Phenazine-photosensitized reduction of CO{sub 2} mediated by a cobalt-cyclam complex through electron and hydrogen transfer
- Osaka Univ. (Japan)
Photoreduction of carbon dioxide (CO{sub 2}) to formate (HCO{sub 2}{sup -}) can be achieved by UV-irradiation of the system involving phenazine (Phen) as a photosensitizer, a cobalt complex of cyclam (CO{sup III}L, L = cyclam = 1,4,8,11-tetraazacyclotetradecane) as an electron mediator, and triethylamine (TEA) as an electron donor. Reduction products from the system are HCO{sub 2}{sup -} and a small quantity of CO and H{sub 2}. The quantum yield is 0.07 for the formation of HCO{sub 2} at {lambda} = 313 nm. Preferential electron transfer from the photoformed radical anion of phenazine (Phen{sup -}) to Co{sup III}L is confirmed by EPR analysis and the reaction between Phen{sup -} and Co{sup III}L with a second-order rate constant, k = 4.3 x 10{sup 9} M{sup -1} s{sup -1}. The resulting Co{sup II}L reacts with phenazinyl radical, giving [CoL(H)]{sup 2+} by hydrogen transfer from phenazinyl radical. The effective insertion of a CO{sub 2} molecule into [CoL(H)]{sup 2+} yields HCO{sub 2} selectively. 51 refs., 9 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 90945
- Journal Information:
- Journal of Physical Chemistry, Vol. 99, Issue 31; Other Information: PBD: 3 Aug 1995
- Country of Publication:
- United States
- Language:
- English
Similar Records
Study of the reactions of platinum macrocyclic complex ions with free radicals formed by pulse radiolysis of aqueous media
Spectroelectrochemical investigations of nickel cyclam indicate different reaction mechanisms for electrocatalytic CO2 and H+ reduction