Correlation between the catalytic and electrocatalytic properties of nitrogen-doped carbon nanoonions and the polarity of the carbon surface: Experimental and theoretical investigations

Abstract Nitrogen atoms were introduced into carbon nanoonion (CNO) cages by annealing aminated nanodiamonds (AM-NDs) under an inert helium atmosphere and reduced pressure. This procedure provided a convenient tool to control the surface properties, such as polarity, and to make CNOs suitable for various applications. Two series of CNOs were produced using different temperatures (1150, 1450 and 1650 °C) and starting materials, unmodified nanodiamonds (NDs) and AM-NDs. Nitrogen-doped CNOs (NCNOs) were prepared by annealing AM-NDs at 1150 °C via a procedure previously reported by our group. Herein, the surface polarity of the NCNOs and their catalytic and electrocatalytic properties were compared with those of the pristine CNOs obtained from non-functionalized NDs under the same experimental conditions. For these purposes, we used several experimental and theoretical methods, such as X-ray photoelectron spectroscopy, water adsorption-desorption measurements supported by the model proposed by Dubinin and Serpinsky, catalytic tests with a gasometric method and electrochemical studies, including cyclic voltammetry and amperometry. All of the CNOs and NCNOs were evaluated for use as biocompatible mediator-free substrates for horseradish peroxidase in hydrogen peroxide detection.