Carbon nanotubes-supported Pt catalysts for decalin dehydrogenation to release hydrogen: A comparison between nitrogen- and oxygen-surface modification

The effect of carbon nanotubes (CNT) surface chemistry on supported Pt catalytic performance in decalin dehydrogenation to release hydrogen was investigated through modifying CNT surface with nitrogen and oxygen functional groups. The results indicate that the mechanism of improving Pt dispersion is different for nitrogen and oxygen groups. Although oxygen groups can improve Pt dispersion, their electron donating feature inhibits the electron transfer from Pt to carbon support. DFT calculations have clarified the negative effect of oxygen group on decalin dehydrogenation in aspect of adsorption energy. Moreover, the abundant oxygen species on catalyst surface lead to a bad wettability of catalyst in non-polar reaction liquid, which significantly weaken the approaching of reactant onto catalyst. Therefore, the introduction of oxygen groups is unfavorable to the catalyst activity. In contrast, the highly dispersed Pt nanoparticles anchored by nitrogen groups may be one reason for the high activity of Pt supported on CNT modified with nitrogen groups. Furthermore, nitrogen groups promote the electron transfer from Pt to CNT, leading to lower Pt d-band and weaker naphthalene adsorption. Meanwhile little change happened on the non-polar characteristics of CNT during nitrogen doping treatment. Therefore, the introduction of nitrogen functional groups is conducive to the catalytic dehydrogenation. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

The modification of carbon nanotubes surface with oxygen and nitrogen functional groups has different effects on the dispersion of Pt and catalytic activity. Oxygen groups inhibit electron transfer from Pt to the carbon support, while nitrogen groups promote electron transfer and enhance activity. Oxygen groups decrease wettability of the catalyst, hindering reactant approach, while nitrogen groups do not significantly change the non-polar characteristics of CNT and are beneficial for catalytic dehydrogenation.