Understanding Electrochemical CO2 Reduction using Polycrystalline Au Electrode in WiS Electrolyte

Thesis advisor: Dunwei WangElectrochemical CO2 reduction reaction (CRR) provides a solution to both the increasing global demand of energy by forming valuable chemical products for fuel production, and global warming by reducing the amount of CO2 in the environment. To efficiently reduce CO2, we sought to understand the reaction mechanism using a polycrystalline Au electrode and the super concentrated LiTFSI solution (WiS) as the electrolyte. By varying both the electrolytic potential and the concentration of WiS, we investigated the factors determining product selectivity and found that reaction kinetics and mass transport together direct the selectivity towards CO. We probed the rate limiting step (RLS) of CO2 reduction by observing the variation of product distribution with water availability in solution, and discovered that the RLS was likely to involve only a single electron transfer to form COO*–. Lastly, we proposed that in WiS, H2O were the dominant proton sources for both CO2 reduction and H2 evolution reactions. In 21m WiS, the competing hydrogen evolution reaction was kinetically inhibited, so CO production was favored with a selectivity of 90% at a potential as early as -0.4V vs RHE. This study demonstrated the great potential of WiS as a platform for studying multi-proton, multi-electron transfer reactions.Thesis (BS) — Boston College, 2018.Submitted to: Boston College. College of Arts and Sciences.Discipline: Scholar of the College.Discipline: Chemistry