Thesis (M. Sc. (Chemistry)) -- University of Limpopo, 2017. / In order to meet the great demand of energy supply globally, there must be a transition from dependency on fossil fuel as a primary energy source to renewable source. This can be attained by use of hydrogen gas as an energy carrier. In the context of hydrogen fuel cell economy, an effective hydrogen generation is of crucial significant. Hydrogen gas can be produced from different methods such as steam reforming of fossil fuels which emit greenhouse gases during production and from readily available and renewable resources in the process of water electrolysis. Hydrogen generated from water splitting using solar energy (photocatalysis) or electric energy (electrocatalysis) has attracted most researchers recently due to clean hydrogen (without emission of greenhouse gases) attained during hydrogen production. In comparison with photocatalytic water splitting directly using solar energy, which is ideal but the relevant technologies are not yet commercialized, electrolysis of water using catalyst is more practical at the current stage. The platinum group noble metals (PGMs) are the most effecting electrocatalysts for hydrogen evolution reactions (HER) but their scarcity and high cost limit their application. In this study, we presented the noble metal free organic-inorganic hybrid composites and their HER electrocatalysis performances were investigated. Polyaniline-metal organic framework (PANI/MOF) composite was prepared by chemical oxidation of aniline monomer in the presence of MOF content for hydrogen production. The properties of PANI, MOF and PANI/MOF composite were characterised for their structure and properties by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), Raman, transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-vis), atomic absorption spectroscopy (AAS), square wave (SWV) and cyclic voltammetry (CV). There was a clear interaction of MOF on the backbone of the PANI matrix through electrostatic interaction as investigated by both Raman and FTIR. The MOF exhibited irregular crystals with further wrapping of MOF by PANI matrix as evidenced by both SEM and TEM analyses. The PANI composite exhibited some nanorods and microporous structure. x The determined energy band gap of the composite was in good agreement with previously reported catalysts for hydrogen evolution reaction (HER). The thermal stability of PANI increased upon addition of MOF. Experiments probing the electrochemical, HER and photophysical properties revealed that the composite was very stable and robust with significant improvement in properties. The resulting composite is a promising low-cost and environmentally friendly hydrogen production material. In this work we also reported about novel poly (3-aminobenzoic acid)-metal organic framework referred as PABA/MOF composite. Spectroscopic characterisations (UV-vis and FTIR) with support of XRD and TGA revealed a successful interaction between PABA and MOF. Morphological characterisation established that PABA is wrapping MOF and the amorphous nature of the materials were not affected. The catalytic effect of PABA and PABA/MOF composites on HER was studied using exchange current density and charge transfer coefficient determined by the Tafel slope method. A drastic increase in catalytic H2 evolution was observed in PABA and composite. Moreover, they merely require overpotentials as low as ~-0.405 V to attain current densities of ~0.8 and 1.5 Am-2 and show good longterm stability. We further demonstrated in the work the electrocatalytic hydrogen evolution reaction of MOF decorated with PABA. These novel MOF/PABA composites with different PABA loading were synthesised via in situ solvothermal synthesis of MOF in the presence of PABA. It was deduced that PABA with different loading amount have an influence on the morphologies, optical properties and thermal stabilities of MOF. Interestingly, the MOF/PABA composites exhibited the great significant on the HER performance and this is potentially useful in HER application for hydrogen fuel cell. / Sasol Inzalo foundation and National Research Foundation of South Africa

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No description available.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 97-114). Also available in electronic version.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 132-145). Also available in electronic version.

Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Parekh, David; Committee Member: Fuller, Thomas; Committee Member: Joshi, Yogendra; Committee Member: Mavris, Dimitri; Committee Member: Wepfer, William. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 100-110). Also available in electronic version.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references. Also available in electronic version.

Hydrogen has gained interest as fuel recently as the harmful effects of fossil fuels on the environment can no longer be ignored. Hydrogen, which produces no pollutants, forms the feed for cleaner fuel cells systems currently in use. Fuel cells, although not as economically viable as fossil fuels, have found a foothold in the energy market in various markets like power backup and use in remote locations. Production of hydrogen is still largely done via fossil fuel reforming and this technology has received renewed interest for use with fuel cells in the form of micro- reformers or fuel processors. This study entailed the performance benchmarking of a so called Best-in-Class commercial micro reformer (as available in 2010), the 1 kW WS FLOX Reformer, and was undertaken under the auspices of the national HySA programme. The study’s focus was primarily on reformate output quality (carbon monoxide concentration), and start up time, thermal efficiency and hydrogen output (15 SCLM). The reformer consisted of a combustion section encased in an outer reforming section consisting of three reactors in series, steam reforming, water gas shift and selective methanation. As-provided temperature control is simplified though the use of only one temperature setpoint in the combustion chamber and temperature control in the CO clean up stages obtained through means of heat transfer with incoming water being evaporated. Combustion takes place through flame combustion or by means of the supplier’s patented FLOX (flameless oxidation) combustion. The purchased FLOX Reformer assembly was integrated into a fully automated unit with all balance of plant components as well as microGC and flue gas analysis for measurement of outlet conditions. The FLOX Reformer was tested at multiple combustion temperatures, combustion flowrates, reforming loads and steam-to-carbon ratios to obtain a wide set of benchmark data. From the testing it was found that the reformer was able to produce the necessary 15 SCLM hydrogen with a carbon monoxide purity of less than 10 ppm as required in fuel cells for all testing if the reaction temperatures were within the recommended limits. Intermediary water gas shift analysis showed methane and carbon monoxide conversion in the reforming and water gas shift stages to be identical to thermodynamic equilibrium conversion – 95% and higher for all temperatures. iii Selective methanation conversion obtained was 99%, but not always at equilibrium conversion due to increased selective methanation temperatures, where carbon dioxide methanation was also observed at the higher temperatures. Temperature control through heat exchange with incoming water in the CO removal stages was found to be less than ideal as the temperature inside these stages fluctuated dramatically due to inaccuracies in the water pump and a lagged response to flowrate changes. Startup times of less than an hour was observed for multiple combustion flowrates and the reformer boasts a standby function to reduce this to less than half an hour. The thermal efficiency was independently confirmed and tested and found to be higher than 70 % for flame combustion and on par with other commercially available fuel processors. The suppliers trademark FLOX combustion only reaching 65% due to decreased combustion efficiency.

School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, South Africa, in fulfillment of the requirements for the degree of Master of Science in Engineering, November 2019 / This research focuses on the co-firing of low-quality coal with refuse derived fuel (RDF) as a means to utilise some of the abundant high-ash coal available in South Africa as a fuel co-fired with RDF in existing pulverised fuel boilers. The use of RDF is also a means to reduce the volume of waste dumped in landfill sites. The physicochemical characteristics of the RDF, run of mine coal (ROM) and discard coal were investigated, along with the co-combustion behaviour and kinetics of the RDFs, coal and their blends at different weight ratios. The blends tested contained 85%, 70%, 50% and 25% coal with the remaining proportion made up of RDF. The gaseous emissions and ash residue from the combustion of coal, RDF and coal/RDF blends were also analysed to determine the environmental impact of co-firing with RDF. The physicochemical analysis revealed that the run-of-mine and discard coal have relatively low calorific values of 21.7 MJ/kg and 16.7 MJ/kg, respectively. The RDF samples were comprised of plastic and paper, as well as smaller amounts of other materials. The RDF sample containing mostly plastic (PL) and the other containing mostly paper (PB) were found to have higher energy contents of 31.2 MJ/kg and 22.4 MJ/kg, respectively. The thermogravimetric analysis was performed in an atmosphere of air, over a temperature range of 25 – 850°C, and the results showed that the RDF samples had lower ignition, devolatilisation, and burnout temperatures compared to the coals. The ignition temperatures for the blended fuel occurs in the lower temperature region when RDF is added to the blend, likewise the peak temperatures and burnout temperatures shifted to a lower temperature zone. The activation energies (Ea) were determined using the Coats-Redfern method. The Ea for the ROM coal of 104.4 kJ/mol, was found to reduce to 31.4 kJ/mol for 75% PB + 25% coal and 35 kJ/mol for 75% PL + 25% coal blends, respectively. The discard coal which had an Ea of 109.9 kJ/mol was reduced to 30.9 kJ/mol with the (paper blend) and 33.5 kJ/mol with the (plastic blend) for the 75% RDF + 25% coal discard blends. The analysis of the ash for the chloride and alkali metal content in the RDFs, coal samples and their blends were determined with the use of ion chromatography and X-ray fluorescence (XRF) techniques. The co-combustion ash of discard coal and RDF showed a decrease in chloride and alkali metal content as the ratio of coal was increased in the blend. The calculated slagging and fouling indices showed that as the coal ratio in the blend increases, the propensity of the fuel to slag and foul the boiler surfaces decreases. The propensity to slag was found to be low for the ash obtained from the co-fired blends, while the propensity to foul decreased from high to medium range for all the blends with less than 75% of the RDF PB. The concentration of gases emitted from the combustion and co-combustion test was determined with the aid of an MGA 11 mobile gas analyzer connected online at 1 scan per second. The co-combustion of RDF with coal showed a decrease in SO2 emissions from (387 ppm) for the discard coal to within the legislated maximum emission for South African new coal fired plants. This was attained with samples containing ˃ 15% PL and ˃ 30% PB RDF. The lowest SO2 emission of 50 ppm was achieved for the blend of 25% discard coal (C2) + 75% PL. The RDF sample (PL) emitted the highest NOx emission of 143 ppm. The peak concentration of NOx emitted was increased with the addition of RDF during co-combustion, however, the duration of the emission was greatly reduced and all samples were within the South African standard limits. There was also an increase in the emissions of CO and CO2 which could be due to the high volatile matter content of the RDF. The lowest CO2 emissions was 6000 ppm and this was achieved with the blend of 85% C2 + 15% PB. It was established in this study that the most favourable fuel blend that could be used for power generation is that of discard coal (70%) and PL (30%). This was based on the activation energy obtained from this blend, with the lowest apparent activation energies of 55.8 kJ/mol and 54.2 kJ/mol for the volatile and char combustion, respectively. This makes this blend the preferred alternative fuel to be fired in the existing pulverised fuel boilers, or other type of industrial boilers, in South Africa. / PH2020