Applied Surface Science, Vol.419, 439-446, 2017
Work function modifications of graphite surface via oxygen plasma treatment
The surface modification of graphite by oxygen plasma was investigated experimentally (X-ray diffraction, nanoparticle tracking analysis, laser desorption ionization mass spectrometry, thermogravimetry, water contact angle) and by molecular modelling (Density Functional Theory). Generation of surface functional groups (mainly-OHsurf) leads to substantial changes in electrodonor properties and wettability gauged by work function and water contact angle, respectively. The invoked modifications were analyzed in terms of Helmholtz model taking into account the theoretically determined surface dipole moment of graphite-OHsurf system (mu = 2.71 D) and experimentally measured work function increase (from 0.75 to 1.02 eV) to determine the-OH surface coverage (from 0.70 to 1.03 x 10(14) groups cm(-2)). Since the plasma treatment was confined to the surface, the high thermal stability of the graphite material was preserved as revealed by the thermogravimetric analysis. The obtained results provide a suitable quantitative background for tuning the key operating parameters of carbon electrodes: electronic properties, interaction with water and thermal stability. (C) 2017 Elsevier B.V. All rights reserved.