Turning Up the Heat, Turning Down Emissions: Temperature-Driven Selectivity in Bicarbonate-Fed CO₂ Electrolysis For Sustainable Fuel Production

Abstract

This thesis investigates an electrochemical carbon dioxide reduction experiment using bicarbonate as a liquid feedstock, which offers a route to integrated carbon capture and conversion, eliminating the energy-intensive CO₂ regeneration steps required in conventional gas-fed systems. This work characterizes the performance of a bipolar membrane electrolyzer with a silver nanoparticle cathode, fed with 1 M KHCO₃, operated galvanostatically at 50 to 200 mA/cm⁻² at ambient temperature 23°C and elevated temperature 50°C. The bipolar membrane enables in situ CO₂ generation from bicarbonate at the cathode interface via proton-driven acid-base conversion. Elevated temperature consistently improved CO Faradaic efficiency and reduced cell voltage across all current densities tested, attributed to faster electrode kinetics, suppression of the hydrogen evolution reaction, and increased local CO₂ availability at the catalyst surface. These results demonstrate that moderate thermal operation is a practical and effective strategy for improving both the selectivity and energy efficiency of bicarbonate-fed CO₂ electrolysis.