New colloidal route for electrostatic assembly of oxide nanoparticle – carbon nanotube composites

A conceptually new colloidal method for the fabrication of metal oxide–multiwalled carbon nanotube (MWCNT) composites is proposed. The approach is based on the use of phosphate ester (PE) for the dispersion of oxide nanoparticles and m-cresolsulfonphthalein (CS) dye for the dispersion of MWCNT. PE imparts a positive charge to the particles in ethanol. The adsorption of anionic CS on MWCNT allows the formation of stable suspensions of negatively charged MWCNT in ethanol. The adsorption of CS on MWCNT is confirmed by Fourier transform infrared and UV–vis spectroscopy. The heterocoagulation of positively charged oxide nanoparticles and negatively charged MWCNT allows the fabrication of advanced nanocomposites with improved dispersion of individual components. The proof of principle is demonstrated by the fabrication of MnO2–MWCNT composite electrodes for electrochemical supercapacitors, which exhibited significant improvement in capacitance at high charge–discharge rates, reduced electrical resistance and good cycling stability. The hybrid cells, containing composite MnO2–MWCNT electrodes, show promising electrochemical performance.