Structural and Electronic Properties of Carbon Nanotubes
and Graphenes Functionalized with Cyclopentadienyl–Transition
Metal Complexes: A DFT Study
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Abstract
In
order to explore possible ways of using metallocene compounds
in heterogeneous catalysis and in sensor applications, we present
a theoretical characterization of cyclopentadienyl (Cp) + transition
metal (TM) complexes adsorbed on boron-doped carbon nanotubes (B-CNTs)
and boron-doped graphenes. Using spin-polarized density functional
theory calculations, we present a systematic study of the geometries,
energetics, and electronic properties of CpTM (where TM = Fe, Ni,
Co, Cr, Cu) adsorbed on both pristine and boron-doped carbon supports.
Our work reveals significant increases of the binding energies between
CpTM and boron-doped CNTs and graphenes (versus pristine carbon supports),
surpassing even the adsorption strength of the isolated metals atoms
(by about 2 eV). According to our electronic structure analysis, both
the delocalization of the TM-d state by the presence of the Cp ring
and the interactions between the Cp ring and the carbon substrate
are responsible for the enhancement of the binding energies. This
stabilization may play an important role in immobilizing ferrocene-based
catalysts. Moreover, tunable metallicities of CpTMs adsorbed on pristine
and on B-CNTs are observed, indicating potential applications of CpTM/B-CNT
complexes in nanoelectronics and as sensors. Using these complexes,
we also probed the adsorption of O<sub>2</sub> molecules, as an initial
indicator of catalytic performance. Both chemisorption (with an elongated
O–O bond) and dissociative chemisorption were found on CpFe/B-CNT
(8,0) complexes