The Experts below are selected from a list of 12900 Experts worldwide ranked by ideXlab platform
Jianjun Chen - One of the best experts on this subject based on the ideXlab platform.
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high temperature hydrogen sensor based on Platinum Nanoparticle decorated sic nanowire device
Sensors and Actuators B-chemical, 2014Co-Authors: Judong Zhang, Jianjun Chen, Mingming WangAbstract:Abstract A single SiC nanowire gas sensor was fabricated, and its fast-response and ultrahigh sensitivity for hydrogen sensing at high temperature was demonstrated. The surface of SiC nanowire was decorated with Pt Nanoparticles as a hydrogen catalyst. The decorated SiC nanowire was mounted on Ag electrodes in ohmic contact. Changes in the current were monitored at the low hydrogen concentration with a 1 V forward bias. An obvious change in current was observed when the nanowire sensor was exposed to the low hydrogen concentration atmosphere. High sensing performances such as fast response (3 s) and recovery (45 s), and high sensitivity (S ≈ 20%) toward H2 were demonstrated at 600 °C. The hydrogen gas sensing characteristics in air as a background gas were investigated. The possible Pt catalytic hydrogen sensing mechanism of the SiC nanowire sensor was also discussed.
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highly efficient photocatalytic hydrogen production of Platinum Nanoparticle decorated sic nanowires under simulated sunlight irradiation
International Journal of Hydrogen Energy, 2014Co-Authors: Mingming Wang, Jianjun Chen, Xin Liao, Zhaoxiang Liu, Judong Zhang, Li GaoAbstract:Abstract Photocatalytic water splitting reaction of Platinum Nanoparticle-decorated SiC nanowire photocatalyst was investigated under the simulated sunlight irradiation. The Pt/SiC catalyst shows an enhanced photocatalytic activity for water splitting, and its average H 2 evolution rate has been up to 4572 μL g −1 h −1 . The average H 2 production rate over the Pt/SiC catalyst is 88% higher than that of SiC nanowires without Pt Nanoparticle-decoration. The XPS spectra exhibit that the surrounding electrons of C atoms can be rapidly transferred to Si and Pt active sites for water splitting. The photoluminescence spectra show that the Platinum acts as an acceptor of photoelectrons to effectively restrain the electron–hole pair recombination of SiC nanowires. The novel Pt/SiC has great potential of being a low-cost, environmentally friendly solar-hydrogen production photocatalyst.
Chuan-jian Zhong - One of the best experts on this subject based on the ideXlab platform.
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Electrocatalytic oxidation of methanol: carbon-supported gold–Platinum Nanoparticle catalysts prepared by two-phase protocol
Catalysis Today, 2005Co-Authors: Mathew M. Maye, Nancy N. Kariuki, Lingyan Wang, Peter N. Njoki, Mark Schadt, H. Richard Naslund, Chuan-jian ZhongAbstract:Abstract This paper describes recent results of an investigation of the electrocatalytic oxidation of methanol at carbon-supported gold and gold–Platinum Nanoparticle catalysts. The exploration of the bimetallic composition on carbon black support is aimed at modifying the catalytic properties for methanol oxidation reaction (MOR) at the anode in methanol oxidation fuel cells. Gold and gold–Platinum Nanoparticles of 2–3 nm core sizes with organic monolayer encapsulation were prepared by two-phase protocol. The Nanoparticles were assembled on carbon black materials and thermally treated. The electrocatalytic MOR activities were characterized using voltammetric techniques, and were compared with commercial catalysts under several conditions. The results have revealed some initial insights into the catalytic activity of gold–Platinum Nanoparticle catalysts. Implications of our findings to the design and manipulation of highly-active gold–Platinum Nanoparticle catalysts for fuel cell applications are also discussed.
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electrocatalytic oxidation of methanol carbon supported gold Platinum Nanoparticle catalysts prepared by two phase protocol
Catalysis Today, 2005Co-Authors: Jin Luo, Mathew M. Maye, Nancy N. Kariuki, Lingyan Wang, Peter N. Njoki, Mark Schadt, Yan Lin, Richard H Naslund, Chuan-jian ZhongAbstract:Abstract This paper describes recent results of an investigation of the electrocatalytic oxidation of methanol at carbon-supported gold and gold–Platinum Nanoparticle catalysts. The exploration of the bimetallic composition on carbon black support is aimed at modifying the catalytic properties for methanol oxidation reaction (MOR) at the anode in methanol oxidation fuel cells. Gold and gold–Platinum Nanoparticles of 2–3 nm core sizes with organic monolayer encapsulation were prepared by two-phase protocol. The Nanoparticles were assembled on carbon black materials and thermally treated. The electrocatalytic MOR activities were characterized using voltammetric techniques, and were compared with commercial catalysts under several conditions. The results have revealed some initial insights into the catalytic activity of gold–Platinum Nanoparticle catalysts. Implications of our findings to the design and manipulation of highly-active gold–Platinum Nanoparticle catalysts for fuel cell applications are also discussed.
Mingming Wang - One of the best experts on this subject based on the ideXlab platform.
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high temperature hydrogen sensor based on Platinum Nanoparticle decorated sic nanowire device
Sensors and Actuators B-chemical, 2014Co-Authors: Judong Zhang, Jianjun Chen, Mingming WangAbstract:Abstract A single SiC nanowire gas sensor was fabricated, and its fast-response and ultrahigh sensitivity for hydrogen sensing at high temperature was demonstrated. The surface of SiC nanowire was decorated with Pt Nanoparticles as a hydrogen catalyst. The decorated SiC nanowire was mounted on Ag electrodes in ohmic contact. Changes in the current were monitored at the low hydrogen concentration with a 1 V forward bias. An obvious change in current was observed when the nanowire sensor was exposed to the low hydrogen concentration atmosphere. High sensing performances such as fast response (3 s) and recovery (45 s), and high sensitivity (S ≈ 20%) toward H2 were demonstrated at 600 °C. The hydrogen gas sensing characteristics in air as a background gas were investigated. The possible Pt catalytic hydrogen sensing mechanism of the SiC nanowire sensor was also discussed.
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highly efficient photocatalytic hydrogen production of Platinum Nanoparticle decorated sic nanowires under simulated sunlight irradiation
International Journal of Hydrogen Energy, 2014Co-Authors: Mingming Wang, Jianjun Chen, Xin Liao, Zhaoxiang Liu, Judong Zhang, Li GaoAbstract:Abstract Photocatalytic water splitting reaction of Platinum Nanoparticle-decorated SiC nanowire photocatalyst was investigated under the simulated sunlight irradiation. The Pt/SiC catalyst shows an enhanced photocatalytic activity for water splitting, and its average H 2 evolution rate has been up to 4572 μL g −1 h −1 . The average H 2 production rate over the Pt/SiC catalyst is 88% higher than that of SiC nanowires without Pt Nanoparticle-decoration. The XPS spectra exhibit that the surrounding electrons of C atoms can be rapidly transferred to Si and Pt active sites for water splitting. The photoluminescence spectra show that the Platinum acts as an acceptor of photoelectrons to effectively restrain the electron–hole pair recombination of SiC nanowires. The novel Pt/SiC has great potential of being a low-cost, environmentally friendly solar-hydrogen production photocatalyst.
Peidong Yang - One of the best experts on this subject based on the ideXlab platform.
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growth and electrical characteristics of Platinum Nanoparticle catalyzed silicon nanowires
Advanced Materials, 2007Co-Authors: Erik C Garnett, Wenjie Liang, Peidong YangAbstract:Silicon nanowires (Si NWs) will likely revolutionize a wide variety of applications ranging from field-effect transistors (FETs) and other nanoelectronics to chemical and biological sensing, and even solar cells. These nanowire devices must be integrated with more traditional electronic or optical components to make a complete usable system, which will probably require standard silicon clean-room processing. Nearly all Si NWs are made using a gold (or gold-based) catalyst and the well-known vapor–liquid–solid (VLS) growth mechanism first discovered by Wagner and Ellis. Because Au creates mid-gap trap states in silicon, it poisons device performance and typically is not allowed for use in electronicsfabrication labs and clean rooms. Therefore a new, electronics-friendly catalyst is critical not only for nanowire electronics, but also for integrated devices incorporating Si NWs in any capacity. Several groups have successfully grown Si NWs with alternative catalyst thin films such as Ti, Al, Pt, and PtSi but extensive electrical characterization that is very important for many device applications has not been conducted. In this report, Pt was chosen as a catalyst because it has a high melting point, can be made into Nanoparticles with a tight size distribution and shows orders-of-magnitudelower leakage current when incorporated into silicon diodes compared to gold. We have developed a chemical-vapor-deposition (CVD) synthesis based on our previous experience with gold catalysts to grow high-quality single-crystalline size-controlled epitaxial Si NWs from various sized Pt Nanoparticles. The nanowires were characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to determine their size distribution, growth direction, and alignment, whereas their electrical properties were tested by making planar FETs. Unlike the Au–Si system, Pt does not form a simple eutectic with Si; rather, there are several stable Platinum silicide compounds in the 800–1000 °C temperature range where Si-NW growth occurs. There is a eutectic formed between PtSi and Si at 979 °C, so at temperatures above this point and at high Si concentrations, it is thermodynamically favorable to precipitate pure Si. Si-NW growth below 979 °C can be explained by two possible mechanisms. First, because the Pt Nanoparticles begin melting (at least surface melting) around 600 °C, which is about 1000 °C lower than the bulk melting point, the bulk phase diagram may not accurately represent the phase transitions occurring in the catalyst Nanoparticle tip. In a very simplistic view, all the phase boundaries should shift down in temperature, with the Pt-rich phases being affected more strongly than the Si-rich phases. With a shift of over 1000 °C at the pure Platinum side of the phase diagram, a 180 °C shift for the PtSi–Si eutectic down to 799 °C at 67 % Si seems likely. Several reports also show that Pt Nanoparticles annealed in a hydrogen atmosphere at temperatures as low as 600 °C on silica substrates form PtxSiy [21,22] Additionally, Wagner and Ellis found that even Pt thin films as thick as 100 nm on Si formed a liquid surface layer at temperatures as low as 850 °C, further supporting a significant temperature decrease of the PtSi eutectic point from the bulk value. The second possible explanation is that the Pt Nanoparticles do not completely melt and instead act as an active site for rapid SiCl4 decomposition and diffusion, leading to a vapor– solid–solid (VSS) rather than VLS growth mechanism. The VSS mechanism has been proposed to explain the growth of several other semiconducting nanowires, particularly III–V compounds, that were originally thought to grow according to the VLS mechanism. In a recent report, Pt thin films deposited on Si were annealed at 800 °C in a hydrogen atmosphere to form PtSi islands which in turn were used to catalyze Si-NW growth at temperatures between 500 and 700 °C through a proposed VSS mechanism. Considering the strong in situ TEM evidence from the literature mentioned above that the Pt Nanoparticles begin melting well below their reaction temperatures, the island formation observed for Pt/Si films near 800 °C, and the evidence of strong eutectic-point depression seen for Pt thin films on Si, the Si NWs in this study most likely grow via the VLS mechanism. However, the VSS mechanism cannot be ruled out without in situ TEM evidence. Pt Nanoparticle catalysts with average diameters of (9.3± 1.2) nm were used to synthesize Si NWs with average diameters of (11.3± 1.6) nm (Fig. 1). The standard deviations of the starting colloid and the resulting wire diameters were C O M M U N IC A TI O N
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Platinum Nanoparticle shape effects on benzene hydrogenation selectivity
Nano Letters, 2007Co-Authors: Kaitlin M. Bratlie, Kyriakos Komvopoulos, Peidong Yang, Hyunjoo Lee, Gabor A. SomorjaiAbstract:Benzene hydrogenation was investigated in the presence of a surface monolayer consisting of Pt Nanoparticles of different shapes (cubic and cuboctahedral) and tetradecyltrimethylammonium bromide (TTAB). Infrared spectroscopy indicated that TTAB binds to the Pt surface through a weak C−H···Pt bond of the alkyl chain. The catalytic selectivity was found to be strongly affected by the Nanoparticle shape. Both cyclohexane and cyclohexene product molecules were formed on cuboctahedral Nanoparticles, whereas only cyclohexane was produced on cubic Nanoparticles. These results are the same as the product selectivities obtained on Pt(111) and Pt(100) single crystals in earlier studies. The apparent activation energy for cyclohexane production on cubic Nanoparticles is 10.9 ± 0.4 kcal/mol, while for cuboctahedral Nanoparticles, the apparent activation energies for cyclohexane and cyclohexene production are 8.3 ± 0.2 and 12.2 ± 0.4 kcal/mol, respectively. These activation energies are lower, and corresponding turnov...
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Platinum Nanoparticle shape effects on benzene hydrogenation selectivity
Nano Letters, 2007Co-Authors: Kaitlin M. Bratlie, Kyriakos Komvopoulos, Peidong Yang, Hyunjoo Lee, Gabor A. SomorjaiAbstract:Benzene hydrogenation was investigated in the presence of a surface monolayer consisting of Pt Nanoparticles of different shapes (cubic and cuboctahedral) and tetradecyltrimethylammonium bromide (TTAB). Infrared spectroscopy indicated that TTAB binds to the Pt surface through a weak C-H...Pt bond of the alkyl chain. The catalytic selectivity was found to be strongly affected by the Nanoparticle shape. Both cyclohexane and cyclohexene product molecules were formed on cuboctahedral Nanoparticles, whereas only cyclohexane was produced on cubic Nanoparticles. These results are the same as the product selectivities obtained on Pt(111) and Pt(100) single crystals in earlier studies. The apparent activation energy for cyclohexane production on cubic Nanoparticles is 10.9 +/- 0.4 kcal/mol, while for cuboctahedral Nanoparticles, the apparent activation energies for cyclohexane and cyclohexene production are 8.3 +/- 0.2 and 12.2 +/- 0.4 kcal/mol, respectively. These activation energies are lower, and corresponding turnover rates are three times higher than those obtained with single-crystal Pt surfaces.
Mathew M. Maye - One of the best experts on this subject based on the ideXlab platform.
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Electrocatalytic oxidation of methanol: carbon-supported gold–Platinum Nanoparticle catalysts prepared by two-phase protocol
Catalysis Today, 2005Co-Authors: Mathew M. Maye, Nancy N. Kariuki, Lingyan Wang, Peter N. Njoki, Mark Schadt, H. Richard Naslund, Chuan-jian ZhongAbstract:Abstract This paper describes recent results of an investigation of the electrocatalytic oxidation of methanol at carbon-supported gold and gold–Platinum Nanoparticle catalysts. The exploration of the bimetallic composition on carbon black support is aimed at modifying the catalytic properties for methanol oxidation reaction (MOR) at the anode in methanol oxidation fuel cells. Gold and gold–Platinum Nanoparticles of 2–3 nm core sizes with organic monolayer encapsulation were prepared by two-phase protocol. The Nanoparticles were assembled on carbon black materials and thermally treated. The electrocatalytic MOR activities were characterized using voltammetric techniques, and were compared with commercial catalysts under several conditions. The results have revealed some initial insights into the catalytic activity of gold–Platinum Nanoparticle catalysts. Implications of our findings to the design and manipulation of highly-active gold–Platinum Nanoparticle catalysts for fuel cell applications are also discussed.
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electrocatalytic oxidation of methanol carbon supported gold Platinum Nanoparticle catalysts prepared by two phase protocol
Catalysis Today, 2005Co-Authors: Jin Luo, Mathew M. Maye, Nancy N. Kariuki, Lingyan Wang, Peter N. Njoki, Mark Schadt, Yan Lin, Richard H Naslund, Chuan-jian ZhongAbstract:Abstract This paper describes recent results of an investigation of the electrocatalytic oxidation of methanol at carbon-supported gold and gold–Platinum Nanoparticle catalysts. The exploration of the bimetallic composition on carbon black support is aimed at modifying the catalytic properties for methanol oxidation reaction (MOR) at the anode in methanol oxidation fuel cells. Gold and gold–Platinum Nanoparticles of 2–3 nm core sizes with organic monolayer encapsulation were prepared by two-phase protocol. The Nanoparticles were assembled on carbon black materials and thermally treated. The electrocatalytic MOR activities were characterized using voltammetric techniques, and were compared with commercial catalysts under several conditions. The results have revealed some initial insights into the catalytic activity of gold–Platinum Nanoparticle catalysts. Implications of our findings to the design and manipulation of highly-active gold–Platinum Nanoparticle catalysts for fuel cell applications are also discussed.