This thesis by Jillian Lee Dempsey, defended in 2010, focuses on the catalytic evolution of hydrogen using cobaloximes, a promising class of small molecules. The work is motivated by the need to develop efficient solar energy conversion processes. The thesis begins with an introduction to solar fuels and the challenges in water splitting, highlighting the importance of catalysts that avoid the formation of high-energy intermediates. It reviews the initial work on cobaloximes by Espenson and recent studies that have revisited their catalytic activity. The next three chapters introduce photochemical methods for detecting catalytic intermediates and determining kinetics associated with the elementary steps of hydrogen evolution. Four catalytic pathways are considered, each starting with the reduction of a CoII-diglyoxime to generate CoI, which reacts with a proton donor to produce a CoIII-hydride. The pathways include homolytic and heterolytic reactions, leading to the formation of H2. Chapter 2 presents kinetics of electron transfer reactions of a Co-diglyoxime complex, revealing a strong thermodynamic preference for a CoIII-hydride homolytic pathway over a heterolytic route. Chapter 3 introduces phototriggered hydride generation and time-resolved spectroscopy as novel methods for mechanistic investigations, showing that the reaction kinetics are consistent with a heterolytic route for hydrogen evolution via a CoII-hydride intermediate. Chapters 4 and 5 extend these mechanistic investigations to aqueous media and focus on the design and construction of second-generation cobaloximes. Chapter 4 discusses the thermodynamic preference for bimolecular reactivity of two CoIII-hydrides in a binuclear cobaloxime. Chapter 5 explores the design of binuclear cobaloximes with covalent alkyl tethers to decrease the volume required for diffusional collisions, while maintaining catalytic activity. Chapter 6 focuses on bifunctional cobaloximes for covalent attachment to silicon electrodes, incorporating a terminal olefin into the glyoxime backbone for surface-based coupling reactions. The chapter also discusses initial efforts to prepare chemically modified electrodes. The thesis concludes with three appendices, including work on photochemical generation of a powerful Os(III) reductant, electron transfer reactions of N,N',3,3'-tetramethyl-4,4'-bipyridinium, and MATLAB scripts for kinetics analysis.This thesis by Jillian Lee Dempsey, defended in 2010, focuses on the catalytic evolution of hydrogen using cobaloximes, a promising class of small molecules. The work is motivated by the need to develop efficient solar energy conversion processes. The thesis begins with an introduction to solar fuels and the challenges in water splitting, highlighting the importance of catalysts that avoid the formation of high-energy intermediates. It reviews the initial work on cobaloximes by Espenson and recent studies that have revisited their catalytic activity. The next three chapters introduce photochemical methods for detecting catalytic intermediates and determining kinetics associated with the elementary steps of hydrogen evolution. Four catalytic pathways are considered, each starting with the reduction of a CoII-diglyoxime to generate CoI, which reacts with a proton donor to produce a CoIII-hydride. The pathways include homolytic and heterolytic reactions, leading to the formation of H2. Chapter 2 presents kinetics of electron transfer reactions of a Co-diglyoxime complex, revealing a strong thermodynamic preference for a CoIII-hydride homolytic pathway over a heterolytic route. Chapter 3 introduces phototriggered hydride generation and time-resolved spectroscopy as novel methods for mechanistic investigations, showing that the reaction kinetics are consistent with a heterolytic route for hydrogen evolution via a CoII-hydride intermediate. Chapters 4 and 5 extend these mechanistic investigations to aqueous media and focus on the design and construction of second-generation cobaloximes. Chapter 4 discusses the thermodynamic preference for bimolecular reactivity of two CoIII-hydrides in a binuclear cobaloxime. Chapter 5 explores the design of binuclear cobaloximes with covalent alkyl tethers to decrease the volume required for diffusional collisions, while maintaining catalytic activity. Chapter 6 focuses on bifunctional cobaloximes for covalent attachment to silicon electrodes, incorporating a terminal olefin into the glyoxime backbone for surface-based coupling reactions. The chapter also discusses initial efforts to prepare chemically modified electrodes. The thesis concludes with three appendices, including work on photochemical generation of a powerful Os(III) reductant, electron transfer reactions of N,N',3,3'-tetramethyl-4,4'-bipyridinium, and MATLAB scripts for kinetics analysis.