Enhanced capacitance textile fibres for supercapacitors via an interfacial molecular templating process

Abstract

The application of poly(2-methoxyaniline-5-sulfonic acid), PMAS, as a molecular template in a bi-layered co-polymerisation process onto a microporous activated carbon fibre is presented. This process produces a bound, compact molecular layer of PMAS, onto which polyaniline (PAni) or polypyrrole (PPy) is co-polymerized as a thin permeable layer coating the surface of the carbon fibre. The physical porous structure of the coated carbon fibre is examined via multi-point isothermal N 2 adsorption at 77 K. Surface area and porosity data, calculated using BET and Density Functional Theory (DFT) models, indicates that the majority of the microporosity of the activated carbon fibre is still accessible after polymer deposition. Voltammetry and impedance data, in an aqueous electrolyte (1 M H 2SO 4), is presented to show the enhancement of the capacitance and resistance properties of the composite material and the benefit of these improvements to its use as a supercapacitor electrode material. Formation of the bi-layer carbon fibre composite resulted in an effective increase in capacitance; from 125 F g −1 for the untreated carbon substrate, to as high as 222 F g −1 for the PAMS/PAni treated sample. The latter result represents a 69% improvement in capacitance and is attributed to the additional pseudocapacitive contribution of the ECP and the preservation of double-layer capacitance through the retention of fibre microporosity. Impedance analysis of the PMAS/PAni composite sample estimates the materials’ intrinsic resistance to be R s = 3.7 Ω and distributed pore resistances (Ω DPR) of 2.8 Ω; compared to R s = 1.8 Ω and Ω DPR = 6.4 Ω for the untreated carbon substrate.