The Application Of Carbon-oxides Composite Materials In Electrocatalysis

Electrocatalyst consists of two parts, including active metal and support. So far,though Pt and Pd based metal catalyst possesses high cost, they are still widely used asmajor electrocatalyst in fuel cells due to their excellent performance for ethanol andformic acid oxidation. Apart from the metal, the support plays a key role in the processof catalysis, however, the traditional carbon support suffers from serious corrosion instrong acid and alkaline environment, thus, developing newly electrocatalyst springsout.As the support of electrocatalyst, it should possess the following properties inorder to promote the performance of electrocatalyst: i) high specific surface area toinsure the metal can be loaded and well-dispersed; ii) good stability and tolerance in aharsh chemical environment; iii) superior electronic conductivity to make the electrontransport be smooth. To achieve the target, a series of newly carbon material which isapplied in electrocatalyst is developed by researchers. The obtained carbon material isprepared by modification by some given oxides.In hence, the thesis focuses on the synthesis of novel carbon material by usingoxides and its corresponding application in electrocatalysis. The work consists ofpalygorskite-carbon compound supported noble metal catalysts for ethanol/formic acidoxidation and nitrogen-doped carbon coated ZrO2as a support for Pt nanoparticles inthe oxygen reduction reaction. In terms of the prepared support and electrocatalyst, aseries of physical measurements are conducted to characterize their ingredient andstructure, and a many electrochemical tests are employed to evaluate the performanceof obtained catalyst for ethanol oxidation, formic acid oxidation and oxygen reductionreaction, respectively. The thesis consists of three parts as following:Part I Palygorskite-carbon compound supported PtSn as efficient electrocatalystfor ethanol oxidationPtSn nanoparticles deposited on a stable electrocatalytic support containingconventional carbon and palygorskite are prepared using pre-treated palygorskite wereevaluated by ethanol oxidation. The electrocatalysts are characterized by XRD, TEMand XPS. The physical characterization showed that the pre-treatment had an effectiveimpact on the morphology of palygorskite, but did not destroy its architecture and the introduction of palygorskite could facilitate the formation of Sn oxides on the surfaceof catalyst. Based on the result of electrochemical measurements, the developed newcomposite support was catalytically more active for ethanol electrooxidation than theconventional carbon support and showed good stability, offering great potential forwidespread application of palygorskite as support for electrocatalysis。Part II Palygorskite-carbon compound supported Pd nanoparticles as highperformance electrocatalysts for formic acid oxidationA nanocomposite, in which acid-treated palygorskite was hybridized with carbon,was prepared and designed as an efficient support for electrocatatlysts. Pd nanoparticleswere deposited on the hybrid support as an electrocatalyst for formic acid oxidation.The hybrid supports and electrocatalysts were characterized by X-ray diffraction(XRD), transmission electron microscopy (TEM) and X-ray photoelectronspectroscopy (XPS). The physical measurement results showed that acid treatment hadan effective impact on the morphology of palygorskite, but did not destroy itsarchitecture. While, the electrochemical results showed that considerableimprovements in electrocatalytic activity toward formic acid oxidation was achievedby using this hybrid support when compared with conventional carbon support.Part III Nitrogen-doped carbon coated ZrO2as a support for Pt nanoparticles inthe oxygen reduction reactionA new nitrogen-doped carbon (CNx) support for Pt electrocatalysts was preparedby carbonizing polypyrrole on the surface of ZrO2(ZrO2@CNx) at high temperature.Well-dispersed Pt nanoparticles were easily formed on the ZrO2@CNx. Theelectrocatalyst was characterized by FT-IR, XRD, TEM, XPS. The electrochemicalperformances (CV, LSV) indicate that the presence of ZrO2modified the electro-structure of Pt on the catalyst surface and that ZrO2@CNxhad superior oxygenreduction activity compared to a nitrogen-doped carbon coated carbon (C@CNx).