The need for renewable energy is increasing as a result of global warming and other environmental challenges. Renewable energy systems are intermittent in nature and require energy storage solutions. Lithium-ion batteries are the first choice for storing electrical energy due to their high energy density, long cycle life, and small size. However, their widespread use in grid-scale applications is limited by high cost, low lithium resources, and security issues. Among the various options, the rechargeable zinc ion water battery has the advantages of high economic efficiency, high safety, and environmental friendliness, and there are great expectations for energy storage on a network scale. Inspired by these benefits, people have put a lot of effort into developing and manufacturing zinc-based energy storage devices. As the main component of zinc ion battery, the cathode material plays an important role in the storage / release of zinc ions during insertion and extraction. Vanadium-based materials are attracting attention due to their various oxidation states, diverse structures, and abundant natural resources. However, the details of suitable cathode materials and Zn2+ storage mechanism for rechargeable zinc ion battery are not yet fully understood. In this thesis, firstly, the prepared zinc pyrovanadate delivers good zinc ion storage properties owing to its open-framework crystal structure and multiple oxidation states. Mechanistic details of the Zn-storage mechanism in zinc pyrovanadate were also elucidated. Then, a calcium vanadium oxide bronze with expanding cavity size, smaller molecular weight, and higher electrical conductivity are proposed to deeply understand the impact of the crystal structure on battery performance. To improve the stability of the cathode in rechargeable zinc ion battery, an artificial solid electrolyte interphase strategy has been proposed by inducing an ultrathin HfO2 layer via the Atomic layer deposition method, which effectively alleviates the dissolution of active material. Finally, a nitrogen-doped 3D laser scribed graphene with a large surface area and uniform distribution of nucleation sites has been used as the interlayer to control Zn nucleation behavior and suppress Zn dendrite growth, which brings new possibilities for the practical rechargeable zinc ion battery.

The following Thesis is comprised of two separate and individual parts, both of which relate to the disposal of hydrogen sulfide. Section One is an investigation into the possibility of developing a hydrogen sulfide decomposition process which would produce both hydrogen and elemental sulfur. Section Two deals with the speciation study of a catalyst used in a traditional process which converts hydrogen sulfide gas into elemental sulfur. / Section 1: <p> The disposal of hydrogen sulfide by electrolysis to produce both hydrogen and sulfur appears to an interesting alternative to the conventional Claus process which wastes the hydrogen content of hydrogen sulfide. The electrolysis at room temperature has been reported in the literature, however, the investigation was somewhat limited by the low conductivity displayed by the electrolysis solution (pyridine/hydrogen sulfide mixture). </p> <p> The primary goal of this research was to construct a suitable apparatus and carry out a series of conductivity measurements of liquid hydrogen sulfide at room temperature with and without the addition of possible electrolytes. The objective was to determine if an electrolyte could be found that would increase the conductivity to a suitably high level to warrant the further investigation of the electrolysis process. </p> <p> Of the six possible electrolytes, only tetrapropyl ammonium iodide increased the conductivity to a desirable level. A 0.4034 M solution of this alkyl ammonium iodide in liquid hydrogen sulfide increased the conductivity (at 23 C) from 7.00 X 10-8 ohm-1cm-1 for the pure solvent to 1.13 X 10-2 ohm-1cm-1. This increase was attributed to the formation of the corresponding hydrogen sulfide adduct and its subsequent dissociation in liquid hydrogen sulfide. </p> </p> Now that it has clearly been established that appropriately high conducting solutions of hydrogen sulfide can be prepared, the further investigation of the electrolysis of hydrogen sulfide as a viable industrial process is warranted. </p> Section 2: <p> This section deals with the investigation of species present in vanadium(IV): citrate solutions over a wide range of pH values. Various spectroscopic methods (UV/VIS, ESR, vanadium Sl FT-NMR) were used to probe this specific system. The accumulated spectroscopic data were rationalized on the basis of thirteen vanadium(IV) containing species, four of which were proposed to be vanadium(IV): citrate species. Based on the observed spectroscopic data an equilibrium diagram was prepared which illustrates the vanadium(IV) species present as a function of pH. </p> / Thesis / Master of Science (MSc)

<p> The crystal structures of VOP2SiO8, VO(PO3)2, V(PO3)3, (VO)2P2O7 and VAsO5 have been determined with the help of x-rays, and are compared with the known structures in the V-P-As-O system. All the vanadium atoms in the mixed oxides are octahedrally coordinated and the V^+4 O6 and V^+5 O6 octahedra are all characterized by one short vanadyl bond. V^+3 O6 groups are nearly regular. The tetrahedral phosphorus is found in structural elements ranging from infinite metaphosphate chains (V(PO3)3, VO(PO3)2), to pyrophosphate groups ((VO)2P2O7) to isolated tetrahedra (VAsO5 and VOP2SiO8). Both structural and substitutional disordering is evident in the V-P-As-O system, and is discussed together with a detailed model for stacking faults in VAsO5.</p> <p> Some of the phases in the V-P-As-O system are known to catalyze the oxidation of butene to maleic anhydride, and certain structural features of the compounds are related to this catalytic activity. α-VPO5 can be related to (VO)2P2O7 through the formation of shears in a manner similar to shear formation in V2O5, and such a mechanism is proposed as a means whereby an α-VPO5 catalyst can change into (VO)2P2O7, the known composition of the spent catalyst.</p> / Thesis / Doctor of Philosophy (PhD)

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