This thesis explores the catalytic hydrogen evolution mediated by cobaloximes, a class of small molecules that can catalytically evolve hydrogen at low overpotentials. The research is motivated by the need to develop efficient solar energy conversion processes. The study investigates the catalytic activity of cobaloximes, which were first reported by Espenson over three decades ago. The research includes photochemical methods for detecting catalytic intermediates and determining the kinetics of hydrogen evolution. Four catalytic pathways are considered, each beginning with the reduction of Co(II)-diglyoxime to generate Co(I), which reacts with a proton donor to produce Co(III)-hydride. In a homolytic pathway, two Co(III)-hydrides react to eliminate H2, while in a heterolytic pathway, protonation of Co(III)-hydride produces H2 and Co(III). The Co(III)-hydride may also be reduced further to Co(II)-hydride, which can react via analogous heterolytic or homolytic pathways. The kinetics of electron transfer reactions of a Co-diglyoxime complex are presented, along with a detailed thermodynamic analysis of proposed hydrogen evolution pathways. A strong thermodynamic preference for a Co(III)-hydride homolytic pathway over a Co(III)-hydride heterolytic route is identified as the key finding. Phototriggered hydride generation is introduced as a novel method for mechanistic investigations. The reaction kinetics are consistent with a heterolytic route for hydrogen evolution that proceeds via a Co(II)-hydride intermediate. The study extends these mechanistic investigations to aqueous media using photoionization and pulse radiolysis methods. Chapters 5 and 6 focus on the design and construction of second-generation cobaloximes. A binuclear cobaloxime is used to probe the thermodynamic preference for bimolecular reactivity of two Co(III)-hydrides. A strategy for covalently grafting cobaloxime derivatives to silicon electrodes is introduced. A terminal olefin is incorporated into a glyoxime backbone, a functionality amenable to surface-based coupling reactions. The bifunctional cobaloxime is an active catalyst, and initial efforts to prepare the chemically modified electrode are discussed. The research also includes work on the photochemical generation of a powerful Os(II) reductant, electron transfer reactions of N,N',3,3'-tetramethyl-4,4'-bipyridinium, and annotated MATLAB scripts utilized for kinetics analysis. The thesis highlights the experimental efforts aimed at elucidating the mechanism of efficient H2 evolution, the development of second-generation catalysts, and the integration of the catalyst and photocathode components. The research contributes to the understanding of the catalytic mechanisms of cobaloximes and their potential applications in solar water splitting devices.This thesis explores the catalytic hydrogen evolution mediated by cobaloximes, a class of small molecules that can catalytically evolve hydrogen at low overpotentials. The research is motivated by the need to develop efficient solar energy conversion processes. The study investigates the catalytic activity of cobaloximes, which were first reported by Espenson over three decades ago. The research includes photochemical methods for detecting catalytic intermediates and determining the kinetics of hydrogen evolution. Four catalytic pathways are considered, each beginning with the reduction of Co(II)-diglyoxime to generate Co(I), which reacts with a proton donor to produce Co(III)-hydride. In a homolytic pathway, two Co(III)-hydrides react to eliminate H2, while in a heterolytic pathway, protonation of Co(III)-hydride produces H2 and Co(III). The Co(III)-hydride may also be reduced further to Co(II)-hydride, which can react via analogous heterolytic or homolytic pathways. The kinetics of electron transfer reactions of a Co-diglyoxime complex are presented, along with a detailed thermodynamic analysis of proposed hydrogen evolution pathways. A strong thermodynamic preference for a Co(III)-hydride homolytic pathway over a Co(III)-hydride heterolytic route is identified as the key finding. Phototriggered hydride generation is introduced as a novel method for mechanistic investigations. The reaction kinetics are consistent with a heterolytic route for hydrogen evolution that proceeds via a Co(II)-hydride intermediate. The study extends these mechanistic investigations to aqueous media using photoionization and pulse radiolysis methods. Chapters 5 and 6 focus on the design and construction of second-generation cobaloximes. A binuclear cobaloxime is used to probe the thermodynamic preference for bimolecular reactivity of two Co(III)-hydrides. A strategy for covalently grafting cobaloxime derivatives to silicon electrodes is introduced. A terminal olefin is incorporated into a glyoxime backbone, a functionality amenable to surface-based coupling reactions. The bifunctional cobaloxime is an active catalyst, and initial efforts to prepare the chemically modified electrode are discussed. The research also includes work on the photochemical generation of a powerful Os(II) reductant, electron transfer reactions of N,N',3,3'-tetramethyl-4,4'-bipyridinium, and annotated MATLAB scripts utilized for kinetics analysis. The thesis highlights the experimental efforts aimed at elucidating the mechanism of efficient H2 evolution, the development of second-generation catalysts, and the integration of the catalyst and photocathode components. The research contributes to the understanding of the catalytic mechanisms of cobaloximes and their potential applications in solar water splitting devices.