过渡金属磷化物的可控制备及其电解水催化性能的研究

发布时间：2018-06-25 14:15

本文选题：水滑石前体 + 表面活性剂　；参考：《北京化工大学》2017年硕士论文

【摘要】：现今社会经济高速发展,对于能源的需求量也越来越大,传统化石能源已不能满足日益增长的社会需求,而且对环境会造成不可挽回的污染,因此寻找清洁、可持续发展的绿色新能源成为大家共同关注的焦点问题。氢能由于其来源广泛、可再生、清洁无污染、能量密度高、转换效率高,而且易储存等诸多优点而备受研究者的重视。目前应用最为广泛的制氢技术为电解水制氢。而影响电解水制氢效率的关键则在于电极催化剂材料的合理选用。目前商业化应用最为广泛的电解水电极催化剂材料分别为:应用于碱性条件下析氧反应的IrO2、Ru02等贵金属氧化物;应用于酸性条件下析氢反应Pt/C等材料。但是由于贵金属催化剂价格昂贵、来源匮乏、而且循环稳定性较差,因此寻找来源丰富、价格低廉的非贵金属电极催化剂来替代贵金属催化剂的使用变得尤为迫切。本文主要以类水滑石材料为前驱体,利用后期磷化和插层等手段,成功制备出不同形貌的过渡金属磷化物(花状CoP/CoP2/A1203和豆荚状Co2P/C),并进一步研究了其作为电解水电极催化剂的性能。主要研究内容如下:1、采用传统共沉淀方法合成花状CoAl-LDH,随后经过还原、磷化等方法制得花状CoP/CoP2/Al2O3复合催化剂材料。该复合物催化剂材料颗粒尺寸分布均一,同时花状结构又能够保证活性位点的充分暴露,从而更近一步提高其催化活性。在1.0MKOH碱性电解质溶液中进行测试,结果显示该催化剂材料作为OER电极材料时,达到10 mA/cm2所需过电势为300 mV,相应的塔菲尔斜率仅为63 mV/dec,作为HER电极材时,达到-10 mA/cm2所需过电势为-138 mV,相应的塔菲尔斜率仅为73 mV/dec,最后将该催化剂同时作为电解水的正负极进行测试,发现达到10 mA/cm2所需电压仅为1.65 V,并且在循环24小时之后电流密度并没有明显的下降。2、根据类水滑石材料的独特层状结构,利用层间阴离子可调变的特性,设计通过使用阴离子型表面活性剂(SDP)插层Co(OH)2层状材料作为前驱体,经过后续程序升温焙烧的方法制得豆荚状Co2P/C复合物催化剂材料。并对其电催化性能进行探究。该制备方法的优势在于通过简单的一步插层法同时引入碳源与磷源,既避免了有机磷源的使用,又同时能够提高该催化剂材料的导电性,进而更进一步的提高其催化活性及其电化学稳定性。在1.0 MKOH碱性电解质溶液中进行测试,结果显示该催化剂材料作为OER电极材料时,达到10mA/cm2所需过电势为320 mV,相应的塔菲尔斜率仅为70 mV/dec,作为HER电极材时,达到-10 mA/cm2所需过电势为-140 mV,相应的塔菲尔斜率仅为63 mV/dec,最后将该催化剂同时作为电解水的正负极进行测试,发现达到10 mA/cm2所需电压仅为1.50 V,并且在循环24小时之后电流密度并没有明显的下降。
[Abstract]:Nowadays, with the rapid development of society and economy, the demand for energy is also increasing. The traditional fossil energy can not meet the increasing social demand, and it will cause irreparable pollution to the environment. Sustainable development of green new energy has become the focus of common concern. Hydrogen energy has attracted much attention due to its advantages such as wide source, renewable, clean and pollution-free, high energy density, high conversion efficiency, and easy storage. At present, the most widely used hydrogen production technology is electrolytic water hydrogen production. The key to the hydrogen production efficiency of electrolytic water is the reasonable selection of electrode catalyst materials. At present, the most widely used electrolytic water electrode catalyst materials are as follows: the noble metal oxides such as IrO2 / Ru02 used for oxygen evolution under alkaline conditions, and the materials such as PT / C for hydrogen evolution under acidic conditions. However, because the precious metal catalyst is expensive, the source is scarce, and the cycle stability is poor, it is urgent to find the cheap non-precious metal electrode catalyst to replace the precious metal catalyst. In this paper, hydrotalcite-like materials were used as precursors, and different morphologies of transition metal phosphates (flower-like CoP / CoP2A1203 and pod-like Co2P / C) were successfully prepared by means of late phosphating and intercalation, and their properties as electrolytic water electrode catalysts were further studied. The main contents of this study are as follows: 1. The flower-like CoAl-LDH was synthesized by the traditional coprecipitation method, and then the flower-like CoP / CoP2Al _ 2O _ 3 composite catalyst material was prepared by reduction, phosphating and other methods. The particle size distribution of the composite catalyst is uniform, and the flower-like structure can guarantee the full exposure of the active sites, so that the catalytic activity can be improved further. The test results in 1.0 MKOH alkaline electrolyte solution show that the overpotential of the catalyst is 300mV when it is used as the electrode material for 10 mA/cm2, and the corresponding Tafel slope is only 63mV / r, which is used as HER electrode material, and the results show that when the catalyst is used as the electrode material, the overpotential is 300mV and the corresponding Tafel slope is only 63mV / r. The overpotential needed to reach -10 mA/cm2 is -138 MV, and the corresponding Taffel slope is only 73 MV / r. Finally, the catalyst is used as the positive and negative electrode of electrolytic water. It is found that the voltage required to reach 10 mA/cm2 is only 1.65 V, and the current density does not decrease significantly after 24 hours of cycle. According to the unique layered structure of hydrotalcite-like materials, the interlayer anions can be adjusted. A pod-like Co _ 2P / C composite catalyst material was prepared by using the anion surfactant (SDP) intercalated Co (OH) _ 2 layered material as the precursor and the subsequent temperature-programmed roasting process. And its electrocatalytic performance was explored. The advantage of this method lies in the simple one-step intercalation method, which can not only avoid the use of organic phosphorus sources, but also improve the conductivity of the catalyst materials. Furthermore, its catalytic activity and electrochemical stability were further improved. The results of measurement in 1.0 MKOH alkaline electrolyte solution showed that the overpotential needed to reach 10mA/cm2 was 320 MV, and the corresponding Tafel slope was only 70 MV / dec.When the catalyst was used as the electrode material, the overpotential of the catalyst was 320 MV, and the corresponding Tafer slope was only 70 MV / deco. The overpotential needed to reach -10 mA/cm2 is -140 MV, and the corresponding Taffel slope is only 63 MV / r. Finally, the catalyst is used as the positive and negative electrode of electrolytic water. It is found that the voltage required to reach 10 mA/cm2 is only 1.50 V, and the current density does not decrease significantly after 24 hours of cycle.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ116.2

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