Electrophoretic Deposition of Carbon Nanotubes onto Zinc Substrates for Electrode Applications
2020
Carbon nanotubes (CNTs) as nanostructured materials have been widely used to improve electrochemical performance of
electrode materials for various batteries and electrolyzers. The purpose of this work was to investigate the electrophoretic
deposition (EPD) of multi-walled CNTs (MWCNTs) onto Zn plates for application in aqueous Zn ion batteries. The
effects of MWCNTs on Zn oxidation and reduction were assessed using cyclic voltammetry. Before EPD, the MWCNTs
were modified using H2
SO4
/HNO3
under reflux to improve dispersion stability in water. Acid modification shortened
the MWCNTs but did not cause significant changes in crystallinity, tube diameter, and interlayer spacing. In a second
step, the acid modified MWCNTs were homogeneously deposited onto a conductive Zn plate by EPD. Cyclic voltammetry
data indicate that the coating of Zn with MWCNTs does not affect the Zn oxidation and reduction potential. Oxidation
of Zn eventually leads to formation of a ZnO film, protecting the Zn surface from corrosion. When the protective ZnO
film is dissolved, the underlying Zn is oxidized, leading to unfavorable loss of Zn. The presence of MWCNTs reduces
oxidation during the cathodic sweep, implying that the MWCNT coating partially protects the underlying Zn surface
from oxidation during charging. In addition, the MWCNT coated electrodes also facilitate hydrogen formation and show
less oxygen limitation reaction, and could thus be envisaged as possible electrode materials for energy storage devices
such as bifunctional electrodes for electrolyzers or air cathodes for batteries or fuel cells.
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