Synthesis and characterization of boron substituted carbon deposits on PFA-derived carbon substrates for hydrogen adsorption. (August 2015)

• Record Type: Journal Article
• Authors: Qajar, Ali; Holbrook, BillyPaul M.; Peer, Maryam; Rajagopalan, Ramakrishnan; Foley, Henry C.; Davis, Michael; Mueller, Karl T.
• Is Part Of: Carbon. Volume 89(2015)
• Page Start: 392
• Page End: 403
• Publication Date: 2015-08
• Subjects: Carbon -- Periodicals; Carbone -- Périodiques; Koolstof; Toepassingen; Electronic journals; 546.681
• DOI: 10.1016/j.carbon.2015.03.053
• Languages: English
• ISSNs: 0008-6223

Abstract

Abstract: The effect of boron substituted carbon (BC x, x ∼ 3–5) coatings on the hydrogen adsorption properties of porous carbons was investigated via spectroscopic characterization and hydrogen adsorption measurements. Thin films of BC x were synthesized by reacting BCl3 and benzene in a chemical vapor and then depositing the product as a solid (CVD). The BC x deposits were collected on microporous carbon substrates and mesoporous silica aerogel. High-resolution solid-state boron NMR, 11 B HR-NMR, detected boron atoms in a symmetric chemical environment with trigonal coplanar coordination. Results from analyses based on NMR, X-ray photoelectron spectroscopy (XPS), and d-spacings, calculated from electron diffraction and X-ray diffraction (XRD) patterns, indicated that 17 at.% boron was substitutionally incorporated into the carbon framework. Thus the material has an empirical formula of BC4.9 . Hydrogen adsorption data were collected at 100 bar and 25 °C. The BC x coatings reduced the surface area of the porous substrates by 30–50%. However, at the same time, they increased the heat of adsorption and the adsorption capacities per unit area by as much as a factor of five. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) revealed wagging energies at 1190 cm −1 attributable to hydrogen interactions with C–B–C bonds.