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Pristine carbon nanotubes have relatively weak electrocatalytic activity. On the other hand, due to the symmetry of the π-electron bands, nanotubes can be doped either donor or acceptor to optimize the kinetics of heterogeneous electron transfer. In this report, we focus on analyzing the effects of acceptor (boron), donor (nitrogen) doping and covalent functionalization of nanotubes with -OH group on the electrocatalysis of cathodic oxygen reduction (ORR) and hydrogen evolution reaction (HER), as well as anodic oxygen evolution reaction (OER). Simulations based on the Gerischer-Marcus model show that acceptor doping slightly shifts the onset of ORR and HER reactions to more negative potentials. At the same time, acceptor doping contributes to increasing the efficiency of the anodic OER by significantly reducing reaction overpotential. On the other hand, donor doping remarkably enhances the kinetics of ORR and HER, whose onset potentials are shifted to less negative potentials with respect of pristine CNTs by more than 0.4 V. We also show that covalent functionalization with an -OH group produces an effect analogous to acceptor doping. Experimental data obtained for pristine and hydroxylated CNT electrodes in aqueous 0.1 M KOH solution confirm the predictions of the Gerischer-Marcus model. The results presented outline a strategy for preparing electrode materials containing nanotubes in such applications as fuel cells, metal-air batteries and water splitting.
Keywords: Carbon nanotubes, acceptor doping, donor doping, Gerischer-Marcus model, oxygen reduction reaction, hydrogen evolution reaction, oxygen evolution reaction© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.