Multiscale simulation of boron-doped nanocarbons in electrochemical applications
The stability, properties, and dispersion of novel organometallic/doped nanocarbon complexes for electrochemical application are investigated in this work with density functional theory (DFT) and molecular dynamics (MD) simulations. We suggest that electrochemical active centers like cyclopentadiene (Cp) transition metal (TM) complexes can be stabilized on boron-doped nanocarbons to create stable and high-performance support materials. We present a systematic study of the geometries, energetics, and electronic properties of CpTM (where TM=Fe, Ni, Co, Cr, Cu) complexes adsorbed on both pristine and boron-doped carbon nanotubes (CNTs) and graphene supports using DFT calculations. Significant stabilization of CpTM on boron-doped CNTs (B-CNTs) and graphenes are found, which surpasses the binding energies (BEs) of the isolated TM atoms by about 2 eV. To evaluate the redox activity (CpFe) on B-doped nanocarbon supports, we calculate the redox potentials of CpFe/B-doped, N-doped and pristine graphene complexes with different doping patterns and concentrations with DFT calculations, combined with a conductor-like polarizable continuum model (CPCM) solvation model. The CpFe/B-doped graphene complexes show potential to be a ferrocene substitute for ferrocene-mediated electrochemical process, such as bio-sensing and dye-sensitized solar cells. The dispersion of B-doped nanocarbons is also investigated in our work. Molecular dynamics (MD) simulations, parameterized by DFT-calculated partial charges are used to investigate the water-induced interactions, the hydration, and the debundling behavior of B-CNTs with varying diameters and B-doping patterns within aqueous solutions. By evaluating the potential of mean force (PMF) of one, two, and three solvated B-CNTs, we demonstrate that the water-induced interactions between B-CNTs extend over prolonged distances, and the B-CNTs are shown to be more reagglomeration resistant. In addition, the hydration behavior of the B-CNTs can be understood by evaluating the water density profiles and hydrogen bonds during the solvation. These results provide guidelines for separating and dispersing B-doped nanocarbons in aqueous environments. Overall, our simulations predict that the CpTM/B-doped nanocarbon complexes are potential candidates for multiple electrochemical applications with significant stability, comparable redox performance to ferrocene, and enhanced dispersibility.