Interactions of Nitrogen and Hydrogen with various 1D and 3D carbon materials probed via in-situ vibrational spectroscopy

Open Access
Author:
Ray, Paramita
Graduate Program:
Chemistry
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
February 04, 2016
Committee Members:
  • John V Badding, Dissertation Advisor/Co-Advisor
  • Angela Lueking, Dissertation Advisor/Co-Advisor
  • Harry R Allcock, Committee Member
  • David Lawrence Allara, Committee Member
  • William Blaine White, Committee Member
Keywords:
  • Nitrogen perturbation
  • Raman spectroscopy
  • carbon nanostructures
Abstract:
Nanostructured carbon materials are perhaps the most widely studied adsorbents, and cryogenic nitrogen adsorption is likely the most common method to assess textural properties of adsorbents. Yet, in-situ vibrational spectroscopic studies of nitrogen’s interactions with three nanostructured carbon materials have provided new insight into carbon-nitrogen interactions. In this dissertation I present the work of 2 projects: (i) Study of the interaction of Nitrogen with different carbon geometries at a molecular level and (ii) exploration of novel C-H interactions on carbon materials via mechano-chemistry. Both of these projects utilize in-situ Raman spectroscopy for exploring gas-surface interactions. Chapters 2 and 3 explore the interaction of molecular Nitrogen on carbon surfaces. With complementary theoretical studies and systematic experimental studies at various temperatures and pressures for different surfaces, I demonstrate how the spectroscopic peak features of N2 gives an indication of gas-surface binding energy, pore structure, and surface chemistry. Using 1D and 3D carbon architectures, spectroscopic perturbation of Nitrogen is probed as a function of adsorption potential and pore dimension, and the spectroscopic response is mapped to the cryogenic volumetric adsorption isotherms. Whereas the latter required multiple days and ~100 mg of sample, the spectroscopic technique provided similar structural information in the matter of a few hours for a few micrograms of the sample. It is anticipated that the development of the site-specific spectroscopic technique will advance the understanding of adsorbent geometry versus chemical functionality in a way not possible with deconstruction of bulk gas adsorption measurements of pore dimension, surface area, and diffusivity. The second project probed mechanochemical means to polymerize aromatics and hydro-aromatics in the presence of hydrogen in an attempt to form localized carbon cages that trap hydrogen. Interesting aspects of the phase change of the carbon structures have been demonstrated with complex characterization techniques utilised throughout this project are described in Chapter 4 and 5. The introduction (Chapter 1) provides an overview on vibrational spectroscopy, porous carbons, theoretical models for porosity measurements and mechanochemistry and Chapter 6 summarises the conclusions with some future directions.