Disclosing the Graphite Surface Chemistry in Acid Solutions for Anion Intercalation

The great interest for graphitic electrodes in ion batteries as well as the graphite electrochemical exfoliation for graphene production are technological processes based on anion intercalation mechanism in the stratified crystal structure when immersed acid solutions. Detriment of the graphite mother-crystal, decomposition of the electrolyte solution or production of unexpected graphite intercalation compounds (GICs) are side effects related to the anion intercalation mechanism. In this work, we studied the surface of highly oriented pyrolytic graphite (HOPG) samples treated with electrolyte solutions of 2 M HClO4 and 1 M H2SO4 in order to identify elemental and molecular species involved in the intercalation processes and, at the same time, find local surface defects through which solvated ions easily reach the HOPG subsurface. Results from cyclic-voltammetry, X-ray photoelectron spectroscopy (XPS), and time of flight secondary ion mass spectrometry (ToF-SIMS) are described and discussed. Large blister ...