1. A Computer Based Simulation Study of Localised Molecular Interactions within Polypyrrole Coated
Multi-walled Carbon Nanotubes, and its effect on Enhanced Pseudocapacitance.
By: Samuel Essien (Supervised By: Prof G Z Chen and Dr A Croft)
1Department of Chemical and Environmental Engineering; 2Faculty of Engineering, University of Nottingham, NG7 2RD.
Enydse@nottingham.ac.uk
www.nottingham.ac.uk
Introduction
• The mechanical instability of π – conjugated conductive polymers, such as
Fenton Treated Polypyrrole (PPy) over a period of prolonged electrochemical
cycles has been a major setback to their utilization as an active material in
supercapacitory devices. The use of chemically treated multi-walled nanotubes
(MWNT) to produce hybridized conjugated polymer nanocomposite films has
shown positive synergistic advantages over conventional material such as
Lithium Oxide and Ruthenium Oxide films as shown experiments conducted
separately by Chen Et al [1], Gao et al [2] and Hammond et al [3].
Project Aims
• It has been proposed that the enhanced capacitance observed in PPy-MWNT
based electrodes films is due to interfacial conjugation as a result of π-π
interactions between proximate PPy and MWNT π orbitals[1]. This project aims
to verify proposed mechanism(s) behind the enhanced pseudocapacitance in
PPy coated MWNT’s outlined in literature[1].
Existing predictive models and data
• Previous experiments have shown charge release by faradic oxidation on
reduction of voltage (-0.4V to -0.8V) during cycling (unloading), returning the
nanocomposite to a low energy neutrally charged state . This is referred to as
the Band Theory (Figure 2).
Acknowledgements: The author would like to thank Prof G Chen, Dr A Croft and Athina Meletiou
for continual support and technical advice during the MEng research programme.
References: 1G. Z. Chen, Met Mater Int. 23 (2013) 245 – 255; 2Gao, et al., J. Phys. Chem. 114
(2010) 19557-19884; 3Hammond, et al. Nat Nanotechnol. 5 (2010) 531–537 4J Chae, et al., 2013.
Development of a Supercapacitory Device, University of Nottingham,UK.
Results
Figure 1. Electron Band Theory[1].
Figure 2. Continuous PPy-MWNT Pilot Production Process Scheme[4]
Figure 3- Partial Charge Transfer as a result of Interfacial Conjugation across
atomic array illustrated in Figure 4
• The task 1 design (Figure 2) scaled up the current batch process of PPY-MWNT
production which was conducted on a lab bench scale (magnitude of grams of
product per day) into a continuous process that could be utilised for a pilot plant
(magnitude of kilograms of product per day)
Discussion & Concluding Remarks
• It has been found that the predominant non-covalent mechanism that causes
increased pseudocapacitance within the composite material specified in the
Task 1 product design is interfacial conjugation as a result of interaction of π-
orbitals, resulting in partial charge transfer across the PPy-MWNT interface
(Highlighted in figure 3 & 4).
• Further work focused on characterisation of the electrostatic interactions
between the negatively charged dopant ions present on the MWNT surface
and the localized positive charges located across the polypyrrole will assist
further development of enhanced PPy-MWNT films, as it has been
highlighted in literature that these interactions also enhance the
pseudocapactive capability of PPy-MWNT composites.