Chemical treatment of CNTs in acidic KMnO4 solution and promoting effects on the corresponding Pd–Pt/CNTs catalyst

Carbon nanotubes (CNTs) were chemically treated in acidic KMnO4 solution. XRD, nitrogen physisorption, FTIR and chemical titration were used to investigate the influence of the treatment conditions on the surface structure, the bulk structure, the types and the amounts of the formed surface oxygen-containing functional groups of CNTs. The results show that the structure is not changed clearly after treatment and the formation of oxygen-containing groups, e.g., carboxyls, on the CNT surface is dependent on the treatment conditions. Under the present conditions, the concentration of the employed sulphuric acid and the weight ratio of the solid KMnO4 and CNTs have clear influence on the formation of carboxyls, however, by comparison, the influence is slight when the treatment temperature is above 95 °C. With the increasing of the amount of carboxyls, the dispersion of the corresponding Pd–Pt metal particles supported on CNTs is increased and the catalytic activity is promoted in the profile reaction of naphthalene hydrogenation to tetralin.

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► Treatment of CNTs in KMnO4 was investigated on formation of surface groups.
► Relationship between treatment conditions and formed groups was investigated.
► Promoting effects on Pd–Pt/CNTs catalyst was illustrated.