2 results
Search Results
Now showing 1 - 2 of 2
- ItemQuinone-decorated onion-like carbon/carbon fiber hybrid electrodes for high-rate supercapacitor applications(Hoboken, NJ : Wiley, 2015) Zeiger, Marco; Weingarth, Daniel; Presser, VolkerThe energy performance of carbon onions can be significantly enhanced by introducing pseudocapacitive materials, but this is commonly at the cost of power handling. In this study, a novel synergistic electrode preparation method was developed by using carbon-fiber substrates loaded with quinone-decorated carbon onions. The electrodes are free standing, binder free, extremely conductive, and the interfiber space filling overcomes the severely low apparent density commonly found for electrospun fibers. Electrochemical measurements were performed in organic and aqueous electrolytes. For both systems, a high electrochemical stability after 10 000 cycles was measured, as well as a long-term voltage floating test for the organic electrolyte. The capacitance in 1 M H2SO4 was 288 F g^−1 for the highest loading of quinones, which is similar to literature values, but with a very high power handling, showing more than 100 F g^−1 at a scan rate of 2 Vs^−1.
- ItemDirect Evidence for Solid-like Hydrogen in a Nanoporous Carbon Hydrogen Storage Material at Supercritical Temperatures(Washington, DC : Soc., 2015) Ting, Valeska P.; Ramirez-Cuesta, Anibal J.; Bimbo, Nuno; Sharpe, Jessica E.; Noguera-Diaz, Antonio; Presser, Volker; Rudic, Svemir; Mays, Timothy J.Here we report direct physical evidence that confinement of molecular hydrogen (H2) in an optimized nanoporous carbon results in accumulation of hydrogen with characteristics commensurate with solid H2 at temperatures up to 67 K above the liquid–vapor critical temperature of bulk H2. This extreme densification is attributed to confinement of H2 molecules in the optimally sized micropores, and occurs at pressures as low as 0.02 MPa. The quantities of contained, solid-like H2 increased with pressure and were directly evaluated using in situ inelastic neutron scattering and confirmed by analysis of gas sorption isotherms. The demonstration of the existence of solid-like H2 challenges the existing assumption that supercritical hydrogen confined in nanopores has an upper limit of liquid H2 density. Thus, this insight offers opportunities for the development of more accurate models for the evaluation and design of nanoporous materials for high capacity adsorptive hydrogen storage.