Electro-catalysis for advanced direct fuel cells using higher energy liquid oxygenates
thesisposted on 2022-03-10, 12:27 authored by Cheng Li
Due to the limitation of fossil fuels supply and the increased concern for carbon emissions which results in global warming, fuel cell has been rapidly developed and is widely regarded as an attractive power supply device which generates electrical energy from the chemical energy of a fuel directly. Electrocatalytic oxidation reaction of the fuel directly harvests chemical energy with significant higher efficiency at a much lower operating temperature. Direct alcohol fuel cells (DAFCs), one of the fast developed fuel cells, are a clean and renewable source of energy making them an ideal a replacement for the traditional fossil fuels. Alcohol is an attractive fuel because it is a stable liquid at room temperature, which makes it easier for storage and transportation.
In this thesis, bare Pd electrocatalyst, supported by glassy carbon (GC), towards alcohol (ethanol and 1-butanol) electrooxidation reaction in alkaline media at different temperatures were firstly studied. Then a series of Pd-based electrocatalysts were developed to improve the activity and stability for ethanol electrooxidation reaction (EOR) and 1-butanol electrooxidation reaction (BOR) in alkaline media. The kinetics of alcohol oxidation reaction on Pd and Pd-based electrocatalysts were investigated and compared based on the activation energy (Ea) calculated by Arrhenius plots using the data obtained from cyclic voltammetry (CV) and chronoamperometry (CA) studies at various temperatures.
When only Pd/GC electrocatalyst was tested for alcohol electrooxidation reaction within ethanol and 1-butanol, the catalysts activities and kinetics were enhanced at higher cell temperature and the peak potentials also positive shifted to higher potential while temperature increased. Ethanol had a higher positive peak current density at all temperatures while 1-butanol had a lower activation energy. The results showed that the reaction activities increased while the activation energy decreased as the length of the carbon chain of the primary alcohols increased.
Then a series of nanoparticle sized Pd-based electrocatalysts were synthesized using Cu, Bi, Nb and BiNi nanoparticles supported on GC to test in the ethanol and 1-butanol oxidation reactions. The results showed that 34% Cu achieved highest current density and lowest activation energy (Ea) for EOR and 48% Cu showed lowest Ea in BOR. In case of Bi, 43% was the optimum coverage for EOR, and in BOR, 42% Bi had lowest Ea while peak current density reached highest at 50%. For the Nb study, it was shown that the best coverage for EOR was 50% and 45% for BOR. The best coverage of BiNi was 43% in EOR, which was the same with Bi, indicating both are very promising co-catalysts for EOR.
The production of T4 and M13 bacteriophage were successful, both in small and large scale, supported by clearly accountable points in plaque assay and phage culture curves and best operation temperature of 37°C was determined. The initial bio-catalyst test of Phage-Cu-Pd/GC was conducted and a promising result in terms of activation energy, with even lower Ea value compared to no phage added, was achieved at 36% Cu overage.
- Aeronautical, Automotive, Chemical and Materials Engineering
- Chemical Engineering