Effects of the addition of graphite oxide to the precursor of a nanoporous carbon on the electrochemical performance of the resulting carbonaceous composites

摘要

Composites of reduced graphite oxide and nanoporous sodium-salt-polymer-derived carbons were prepared with 5 or 20 weight% graphite oxide. The materials were characterized using the adsorption of nitrogen, SEM/EDX, elemental analysis and potentiometric titration. DC conductivity was also measured. The performance of the carbon composites in energy storage was linked to their surface features and the effects of the graphene phase addition on these features. Even though the graphene phase increases the electronic conductivity of all materials, the porosity, and especially pores smaller than 0.8 nm, is the main factor governing the capacitive behavior. Owing to the sodium in the carbon precursor and the presence of graphene layers, unique small pores, similar in size to the electrolyte ions are developed in the resulting composites. These pores increase the capacitance by an electrical double layer mechanism. The composites obtained exhibit noticeable redox reactions due to the presence of oxygen and sulfur in the carbon matrix. An increase in the heat treatment temperature increases the capacitance retention ratio at higher currents owing to an increase in the conductivity and chemical stability of the surface.