Green Bioenergy and Green Molecule Production from Cellulose Derivatives via Direct Alkaline Fuel Cell

Cellulose is the most abundant polymer on earth. Its use within the bioenergy and bio-materials sector to provide raw feedstock molecules is critical to supplant petrochemical-derived resources. The alkaline carbohydrate fuel cell has recently been of growing interest as it has been shown to produce power directly from monosaccharides without further breakdown and combustion steps that introduce substantial energetic losses. The development of the direct alkaline carbohydrate fuel cell is currently in its infancy, with developments needed to refine understandings of cell geometry, charge mediation and industrial application pathways. The findings of this thesis represent contributions to these areas, demonstrating greater mechanistic understanding of these devices and new pathways forward. Mechanistic insights were gained through examining simple geometric design considerations that proved capable of significantly improving fuel cell performance. Decreasing the distance between electrodes from 20 to 6 mm increased power outputs by ~35 % and increasing the density of the nickel foam anode from 250 mg cm3 to 1000 mg cm3 increased power outputs by ~30 %. Further, indigo carmine was found to be unstable in highly alkaline solutions. Breakdown of the dye produced significant amounts of current without any carbohydrate present, calling into question the previously reported relationship between the indigo carmine concentration and power generation within an alkaline carbohydrate fuel cell. As pure carbohydrate fuels may raise ethical concerns about food security, new organic fuels were proposed and new cellulose to energy pathways examined. III A novel low-temperature hydrothermal cellulose degradation process was developed to create new cellulose-derived alternatives. The process converted over 61 % of microcrystalline cellulose to soluble aldaric acids whilst simultaneously producing value-added magnetic nanoparticles. Finally, a new novel fuelling approach was reported in which the selected fuel was reverse-engineered from the desired oxidation products. Within the fuel cell, the oxidation pathway between 5-HMF and FDCA was exploited to generate 6.5 x the power of the equivalent glucose fuel cell, whilst synthesising high-value molecules known to be useful for bioplastics. As the scale of bio-molecule production increases, this passive energy generation scheme presents an opportunity to produce significant power from an otherwise untapped chemical process, increasing the green chemical industry’s energy efficiency. Overall, this thesis entails optimisations towards enhancing energy production within the alkaline organic fuel cell and explores new novel applications which broaden the scope of these green electricity-generating devices