Carbon-based chemicals and materials such as charcoal, gasoline, diesel, and natural gas are well-known fuel sources that have powered humanity through the industrial revolution and have helped make modern living possible. However, the pollution and greenhouse gas emissions resulting from their combustion is proving to be more than the Earth can handle, which gives reason for looking for alternative methods of creating and storing electricity. Less well-known is the unique combination of properties found in carbon-based materials such as activated carbon and charcoal including low density, high surface area, low-toxicity, chemical inertness, and, importantly, high electrical conductivity. These properties allow carbon materials to play key roles in many new and emerging energy technologies like batteries and fuel cells. In a clever twist of fate, carbon materials may supply the necessary characteristics to make such technologies viable, thereby helping to alleviate the pollution caused by the combustion of the same materials during the past few centuries.
Although carbon materials naturally exhibit many desirable traits, a variety of techniques exist to tailor their properties to meet the needs of an application. Among these are doping and surface modification. Doping refers to the purposeful incorporation of non-carbon atoms into the material structure. This is typically accomplished by a judicious selection of an organic precursor used to make the carbon, which contains the desired elements. Since some elements are easy to find in carbon precursors (e.g. O, N, S), these are relatively easy to use as dopants. However, the unique chemistry of transition metals (e.g. Fe, Co, Cu) makes doping with these elements attractive, despite the increased difficulty of incorporating them. In this thesis, Fe-doping of carbon materials is accomplished by using a simple method of dissolving an Fe salt into the organic carbon precursor. The effect of the salt anion on the carbon’s structure and composition is systemically studied and the resultant materials are used as catalysts in polymer electrolyte membrane fuel cells (PEMFCs). Overall, the anion has a profound influence on the properties of the carbon materials.
Another technique used in this thesis is surface modification, wherein small, organic groups are directly attached to the carbon surface. The relatively unreactive carbon surface requires harsh reaction conditions for the surface functionalization to take place to a significant extent, which has led to a dearth of suitable methods. Herein, an alternative, two-step route for the surface modification of carbon materials is proposed and explored. This two-step scheme, referred to as bromomethylation, boasts many advantages over other surface modification methods including mild reaction conditions, high surface coverages, and negligible damage to the carbon structure. Using this method, a total of twelve unique surface-modified carbons are made. Four of these materials were used as hosts for sulfur in lithium-sulfur (Li-S) batteries and all show greatly enhanced performance relative to the unmodified parent carbon. These results demonstrate the potential benefits that bromomethylation can bring to applications requiring the use of carbon materials.