Novel nanotubes based on methylene-bridged cycloparaphenyleneas as highly efficient catalysts for oxygen evolution reaction

Nanotubes constructed from methylene-bridged cycloparaphenyleneas (MCPPs) are investigated using density functional theory. The dynamical stability is indicated by the real vibrational frequencies of the infrared spectra. MCPPs are semiconductors with an energy gap of similar to 2.9 eV that significantly decreases in the finite nanotubes. This decrease is a result of the interactive molecular orbitals that are localized at the pentagonal rings linking MCPPs. The UV-vis spectra show that transitions from the highest occupied and neighbor orbitals to the lowest unoccupied orbital dominate the primary absorption peaks. Oxygen evolution reaction shows that all the reaction intermediates, HO, O, and HOO are adsorbed by the pentagonal active sites. The considered nanotubes show good catalytic performance but the best performance is observed in the wider nanotubes with an overpotential of 0.10 V. This remarkably low overpotential in addition to the abundant active sites makes finite nanotubes from MCPPs exceptional catalysts for oxygen evolution.