Controlled Synthesis And Electrocatalytic Properties Of Ternary Tungsten-based Nanostructured

As far as electrocatalytic water splitting is concerned,its reaction rate is mainly determined by complex and kinetically sluggish of oxygen evolution reaction（OER）.Current OER catalysts are still facing with some problems such as high cost,low efficiency,and poor stability.Therefore developing new electrocatalyst is of great significance.As important inorganic functional materials,metal tungstates have the wide range of applications in sensor,photoluminescence,catalysis and corrosion.There have few reports on tungstates that were used as electrocatalysts.In this dissertation,the electrocatalytic OER performance of ternary W-based compounds was significantly enhanced through some new strategies including crystal facets engineering,defect tuning,and combined with conductive material.The main points are as follows:（1）Using Bi（NO₃）₃·5H₂O,Na₂WO₄·2H2O as raw materials,and oleylamine as surfactant,blue Bi₂WO₆ concave nanoplates（CNPs）were synthesized through a facile solvothermal reaction at 220 °C for 6 h.XRD,FE-SEM,TEM,XPS,EDX,UV-visible diffuse reflectance spectroscopy were used to characterize the morphology and structure of the products.The as-obtained Bi₂WO₆ CNPs with oxygen vacancies enable electrocatalytic OER under neutral conditions with high activity and good durability.To the best of our knowledge,this is the first example on W-based electrocatalyst containing no first-row transition metal or precious metal elements for OER in near-neutral water.Experimental results and first-principles calculations revealed that the presence of oxygen vacancies in Bi₂WO₆ CNPs could significantly decrease charge-transfer resistance and adsorption barrier of H2 O molecules in the process of electrochemistry,and thus benefiting the improvement of OER activity.The fabrication of concave surfaces with high energy facets could further enhance OER activity of the Bi₂WO₆ NPs electrocatalysts.As a result,the synergistic effect of oxygen vacancies and concave surfaces endowed impressive performance of Bi₂WO₆ CNPs for OER,which is comparable to the best electrocatalysts among known inorganic non-precious metal compounds.The present strategy on the combination of defect and crystal facet engineering could open a new avenue to design new and highly efficient OER electrocatalysts.（2）Using CoCl₂·6H₂O,Na2WO₄·2H₂O as reactants we synthesized two different morphologies of Co WO₄.The resultant products were characterized through XRD,FE-SEM,HRTEM,XPS and EDX in detail.The experimental results showed that the electrochemical OER performance of Co WO₄ nanorods were obviously superior to that of Co WO₄ nanoparticles.The different OER activities between them mainly resulted from different electrochemical active areas.Co WO₄/Nitrogen doped graphene oxides（N-RGO）composites were obtained under the same synthetyic conditions as those of Co WO₄ nanorods except that graphene oxides were added.As a result,Co WO₄/N-RGO composites showed enhanced electric catalytic activity due to good electrical conductivity of nitrogen doped graphene oxides.