Experimental and Theoretical Study of the Effect of Functionalized Pyrene Polymerization on Carbon Electrode Surfaces for Electrochemical Storage. Issue 6 (15th March 2021)

• Record Type: Journal Article
• Authors: Anothumakkool, Bihag; Sayed‐Ahmad‐Baraza, Yuman; Massuyeau, Florian; Brousse, Thierry; Ewels, Chris; Gaubicher, Joel
• Is Part Of: Batteries & supercaps. Volume 4:Issue 6(2021)
• Page Start: 1018
• Page End: 1031
• Publication Date: 2021-03-15
• Subjects: adsorption mechanism -- electropolymerization mechanism -- pyrene -- density functional theory -- Li metal hybrid supercapacitor; Electrochemistry -- Periodicals; Electrodes -- Periodicals; Electric batteries -- Periodicals; 621.31242
• DOI: 10.1002/batt.202000329
• Languages: English
• ISSNs: 2566-6223

Abstract

Abstract: We report the effect of −(CH2 ) n −COOH ( n =0, 1, 3) functional groups on pyrene adsorption and associated electropolymerization mechanisms on carbon nanotube model electrodes, as well as resulting electrochemical charge‐storage properties in a Li metal supercapacitor configuration. The impact of pyrene functional groups is tested by varying the alkyl chain length as well as the composite electrode formulation protocol. From experiment and DFT calculations we conclude that (i) all pyrene derivatives bind strongly to the MWCNT (multiwall carbon nanotube) surface with submonolayer loadings. Intermolecular forces and/or packing configurations rather than charge transfer between MWCNT and substrate likely play a major role in the extent of self‐adsorption process (ii) trends of predicted ionization energies (‐HOMO levels) and Hammett substituent constants match with (measured) oxidation potentials of adsorbed monomers. However, this correlation fails for unsubstituted pyrene presumably because of molecular aggregation, an argument supported by excimer formation in supernatent solutions, (iii) fusion rather than linear‐type oligomerization takes place and is described for the first time and, (iv) longer alkyl chains lead to more extended functionalized oligomers which in turn enhances p‐doping (reversible capacity). In a Li metal hybrid supercapacitor configuration, best capacity‐power compromise was found with 55 wt% 1‐pyreneacetic, resulting in a 5‐fold capacity increase from 13 mAh/gelectrode (19 F/gelectrode ) for untreated MWCNT to 68 mAh/gelectrode (102 F/gelectrode ) between 2–4.4 V vs . Li + /Li. Abstract : Looking for the perfect match : The effect of functional groups on pyrene adsorption and related electropolymerization mechanisms on MWCNT model electrodes, as well as resulting electrochemical charge‐storage properties in a Li metal supercapacitor configuration are reported based on experiment and DFT calculations. Trends of predicted ionization energies (‐HOMO levels) and Hammet substituent constants generally match with (measured) oxidation potentials of self‐adsorbed monomers. Fusion rather than linear‐type oligomerization takes place. Optimization of functional group and electrode loading allows 5‐fold capacity increase thanks to p‐doping of oligomers.