Design and Characterization of Carbon Nanomaterial-Based Electrodes for Use in Harsh Environments

Abstract

Electrode degradation in harsh environments is a problem that plagues many devices. Traditional metallic and carbon-based electrodes are often reactive and can fail over time, leading to reduced efficiency and increased operational costs. Carbon nanomaterials can potentially offer improvements over traditional electrodes due to their high surface area and the robust nature of sp2 hybridization. This dissertation focuses on the study of two carbon allotropes with nanoscale features: carbon nanowalls and multiwalled carbon nanotubes, and their use as electrode materials in harsh environments. Specifically, the use of carbon nanotubes as a material for field emission electrodes in radiative environments was researched, and carbon nanowalls were explored as an electrode material for phosphoric acid fuel cells.The use of carbon nanotubes as field emission electrodes in radiative environments is researched by characterizing the effects of gamma and proton radiation on carbon nanotube structural properties and field emission performance. It was determined that both proton and gamma radiation affect the crystalline structure of carbon nanotubes by reducing defect density, which leads to an increase in the applied field required to induce electron emission. However, the effects due to radiation are smaller in magnitude compared to the effects of adsorbates on field emission performance.To explore the use of carbon nanomaterials as an electrode material for use in phosphoric acid fuel cells, carbon nanowalls were prepared in a microwave plasma chemical vapor deposition reactor. The ability to modify the structure of the resulting films was demonstrated by changing the ratio of the growth gases. Platinum nanoparticles were deposited from solution onto the carbon nanowalls, and their surface area and hydrogen adsorption capabilities were characterized using scanning electron microscopy and cyclic voltammetry. It was determined that while functional, the carbon nanowall electrodes had lower platinum loading compared to electrodes made from carbon black, and were more susceptible to degradation in phosphoric acid at an elevated temperature.