Preparation of titanium dioxide/bamboo based carbon composite as electrode

Abstract

In this research, we report a novel method for preparation of the titanium dioxide/carbon nanocomposite with high thermal stability for application in a capacitor using the disposed bamboo chopsticks as carbon source. The proposed preparation method contains 2 steps which are impregnation of the bamboo powder with a solution of titanium tetraisopropoxide in 2-propanol and subsequently carbonization at a required temperature. The effect of carbonization temperatures was studied at 500, 600 and 700°C. The XRD data showed that crystalline TiO2 was readily formed as anatase structure at all of the three temperatures. It is very interesting that rutile phase was not observed at all. It is well known that titanium dioxide prepared by other methods normally undergoes anatase-to-rutile phase transformation in the temperature range from 600 to 700°C and anatase is completely converted to rutile above 700°C. It indicates that carbon from bamboo can obviously stabilize the nano-anatase phase up to 700°C. The crystal size of anatase is affected by the carbonization temperature and method of preparation. This method provided nanocrystals of anatase with about one half smaller crystal sizes than that prepared by the conventional method which was performed in the alternative sequence of preparation steps. SEM was used for the identification of the surface morphology and particle size. The adsorption isotherms of the composites show the characteristic of micropores. The composite prepared by this novel method has lower BET specific surface area than that prepared by the conventional method. It can be explained that TTIP can penetrate into wide pores of the bamboo texture and convert to nanocrystals of anatase inside the pores of resulted porous carbon. Simultaneously, carbonization results in encapsulation of the anatase particle within the pores of carbon. The composites from the conventional method contain TiO2 outside the pores of carbon. The latter causes relatively larger crystals on the outer surface of carbon and leaves more space inside the carbon pores. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to characterize the electrochemical performances of the composite electrode. The specific capacitance of the composite electrode is affected by the carbonization temperature and TiO2 content in the composite. However, the composite treated by phosphoric acid shows an enhanced specific capacitance. The composite is potential to be applied further as electrode materials for electric double layer capacitors.