Effects of surface oxidation of carbon nanofibers in mixed concentrated HNO3-H2SO4 acid solution on dispersion state of supported Pd-Pt catalyst particles

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 N-2-physisorption. The formation of the surface oxygen-containing groups on the surface of the carbon nanofibers was investigated by DRIFT FTIR 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 degrees C. 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.