University of Limpopo, School of Physical and Mineral Sciences, Department of Chemistry, Private Bag X 1106, Sovenga, South Africa
Mkhondo, N.B., University of Limpopo, School of Physical and Mineral Sciences, Department of Chemistry, Private Bag X 1106, Sovenga, South Africa; Magadzu, T., University of Limpopo, School of Physical and Mineral Sciences, Department of Chemistry, Private Bag X 1106, Sovenga, South Africa
The effects of various acids on the nanostructure and hydrogen storage performance of multi-walled carbon nanotubes (MWCNTs) were investigated. MWCNTs were sonicated in nitric acid (HNO3), hydrogen peroxide (H2O2), sulphuric acid (H2SO4) and their mixtures. FTIR revealed that the ratio of oxygen-containing groups on the surface of CNTs depends on the type of oxidiser. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Thermal gravimetric analysis (TGA) showed an intact and stable nanostructure of MWCNTs treated by H2O2+HNO3, with an improve functionality due to different kinds of pores. The Brunauer-Emmett-Teller (BET) surface area of MWCNTs treated by H2O2+HNO3increased to 343.1 m2/g, as compared to 251.5 and 223.7 m2/g of the raw and HNO3+H2SO4treated MWCNTs, respectively. The MWCNTs treated by a mixture of H2O2+HNO3gave the highest discharge capacity of 72.6 mAh/g (electrochemical hydrogen storage of 0.27 wt.%), as compared to a preferred mixture of HNO3+H2SO4, which gave a discharge capacity of 3.0 mAh/g; due to a structural damage of MWCNTs walls and low BET surface area. A H2O2+HNO3mixture promotes larger BET surface area and low reductive overpotential of hydrogen at the electrode. © 2014 Inst Materials Physics. All rights reserved.