三元钨基纳米材料的可控合成及电分解水性能研究

发布时间：2018-05-01 08:26

本文选题：Bi_2WO_6 + CoWO_4　；参考：《温州大学》2016年硕士论文

【摘要】：析氧反应是电催化分解水的决速步。当前用于析氧反应的催化剂仍具有成本高、效率低、稳定性差等缺点。因此开发新型电催化剂具有重要意义。钨酸盐材料在传感、发光、催化、缓蚀等领域有着广泛的应用,但是用于电催化分解水方面鲜有报导。本论文通过晶面工程、缺陷调控以及与导电材料复合策略,显著提高了三元钨基材料的电催化析氧性能。论文主要工作如下:(1)以五水合硝酸铋,二水合钨酸钠为原料,以油胺为表面活性剂,采用溶剂热法,合成了具有氧空位的凹面钨酸铋纳米片。利用XRD、FE-SEM、TEM、XPS、EDX、紫外-可见漫反射光谱等表征手段对产物进行了形貌和结构表征。所合成的氧空位凹面钨酸铋纳米片在近中性的条件下具有稳定的电化学分解水产氧性能。据我们所知,这是第一个不含第一行过渡金属及贵金属的钨基电催化剂用于近中性析氧反应的报道。实验结果和第一性原理表明,氧空位的存在能够在电化学过程中减少电荷转移阻力及水分子的吸附阻力,提高了电化学产氧的活性。此外,凹面的存在也增强了钨酸铋纳米片的电化学产氧活性。由于高能晶面和氧空位的协同效应,具有氧空位的凹面钨酸铋纳米片的电化学产氧性能可以与报道的最好的无机非贵金属催化剂相媲美。缺陷工程与晶面工程相组合的策略为设计新型、高效析氧电催化剂开辟了新途径。(2)以六水合氯化钴、二水合钨酸钠为原料,采用溶剂热法合成了两种形貌不同的钨酸钴纳米材料。通过XRD、FE-SEM、HRTEM、XPS、EDX等分析技术对合成的产物进行详尽表征。产物的电化学产氧性能研究结果表明:钨酸钴纳米棒的电化学产氧性能优于钨酸钴纳米颗粒。经过系统分析,两种不同形貌的电催化剂性能差异主要来自于不同的化学活性面积。在此基础上,筛选出性能良好的棒状钨酸钴加入氧化石墨烯,一锅煮法合成Co WO_4/氮掺杂-还原氧化石墨烯复合材料。研究结果表明,由于氮掺杂的还原氧化石墨烯良好的导电性,Co WO_4/氮掺杂-还原氧化石墨烯复合材料显示了增强的电催化活性。
[Abstract]:Oxygen evolution is a rapid step in the electrocatalytic decomposition of water. The current catalysts for oxygen evolution still have the disadvantages of high cost, low efficiency and poor stability. Therefore, it is of great significance to develop new electrocatalysts. Tungstate materials have been widely used in sensing, luminescence, catalysis, corrosion inhibition and so on, but they are rarely reported in the field of electrocatalytic decomposition of water. In this paper, the electrocatalytic oxygen evolution of the ternary tungsten based materials is improved significantly by surface engineering, defect control and composite strategy with conductive materials. The main work of this paper is as follows: (1) Bismuth bismuth pentahydrate and sodium tungstate dihydrate were used as raw materials and oleamine as surfactant. Bismuth concave bismuth tungstate nanoparticles with oxygen vacancy were synthesized by solvothermal method. The morphology and structure of the products were characterized by means of XRDX FE-SEMX and UV-Vis diffuse reflectance spectroscopy. The synthesized oxygen vacancy concave bismuth tungstate nanocrystals have stable electrochemical decomposition of aquatic oxygen under near neutral conditions. To our knowledge, this is the first tungsten based electrocatalyst without the first row of transition metals and precious metals for near-neutral oxygen evolution. The experimental results and first principles show that the presence of oxygen vacancies can reduce the charge transfer resistance and the adsorption resistance of water molecules in the electrochemical process and improve the electrochemical oxygen production activity. In addition, the presence of concave surface also enhanced the electrochemical oxygen production activity of bismuth tungstate nanoparticles. Due to the synergistic effect of high energy crystal plane and oxygen vacancy, the electrochemical oxygen production performance of concave bismuth tungstate nanocrystalline with oxygen vacancy is comparable to that of the best inorganic non-noble metal catalyst reported. The strategy of the combination of defect engineering and crystal plane engineering opens up a new way for the design of new and efficient oxygen evolution electrocatalysts. It uses cobalt chloride hexahydrate and sodium tungstate dihydrate as raw materials. Two kinds of cobalt tungstate nanomaterials with different morphologies were synthesized by solvothermal method. The synthesized products were characterized in detail by XRDX FE-SEMX HRTEMN XPS edX and other analytical techniques. The results show that the electrochemical oxygen production of cobalt tungstate nanorods is better than that of cobalt tungstate nanoparticles. Through systematic analysis, the difference of the performance of the two kinds of electrocatalysts with different morphology mainly comes from the different chemical active area. On this basis, Co WO_4/ nitrogen-reductive graphene oxide composites were synthesized by one-pot boiling method, in which the rod-like cobalt tungstate was added into graphene oxide. The results show that the nitrogen-doped reduced graphene oxide composite exhibits enhanced electrocatalytic activity due to its good electrical conductivity Co WO_4/ nitrogen-reduced graphene oxide composite.
【学位授予单位】：温州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36

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