碳纳米纤维在浓硝酸-浓硫酸溶液中表面氧化对其负载的Pd-Pt催化剂颗粒分散状态的影响

Effects of Surface Oxidation of Carbon Nanofibers in Mixed Concentrated HNO_3-H_2SO_4 Acid Solution on Dispersion State of Supported Pd-Pt Catalyst Particles

用混合的浓硝酸和浓硫酸在不同温度下氧化处理催化生长的碳纳米纤维.利用X射线衍射、N2物理吸附、FTIR和离子交换研究了氧化处理对碳纳米纤维织构性质和表面含氧基团生成的影响.采用等体积浸渍法制备碳纳米纤维负载Pd-Pt催化剂,并利用高分辨电镜和脉冲H2化学吸附对Pd-Pt金属颗粒的分散状况进行了研究.结果表明,经过氧化处理的碳纳米纤维表面生成了含氧基团,生成量随着处理温度的升高而升高,负载的Pd-Pt催化剂的分散程度也随着表面含氧基团浓度的增大而提高,同时对后者的作用机理进行了讨论.

Catalytically grown carbon nanofibres were treated with a mixture of concentrated nitric and sulphuric acids at different temperatures. The effects of the oxidation treatment on the graphite structure and texture properties were studied by X-ray diffraction and N2-physisorption. The formation of the surface oxygen-containing groups on the surface of the carbon nanofibers was investigated by DRIFT FFIR and the ion-exchange method. The Pd-Pt catalysts supported on the fresh and treated carbon nanofibres were prepared with the incipient wetness impregnation method. The Pd-Pt metal dispersion and the interaction of them with the carriers were studied by the pulses of hydrogen, the high-resolution electron microscopy and the TPR-FTIR. The results demonstrated that there were no clear changes of the bulk structure and the texture properties of carbon nanofibers after the treatment in the mixed acids below 150 ℃. The concentration of the formed oxygen-containing surface groups increased with raising the treatment temperatures and it could produce a pronounced promoting effect in the dispersion of metal in the carbon nanofibers. The mechanism of the role of the surface oxygen-containing groups in improving the dispersion of Pd-Pt particles was also discussed.