Computational Study on Adsorption Characteristics of Phenol and Guaiacol
Over Single and Multiple Nitrogen Doped Graphene
Abstract
The experimental synthesis of nitrogen doped graphene has opened the
door for its application in many catalytically important processes and
to name a few are deoxygenation and hydrotreatment of raw bio-oil and/or
its model compounds. In this study, the authors reported the properties
of nitrogen doped graphene which include the electron density
distribution, charge distribution, electrostatic potential, etc.
Subsequently, the adsorption characteristics such as the charge
transfer, adsorption energy, dipole moment change, etc are presented for
the bio-oil model compound (phenol and guaiacol) to realise the
potential of nitrogen doped graphene in bio-oil upgrading. Density
functional theory (DFT) method is employed for calculating all
aforementioned properties. The present approach of obtaining surface
adsorption characteristics on N-doped graphene has also been validated
with appropriate comparison with the literature results for the case of
CO2 adsorption over N-doped graphene; and found excellent agreement. It
is found that doping with nitrogen significantly alters the electronic
properties of graphene in a favourable manner; and the same is witnessed
in terms of highly irregular spin density distribution and charge
distribution. For a strong adsorption, either a high charge transfer
between the catalyst and the model compound, and/or a strong
delocalization of the charge on the surface is found to be beneficial.
Both phenol and guaiacol adsorption have similar adsorption energy on
non-defective and defective nitrogen doped graphene. Although increasing
the nitrogen atoms in the sheet altered the electronic properties to a
larger degree than single nitrogen doping; however, the adsorption
strength does not appear to change.