Da-Ming Gu

Ultrahigh stable carbon riveted Pt/TiO2–C catalyst prepared by in situ carbonized glucose for proton exchange membrane fuel cell

Highly active Pt/TiO2–C catalyst has been synthesized by a microwave-assisted polyol process. The obtained Pt/TiO2–C sample was characterized by XRD, EDAX, HRTEM, XPS, and electrochemical measurements. The results show that the Pt/TiO2–C catalyst possesses substantially enhanced stability and identical activity in comparison with Pt/C prepared by the same procedure. Furthermore, carbon riveted Pt/TiO2–C composite with a novel structure based on in situ carbonization of the glucose was designed and synthesized. The results of TEM and electrochemical measurements indicate that the carbon riveted Pt/TiO2–C catalyst has much greater stability than Pt/TiO2–C and Pt/C with similar activity. The significantly enhanced stability for carbon riveted Pt/TiO2–C catalyst is ascribed to: (1) the excellent stability of anatase TiO2; (2) the strong metal-support interaction between Pt and TiO2; (3) the anchoring effect of the carbon layers formed during the carbon riveting process. These findings indicate that carbon riveted Pt/TiO2–C is a promising catalyst for proton exchange membrane fuel cells which are under long term operation.

A Novel Structural Design of a Pt/C-CeO2 Catalyst with Improved Performance for Methanol Electro-Oxidation by β-Cyclodextrin Carbonization

Although the direct methanol fuel cell (DMFC) is considered to be a promising power source for portable electronic devices and electric vehicles, [ 1–8 ] some obstacles, such as the low methanol electrooxidation kinetics from the poisoning of intermediates during the oxidation processes and methanol crossover from anode to cathode, still exist and impede its commercialization. [ 7 , 9–13 ] Aiming at the CO poisoning issues, the most widely accepted strategy is to develop Pt-based alloys such as Pt-Sn, [ 14–20 ] Pt-Ni, [ 21–23 ] or Pt/ metal oxide composite catalysts such as Pt-TiO 2 [ 24–26 ] based on the bifunctional mechanism and the electronic effect, [ 27–31 ] and the latter is also related to other factors including the size and shape of metal oxide nanocrystals, the surface areas, and the support effect. [ 32–35 ] Among various possible metal oxide supports, cerium oxides (CeO 2 ) are of particular interest due to higher oxygen storage capacity and much lower price, as well as the good mechanical resistance and anticorrosion ability in acidic media, which may signifi cantly promote methanol oxidation and reduce the catalyst preparation cost. Therefore, to explore the possibility of employing CeO 2 as a co-catalyst in methanol electro-oxidation is very necessary and meaningful. However, due to the low electron conductivity of CeO 2 at the cost of catalytic performance, it necessarily deserves the investigation of the structural design of catalysts to weaken the sideeffects resulting from the low electron conductivity and the lack of attachment of Pt and CeO 2 . Recently, many researchers have investigated the CeO 2 as a co-catalyst for methanol or other alcohol oxidation, [ 36,37 ] but very few papers have focused on the structural design of CeO 2 -based catalysts to enhance the electron conduction and synergistic effect. Xia [ 38 ] and co-workers synthesized the Pt/CeO 2 hybrid nanostructure catalyst in the aqueous phase through electrostatic attraction between negatively charged PtCl 4 2precursors and the positively charged surface of 6-aminohexanoic acid (AHA)-stabilized CeO 2 nanocrystals, and it exhibited a higher resistance to poisoning during the catalytic reduction of p -nitrophenol into p -aminophenol by

Carbon riveted microcapsule Pt/MWCNTs-TiO2catalyst prepared by in situ carbonized glucose with ultrahigh stability for proton exchange membrane fuel cell

Pt/MWCNTs (Multi-walled carbon nanotubes, MWCNTs) and microcapsule Pt/MWCNTs-TiO2catalysts have been prepared by microwave-assisted polyol process (MAPP). Electrochemical results show that microcapsule Pt/MWCNTs-TiO2catalyst has higher activity and stability than Pt/MWCNTs due to more uniform dispersion and smaller size of Pt nanoparticles. Furthermore, carbon riveted microcapsule Pt/MWCNTs-TiO2catalyst has been designed and synthesized on the basis of in situ carbonization of glucose. The physical characteristics such as XRD, TEM, HRTEM, STEM, and XPS have indicated that the anatase TiO2 indeed entered the inside of the MWCNTs and formed the microcapsule support of MWCNTs with TiO2. The accelerated potential cycling tests (APCT) indicate that the carbon riveted microcapsule Pt/MWCNTs-TiO2catalyst with similar activity to microcapsule Pt/MWCNTs-TiO2 and Pt/C possesses 7.5-times as high stability as that of Pt/C and has 3-times as long life-span as that of carbon riveted Pt/TiO2-C reported in our previous work. The significantly enhanced stability for carbon riveted microcapsule Pt/MWCNTs-TiO2catalyst is assignable to: (1) the inherently excellent mechanical resistance and stability of anatase TiO2 and MWCNTs in acidic and oxidative environments; (2) strong metal-support interaction between Pt nanoparticles and the microcapsule support; (3) the anchoring effect of the carbon layers formed during the carbon riveting process.

Investigation on performance of Pd/Al2O3–C catalyst synthesized by microwave assisted polyol process for electrooxidation of formic acid

A Pd/Al2O3–C catalyst with α-Al2O3 and Vulcan XC-72 carbon black as a mixture support for direct formic acid fuel cell (DFAFC) has been prepared by a microwave-assisted polyol process for the first time. The as-prepared Pd/Al2O3–C catalysts with different mass ratios of α-Al2O3 to XC-72 carbon have been characterized by XRD, EDAX, XPS, TEM, HRTEM, and electrochemical measurements in this study. The results show that the activity of the catalyst with α-Al2O3 as the support is lower than that of the catalyst with carbon black as the support, owing to α-Al2O3 having poor electrical conductivity. However, the activity of the catalyst with α-Al2O3 and Vulcan XC-72 carbon black as a mixture support is evidently enhanced. The Pd/Al2O3–C catalyst with a mass ratio of α-Al2O3 to XC-72 carbon of 1u2006:u20062 presents the narrowest particle size distribution on the surface of the mixture support, which exhibits the best activity and stability for formic acid electrooxidation among all the samples. Its current density of the positive anodic peak of formic acid electrooxidation is up to 36.97 mA cm−2. Pd/Al2O3–C catalyst with a suitable ratio of α-Al2O3 to XC-72 carbon shows a better catalytic activity for formic acid electrooxidation and a higher stability than Pd/C, resulting from the addition of α-Al2O3 improving its electrooxidation ability for formic acid due to an anti-corrosion property of α-Al2O3 and a metal–support interaction between the Pd nanoparticles and the α-Al2O3.

The effect of hydrothermal treatment time and level of carbon coating on the performance of PtRu/C catalysts in a direct methanol fuel cell

A carbon-riveted PtRu/C catalyst of high stability has been prepared by in situ glucose carbonization using a hydrothermal method (GICH). Its mode of action and its practical application have been investigated by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, a single-fuel cell test, and by conventional electrochemical measurements. The single-fuel cell test has demonstrated that the GICH hydrothermal method has high applicational usefulness. After 100 h the maximum power density of a single cell using carbon-riveted PtRu/C as anode catalyst fell by only 12.0%, from 76.6 to 67.4 mW cm−2, compared with 28.4%, from 73.2 to 52.4 mW cm−2, for traditionally prepared PtRu/C. In addition, when the optimal hydrothermal treatment time was 4 h and the level of carbon coating was 9%, a carbon-riveted PtRu/C catalyst with a 3.5 nm carbon coating gave the best stability, with similar initial activity to traditionally prepared PtRu/C. The significantly increased stability of carbon-riveted PtRu/C may be attributed to two factors: (1) the anchoring effect of the carbon nanolayer formed during in situ glucose carbonization by the hydrothermal method; and (2) the increased content of Pt(0), Ru(0), sp3-hybridized carbon and the C–OR group composition, and the clear decrease in PtO2 and RuOxHy following the carbon-riveting procedure.