Abstract
On thermal treatment, eight different graphite materials became resistant to air aging for at least nine weeks compared to the usual time of hours to a few days when assayed in 1mM ferri-ferrocyanide solution. In addition, resistance to aging was found for at least seven days, when immersed in 1mM ferri-ferrocyanide solution compared with the frequently reported few minutes to hours. Experimental results confirm that with heat treatment, HOPG-ZYH, graphite rods, pyrolytic graphites, graphite felts, and natural and artificial graphites undergo structural reorganization which leads to the restructuring of their electronic nature. It is this electronic restructuring that enhances and sustains their electrochemical properties. The extent of this reorganization is dependent on the initial disordered state, which in turn is important to the final structural and electronic conditions. Our results strongly suggest that the primary factor enhancing the electronic response of heat-treated materials is from an overall higher density of states localized on delocalizing π bonds compared to their controls. This structural reorganization of the graphites also supports a degree of crystallinity along the lattice sites that enable carrier hopping irrespective of adventitious oxygen-containing and hydrocarbon moieties that is synonymous with aging induced sluggish electron transfer kinetics. The attributes of this electronic structure demonstrate a strongly correlated system which exhibit a non-perturbative behavior. A one-dimensional Hubbard model is applied to describe this behavior that explains the surface-to-electronic chemistry of treated graphites by addressing both their enhanced electrochemical performance and their depressed aging effects. Additionally, these thermally treated graphites were used as support systems for the growth of Prussian Blue nano particles. The PBNP doubled the capacitance of the high surface area graphite felt; a property that lends these PBNP@graphite felts for, amongst other things, ion-sieving, energy storage and conversion purposes. Since, increased electron transfer kinetics make materials more prone to corrosion, both the structure and corrosion resistance of the treated and pristine graphites were performed. The data collated suggest that the thermally treated graphites, with increased electron transfer kinetics, had similar corrosion resistance properties to the pristine and their work functions were no much different. Yet, the charge transfer parameter of the treated pyrolytic graphites was some three order of magnitude less to the pristine. The results suggest that a correlated electronic structure with enhanced quantum tunneling of electrons through the graphite surfaces, irrespective of surface functional groups or even edges, was responsible for the corrosion resistant nature of the treated graphites.