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Hollow Platinum Nanospheres and Nanotubes templated by Shear Flow-Induced lipid Vesicles and Tubules and Their Applications on Hydrogen Evolution Yinan Wang, Shenghua Ma, Qingchuan Li, Ying Zhang, Wang Xuejing, and Xiaojun Han ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b00444 • Publication Date (Web): 01 Jun 2016 Downloaded from http://pubs.acs.org on June 2, 2016

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ACS Sustainable Chemistry & Engineering

Hollow Platinum Nanospheres and Nanotubes templated by Shear Flow-Induced lipid Vesicles and Tubules and Their Applications on Hydrogen Evolution Yinan Wang#, Shenghua Ma#, Qingchuan Li, Ying Zhang, Xuejing Wang and Xiaojun Han* State Key Laboratory of Urban Water Resource and Environment, School of Chemical Engineering and Technology, Harbin Institute of Technology, 92 West Da-Zhi Street, Harbin, 150001, China. E-mail: [email protected] *These authors contributed equally to this work. Keywords: Microfluidics, DC8,9PC, Hollow Pt nanospheres, Pt nanotubes, Hydrogen evolution reaction

Abstract Shear rate was utilized for synthesis of 1,2-bis(10, 12-tricosadiynoyl)-sn-glycero-3phosphocholine (DC8,9PC) vesicles and tubules in a microfluidic device. Lipid vesicles and tubules as templates were exploited to fabricate hollow platinum nanospheres and nanotubes, respectively, for the first time in a mild manner. The Pt nanosphere is ~190 nm in diameter with wall thickness of ~32 nm. The Pt nanotube is ~ 280 nm in diameter, ~ 30 µm in length with wall thickness of ~15 nm. The Pt nanospheres and nanotubes as hydrogen evolution reaction (HER)

ACS Paragon Plus Environment

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catalyst both exhibited all-time high HER catalytic activity, with overpotentials of 31 mV and 27 mV at current densities of 10 mA cm-2, Tafel slopes of 23 mV dec-1 and 21 mV dec-1 respectively, in acidic electrolytes. The value of exchange current density of Pt nanosphere and Pt nanotube catalysts are obtained as 0.87, 0.93 mA cm-2 by extrapolating the Tafel plot, which are the largest among all HER catalyst in acidic electrolytes. Their catalytic activity can be maintained for at least 19 hours.

Introduction Over past decade, enormous efforts have been focused on rationally synthesizing nanoscale materials such as wires, rods, belts and tubules due to their potential applications in catalysis,1,2 electronics,3,4 photonics,5,6 and bioengineering.7 So far, the fabrication methods for nanomaterials can be classified into four major groups, i.e., the solvothermal method,8,9 chemical vapor deposition,10,11 template-directed synthesis12-14 and coprecipitation method.15 Among them, template-directed synthesis is a typical and effective method for fabricating nanostructures.16-20 The templates includes hard and soft templates, such as polymeric cores, silica spheres, vesicles, and liquid droplets. In addition, there are some other methods involving electrospinning,21 ultrasound1,22 and microfluidic technology. Microfluidic technology has advantages in continuous and automatic processing, and precise control over synthetic conditions. It has been successfully used for a wide range of material synthesis such as inorganic nanoparticles,4 organic/inorganic hybrid materials.23,24 Hydrogen is regarded as a promising candidate to replace fossil fuel due to its renewable and high energy properties.25,26 Water electrolysis requires effective electrocatalysts for the hydrogen evolution reaction (HER) to attain high current density at low overpotential. Pt nanomaterial is


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the best HER catalysts, which were synthesized by various techniques.27-29 Most of these methods involve the reduction of platinum salts in the presence of organic surfactants or polymeric stabilizers at elevated temperature. Nevertheless, it still remains as significant challenges to develop facile, efficient and economical route for large-scale synthesis of platinum nanostructures with remarkable performance in hydrogen evolution reaction (HER). The

nanoarchitectonics30,31

of

1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine

(DC8,9PC) includes lipid tubules and lipid vesicles. It is typical to form tubules via self-assembly method.32,33 DC8,9PC vesicles were usually formed via extrusion method.34 To the best of our knowledge, DC8,9PC lipid vesicles and tubules haven’t been formed via microfluidic technology yet, as well as there is also no report on using DC8,9PC lipid vesicles as templates for fabricating hollow noble metal microsphere or nanosphere. Herein, we demonstrated a method to fabricate DC8,9PC vesicles and tubules in a Y-shape microfluidic channel by varying total flow rate. The obtained DC8,9PC vesicles/tubules were used as templates to synthesize Pt nanospheres/nanotubes, which showed unprecedented catalytic activity toward hydrogen evolution reaction (HER) under strongly acidic conditions. Experimental section Materials Hexachloroplatinic acid (H2PtCl6·6H2O) was purchased from Shenyang Jinke reagents (China). Formic acid (HCOOH) was purchased from Xilong Chemicals (China). Ethanol and H2SO4 was purchased

from

Tianjin

Reagents

(China).

1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-

phosphocholine (DC8,9PC) were purchased as powders from Avanti Polar Lipids (USA). Texas red-labeled 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine, triethy-lammonium salt


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(TR-DHPE) and fluorescence-labeled 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine N -(7nitro-2-1,3-benzoxadiazol-4-yl) (NBD PE) were obtained from Invitrogen (China). Millipore Milli-Q water with a resistivity of 18.2 MΩ cm was applied for solution preparation in all experiments. Microfluidic experiments were conducted using AL-1000 syringe pumps from world precision instruments (USA). Commercial Pt/C (E-TEK, 20 wt% Pt nanoparticles on Vulcan XC-72 carbon) catalysts were obtained from Sigma-Aldrich. Microfluidic chip fabrication The chip fabrication was described in details elsewhere.35-37 In brief, SU-8 layer (MicroChem, USA) was spun onto the wafers with 100 µm in thickness subsequently followed by soft baking at 65 °C for 10 min and at 95 °C for 30 min, respectively. The wafers were then exposed to UV light (365 nm) through a Y-shape mask with a dose of 550 mJ/cm2, followed by a post baking at 65 °C for 1 min and 95 °C for 10 min respectively. The wafers were developed in microposit EC solvent (Shipley, USA) for 1 min in a sonication bath. The height of SU-8 channel was measured to be 98 ± 4 µm. The masters were then silanized by t(1H,1H,2H,2H- perfluorooctyl)silane using a vapor method. Liquid polydimethylsiloxane (PDMS) was poured onto the master with a 10 : 1 mixture of silicone elastomer base and curing agent (Sylgard 184, Dow Corning, USA). After curing at 80 °C for 4 h, the solid transparent PDMS was easily peeled off from the masters. The inlets and outlets in the PDMS were punched with a blunt needle. The PDMS was then bonded with a glass slide after plasma treatment. Hollow Pt nanosphere and nanotube fabrication The fabrication of hollow Pt nanospheres and nanotubes includes two steps as described below. (1) Lipid vesicle and tubule formation


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Lipid vesicle and tubule formation were conducted in a Y-shape microfluidic device. The main channel is 2 cm long with a width and height of 200 and 100 µm, respectively. The self-assemble process was triggered by 0.3 mg/ml DC8,9PC C2H5OH solution meeting water flow at the junction to enter the main channel in the microfluidic chip. The vesicles or nanotubes were obtained by varying the total flow rate (Qt) of two flows at fixed flow rate ratio of 1:1. At Qt of 140 µl/min, the vesicles were produced, while at Qt of 20 µl/min the lipid nanotubes were obtained. (2) Electroless plating In a typical synthesis, hexachloroplatinic acid (0.003g) and 0.5 ml formic acid (HCOOH) were added simultaneously to 5 ml lipid vesicle/tubule solution. The reactions were both conducted at room temperature up to 16 h with the solutions turning from golden to black color. The Pt nanospheres and nanotubes were successfully fabricated after the lipid templates were removed with ethanol. Characterizations The sizes of lipid vesicles and hollow Pt nanospheres were measured by a Malvern Zetasizer Nano ZSP instrument. Fluorescence microscopy images were obtained from a Nikon 80i fluorescence microscope equipped with a Nikon DS-Fi1 camera. Scanning electron microscope (SEM) was performed with Quanta 200 FEG scanning electron microscopy at an accelerating voltage of 20 kV for characterizing the morphology of the vesicles or tubes. Transmission electron microscopy (TEM) measurements were carried out on H-7650 transmission electron microscope (Hitachi, Japan). Powder X-ray diffraction (XRD) was measured in the reﬂection mode (Cu K radiation) on a D/Max-RB diffractometer. Differential Scanning Calorimeter


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thermogram was carried out on Differential Scanning Calorimeter (DSC1, Switzerland). Fourier transform infrared spectra (FTIR) were acquired from a Thermo Scientific 50 Nicolet iS10 spectrophotometer. Electrochemical measurements were performed with an Autolab electrochemical workstation (PGSTAT320N, Switzerland) at room temperature (25 ℃). A three-electrode electrochemical system was used for LSV measurements with a glassy carbon electrode (4 mm in diameter), a platinum wire, and a saturate calomel electrode (SCE) as working, counter, and reference electrodes, respectively. All the experiments were carried out without activation process at ambient temperature. Potentials were referenced to reversible hydrogen electrode (RHE) by adding a value of (0.242 + 0.059 pH) V. Pt nanosphere and nanotube ink were both prepared by dispersing 2 mg in 400 µl C2H5OH. Then 8 µl of the catalyst ink were dropped onto the freshly polished glassy carbon electrode surface and dried at room temperature. A Nafion solution (5 µl) was cast onto the surface of the catalyst-modified glassy carbon electrode and dried in air. Onset overpotentials were determined based on the beginning of linear regime in the Tafel plot. Results and discussion Preparation of DC8,9PC lipid vesicles/tubes A two-step process was used to fabricate Pt nanospheres and nanotubes, as schematically shown in Figure 1. The process involves self-assembly of lipid vesicle and tubule templates in the microfluidic channel (step 1), and electroless plating templates to form Pt nanospheres and nanotubes followed by template removal (step 2).


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Figure1. Schematic illustration of the fabrication process of Pt nanospheres and nanotubes. (1) Self-assembling lipid molecules into lipid vesicles and tubules at different flow rates. Inlet a and b are for H2O and DC8,9PC C2H5OH solution, respectively. (2) Plating templates to form hollow Pt nanospheres and nanotubes followed by template removing. Generally, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC8,9PC, Figure S1) vesicles and tubules were fabricated by extrusion method38 and precipitation method, respectively.39,40 Microfluidic technology was first time used for DC8,9PC lipid vesicle/tubule formation. In microfluidic channel, the self-assembly of DC8,9PC was triggered by DC8,9PC C2H5OH solution meeting water at the junction. Because of the low Reynolds number in microchannel, the two miscible fluids formed a laminar flows with well-defined mixing.

41

The

diffusive boundaries between the miscible streams provide a precisely regulated environment for the rapid and continuous self-assembly of DC8,9PC. By controlling the flow rate of each fluid, different morphological structures obtained, i.e., vesicles, tubules and their mixtures. The vesicles were generated at volumetric flow rate of

Q DC 8，9 PC =70 µl/min and QH 2O =70 µl/min, as

shown in Figure.2a. The red dots represent vesicles. The red color comes from 1% Tex-red


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DHPE doped in DC8,9PC lipids. The average diameter of vesicles is ~ 164 nm measured by Malvern Zetasizer Nano ZSP instrument. The small size of vesicle also explains why we see dots in Figure 2a. When the volumetric flow rate fell to

Q DC 8，9 PC =10 µl/min and QH 2O =10 µl/min,

lipid tubules appeared, as seen in Figure 2b. The tubules are in big density and in the tens of micrometers in length. The green color comes from 1% NBD PE doped in DC8,9PC lipid tubules. The average length of lipid tubules is approximately 33 µm. When the volumetric flow rates of

Q DC 8，9 PC : QH 2O are 30:30 and 50:50 µl/min, the products contained the mixture of vesicles and tubules. The FTIR spectra of DC8,9PC tubules in Figure S2 showed DC8,9PC bands at 1470 (CH2 scissors), 2849 ( -CH2 stretch), 2919 ( -CH2 stretch) and 1724 cm-1 (C=O stretch) 826 cm-1 (P-O stretch), which are in good agreement with previous results.42 Because the diacetylene groups are in a symmetric environment far from any polar moieties, the C≡C stretching is too weak in the infrared to be invisible. The lipid nanotubules are thermostable below 43.7 ℃ (Figure S3), which is probably determined by the phase transition temperature of DC8,9PC.


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Figure.2. Fluorescence images of vesicles (a) at volumetric flow rate

Q DC 8，9 PC =70 µl/min ,

QH 2O =70 µl/min, and lipid tubules (b) at volumetric flow rate Q DC 8，9 PC = 10 µl/min, QH 2O =10 µl/min. In bulk solution, once water was added to DC8,9PC C2H5OH solution, DC8,9PC tubules appeared quickly by lipid molecule self-assembly into one dimensional structure. In microfluidic condition, the themodynamic stable structure is probably broken by shear rates. In order to understand the formation mechanism of vesicles and tubules, concentration distribution and shear rate corresponding to different volumetric flow rates were simulated using COMSOL Multiphysics 4.3 (Figure 3), with an assumption that the diffusion of two neighboring streams only occurred within two dimensional plane in the transverse direction as an ideal mixing process in laminar flow. Two positions with one close to mixing junction and the other close to outlet in the main channel, i.e., 30 µm and 30 cm far away from the mixing junction, were analyzed specifically. There are obvious transition region of DC8,9PC self-assembling in the microchannel, as seen in figure 3a. The shear rates of corresponding positions at 30 µm and 30 cm away from the mixing junction were simulated. As shown in figure 3b and 3c, the increase of total volumetric flow rates leads to the increase of shear rates in both positions. Hence, we believe that the low flow rate condition was similar to the static situation, consequently the corresponding shear rate had little effect on DC8,9PC self-assembly into tubules. In other words, the DC8,9PC has enough chance to assemble into the tubules under volumetric flow rate of

Q DC 8，9 PC =10 µl/min and QH 2O =10 µl/min. When the volumetric flow rate increased, the corresponding shear rate grew as well, which made the self-assembly process of DC8,9 PC insufficient, thus yielding the mixture of vesicles and tubules. At the condition of

Q DC 8，9 PC = 70


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µl/min and

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QH2O =70 µl/min, the shear rate was large enough to cause DC PC self-assembling 8,9

into vesicles. The variation of shear rate can be easily obtained in a microfluidic device, but impossible in bulk solution. The simulation conducted in our work showed the detailed variation of shear rate in this system, which is also a good demonstration of the difference between the bulk solution and fluid microreactor.

Fiure.3. (a) Images of simulated DC8,9PC concentration distribution profiles at

Q DC 8，9 PC : QH2O

of (1)10:10, (2)30:30, (3)50:50 and (4)70:70 µl/min. (b) and (c) are the corresponding shear rates


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of fluid at the 30 µm and 30 cm far away from the mixing junction of the channel, respectively.

Q DC 8，9 PC : QH 2O is 10:10, 30:30, 50:50 and 70:70 µl/min from bottom to top. Synthesis of hollow Pt nanosphere and Pt nanotube At room temperature, the chemical reduction of H2PtCl6 by HCOOH produced Pt nuclei, which deposited on the surface of lipid vesicles and tubules and acted as active sites for further plating. Then Pt plating was accelerated through an autocatalytic reduction process,43 i.e., Pt nanospheres / nanotubes were grown directly on the surface of the lipid vesicles and tubules, without using any ligands or protecting group,44 which both simplified the synthesis process and was also helpful for accurately controlling the morphology of nanostructures. The structure and morphology of hollow Pt nanospheres and Pt nanotubes were investigated by scanning electron microscopy (SEM), as shown in Figure 4a and b, respectively. Form Figure 4a, it shows average diameter of Pt nanospheres close to 190 nm with smooth surface. Hollow structure of Pt nanosphere with 32 nm wall thickness was clearly seen in the inset of Figure 4a. The size of Pt nanosphere is consisted with that of DC8,9PC vesicle. Similarly, as shown in the top-right inset of Figure 4b, the Pt nanotubes are hollow with wall thickness to be ~15 nm. The hollow Pt nanotubes are typically approximate 280 nm in diameter. Figure 4b shows the Pt nanotubes are about 30 µm in length, which is consistent with the length of the lipid tubule templates. It is also clearly seen that the Pt nanotubes with smooth external and internal surface are open-ended from the bottom-left inset of Figure 4b. Figure S4 shows FTIR measurements of DC8,9PC tubules (red curve), Pt nanotubes with DC8,9PC lipid tubules (black curve) and Pt nanotubes without lipid tubules (blue curve). The characteristic absorption peak at 826 cm-1 of pure was masked to some extent after Pt plating. After removing the template, the characteristic absorption peaks of


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DC8,9PC were disappeared. In addition the peaks at 1724 cm-1 and 1470 cm-1 also disappeared after removing the templates. These results proved that the templates were removed completely. The high-magnification TEM images (Figure S5b) showed that the wall of the Pt hollow nanotubes were actually composed of many inter-connected ultra-thin Pt nanowires with diameters of ~4 nm. The strong diffraction peaks at the Bragg angles of 39.9°, 46.3°, 67.5° and 81.5° in the XRD pattern of Pt nanospheres and nanotubes (Figure 4c) correspond to the (1 1 1), (2 0 0), (2 2 0) and (3 1 1) reflections, respectively, which reveals that the Pt nanospheres and nanotubes exhibit a representative face-centered-cubic (fcc) lattice structure. The energy dispersive spectrum (EDS) analyses of hollow metal nanospheres and nanotubes (Figure 4d and e) suggest that they are both made of Pt element according to the major peaks corresponding to platinum crystal.


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Fig4.SEM images of Pt nanospheres (a) and Pt nanotubes (b). (c) XRD pattern of Pt nanospheres (black curve) and Pt nanotubes (red curve). EDS of Pt nanospheres (d) and nanotubes (e). Electrochemical evaluation of Pt nanospheres/nanotubes as HER catalysts Hydrogen evolution from electrochemical reduction of water is an important component of several emerging clean-energy technologies. It is well known that Pt nanomaterials are the good candidates as catalysts for HER.45 The electrocatalytic HER performance of Pt nanospheres, Pt nanotubes, and commercial Pt/C deposited on the glassy carbon electrodes (GCEs) with the same loading of approximately 0.566 mg cm-2 was investigated in 0.5 M H2SO4 with a scan rate of 2 mV s-1. An optimal HER catalyst is a material that could give the highest current at the lowest overpotential, as well as a low HER onset potential (i.e., the potential at which HER activity


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begins). For comparison, bare GCE was also examined. Figure 5a shows the polarization curves (i-V plot) without IR compensation of bare GCE, Pt nanospheres, Pt nanotubes, and commercial Pt/C modified GCE. The bare GCE shows very poor HER performance (black curve). However Pt nanospheres / nanotubes and commercial Pt/C modified GCE achieved current densities of 10 and 20 mAcm-2 at overpotentials of 31 mV and 39 mV and , 27 mV and 37 mV, and 72 mV and 106 mV respectively, as shown in the inset of figure 5a. These values of Pt nanospheres / nanotubes are better than those of Pt-based HER catalysts in acidic media, such as commercial Pt/C (20 wt % Pt/XC-72) either from our data or reported results 46,47 and Pt/CNT.48 Figure 5b shows the corresponding Tafel plots of the Pt nanosphere, Pt nanotube and commercial Pt/C catalysts, respectively. The linear portions of the Tafel plot are fitted with the Tafel equation (ƞ = a + b log (j), where ƞ is the overpotential, j is the current density and b is the Tafel slope), yielding Tafel slopes of 23 mV, 21 mV and 30.7 mV per dec for Pt nanosphere, Pt nanotube and commercial Pt/C catalysts, respectively. The Tafel slopes are inherent property of catalyst materials and reveal the HER proceeds via a Volmer-Heyrovsy mechanism.49 Besides, a smaller Tafel slope is preferred as it means a faster increase of hydrogen generation rate.50 Notably, the Tafel slopes for Pt nanosphere and Pt nanotube catalysts are lower than 30 mV dec-1 of other Pt-based HER catalysts.51 The value of exchange current density of Pt nanosphere, and Pt nanotube catalysts are calculated to be 0.87, 0.93 mA cm-2 by extrapolating the Tafel plot, which are larger than other catalyst47,52 including commercial Pt/C’s exchange current density (0.44 mA cm-2) in acidic electrolytes. To measure the faradic efficiency, theoretical and practical amounts of H2 production were measured. The theoretical hydrogen production was calculated from galvanostatic electrolysis and practical hydrogen production was measured by a water-gas displacing method. As shown in Figure S6, the theoretical hydrogen production value is almost


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the same with that of practical hydrogen production. So the faradic efficiency was achieved to be ~100%. To evaluate the durability of the Pt nanosphere and Pt nanotube catalysts during electrocatalytic hydrogen evolution in 0.5 M H2SO4, the cathodic current density as a function of reaction time at fixed overpotential was measured. Figure 5c shows Pt nanospheres, Pt nanotubes and commercial Pt/C maintained catalytic activity for at least 19 hours. The current densities of Pt nanospheres and Pt nanotubes decreased a little bit from an initial value of 53, 58 mA/cm2 to 50, 55 mA/cm2 at the end of electrolysis for 19 hours, respectively. The final current densities of Pt nanospheres / nanotubes were higher than commercial Pt/C. It indicated better stability of Pt nanosphere and Pt nanotube catalyst than commercial Pt/C in a long-term electrochemical process. The SEM of Pt nanotubes after HER in Figure S7 shows the Pt nanotubes surface becomes rough but still intact.


15

0 -5

-10

0

-15

-2 -4 -6 -8

-10

-0.15

-0.10

-0.05

0.00

E / V vs RHE

-20 -25 -30 -0.20

Bare GCE Pt nanospheres Pt nanotubes Commercial Pt/C

-0.15

b

0.06

Overpotential / V

a

j / mA cm -2

0.05

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Pt/C Pt nanospheres Pt nanotubes

0.04 0.03

30.7 mv / dec

23 mv / dec

0.02 0.01

21 mv / dec

0.00 -0.10

-0.05

E / V vs RHE c -20

j / mA cm-2

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

j / mA cm-2


-30

0.00

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

-2

Log ( j / mA cm ) Commercial Pt/C Pt nanospheres Pt nanotubes

-40 -50 -60 0 2 4 6 8 10 12 14 16 18 20

Time / h Fig5. (a) Polarization curves of bare GCE（black）, Pt nanospheres (dark cyan) , Pt nanotubes (red) and commercial Pt/C (pink) in 0.5 M H2SO4 with a scan rate of 2 mV s-1. (b) Tafel plots of Pt nanospheres, Pt nanotubes and commercial Pt/C. (c) Time-dependent current density curve for Pt nanospheres, Pt nanotubes and commercial Pt/C under fixed overpotential for 19 h.

Conclusions In this study, microfluidic technology was successfully applied on fabricating D C8,9PC lipid vesicles and tubules for the first time, which were then successfully used as templates to


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fabricate hollow Pt nanospheres and open-ended Pt nanotubes in a mild manner. They exhibited a Tafel slope of 23 mV dec-1 and 21 mV dec-1 respectively in acidic electrolytes. The exchange current densities of Pt nanosphere and Pt nanotube catalysts are calculated to be 0.87, 0.93 mA cm-2 by extrapolating the Tafel plot, which are the largest among all HER catalyst in acidic electrolytes. They could lead to important advances in HER research. This work enrich DC8,9PC lipid vesicle and tubule fabrication method, meanwhile demonstrates the vesicles can be templates for synthesis of nano hollow noble metal structures. Supporting Information The chemical structure of DC8,9PC, FTIR spectra of DC8,9PC lipid tubules and Pt tubes, DSC curve of lipid tubules, HRTEM of Pt nanotubes, measurement of Faradic efficiency, SEM of Pt nanotubes after HER were supplied as Supporting Information. Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant Nos. 21273059 and 21003032), the State Key Laboratory of Urban Water Resource and Environment (Harbin Institute of Technology; Grant No. 2014DX09), the Fundamental Research Funds for the Central Universities (Grant No. HIT. KISTP.201407), and Harbin Science and Technology Research Council (Grant No. 2014RFXXJ063). References (1) Zhang, S.; Yang, S.; Lan, J.; Tang, Y.; Xue, Y.; You, J. Ultrasound-induced switching of sheetlike coordination polymer microparticles to nanofibers capable of gelating solvents. J Am Chem Soc 2009, 131, 1689-1691. (2) Zhu, C.; Guo, S.; Dong, S. PdM (M = Pt, Au) bimetallic alloy nanowires with enhanced electrocatalytic activity for electro-oxidation of small molecules. Adv Mater 2012, 24, 23262331. (3) Yu, J.; Xiang, Q.; Zhou, M. Preparation, characterization and visible-light-driven photocatalytic activity of Fe-doped titania nanorods and first-principles study for electronic


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For Table of Contents Use Only

Hollow Platinum Nanospheres and Nanotubes templated by Shear Flow-Induced lipid Vesicles and Tubules and Their Applications on Hydrogen Evolution Yinan Wang#, Shenghua Ma#, Qingchuan Li, Ying Zhang, Xuejing Wang and Xiaojun Han*

Hollow platinum nanospheres / nanotubes fabricated by templating shear flow-induced lipid vesicles / tubules show excellent performance on HER.


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