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The first part of this thesis focused on methodological developments of single- crystal resonance Raman spectroscopy (SCRR) and its novel combination with X-ray crystallography to assign and validate redox and ligand states. The utility of both methods was initially tested on CYTcp from Alcaligenes xylosoxidans (AXCP) crystals as it has been well characterised in solution including resonance Raman spectroscopy and is represented in chapter 4. The novel approach has been used for the spectroscopic validation of all crystal structures presented in this thesis. AXCP shares a similar heme environment with CYTcp from Rhodopseudomonas palustris (RPCP), which exists entirely as a monomer. Research has indicated that the unusual'distal-to-proximal' NO conversion in AXCP is highly dependent on the proximal Arg124 and distal Leu16 residue. The effect of the distal Leu residue in AXCP and RPCP has been explored in chapter 5 and 6 by site-directed mutants to make more room at the distal site and lift steric hindrance. The ligand-bound CYTcp were structurally, kinetically and spectroscopically characterised. The L 16VAXCP, L 161AXCP and L 121RPCP mutants showed a dramatic boost in NO affinity of the distal 6c-NO complex and hindering the conversion to the proximal 5c-NO. Both AXCP mutants displayed a -30-fold faster kon(NO) and -10-2-fold slower koff(NO) indicating that the distal residue modulates the balance of affinities of both heme sites. In contrast, the high distal koff(NO) in AXCP supports a fast distal NO release compared to the proximal NO in the

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Adsorption of small molecules on the Ni{111} and NiO{111} surfaces is investigated under UHV and elevated pressures (~10-1 mbar) of hydrogen and water. The molecules considered are chosen for their relevance to understanding the mechanism of enantioselective hydrogenation on Raney Nickel modified by chiral molecules. Adsorption of water onto, and its subsequent reaction with, oxygen-covered Ni{111} is dependent on the initial atomic oxygen coverage. An OH species (O1s binding energy 531.5eV), oriented perpendicular to the surface, forms at atomic oxygen coverages <0.25ML. The reaction does not consume all the adsorbed oxygen for coverages ≥0.12ML. The p(2×2) atomic oxygen uperstructure is unreactive, while an OH species is formed on the p(√3×√3) superstructure at binding energy 530.9eV. L-alanine is adsorbed on Ni{111} as a model chiral modifier molecule. At low coverages, alanine forms a presumed tridentate alaninate species for coverages ≥0.11ML at 250K. A minority, bidentate zwitterionic species forms at coverages >0.11ML, but was not observed at 300K. Saturation occurs at 0.25ML. At high alanine coverages (≥0.19ML) and H2 pressure (≥1×10-2 mbar), the tridentate L-alaninate converts to bidentate zwitterionic L-alanine at 300K. Thermal evolution of L-alanine on Ni{111} under varying hydrogen pressures is examined. Adsorption of L-alanine onto hydroxylated NiO{111} at 300K in UHV, mimicking a catalyst surface under aqueous conditions, yields the tridentate alaninate which is immune to the effects of elevated hydrogen pressure. Exposing the L-alanine/Ni{111} adsorption system to water (≤10-1 mbar) oxidises the surface and recreates the L-alanine/hydroxylated NiO{111} system. Pyruvic acid on Ni{111} is examined as a model for hydrogenation substrate adsorption. Behaviour is coverage dependent and several conformations are possible at low coverages (≤0.1ML). Annealing at coverages <0.2ML causes a condensation reaction, releasing water onto the surface. High coverages do not condense and a saturation coverage of ~0.35ML is found.

Heterogeneous catalysis is crucial in many areas of the chemical and energy industries, which was estimated to be used in 90% of all chemical processes despite its importance, most catalysts were found using trial-and-error approaches. Methods that can design new catalysts rationally is highly necessary. One promising approach is to take the advantage of the increasing computational capacity and the state-of-the-art calculation method to screen and design new heterogeneous catalysts. Such an approach requires not only a deep understanding of reaction mechanisms and activities in heterogeneous catalysis, but also rational design schemes. Therefore, in the first half part of the thesis, first-principle calculations within the Density Functional Theory (DFT) framework together with micro-kinetic modelling were used to understand the mechanisms and activities in heterogeneous catalysis. In the second half, some design schemes were proposed including the multi-phase surface design, gradient based optimization and inverse design using activity contribution equation.