Micro-channel development and hydrogen adsorption properties in templated microporous carbons containing platinum nanoparticles |
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| Authors: | Yunxia Yang Craig M Brown Chunxia Zhao Alan L Chaffee Burke Nick Dongyuan Zhao Paul A Webley Jacob Schalch Jason M Simmons Yun Liu Jae-Hyuk Her CE Buckley Drew A Sheppard |
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| Affiliation: | aEarth Science and Resources Engineering, CSIRO, VIC 3168, Australia;bNational Institute of Standards and Technology Centre for Neutron Research, 100 Bureau Drive, MS 6102, Gaithersburg, MD 20899, USA;cSchool of Materials Science and Engineering, Wuhan University of Technology, Hubei, Wuhan 430070, PR China;dSchool of Chemistry, Monash University, VIC 3168, Australia;eDepartment of Chemical Engineering, Monash University, Australia National Hydrogen Materials Alliance, VIC 3168, Australia;fOberlin College, 70 N Professor St, Oberlin, OH 44074, USA;gDepartment of Chemical Engineering, University of Delaware, Newark, DE 19716, USA;hDepartment of Material Science and Engineering, University of Maryland, College Park, MD 20742, USA;iGE Global Research, Niskayuna, NY 12309 USA;jDepartment of Imaging and Applied Physics, Curtin University of Technology, GPO Box U 1987, Perth, 6845 WA, Australia |
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| Abstract: | Ordered microporous carbons containing dispersed platinum nanoparticles were fabricated and chosen as suitable models to investigate micro-structure development and hydrogen transport properties of zeolite-templated carbons. X-ray photoelectron spectroscopy analysis revealed that the enhanced heat of adsorption is related to the narrow micro-channels templated from the zeolite and the presence of certain C O groups on the carbon. The lack of a well-defined and intense rotational transition line and the persistent broad H2 recoil spectrum in neutron scattering results suggests a distribution of binding sites. Most interestingly, hydrogen diffusion occurs on two time scales, consisting of a fast liquid-like jump diffusion on the timescale of picoseconds along with an even faster bulk-like diffusion. The liquid-like motion is characterized by a diffusion constant of (2.1 ± 0.3) × 10−8 m2/s with an activation energy of ca. 77 K; both values indicate somewhat lower mobility than similar dynamics of H2 on nanotubes, activated carbon XC-72, or Grafoil, yet greater mobility than that of bulk liquid. These unusual characteristics for hydrogen in carbons are believed to arise from the network of narrow pores in this zeolite-templated image of the zeolite. In fact, the diffusion constants of the templated carbons are extremely similar to those measured for zeolite 13X. |
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