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The electrochemical oxidation of methanol as applicable to low temperature fuel cell environments, has been investigated. The case for the use of methanol as a directly oxidisable fuel in alkaline electrolyte is presented. Initial work was targeted at establishing a non-noble metal electrode at which methanol could be oxidised in an aqueous alkaline electrolyte. Nickel, as an established electrode material for alkaline cells, was investigated by cyclic voltammetry and potentiostatic polarisation in both hydroxide and carbonate electrolytes, and noted features studied. The relative methanol oxidation performance of a selection of potential electrocatalysts, introduced through surface modification of porous and non-porous nickel structures, was later demonstrated.

Abstract: Oil and gas industry have faced significant operational, economic, and environmental challenges in recycling produced water. The treatment of produced water is highly researched, but few studies have evaluated the performance of treated produced water when used for hydraulic fracturing and enhanced oil recovery (EOR) operations. In this study, we treated various aqueous solutions, including synthetic formation brine (FB), sodium chloride (NaCl), calcium chloride (CaCl2), and sodium sulfate (Na2SO4), using an electro-oxidation (EO) process. The brine properties, including density, surface tension (ST), oil−water interfacial tension (IFT), viscosity, and pH, were compared before and after the treatment. Then, we conducted systematic contact-angle (CA) measurements and spontaneous imbibition tests using treated and untreated brine to study the effects of water treatment on rock−fluid interactions and its impact on oil recovery. The experimental results show that the effect of the EO process on ST, density, viscosity, and IFT was insignificant. However, the CA results show that the treated FB, NaCl, and Na2SO4 solutions exhibit stronger wetting characteristics compared with the untreated ones, while the treated CaCl2 solution exhibit weaker wetting characteristics compared with the untreated ones. We hypothesized that the change in the wetting characteristics was due to the generated oxidants from the EO process. We added OH−, H+, hydrogen peroxide (H2O2), and sodium hypochlorite (NaOCl) into untreated brine to test this hypothesis and monitored the CA variations. The results suggest that H2O2 and OH− can alter the wettability to more water-wet conditions in the NaCl solution but not in the CaCl2 solution. Furthermore, NaOCl results in wettability alteration to more oil-wet conditions in NaCl and CaCl2 solutions. The change in wettability to more water-wet conditions is mainly the result of the oxidation of dissolved organic matters, and the change to more oil-wet conditions is the result of the dissolution of high-valence cations, causing the cation bridging effect. We also studied the compatibility between produced formation brine and hydrolyzed polyacrylamide (HPAM). In our study, we conducted dynamic viscosity, particle size distribution, and viscoelasticity measurements to evaluate the performance of HPAM in DI water and formation brine (FB). The experimental results suggest that HPAM in FB has a much lower dynamic viscosity and shear stress profiles than in DI water. The storage modulus is higher than the loss modulus in the entire measured range when adding HPAM into FB, indicating a considerable curling of HPAM in the FB. We also conduct a sensitivity analysis to identify the problematic ions and their threshold concentration in the FB through dynamic viscosity measurement. Our results show that HPAM can only resist monovalent ions at low concentrations (

Electrochemical upgrading of biomass compounds to value-added platform chemicals is a sustainable route towards reducing reliance on fossil fuels and greenhouse gas emissions. When powered by renewable electricity, the electrochemical upgrading of biomass can be used to generate green hydrogen cost-efficiently. 5-Hydroxymethyl furfural (HMF), derived from acid-catalysed dehydration of sugars, is a representative biomass compound capable of yielding several useful platform chemicals. 2,5-Furandicarboxylic acid (FDCA) generated from the alkaline electrooxidation of HMF (HMFOR) has been studied extensively as a renewable building block that can substitute petroleum for making monomers, medicine, agrochemicals, and specialty chemicals. For these reasons, there have been considerable efforts in researching active electrocatalyst materials for HMFOR. This thesis focuses on application of Prussian blue analogues (PBAs) as an HMFOR electrocatalyst material. PBAs are a class of porous coordination polymers with branching applications in bio-sensing, gas adsorption, energy storage, and electrocatalysis. These materials are ideal electrocatalyst materials due to their easy synthesis, tuneable structure, large concentration of metal sites, and porous structure which allows for the easy diffusion of electrolyte species. In alkaline solutions, they transform into oxide/hydroxide structures with superior electrocatalytic activity to their conventional counterparts due to the presence of defects. Despite these advantages, the catalytic performance of PBA-derived electrocatalysts is still limited by their relatively poor conductivity. This limitation is largely due to the conventional wet precipitation methods used to synthesise PBAs, which limit the amount of active site exposure and interfacial adhesion with the anode current collector. Utilising binder-free synthesis methods like electrodeposition can potentially overcome these limitations and maximise the electrochemical activity of these materials.

Electrochemical oxidation is a common method for the degradation of chemicals by applying potential at a definite value. In this research, ‘cyclic voltammetry’ experiments were conducted to find out the oxidation potential for 8 different pharmaceuticals. Mainly, 3 different pH solutions (pH 6.0, 7.5, 9.0) and 9 different concentrations (1, 2, 5, 10, 20, 50, 100, 200, 500 µM) were studied for each of the pharmaceuticals in this experiments. Acetaminophen, Ibuprofen, Naproxen Sodium, Caffeine showed oxidation peak at 0.34-0.79V, 1.37- 1.39V, 0.94-1.01V, 1.44-1.55V respectively at different pH and concentrations. Antibiotic and antihistamine pharmaceuticals i.e. Erythromycin Hydrate, Triclosan, Sulfanilamide, Diphenhydramine Hydrochloride showed oxidation peak at 0.91-1.19V, 0.58-1.03V, 0.86-1.11V, 0.79-1.22V respectively at different pH and concentrations. The oxidation potential varies with both pH and concentration for every pharmaceutical. The chronoamperometry experiments were performed to determine the relationship between the concentration of the pharmaceuticals and the current. The sensor curves have been developed from the data of the chronoamperometry experiments. To observe the electrochemical degradation, the potential (higher than the oxidation potential found by the cyclic voltammetry experiments) have been applied to the pharmaceutical solutions and samples were collected at different time from the solutions during the period of applying potential. The samples were then analyzed in HPLC instrument. Triclosan and Sulfanilamide have shown successful degradation. The 1st order reaction constants are 0.0039 min-1 and 0.0148 min-1 for the degradation of sulfanilamide and Triclosan respectively.

In this study, phenol was used in a sodium chloride or sulfate matrix as a representative pollutant to systematically study which operating conditions have the largest impact on chlorine forms in an electrochemical treatment system. Initially, an HPLC method was developed and validated to simultaneously determine phenol and potential intermediates from hydroxylation and hypochlorination pathways during electrooxidation in the presence of chloride. In a combined-reactor configured with a boron-doped diamond (BDD) anode, samples were analyzed to identify and quantify organic intermediates and inorganic chlorine species generated during the electrooxidation of phenol. Ionic strength was kept constant at 50 mM and the applied current density was 12 mA/cm2. The effects of chloride-to-phenol ratio on contaminant removal efficiency and byproduct formation were studied. Experimental results showed that phenol was removed faster at higher chloride-to-phenol ratios but more chlorinated intermediates and chlorate were produced. The impact of initial chloride concentration on the chlorate formation rate was stronger than its impact on phenol removal rate. Analysis of variance (ANOVA) was used to evaluate the statistical significance of operational factors in a full 24 factorial design. Factors studied were anode type (BDD vs. graphite), initial phenol concentration (0.25 – 0.5 mM), initial chloride concentration (5 – 50 mM) and applied current density (12 – 25 mA/cm2), on responses such as phenol removal rate and chlorate production rate. Results showed that anode type and chloride concentration had the most significant effects either individually or interactively on the phenol removal rate, and that chloride concentration had a considerable effect on the chlorate production rate. Additionally, applied current density had a significant effect on the free chlorine production rate after breakthrough if and when it occurred with BDD in the presence of excess chloride. A 23 factorial design with a given reactor configuration with either BDD or graphite anode was optimized using response surface methodology (RSM) with respect to phenol removal and control of chlorate production. Linear regression results showed that the phenol removal rate was highest at low phenol concentration and high chloride concentration, whereas low chloride concentration minimized chlorate production. In addition to the ANOVA analyses, kinetics of the electrochemical oxidation of phenol and intermediates formed in the presence of chloride were explored for the different anodes at various chloride-to-phenol ratios. Comparison of rate constant k values of the first-order reactions showed that hypochlorination and hydroxylation pathways were in competition and hypochlorination pathway was more favored and 2-chlorophenol was the most dominant species in most cases. Mass balances around carbon and chlorine for measured species were also considered. Lack of closure for both indicated possible formation of other by-products that were not identified by HPLC. LC-QTOF-MS was used to qualitatively investigate the unknown by-products formed during phenol electrooxidation in the presence of chloride at two levels (5 mM and 50 mM) using the BDD anode. Results showed formation of chlorinated dimers and trimers of phenol, including potential formation of polychlorinated dibenzo-p-dioxins (PCDDs).