Zinc (hydr)oxide/graphite based-phase composites: effect of the carbonaceous phase on surface properties and enhancement in electrical conductivity

Abstract

Composites of zinc hydroxide with graphite-oxide and graphite derived material are prepared using in situ precipitation of Zn(OH)2 in the presence of the dispersed graphite-based phases. The new materials are characterized by a range of methods, including SEM, infrared and Raman spectroscopy, thermal analysis, potentiometric titration, nitrogen adsorption, XPS, and electrical measurements. The results indicate that the final properties of the composites are determined by a complex interplay between the two components. When graphite-oxide is used, its oxygen containing functional groups are involved during synthesis with a zinc hydroxide precursor, leading to the formation of interface bonds between the inorganic and carbon-based phase. This new interface not only affects the chemistry of the materials but also determines texture and porosity. Another conversion of the inorganic phase to zinc oxide via thermal treatment further affects the properties of the composite, leading to the formation of additional chemical bonds between the zinc oxide and graphite-oxide phases. Even though the addition of graphite-oxide results in a highly porous material of heterogeneous nature, the thermally treated composite has a comparable electrical conductivity to the zinc hydroxide–graphite derived material composite, although having a lower density. This is attributed to the increased abundance of sp2 hybridization, the presence of Zn0, and improved local electrical connectivity between the two phases of the composite through the new interface bonds.