Electrochemical Hydrogen Evolution by Cobalt (II) Porphyrins: Effects of Ligand Modification on Catalytic Activity, Efficiency and Overpotential. Issue 9 (8th June 2018)

• Record Type: Journal Article
• Authors: Beyene, Belete B.; Mane, Sandeep B.; Hung, Chen-Hsiung
• Is Part Of: Journal of the Electrochemical Society. Volume 165:Issue 9(2018)
• Page Start: H481
• Page End: H487
• Publication Date: 2018-06-08
• Subjects: electrocatalysis -- Hydrogen evolution -- Metalloporphyrin; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0481809jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : Electrochemical H2 evolution of a series of cobalt(II) porphyrins with electron-withdrawing (EW) and electron-donating (ED) substituents at the para positions of the meso -phenyl rings has been investigated in DMSO using acetic acid as a proton source. Our study showed that the nature of substituents significantly influences catalytic activity, efficiency, and the potential at which catalysis occurs. Faradaic efficiencies (FE) ranging from 44 to 99%, turnover numbers (TONs) from 1.5 to 104 (∼11 h electrolysis), turnover frequencies (TOFs) from 0.23 to 9.1 h −1, and onset overpotentials from 25 to 445 mV were obtained by tuning the porphyrinic substituents. Cobalt porphyrins with -SO3 H, -COOH, or -NH2 groups as the substituents showed high activity and efficiency with more positive onset potentials as compared to the parent [Co(TPP)]. Supports also from the low hydrogen generation activities for complexes with -COOMe, -OMe and -OH groups as the substituents suggest that the acidity of the meso -phenyl substituent plays a key role in enhancing the hydrogen evolution activities during the catalytic processes.