhou, Y. Wang
and Y. Du, Nanoscale, 2020, 12, 3411–3417.
5 L. Jin, H. Xu, C. Chen, H. Shang, Y. Wang, C. Wang and
Y. Du, ACS Appl. Mater. Interfaces, 2019, 11, 42123–42130.
6 K. Maiti, J. Balamurugan, S. G. Peera, N. H. Kim and
J. H. Lee, ACS Appl. Mater. Interfaces, 2018, 10, 18734–18745.
7 J. Fan, S. Yu, K. Qi, C. Liu, L. Zhang, H. Zhang, X. Cui and
W. Zheng, J. Mater. Chem. A, 2018, 6, 8531–8536.
8 B. E, Q. Shao, L. Bu, S. Bai, Y. Li and X. Huang, Adv. Energy
Mater., 2018, 8, 1703430.
9 Y. Sun, Y. Liang, M. Luo, F. Lv, Y. Qin, L. Wang, C. Xu, E. Fu
and S. Guo, Small, 2018, 14, 1702259.
10 A. Mahmood, N. Xie, M. A. Ud Din, F. Saleem, H. Lin and
X. Wang, Chem. Sci., 2017, 8, 4292–4298.
on Pt surface (Pt–(CO)ads) (eqn (1)).67,68 In the meantime,
Because TiO2 is naturally
a hydrophilic substance, H2O
molecules can be dissociated. Owing to water decomposition
on the surface of the TiO2, abundant hydroxyl groups are
adsorbed to the surface of TiO2 in acidic electrolytes (TiO2–OH)
(eqn (2)).69 The TiO2–OH can quickly oxidize COads species to CO2
(eqn (3)), which is conducive to the release of free Pt active sites in
the electrooxidation process of methanol.58
Thus, the Pt–CuO–TiO2/C catalyst displays not only high
electrocatalytic activity but also excellent electrochemical stability
toward MOR in acidic solution. After a series of advanced
characterizations and mechanism studies, have found that the
excellent electrocatalytic properties were attributed to the intro-
duction of CuO–TiO2 nanotubes. For one thing, the nanotube-like
TiO2 could provide rich surface active sites available for reactants
and intermediates. For another, the Cu doping lowered the
bandgap and modified the electronic structure of the TiO2,38–41
leading to enhanced electrocatalytic activity and stability toward
the MOR in a harsh environment.
11 L. N. Zhou, X. T. Zhang, Z. H. Wang, S. Guo and Y. J. Li,
Chem. Commun., 2016, 52, 12737–12740.
12 D.-X. Yu, A.-J. Wang, L.-L. He, J. Yuan, L. Wu, J.-R. Chen and
J.-J. Feng, Electrochim. Acta, 2016, 213, 565–573.
13 S. Jing, X. Guo and Y. Tan, J. Mater. Chem. A, 2016, 4, 7950–7961.
4. Conclusions
To summarize, we have developed a facile wet chemical method 14 X. Peng, D. Chen, X. Yang, D. Wang, M. Li, C. C. Tseng,
for the synthesis of a Pt–CuO–TiO2/C nanocatalyst, in which the
CuO doping in the TiO2 could greatly modify its electronic
R. Panneerselvam, X. Wang, W. Hu, J. Tian and Y. Zhao, ACS
Appl. Mater. Interfaces, 2016, 8, 33673–33680.
structure and significantly promote the tolerance of CO-like 15 R. Li, Z. Ma, F. Zhang, H. Meng, M. Wang, X.-Q. Bao, B. Tang
intermediates. Moreover, the nanotube-like structure enabled and X. Wang, Electrochim. Acta, 2016, 220, 193–204.
the TiO2 to anchor Pt nanoparticles to expose more surface 16 J. Chang, L. Feng, K. Jiang, H. Xue, W.-B. Cai, C. Liu and
active sites, thereby contributing to substantial enhancement in W. Xing, J. Mater. Chem. A, 2016, 4, 18607–18613.
the electrocatalytic performance toward the MOR. Furthermore, 17 X. Xu, Y. Zhou, J. Lu, X. Tian, H. Zhu and J. Liu, Electrochim.
the synergistic effects between the CuO–TiO2 and the carbon Acta, 2014, 120, 439–451.
material greatly promoted the stability of the Pt nanocatalyst for 18 J. R. Rodriguez, R. M. Felix, E. A. Reynoso, Y. Gochi-Ponce,
´
´
˜
the electrocatalytic MOR. All of these electronic and geometric
structure advantages greatly promoted the electrocatalytic
Y. V. Gomez, S. F. Moyado and G. Alonso-Nu´nez, J. Energy
Chem., 2014, 23, 483–490.
performance of the Pt–CuO–TiO2/C nanocatalyst, thereby 19 L. Bu, Q. Shao, B. E, J. Guo, J. Yao and X. Huang, J. Am.
making it a promising electrocatalyst for fuel cells. It is believed Chem. Soc., 2017, 139, 9576–9582.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021
New J. Chem., 2021, 45, 5872–5878
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Paper
20 H. Fan, H. Yu, Y. Zhang, Y. Zheng, Y. Luo, Z. Dai, B. Li, 45 X. W. Li, J. D. Wei, Y. Z. Chai and S. Zhang, J. Colloid
Y. Zong and Q. Yan, Angew. Chem., 2017, 56, 12566–12570. Interface Sci., 2015, 450, 74–81.
21 Z. Li, L. Ye, F. Lei, Y. Wang, S. Xu and S. Lin, Electrochim. 46 C. R. Parkinson, M. Walker and C. F. McConville, Surf. Sci.,
Acta, 2016, 188, 450–460. 2003, 545, 19–33.
22 H. Xu, P. Song, Y. Zhang and Y. Du, Nanoscale, 2018, 10, 47 X. Du, H. Su and X. Zhang, ACS Sustainable Chem. Eng.,
12605–12611. 2019, 7, 16917–16926.
23 Y. Jiang, X. Wu, Y. Yan, S. Luo, X. Li, J. Huang, H. Zhang and 48 L. Ye, Z. Li, L. Zhang, F. Lei and S. Lin, J. Colloid Interface
D. Yang, Small, 2019, 15, e1805474. Sci., 2014, 433, 156–162.
24 C. Hao, Y. Wu, Y. An, B. Cui, J. Lin, X. Li, D. Wang, M. 49 S. B. Chen, X. Li, W. Y. Zhou, S. S. Zhang and Y. P. Fang,
Jiang, Z. Cheng and S. Hu, Mater. Today Energy, 2019, 12,
453–462.
25 V. Ramalingam, P. Varadhan, H. C. Fu, H. Kim, D. Zhang,
S. Chen, L. Song, D. Ma, Y. Wang, H. N. Alshareef and
J. H. He, Adv. Mater., 2019, 31, e1903841.
26 L. Yang, Z. Zhang, G. Nie, C. Wang and X. Lu, J. Mater.
Chem. A, 2015, 3, 83–86.
27 R. Kannan, A. R. Kim, K. S. Nahm, H. K. Lee and D. J. Yoo,
Chem. Commun., 2014, 50, 14623–14626.
Appl. Surf. Sci., 2019, 466, 254–261.
50 Q. Q. Shi, G. C. Ping, X. J. Wang, H. Xu, J. M. Li, J. Q. Cui,
H. Abroshan, H. J. Ding and G. Li, J. Mater. Chem. A, 2019, 7,
2253–2260.
51 Y. Zhu, L. Bu, Q. Shao and X. Huang, ACS Catal., 2020, 10,
3455–3461.
52 N. Zhang, L. Bu, S. Guo, J. Guo and X. Huang, Nano Lett.,
2016, 16, 5037–5043.
53 W. H. Wang, X. L. Lu, M. D. Zhu, Z. Z. Cao, C. H. Li,
Y. F. Gao, L. J. Li and J. R. Liu, Electrochim. Acta, 2015, 176,
1338–1342.
28 Y. Yang, J. Liu, S. Guo, Y. Liu and Z. Kang, J. Mater. Chem. A,
2015, 3, 18598–18604.
29 J. Wang, C. Liu, A. Lushington, N. Cheng, M. N. Banis, 54 H. Xu, A. L. Wang, Y. X. Tong and G. R. Li, ACS Catal., 2016,
A. Riese and X. Sun, Electrochim. Acta, 2016, 210, 285–292. 6, 5198–5206.
30 W. Du, G. Yang, E. Wong, N. A. Deskins, A. I. Frenkel, D. Su 55 M. Jin, S. Y. Lu, X. J. Zhong, H. Liu, H. Liu, M. Y. Gan and
and X. Teng, J. Am. Chem. Soc., 2014, 136, 10862–10865. L. Ma, ACS Sustainable Chem. Eng., 2020, 8, 1933–1942.
31 T. Takashima, K. Hashimoto and R. Nakamura, J. Am. Chem. 56 J. Zhang, R. Wang, X. Hu, Z. Sun, X. Wang, Y. Guo, L. Yang,
Soc., 2012, 134, 1519–1527. M. Lou and P. Wen, Appl. Surf. Sci., 2020, 533, 147319.
32 Z. Jin, Q. Wang, W. Zheng and X. Cui, ACS Appl. Mater. 57 X. Y. Yue, Y. G. Pu, W. Zhang, T. Zhang and W. Gao, J. Energy
Interfaces, 2016, 8, 5273–5279. Chem., 2020, 49, 275–282.
33 N. Su, X. Hu, J. Zhang, H. Huang, J. Cheng, J. Yu and C. Ge, 58 J. Deng, J. Zhang, J. Chen, Y. Luo, Y. Chen, Y. Xue, G. Wang
Appl. Surf. Sci., 2017, 399, 403–410. and R. Wang, J. Electroanal. Chem., 2020, 874, 114468.
34 Z. Zhang, A. Li, S. W. Cao, M. Bosman, S. Li and C. Xue, 59 Z. Qiu, H. Huang, J. Du, X. Tao, Y. Xia, T. Feng, Y. Gan and
Nanoscale, 2014, 6, 5217–5222. W. Zhang, J. Mater. Chem. A, 2014, 2, 8003–8008.
35 A. Naldoni, F. Riboni, M. Marelli, F. Bossola, G. Ulisse, A. Di 60 P. P. Yang, X. L. Yuan, H. C. Hu, Y. L. Liu, H. W. Zheng,
´ˇ
Carlo, I. Pıs, S. Nappini, M. Malvestuto, M. V. Dozzi,
D. Yang, L. Chen, M. H. Cao, Y. Xu, Y. L. Min, Y. G. Li and
Q. Zhang, Adv. Funct. Mater., 2018, 28, 8.
61 H. Zhang, L. Ma, M. Gan, F. Xie, H. He, L. Hu and M. Jiang,
New J. Chem., 2019, 43, 10784–10791.
62 H. Yan, M. Meng, L. Wang, A. Wu, C. Tian, L. Zhao and
H. Fu, Nano Res., 2016, 9, 329–343.
63 H. Xu, P. Song, C. Fernandez, J. Wang, M. Zhu, Y. Shiraishi
and Y. Du, ACS Appl. Mater. Interfaces, 2018, 10,
12659–12665.
R. Psaro, E. Selli and V. Dal Santo, Catal. Sci. Technol.,
2016, 6, 3220–3229.
36 Y. Hu, A. Zhu, C. Zhang, Q. Zhang and Q. Liu, Int.
J. Hydrogen Energy, 2015, 40, 15652–15662.
37 A. Leelavathi, G. Madras and N. Ravishankar, J. Mater.
Chem. A, 2015, 3, 17459–17468.
38 L. F. Pelawi, S. Slamet and T. Elysabeth, in International
Energy Conference Astechnova 2019, ed. A. N. I. Wardana,
S. Purwono and P. H. Liem, Amer Inst Physics, Melville, 64 H. Xu, B. Yan, K. Zhang, C. Wang, J. Zhong, S. Li, P. Yang
2020. and Y. Du, Int. J. Hydrogen Energy, 2017, 42, 11229–11238.
39 S. Qian, S. Pu, Y. Zhang, P. Wang, Y. Bai and B. Lai, 65 Y. Zhu, L. Bu, Q. Shao and X. Huang, ACS Catal., 2019, 9,
J. Environ. Sci., 2021, 100, 99–109. 6607–6612.
40 A. Khlyustova, N. Sirotkin, T. Kusova, A. Kraev, V. Titov and 66 N. Zhang, Y. Zhu, Q. Shao, X. Zhu and X. Huang, J. Mater.
A. Agafonov, Mater. Adv., 2020, 1, 1193–1201.
41 S.-H. Seo and B.-I. Kim, Appl. Sci., 2020, 10, 7334.
42 X. Li, L. Luo, F. Peng, H. Wang and H. Yu, Appl. Surf. Sci.,
2018, 434, 534–539.
Chem. A, 2017, 5, 18977–18983.
67 V. C. Anitha, R. Zazpe, M. Krbal, J. Yoo, H. Sopha, J. Prikryl,
G. Cha, S. Slang, P. Schmuki and J. M. Macak, J. Catal., 2018,
365, 86–93.
43 H. Xu, H. Shang, C. Wang, L. Jin, C. Chen, C. Wang and 68 J. Zhang, L. Ma, M. Gan, S. Fu and Y. Zhao, J. Power Sources,
Y. Du, Appl. Catal., B, 2020, 265, 118605. 2016, 324, 199–207.
44 H. Xu, H. Shang, C. Wang and Y. Du, Adv. Funct. Mater., 69 C. C. Ting, C. H. Liu, C. Y. Tai, S. C. Hsu, C. S. Chao and
2020, 2000793.
F. M. Pan, J. Power Sources, 2015, 280, 166–172.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021
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