The electrolysis of water was evaluated as a potentially efficient, as a low cost means of hydrogen production. The theoretical energy, voltage, current, and energy efficiencies of water electrolysis were considered by using various catalyst materials used in the fabrication of membrane electrode assemblies used in low temperature water electrolysis systems. Traditionally, iridium based catalysts have shown to be the most suitable material for its use on electrocatalysis of water to form hydrogen. This study showed that a combination of various elements as a binary and or ternary mixture in the base catalyst that was applied to the anode and cathode by using the Adam’s method had shown to give comparatively good results to that of using iridium oxide on its own. These catalysts were characterized by cyclic voltammetry, at different temperatures (30oC-80oC) with a range of catalyst loading of 0.2-0.5 mg.cm-2 noble metals. The study showed that the Ir40Co40 mixture as an anode catalyst was found to show highest hydrogen efficiency of 73 percent with a relatively low over potential of 0.925V at higher temperature of 80oC. The mixture also showed to give the best electrocatalytic activity with a low Tafel slope of 30.1mV.dec-1. Whereas the Ir50Pt50 showed a comparatively lower hydrogen efficiency of 65 percent with a lower over potential of 0.6V at 50oC. Ternary mixed oxide of Ir20Ru40Co40 showed an even lower over potential of 0.5- 0.6V over a large range of temperatures with a low hydrogen efficiency of 44 percent but gave good electrocatalytic activity in terms of the Tafel slope analysis. On the other hand, mixtures with relatively cheaper material such as Nickel in binary mixture systems such as Pt50Ni50 as cathode catalyst was found to show promising performance of a relatively low over potential that was less than 1.4 V with a low hydrogen efficiency of 62.1 percent Ternary cathode catalyst materials such as Pt33Ni33Co33 exhibited good performance with higher hydrogen efficiency of 65.2 percent at lower over potential of 1.2 V and a higher Tafel slope of 133.9 mV.dec-1 at 80 0C.

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The longitudinal and transverse nuclear relaxation times, T₁ and T₂, have been measured in normal H₂ gas at 77.5°K in the pressure range 0.05 to 2 atmospheres. In this region T₁ goes through a minimum, and T₂ deviates significantly from a linear dependence on the density. Comparison of the experimental data with existing theory establishes the following results for the J=1 state of orthohydrogen: i. autocorrelation functions of the molecular angular momentum operators are exponential or nearly so, ii. the ratio of the correlation times , Ʈ₁, Ʈ₂, which are associated with operators of the form J₊, and J²₊ respectively, lies within the limits 0.6 ≤ Ʈ₁ / Ʈ₂ ≤ 1, iii. the splitting of the molecular Zeeman levels cannot be neglected as in the original Schwinger theory. T₁ for the proton and deuteron in HD gas and for the deuterons in normal D₂ gas was measured as a function of temperature and pressure in the range 20 to 373°K and 0 to 8 atmospheres. To within experimental error the dependence of T₁ on the density p is linear. In HD below 65°K, when only the J=0 and J=1 states of the molecule are appreciably populated, the temperature dependence of T₁/p is identical for both proton and deuteron, leading to a value of Ʈ₁/Ʈ₂ = 1,07/± 15% for the J=1 state of HD. Above 100°K, T₁/p for the proton is inversely proportional to the temperature, whereas for the deuteron T₁/p is almost temperature independent. The experimental results are interpreted as evidence that in HD gas the process of molecular reorientation is dominated by the anisotropic intermolecular force arising from the separation of the centres of mass and charge of the molecule. In D₂ gas two relaxation times were found, one associated with the S=1 spin state of paradeuterium and the other associated with the S=2 spin state of orthodeuterium. At 40°K (T₁/p)s=₂ appears to go through a minimum; the analogous quantity in H₂ measured by previous workers also goes through a minimum, but at 80°K. This is consistent with interpreting the minimum as a quantum mechanical diffraction effect. The J=2 component of (T₁/p)s=₂ however, does not go through a minimum, which suggests that the intermolecular interactions are significantly different for the J=1 and J=2 states of the molecule. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In order to elucidate the mechanism of hydrogen sulphide oxidation, the photo-oxidation and thermal oxidation of hydrogen sulphide were studied, using gas chromatography for the analysis of final products. Photo-oxidation was studied at 130° and 150°C. Products found were sulphur dioxide, hydrogen, water and sulphur. Production of sulphur dioxide was found to be inhibited by an increase in surface area. Whether in photo- or thermal oxidation, the yield of sulphur dioxide increased drastically with slight increases in (O₂)/H₂S) ratio. This was also observed in the yield of hydrogen in photo-oxidation. Thermal oxidation was studied at 160°, 170°, 190°, 210°, 225°, 240°, and 260°C. Products were sulphur dioxide, water, and sulphur. No hydrogen was found. An expression for the production of sulphur dioxide was obtained: [formula omitted] = k (H₂S)⁻¹→⁺¹ (O₂)³ The overall activation energy was found to be 21.2±2k.cal./mole. Comparison with previously reported works was made and a mechanism proposed. / Science, Faculty of / Chemistry, Department of / Graduate

The generally accepted, though approximate, theory of the relaxation time T₁ of the nuclear spin system in ortho H₂ at low temperatures was developed by Schwinger (see Bloembergen (1948)). In this thesis Schwinger's theory is generalized to the case of arbitrary temperatures. An expression for T₁ is obtained which reduces to the Schwinger formula at low temperatures and ordinary pressures and to a slightly modified Schwinger formula at low temperatures and low pressures. The method used here to calculate T₁ is somewhat different from the method used by Schwinger. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The thesis describes a kinetic study of the reactions between cupric salts and hydrogen in aqueous solution. The first part is concerned with the homogeneous activation of hydrogen in solution by cupric perchlorate, as evidenced by its catalytic effect on the reaction between dichromate and hydrogen. These studies, which were conducted on solutions of higher acidity than previously investigated, provide further support for the mechanism proposed for this reaction, i.e., Cu⁺⁺ + H₂[formula omitted] CuH⁺+ H⁺ CuH⁺ + Cu"⁺⁺" □(→┬(k₂) ) 2Cu⁺ + H⁺ 2Cu⁺ + substrate □(→┬fast ) 2Cu⁺⁺ + products and the corresponding rate equation: (d[H^2])/dt = (k^₁ [Cu^(++) ]^2 [H^2])/((k^(-1)/(k^2 [H^+ ] )+[Cu^(++)]) The second part deals with the thermodynamics and kinetics of the precipitation of metallic copper from aqueous solution by H₂. The reduction reactions were studied in both cupric perchlorate and cupric sulphate solutions and the effects of a number of variables on the reaction rate in both systems are compared. The rate, which was initially fast, decreased gradually until an apparent steady-state condition was approached. This behavior was common to both systems, although the rates were much higher and the. residual copper concentration lower in the sulphate system. This apparent steady-state is not predicted by thermodynamics and is considered to result from kinetic factors. The dependence of the reaction rate on a number of variables can be predicted from the mechanism Cu⁺⁺ + H₂[formula omitted]CuH^++H⁺ CuH⁺ + Cu⁺⁺□(→┬(K₂) ) 2Cu⁺ + H⁺+ + 2Cu² □(→┬fast ) Cu° + Cu⁺⁺ which corresponds to an overall reaction of Cu⁺⁺ + H₂ → Cu° + 2H⁺ Reasonably good quantitative agreement between the predicted and measured kinetic dependence on Cu⁺⁺, H⁺ and H₂ concentration suggests that the rate of reduction of cupric salts is determined by the homogeneous activation of H₂ by Cu⁺⁺+ or a cupric complex. Although the initial decrease in rate can be predicted by this mechanism, the apparent steady-state condition approached cannot be fully explained. The equilibrium constant for the reaction 2Cu⁺ ⇌ Cu⁺⁺ + Cu° was also determined experimentally at several temperatures and compared with calculated values. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

The kinetics of the homogeneous reduction of mercuric salts by-molecular hydrogen in aqueous solution have been examined over a wide range of solution composition, temperature and hydrogen partial pressure. In perchlorate solutions, where Hg⁺⁺and Hg₂⁺⁺ are uncomplexed the kinetic results can be expressed by the equation: -d[H₂]J/dt = k₁[H₂][Hg⁺⁺] + k₂[H₂][Hg₂⁺⁺] where k₁ = 4.2 x 10¹⁰ exp [-18100/RT] 1.mole⁻¹ sec.⁻¹ and k₂ = 1.2 x 10¹¹ exp [-20400/RT] 1.mole⁻¹ sec.⁻¹ It was concluded that the rate-determining process of the reaction involves the bimolecular interaction of one H₂ molecule with either Hg⁺⁺ or Hg₂⁺⁺ , i.e., Hg⁺⁺ + H₂ [symobal omitted] Hg + 2H⁺ Hg₂⁺⁺ + H₂ [symbol omitted] 2Hg + 2H⁺ The Hg atoms thus formed undergo further rapid reactions to yield the observed products (Hg₂⁺⁺ or metallic mercury) the nature of which is determined by •' thermodynamic considerations. Mercuric complexes also reacted homogeneously with hydrogen but in most cases more slowly than the simple Hg⁺⁺ ions. The order of decreasing reactivity of the complexes, HgAc₂ > HgCl₂ > HgBr₂ > Hg(ethylenediamine)₂⁺⁺, is the same as the order of their increasing stability. This is attributed to the reduction of the electron affinity of Hg⁺⁺ through electron donation from the complexing ligand. The reactivity of mercuric complexes such as HgAc₂ and Hg(ethylenediamine)₂⁺⁺ is increased by anions such as 0H⁻, CO₃⁼, Ac⁻, etc., the influence of which increases in the same order as their basicity. This is attributed to stabilization, by the anions, of the H⁺ ions which are released in the rate-determining step of the reaction. Some conclusions are drawn concerning the mechanism of heterogeneous activation of hydrogen by solid catalysts. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The static field induced absorption spectrum of hydrogen has been investigated at high resolution and with reliable frequency calibration over the density range from 1.5 amagat to 28 amagat. Frequencies have been extrapolated to zero density in order to obtain molecular constants for the isolated molecule. Line profiles have been compared with various functions and the simple dispersion profile seems to fit the data best over the density range studied. The linewidth, however, decreases with density until it reaches a minimum at about 2.5 amagat below which it starts to increase again. The minimum width is about 4 times less than the width of the classical doppler line. This behavior of the line width is consistent with the phenomena of "collision narrowing" in the infrared. From the intensities of the lines we obtain the isotropic polarizability (α )₁₋₀ = 1.21 cm³. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Optical techniques have been used to study the behaviour of ethylene and hydrogen near their liquid-vapour critical points. From measurements of the coexistence curve of ethylene over the reduced temperature range 1.5 x 10⁻⁶ < t < 4.5 x 10⁻², where t — (Tc — T)/Tc and Tc is the critical temperature, we find the critical exponent β = 0.327±.002 and the corrections-to-scaling exponent ∆ = 0.46±.02. Similar measurements for hydrogen over the range 3.2 x 10⁻⁵ < t < 7.0 x 10⁻² give β = 0.326 ± .002 and ∆ = 0.46 ± .02. Measurements of the compressibility of hydrogen give the critical exponent [Formula Omitted] = 1.19 ± .05 and the critical amplitude ratio [Formula Omitted] = 5.2 ± .4. With the exception of ∆, which is slightly lower than its predicted value of 0.5, the results for these universal quantities are in agreement with theoretical predictions. The leading coexistence curve amplitude for hydrogen, B₀ = 1.19±.03, is lower than the corresponding values for ethylene, B₀ = 1.56 ± .03, and for other room-temperature fluids. This decrease is in qualitative agreement with the predictions of a theory of quantum effects on critical behaviour. Measurements of the coexistence curve diameter for both fluids show an anomaly near the critical point having a form consistent with the predicted t¹⁻α temperature dependence. These results are in agreement with a recent theory of the effects of many-body forces on the diameter; the hydrogen data indicate that these forces are attractive in that fluid. This suggests that quantum mechanical exchange interactions are important near the critical point of hydrogen. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Pulsed magnetic resonance studies are reported for a gas of hydrogen atoms at densities of 3-10¹³ X 10 cm⁻³ and temperatures of 4.2-77 K. The gas was produced by dissociation in a room temperature R.F. discharge, and piped through glass tubing into the cryogenic apparatus for study. The magnetic resonance transition observed is between the two lowest hyper-fine levels of the 1s atom in a magnetic field of 6481 Gauss where this splitting has its minimum value of about 765.5 MHZ. At 77 K, spin-exchange broadening of the resonance is observed. By varying the number density of hydrogen atoms, the ratio of spin-exchange broadening to atomic hydrogen density is obtained, and from this ratio the spin-exchange cross section for this transition is calculated. The cross section obtained is 60% of the theoretical value. At liquid helium temperatures, the spin-exchange cross section is shown to be at least 15 times smaller than that at liquid nitrogen temperatures, as. predicted by theory. He⁴ and H₂ buffer gases . are used to limit the diffusion broadening of the resonance, allowing the observation of small frequency shifts of the free induction signal. A model is proposed in which interactions of the hydrogen atoms with the flow tube walls cause these shifts. From the diffusion broadening of the resonance, the diffusion cross sections for H in He⁴ at 4.2 K and H in H₂ at 5-9 K are inferred to be 500 Ų and 250 Ų respectively. / Science, Faculty of / Physics and Astronomy, Department of / Graduate