Paper- Restricted to Campus Access
Carbon dioxide (CO2) is an overabundant atmospheric component due to anthropogenic activities such as transportation and electricity generation. Scientific efforts to catalytically transform CO2 into alternative, useful products leave much room for improvement, as current catalysts fail to address photosensitization, efficiency, and cost-effectiveness simultaneously. Herein, the CO2 reduction abilities of protonated pyrazine and asymmetric pyrazine-substituted cyanoferrate compounds (abbreviated FepzH = monomer, FeFepzH = dimer) are discussed. Following qualitative CO2 reduction tests using cyclic voltammetry, quantitative electrochemical studies were undertaken by performing bulk electrolysis of CO2 at a potential of –1.6 V vs. SSE using each of the three chemical species. The experimental setup was then modified to perform photolysis using irradiation with 480-nm light, ascorbic acid as sacrificial electron donor, and either FepzH or FeFepzH as the reduction catalyst. Gas chromatography/mass spectrometry indicated that the product of both electrolysis and photolysis was methanol. FepzH achieved significantly higher CO2-to-methanol turnover numbers than did FeFepzH electrochemically, while the two species performed comparably during photolysis. The quantities of methanol generated photolytically by the monomer and dimer were greater than those detected after electrolysis using protonated pyrazine alone. High quantum efficiencies were also achieved during photolysis experiments with FepzH and FeFepzH. Future elucidation of the electron transfer mechanisms should allow for insight into the lifetimes and limitations of the catalysts. If optimized to perform efficient photolysis, pyrazine-modified cyanoferrate complexes could offer an industrially-applicable CO2 reduction system due to their ease and low cost of synthesis.
Paris, Aubrey R., "Pyrazine and Asymmetric Pyrazine-Modified Cyanoferrate Complexes in the Electro- and Photochemical Reduction of Carbon Dioxide" (2015). Chemistry Honors Papers. 1.