Studies of cobalt-mediated electrocatalytic CO2 reduction using a redox-active ligand.
The cobalt complex [Co(III)N4H(Br)2](+) (N4H = 2,12-dimethyl-3,7,11,17-tetraazabicyclo-[11.3.1]-heptadeca-1(7),2,11,13,15-pentaene) was used for electrocatalytic CO2 reduction in wet MeCN with a glassy carbon working electrode. When water was employed as the proton source (10 M in MeCN), CO was produced (fCO= 45% ± 6.4) near the Co(I/0) redox couple for [Co(III)N4H(Br)2](+) (E1/2 = -1.88 V FeCp2(+/0)) with simultaneous H2 evolution (fH2= 30% ± 7.8). Moreover, we successfully demonstrated that the catalytically active species is homogeneous through the use of control experiments and XPS studies of the working glassy-carbon electrodes. As determined by cyclic voltammetry, CO2 catalysis occurred near the formal Co(I/0)redox couple, and attempts were made to isolate the triply reduced compound ("[Co(0)N4H]"). Instead, the doubly reduced ("Co(I)") compounds [CoN4] and [CoN4H(MeCN)](+) were isolated and characterized by X-ray crystallography. Their molecular structures prompted DFT studies to illuminate details regarding their electronic structure. The results indicate that reducing equivalents are stored on the ligand, implicating redox noninnocence in the ligands for H2 evolution and CO2 reduction electrocatalysis.
Joint Center for Artificial Photosynthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.
David C
DC
Lacy
Charles C L
CC
McCrory
Jonas C
JC
Peters
D002244:Carbon / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry*; D002248:Carbon Monoxide / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D055664:Electrochemical Techniques; D004566:Electrodes; D006859:Hydrogen / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction
D008024:Ligands; D009942:Organometallic Compounds; D002245:Carbon Dioxide; D003035:Cobalt; D002244:Carbon; D002248:Carbon Monoxide; D006859:Hydrogen