UC San Diego

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.