Construction Of Palladium Supported On Niobium Oxide-based Carrier And Study On Its Electrocatalytic Performance

Since the development of human beings,all economy and survival have depended on energy.Energy is a symbol of a country’s economic strength.Facing the problem of energy shortage,direct alcohol fuel cells（DMFC）stand out as a leader in the field of batteries,and have become a hot spot for research and development in various countries.As a new type of device,DMFC can be applied in the fields of automobiles,ships and small power stations.The simple structure of DMFC,which are not restricted by Kano cycle,high efficiency,no pollution,etal.,the most important thing is that the fuel consumed is alcohols from renewable resources.At present,most of the commercial platinum carbon used has the disadvantages of poor stability and high cost.In this paper,a series of synthetic studies on the control of morphology,surface modification,and heterogeneous composites are designed with niobium oxide based nanomaterials as the carrier to improve its electrocatalytic oxidation performance in ethylene glycol and glycerol.The main research contents are as follows:（1）Orthorhombic urchin-like Nb₂O₅ nanospheres was prepared by hydrothermal method,and Pd nanoparticles were supported on Nb₂O₅ microspheres to obtain electrocatalyst Pd/Nb₂O₅.The catalyst Pd/Nb₂O₅ was synthesized by reflow method.The crystal structures and morphology of the samples were tested by X-ray diffraction analysis（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and high resolution transmission electron microscopy（HRTEM）.The catalyst was tested by electrochemical workststion under alkaline condition,such as cyclic voltammetry（CV）,electrochemical impedance spectroscopy（EIS）.The results show that the pure phase Nb₂O₅ has a large exposed surface,and Pd nanoparticles uniformly support its surface,and produce a strong interaction,which makes the catalyst have good electrocatalytic activity,anti-poisoning ability and cycle stability for ethylene glycol and glycerol.（2）Since the carrier Nb₂O₅ is a semiconductor,the band gap is about 3.4ev,and the conductivity is not high.Urchin-like Nb₂O₅ nanospheres were modified by doping Fe³⁺,Co²⁺,Ni²⁺,then Pd nanoparticles were supported on doped niobium pentoxide obtain Pd/X-Nb₂O₅ catalysts（X=Fe,Co,Ni）.The Crystalline form,morphology and composition of the catalyst were characterized by XRD,SEM,TEM,X-ray photoelectron spectroscopy（XPS）and other techniques.The results show that the conductivity of urchin-like Nb₂O₅ nanospheres is enhanced due to the addition of transition metals,and cause lattice distortion and form an amorphous structure.The catalyst was tested under alkaline conditions by electrochemical test technology.The catalyst’s electrocatalytic activity and stability to ethylene glycol and glycerol were better than commercial Pd/C（10%）,indicating that the conductivity of the carrier also has a great influence on the electrocatalytic activity.（3）CeO₂ and urchin-like Nb₂O₅ nanospheresares were recombined by hydrothermal method,in which the molar ratio of Ce and Nb was changed,and Pd/CeO₂-Nb₂O₅ was synthesized by the reflux method.Due to the addition of CeO₂,a heterojunction structure is formed with Nb₂O₅,which accelerates the surface electron transfer rate,at the same time,the synergy between the support and Pd nanoparticles can greatly improve the electrocatalytic performance of the composite catalyst,and the composite material has a good alkaline stability.Through a series of characterization methods,compared with commercial Pd/C（10%）,Pd/Nb₂O₅ and Pd/CeO₂,the prepared Pd/CeO₂-Nb₂O₅（Ce:Nb=3:1）showed the best electrocatalytic activity.