Design And Synthesis Of Niobium Based Electrocatalysts And Their Application In Direct Alcohol Fuel Cells

In recent years,the energy crisis and environmental pollution situation have attracted the attention of all over the world.Fuel cells are used as an energy conversion device with low pollution and high efficiency.The development of fuel cells is very significant to solve these problems.In terms of research and development for direct alcohol fuel cell,they can’t be commercialized on a large scale.The biggest problem is the development of efficient catalysts.At present,most of the commercialized catalyst are platinum-based materials.However,these materials are also facing many problems,such as their high cost,low availability and low CO poisoning resistance.Therefore,this work studies that the synthesis of a series of high efficiency niobium oxide（Nb₂O₅）-based catalysts.In order to improve the electrocatalytic activity of these catalysts,Nb₂O₅ is modified using the rare earth doping,metal nanoparticles loading and multiphase composite.The research content of this work can be summarized as the following aspects:1.The Nb₂O₅ particles are prepared by calcination method.The R-Nb₂O₅（R=La,Eu,Tb,Ce）catalysts are synthesized with rare earth ions doping using hydrothermal method.The crystal phase,morphology and composition of these R-Nb₂O₅ catalysts were characterized with X-ray diffraction（XRD）,scanning electron microscopy（SEM）and X-ray photoelectron spectroscopy（XPS）.The electrocatalytic activity of these catalysts was further tested using cyclic voltammetry（CV）.The results show that these catalysts have good electrocatalytic activity toward methanol and ethanol oxidation in acid and alkaline medium.The electrocatalytic activity of Nb₂O₅ is improved with rare earth ions doping.2.The morphology of Nb₂O₅ was controlled by different prepare methods.The nanorod-like Nb₂O₅ is successfully prepared using the hydrothermal method.Metal Pd nanoparticles were loaded onto Nb₂O₅（Pd/Nb₂O₅）by reflux method.Finally,the Pd/Nb₂O₅-rGO catalyst was prepared by Pd/Nb₂O₅ and graphene（rGO）composite.The crystal phase,morphology and composition of Pd/Nb₂O₅-rGO catalyst are carried out by XRD,SEM,transmission electron microscopy（TEM）,XPS,CV.The results show that the electrocatalytic activity of Nb₂O₅ is improved with Pd nanoparticles loading and rGO composite.In addition,the electrocatalytic activity of Pd/Nb₂O₅-rGO catalyst toward the methanol oxidation is better than 10%commercial Pt/C in alkaline medium.3.N doped iron carbide nanotubes（Fe₃C@NCNTs）were prepared using calcination method,then Nb₂O₅ and Fe₃C@NCNTs composite（Nb₂O₅-Fe₃C@NCNTs）material are synthesized by niobium oxalate and Fe₃C@NCNTs mixture calcination.Finally,Pd loading onto Nb₂O₅-Fe₃C@NCNTs（Pd/Nb₂O₅-Fe₃C@NCNTs）catalyst is prepared by reduction method.The test results show that the catalyst has good electrocatalytic activity for alcohols oxidation in alkaline environment,and its catalytic performance is better than the 10%commercial Pt/C one.The research result has great significance to develop the catalysts with high electrocatalytic activity.