Vanadyl(IV) acetylacetonate was anchored onto two different amine-functionalised activated carbons. The starting activated carbon supports were air (A2) and nitric acid oxidised (B1) carbons; the phenol surface groups of carbon A2 were subsequently treated with (3-aminopropyl)triethoxysilane (A3) and afterwards the free amine groups were used for Schiff condensation with [VO(acac) 2 ] (A4). Carbon B1, which possesses carboxylic surface groups, was treated with thionyl chloride to give surface acyl chloride groups (B2), which were then reacted with the amine groups of bis(3-aminopropyl)amine (B3); subsequent attachment of [VO(acac) 2 ] was also achieved by Schiff condensation between the free amine groups of the functionalised carbon and the ligand oxygen atoms (B4). All the materials were characterised by XPS, and the [VO(acac) 2 ]-based materials were also characterised by
In this work it is described the preparation and characterization of multi-walled carbon nanotubes and graphene flakes doped with heteroatoms, namely N, P, B, and S, through simple ball milling procedures with adequate precursors, followed by thermal treatments. Ball milling the carbon nanomaterials with melamine resulted in the introduction of pyrrolic, pyridinic and quaternary N atoms on the graphitic structure. Using triphenylphosphine as the phosphorous precursor induced the formation of RÀO-PO(OH) 2 functionalities. Materials prepared with boric acid showed the presence of boronic groups (C-BO 2 ) and B atoms in B 2 O 3 . S-doped materials presented tiophene-S type atoms. The catalytic studies showed that all the doped carbon materials were active catalysts in the reduction of 4-nitrophenol (4-NP), and that the modifications introduced by the doping procedures, overall yielded catalysts with superior activity in regard to their pristine counterparts. Reusability experiments revealed no loss of catalytic activity up to three catalytic cycles for the doped carbon nanotubes, whereas the graphene flake materials showed some deterioration of catalytic performance.
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