Understanding the enhanced electrical properties of free-standing graphene paper: the synergistic effect of iodide adsorption into graphene

Free-standing graphene (FSG) paper plays a vital role in a wide variety of applications as an electrode material. Specifically, the electrical properties of FSG are the most important factor affecting its use as an electrode material. Herein, the vacuum filtration technique is utilized to fabricate GO paper, which is then reductively treated with HI. Initially, the electrical conductivity is measured for GO papers with different thicknesses by varying the concentration of GO precursor as well as the reduction time. The FSG paper with a thickness of 3 microns exhibits the lowest sheet resistance and further characterization is carried out to reveal the origin of this enhancement of electrical properties. The low resistance is attributed to its crystalline nature, stacking height (L(c)), in-plane crystallite size (L(a)) and defect density (n(D)). Meanwhile, iodide ions intercalated into the graphene layers act as hole-carriers, and their intercalation is favoured over adsorption at the surface.