Effect of phenolic molecules on electrophoretic deposition of manganese dioxide–carbon nanotube nanocomposites

Electrophoretic deposition (EPD) method has been developed for the fabrication of manganese dioxide (MD)–multiwalled carbon nanotubes (MWCNTs) nanocomposites. Cationic tyramine hydrochloride (TA) and anionic gallic acid (GA), chromotropic acid disodium salt (CA) and benzoic acid (BA) were investigated as charging additives. The results of deposition yield measurements, quartz crystal microbalance studies and Fourier transform infrared spectroscopy data showed that OH groups are involved in the adsorption of the phenolic compounds on the MD nanoparticles. The adsorption mechanism is based on the deprotonation of the OH groups and surface complexation of Mn ions. It was shown that the phenolic molecules, such as TA, GA and CA can be used as charging additives for the EPD of MD. Composite MD–MWCNTs films were prepared by cathodic and anodic EPD using TA and GA, respectively. In this approach, TA and GA were used as common charging additives for two different materials: MD and MWCNTs. Scanning electron microscopy studies showed the formation of composite films containing well-dispersed MWCNTs in the MD matrix. The results of the thermogravimetric analysis demonstrated that the amount of the MWCNTs in the composite materials can be varied. The composite films were studied for the application in electrochemical supercapacitors (ES). The ES electrodes showed good capacitive behavior in the 0.5 M Na2SO4 electrolyte in a voltage window of 0–0.9 V versus a standard calomel electrode (SCE). The films prepared by cathodic EPD showed higher specific capacitance (SC) compared to the films prepared by anodic EPD with the highest SC of 553 F g−1 at the scan rate of 2 mV s−1.