Preparation Of Transition Metal Doped Tungsten Based Materials And Its Electrocatalytic Performance

Fuel cells have broad application prospects because of its clean,no pollution and high energy conversion efficiency.At present,platinum based catalysts are still the most common used cathode catalysts for fuel cell,especially platinum supported carbon catalyst?Pt/C?,but its high cost and the lower stability are still the main obstacles for the real commercialization of fuel cell.The active species and support involved in catalysts can be considered to solve the above problems.Tungsten oxide has been widely used in the electrocatalysis because it usually has plenty of defects caused by the varying oxidation state.The composite catalyst can be prepared by loading a small amount of precious metals onto tungsten oxide support material.In this way,the synergy effect between tungsten oxide?WO₃?and Pt?Pd?can be employed to improve catalytic performance of this composite catalyst for the oxygen reduction reaction.Also the decreased loading amounts of noble metal will lead to a lower cost of catalyst.However,the prepared catalysts still have a poor electrical conductivity,instability in the alkaline medium and the poor catalytic activity in acid medium only with tungsten oxide as catalyst support materials.Therefore,a certain proportion of other transition metal elements are doped into the tungsten oxide,which can cause the better catalytic properties of oxygen reduction not only because the synergy effect between tungsten oxide and noble metal,but also take the advantage of the oxygen defects generated by doping.The main research can be summarized as follows:?1?In this work,we prepared the stoichiometric WO₃ and the non stoichiometric W₁₈O₄₉ respectively by hydrothermal synthesis method.At the same time,the effects of different factors on the product morphology from several aspects have been discussed,such as the different tungsten source,concentration of tungsten chloride and the choice of solvent.In addition,the work also compared the difference in the structure of the WO₃ and W₁₈O₄₉.Ultimately,W₁₈O₄₉ with special morphology and a lot of oxygen defects as support material was synthesized by choosing a certain concentration of chloride as the source of tungsten,alcohol solvent as reaction system and through the alcoholysis reaction.?2?In this section,we used W₁₈O₄₉ with oxygen defects as the precursor and prepared Ni-W-O solid solution with different proportion by hydrothermal synthesis method.By cyclic voltammetry,linear sweep voltammetry and other electrochemical characterization methods,we determined the optimal performance of the catalyst when the mole ratio of W/Ni is 1:1.Then,a small amount of Pt is loaded on the Ni WOx support.The synthesized Pt/Ni WOx catalyst showed enhanced performance for oxygen reduction in alkaline medium.?3?In this section,we used W₁₈O₄₉ with oxygen defects as the precursor and explored the effects of the different Mo doping ratios on W₁₈O₄₉ morphology,structure and catalytic performance.The result indicated that the performance was optimal when the doping amount of Mo was 30%.Then a small amount of Pt was loaded onto the synthesized 30%Mo-W₁₈O₄₉ support and electrochemical tests were carried out.It is found that the Pt/30%Mo-W₁₈O₄₉ electrocatalyst had not only good catalytic performance,but also good stability for oxygen reduction reaction in acidic medium...