Catalytic Performance Of Carbon Nanotubes Supported Transition Metal In Oxidation Reaction

As a one-dimensional material, carbon nanotubes ?CNTs? possesses a series of unique features, such as large surface area, high mechanical strength, good thermostability and excellent electrical conductivity, all of which make CNTs full of promise to be a novel support. In the present work, we perpared catalysts that transition metals supported on CNTs by a novel spontaneous redox method.Interaction between CNT structure and transition metals and the influence on catalytic performance were studied.?1? Mn₃O₄, NiO and Ni supported on the out surface of CNTs were synthesized by spontaneous redox between CNTs and metal oxides at high temperature. Results showed that Mn and Ni species had a synergistic effect and the metallic Ni that formed by spontaneous redox could preferentially adsorb and activate oxygen molecular, which would have a promoting effect towards benzyl alcohol oxidation.?2? K-birnessite MnO₂ was filled in CNTs using spontaneous redox at room temperature. When MnO₂ was confined in CNTs, it exhibited better redox property which could promote the activation of benzyl alcohol, thus made catalyst have better catalytic performance than the catalyst that MnO₂ was supported on the out surface of CNTs. In addition, K+ was essential to inhibit the transformation of Mn⁴⁺ to Mn³⁺which had poorer activity.?3? Ni?OH?₂ was loaded on a dual-bed catalyst support that possessed a morphology of MnO₂ wrapped CNTs. Results showed that Ni?OH?₂/MnO₂/CNTs catalyst had a good performance towards electrooxidation of glucose. The synergistic effect of Mn and Ni species and good electrical conductivity of CNTs accounted for the high performance.?4? The influence of curvature effect of CNTs on ethylbenzene dehydrogenation was studied by supporting CeO₂ nanoparticles on five kind of CNTs that had different out diameter. When the out diameter of CNTs was less then 30 nm, with the increase of curvature, the thermal stability of CeO₂/CNTs catalyst, the reduction temperature of CeO₂ and the Ce⁴⁺/Ce⁴⁺+Ce³⁺ value all decreased, it would then increase the catalytic performance. However, when the out diameter of CNTs was more than 30 nm, the curvature effect of CNTs was weak due to the surface of CNTs became plane.?5? In order to study the influence of structure defect on the confinement effect of CNTs, MnO₂ nanoparticles were filled in CNTs with different defect density by spontaneous redox between CNTs and KMnO4. Results showed that defects had a significant effect on the MnO₂ loading, however it had little influence on the redox property of MnO₂. Thus, defects on CNTs had small influence on the catalytic performance when nanoparticles were filled in CNTs.