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With rising atmospheric CO2 levels and a growing demand for sustainable energy, it is imperative to search for a means of a carbon-neutral fuel source that can replace the current global energy infrastructure. Electrochemical and photoelectrochemical CO2 reduction (CO2R) are promising paths towards producing carbon-neutral fuels like methanol. Recently, immobilized molecular catalysts (CoPc) on carbon nanotubes have been growing in interest as they exhibit extraordinary catalytic properties, such as high current density, high product selectivity, long-term stability, high turnover-frequency, low overpotentials, and the ability to operate in aqueous environments. To improve upon these hybrid CO2R systems, it is crucial to understand how the molecular catalyst interacts with the graphitic support to further tailor the catalyst or the local microenvironment. This dissertation will be focusing on discussing the local microenvironments surrounding the catalysts and multiwalled carbon nanotube (MWCNT) support. First, a broad overview of catalyst types in electrochemistry is discussed, which gives context to the current field of immobilized molecular catalysts on graphitic supports for CO2 reduction. The following chapter discusses how the preparation methods of these hybrid catalyst/MWCNT electrodes can affect the surface morphology, electrochemical behavior, and catalysis. Next, in-situ XAS electrochemical measurements were taken of Re(tBu-bpy)(CO)3Cl on MWCNT to study their electronic coupling and molecular interactions. The next chapter discusses how applied bias and mass transport affect the selectivity of immobilized CoPc on MWCNT for selective methanol generation, and the role of CO as a reactive unbound intermediate. This model catalyst layer preparation was integrated onto a 3-terminal tandem device (3TT) for a photoelectrochemical CO2R cascade scheme to generate methanol using light in a near neutral pH aqueous system. The last chapter is focused on providing ide

Carbon dioxide reduction has been an increasingly popular research in the renewable energy development as it can be used to store the solar energy in the form of chemical energy in liquid fuels, like gasoline and diesel. There are two main catalytic approaches to overcome the thermodynamically unfavored conversion of carbon dioxide (CO2) to carbon-based species, such as carbon monoxide and format: photochemical reduction using direct sunlight, and electrochemical reduction using electricity generated by solar panels. In a typical photochemical system using rhenium or manganese bipyridine catalysts, previous work has been done on ligand modification to improve the quantum yield of carbon monoxide (CO) and other carbon species production. The work presented in this dissertation focuses on the structural modification of these catalysts to eliminate dimerization of manganese bipyridine catalyst upon first reduction and facilitate electron transfer from singly reduced photosensitizer to catalyst through non-covalent supramolecular assembly. In the former method, the bromide ligand of the manganese bipyridine catalyst (Mnbpy(CO)3Br) was replaced with a cyanide ligand (Mnbpy(CO)3CN) to reach an alternative reaction mechanism, in which disproportionation of two singly reduced manganese bipyridine catalyst occurs to give the active species without dimerization. In the latter method, electron transfer between the singly reduced photosensitizer and the catalyst is facilitated by the closer proximity of the two through non-covalent hydrogen bonding. Both method, unexpectedly, discovered the role of solvents in photocatalysis on product selectivity. One of the biggest obstacles of electrochemical reduction of carbon dioxide in large-scale application is the immobilization of catalysts onto electrode surface. Most of the attachment methods in the literature face the issues of catalysts detachment and deactivation, and poor electrical contact between the catalyst and the electrode

Carbon dioxide reduction has been an increasingly popular research in the renewable energy development as it can be used to store the solar energy in the form of chemical energy in liquid fuels, like gasoline and diesel. There are two main catalytic approaches to overcome the thermodynamically unfavored conversion of carbon dioxide (CO2) to carbon-based species, such as carbon monoxide and format: photochemical reduction using direct sunlight, and electrochemical reduction using electricity generated by solar panels. In a typical photochemical system using rhenium or manganese bipyridine catalysts, previous work has been done on ligand modification to improve the quantum yield of carbon monoxide (CO) and other carbon species production. The work presented in this dissertation focuses on the structural modification of these catalysts to eliminate dimerization of manganese bipyridine catalyst upon first reduction and facilitate electron transfer from singly reduced photosensitizer to catalyst through non-covalent supramolecular assembly. In the former method, the bromide ligand of the manganese bipyridine catalyst (Mnbpy(CO)3Br) was replaced with a cyanide ligand (Mnbpy(CO)3CN) to reach an alternative reaction mechanism, in which disproportionation of two singly reduced manganese bipyridine catalyst occurs to give the active species without dimerization. In the latter method, electron transfer between the singly reduced photosensitizer and the catalyst is facilitated by the closer proximity of the two through non-covalent hydrogen bonding. Both method, unexpectedly, discovered the role of solvents in photocatalysis on product selectivity. One of the biggest obstacles of electrochemical reduction of carbon dioxide in large-scale application is the immobilization of catalysts onto electrode surface. Most of the attachment methods in the literature face the issues of catalysts detachment and deactivation, and poor electrical contact between the catalyst and the electrode

To create fully sustainable energy systems requires multiple stages of engagement across different fields. The work presented in this dissertation represents a small survey of two major branches of sustainable chemistry – the improved efficiency for converting from renewably sourced fuels to power and the utilization of renewable sources of electricity to produce valuable chemicals from renewable carbon feedstocks. Electrochemistry and photoelectrochemistry are powerful tools for interconversion between chemical and electrical energy and for using light to drive chemical change. Light can be used to overcome both the kinetic and thermodynamic barriers found in electrochemistry. In a proposed fuel cell device, the feasibility of using multi-carbon fuels like n-hexane at ambient temperatures and pressures may be made possible by using light activated materials to overcome the kinetic barriers to fuel oxidation. The energy to produce the light may be sourced from the fuel cell itself and fed back into the oxidation process. In an electrolysis reaction, light may be used to drive the uphill reaction by creating sufficient photovoltage and photocurrent. In a paired electrolysis, CO2 and a lignin derived substrate syringaldehyde are simultaneously upgraded using a customized photovoltaic device to drive both catalytic processes. In both of these implementations, electricity plays the crucial role of connecting light energy to chemical change and provides two examples where it can be used in sustainable chemical methods.

To create fully sustainable energy systems requires multiple stages of engagement across different fields. The work presented in this dissertation represents a small survey of two major branches of sustainable chemistry – the improved efficiency for converting from renewably sourced fuels to power and the utilization of renewable sources of electricity to produce valuable chemicals from renewable carbon feedstocks. Electrochemistry and photoelectrochemistry are powerful tools for interconversion between chemical and electrical energy and for using light to drive chemical change. Light can be used to overcome both the kinetic and thermodynamic barriers found in electrochemistry. In a proposed fuel cell device, the feasibility of using multi-carbon fuels like n-hexane at ambient temperatures and pressures may be made possible by using light activated materials to overcome the kinetic barriers to fuel oxidation. The energy to produce the light may be sourced from the fuel cell itself and fed back into the oxidation process. In an electrolysis reaction, light may be used to drive the uphill reaction by creating sufficient photovoltage and photocurrent. In a paired electrolysis, CO2 and a lignin derived substrate syringaldehyde are simultaneously upgraded using a customized photovoltaic device to drive both catalytic processes. In both of these implementations, electricity plays the crucial role of connecting light energy to chemical change and provides two examples where it can be used in sustainable chemical methods.