Document Type

Dissertation

Degree

Doctor of Philosophy

Major

Physics

Date of Defense

11-13-2018

Graduate Advisor

Eric H. Majzoub

Co-Advisor

Alexey Yamilov

Committee

Philip Fraundorf

Stephen M. Holmes

Julia E. Medvedeva

Abstract

Nanoporous carbons (NCs) have become increasingly popular in various fields of research due to their unique properties including tunable pore sizes, higher pore volumes and higher surface areas, as well as being able to produce controlled nanostructures. The work presented here uses NC scaffolds with as active hosts for (1) Li-ion battery electrodes and (2) confined metal hydrides (MH) for hydrogen storage applications. In (1) we investigate the Li diffusion characteristics in hard carbons (HCs) that are important for electrochemical applications. We develop a novel method named Voltage-Relaxation Galvanostatic Intermittent Titration Technique (VR-GITT). Parameters derived from the fitting of electrochemical data provide both the diffusion constants as well as morphological information about the diffusion geometry. The VR-GITT method also allows determination of the diffusion constant in the two-phase region of many materials, where the standard GITT method fails. In (2) it is already known that confining MHs in NCs. can alter the kinetics of de/re-hydriding reactions. We investigate the effects of changing the surface electron density in these HCs by the addition of nitrogen (N). The various chemical environments for the surface nitrogens include pyridinic and pyrrolic. The pyridinic N contains a lone pair of electrons that should be available to form Lewis-acid/base complexes that interact with confined MHs, and provide a favorable (wetting) surface energy for incorporation of AlH3, LiBH4, and other hydrides into the carbons. Our results indicate that both B and Al interact with these pyridinic Ns upon introduction to the HCs. The infiltration of LiBH4 is straightforward, while the infiltration of AlH3 requires oxygen reduction techniques during the carbon scaffold synthesis.

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