Studies On Catalytic Graphitization Of Carbon Material And Electrocatalytic Performance Of Titania Nanomaterial

Carbon materials have attracted tremendous attention due to their high strength, high modulus, high thermal conductivity, low-coefficent of thermal expansion, low-electronic resistivity and light weight. They are widely applied in different fields, such as aerospace, industry, sporting goods, etc. The performance of carbon materials is closely associated with their structure. The graphitization is one of the most important structure parameters of carbon materials. Many efforts indicated that improving graphitization at lower temperatures or increasing the degree of graphitization at a certain treatment temperature were achieved by the addition of either organic or inorganic chemical additive. Therefore, the catalytic graphitization is the key point of carbon material research. Nano-titania material has special structure, which results in series of unique physical and chemical properties, such as high surface area, strong adsorptive capacity, tolerance for chemical etching, stabilization, good light receptivity, harmless to the human body, etc, applied in photochemical catalyst, organic synthesis, sewage treatment, solar cells, fuel cells, and so on. The research on nano-TiO₂ has a vital significance for developing new functional materials. Based on this, the paper has studied the catalytic graphitization of carbon fibers and the electrocatalytic performance of TiO₂ nanomaterial, respectively. The details are summarized as follows:(1) The catalytic graphitization of PAN-based carbon fibers by anodization and Ni-P catalysts: a one-step pretreatment, anodization, was used to activate the Polyacrylonitrile based carbon fibers instead of the routine two-step pretreatment, with SnCl2 sensitization + PdCl2 activation; Compared with the pretreatment of SnCl2 sensitization + PdCl2 activation, anodization is simpler for operator, lower cost (does not need to use precious metal Pd), better activated effect; The effect of the anodization pretreatment on the graphitization of PAN-based carbon fibers was investigated as a function of Ni-P catalyst; The structural changes of carbon fibers were characterized by X-ray diffraction and Raman spectroscopy, both of which indicated that the graphitization of PAN-based carbon fibers were accelerated by both anodization treatment and Ni-P catalysts.(2) The catalytic graphitization of PAN-based carbon fibers by Ti-B catalysts: a sol-gel synthesis method was used to modify Ti-B catalysts on the surface of PAN-based carbon fibers, which can instead of electroless/electronic plating due to its simplicity for operator, uniform dispersion, control of ingredient and good catalytic effect. The effects of the Ti, B and Ti-B on the graphitization of PAN-based carbon fibers were investigated. The research showed that the catalytic effect of Ti-B was better than single both Ti and B, and a synergistic catalytic effect of Ti-B catalytic system was observed. The highest catalytic graphitization effect was achieved in treating the PAN-based fibers using a Ti-B sol catalysts, mole composition TiCl4/H3BO3=0.228/1.33, with 2400°C heat treatment, resulting in a d002 of 0.3360 nm and a Lc(002) of 24.3 nm. X-ray diffraction analysis showed that TiC and TiB2 were primary catalysts formed at high temperature, but no boron nor boron carbide phase were observed.(3) The preparation and electrocatalytic performance of TiO₂\CNT\PtRu electrode: highly ordered anodic titania nanotube arrays were used as the substrate for the CVD growth of carbon nanotubes (CNTs). Pt and Ru nanoparticles, approximately 3 nm in diameter, were uniformly electrodeposited on the as synthesized titania-supported carbon nanotubes(TiO₂\CNT), constructing a novel TiO₂\CNT\PtRu catalyst. The electrocatalytic performance of TiO₂\CNT\PtRu electrode for the oxidation of methanol was investigated. An enhanced catalytic activity is obtained due to the uniformly dispersed Pt and Ru nanoparticles, and the large CNT network facilitating the electron transfer, the adsorbed methanol molecules and the synergistic catalytic effect of Ti. An oxidation peak current density of 55 mA/cm2 is achieved at a low Pt load of 0.126 mg/cm² with a Pt/Ru mole ratio of 1:1.