Conductive core/shell polymer nanofibres as anode materials for direct ethanol fuel cells

Abstract

A conductive polymer-supported electrocatalyst in the form of fibrous mat has been developed that can be employed as a polymer-based electrode for direct ethanol fuel cells (DEFCs) with promoting effects to the state-of-the art Pd based catalysts. A series of conductive polyaniline (PANI)-containing polymer fibres-supported Pd electrocatalytic electrodes were successfully prepared and tested for the ethanol electro-oxidation reaction (EOR) in alkaline medium. The polymer support was a robust fibrous mat, where the fibres possessed a core-shell configuration. The core part was produced via electrospinning using a mixture of polyacrylonitrile (PAN) and 1-butyl-3-methylimidazolium chloride [BMIm]Cl ionic liquid (IL). The shell was a PANI layer deposited via the chemical polymerisation of aniline monomer. Pd was then electrodeposited on the fibres and the catalysts were tested for the EOR via cyclic voltammetry (CV) in a half-cell configuration and in a temperature range between 25 and 60 °C. The activity of the catalysts tested was measured in terms of activation energy and forward peak current density in the CV and compared to that of glassy carbon (GC)-supported Pd/PANI/PAN/IL fibrous catalysts. The polymer fibre-catalyst samples showed a higher active surface area and significantly lower activation energy than the GC-based ones. Even though the GC-supported catalysts showed a higher activity in terms of current, the Pd/(PAN/IL)-core/PANI-shell fibrous mats were active as well and, in some cases, demonstrated a promoting effect of PANI on Pd for EOR and a much better stability and robustness compared to the former. Furthermore, a series of promoting metals were investigated for these mats, such as Ag, Bi and Cu, with Ag and Bi demonstrating promoting effects compared to monometallic Pd/(PAN/IL)-core/PANI-shell mats in terms of both activation energy and peak current density. This work demonstrates a promising strategy in the arena of development of polymeric mats as anode electrodes for DEFCs, exploiting the benefits of PANI in terms of ease of synthesis, catalyst poisoning prevention, cost and promoting effects.