, 2797 (2017)
ISSN: 2365-6549, SCIE
Atomic Transport at Charged Graphene: Why Hydrogen and Oxygen Are So Different
Manh-Thuong Nguyen and Pham Nam Phong
Atoms on charged graphitic carbon surface are relevant to
various electrochemical problems, understanding the adsorption and diffusion of adatoms under charging conditions is essential towards using graphene-like materials in electrochemistry. Using density functional calculations, we show that electron or hole doped graphene can strongly change the mobility of H and O adsorbed atoms. Interestingly, charge doping affects the diffusion of H and O in opposite ways, namely, electron doping increases/reduces, while hole doping reduces/increases the diffusion barrier of H/O respectively. Specifically, on neutral graphene the diffusion barriers of H and O are 1.01 and 0.74 eV, which are, upon a hole doping level of +5.9x10^13 cm2, 0.77 and 0.90 eV, and upon an electron doping level of -5.9x10^13 cm2, 1.36 and 0.38 eV. Thus, within the harmonic transition state theory, at room temperature, the
diffusion rate of O can be decreased or increased by 470 or 1x10^6 times, while that of H can be increased or decreased by 1x10^4 or 7x10^5 times, respectively for the above hole or electron doping density. The difference between H and O atomic transport at charged graphene is interpreted in terms of the difference in geometric and bonding changes upon charge doping.