【作者】 杜晶晶；

【导师】 陈白珍； 杨喜云；

【作者基本信息】 中南大学 ， 电化学工程， 2014， 博士

【摘要】 摘要：氢能是一种可再生的清洁能源,具有资源丰富、易储存等许多突出的优点。随着化石燃料的枯竭及环境问题的日益严重,氢能越来越受到人们的重视。电解水是大规模制氢的重要途径,为了降低阴极过电位以节约能耗,研究低析氢过电位、高催化活性的阴极材料具有重要的意义。影响析氢材料催化活性的因素主要有能量因素和几何因素。因此,制备高催化活性的析氢阴极材料,主要通过两种方式实现：一是寻找高催化活性的新型催化材料,提高电极本身的电化学活性；二是提高电极的真实比表面积,即增大电极的表面粗糙度,使电解过程中电极表面的真实电流密度降低,达到降低析氢过电位的目的。本论文采用电沉积法制备纳米多级孔镍合金复合电极,利用SEM、EDS、TEM以及XRD对合金电极的表面进行了表征,并比较了不同复合电极在质量分数为25%KOH溶液中的电催化析氢性能,为实现低能耗、高效率电解水制氢提供技术支持和理论支持,论文的主要研究内容如下：1、探讨了在柠檬酸体系中主要组份及工艺参数对电沉积Ni-W合金的成分和表面质量的影响,得出电沉积Ni-W合金的最佳配方和工艺参数,获得Ni的质量分数为74.22%,W的质量分数为25.78%的光亮Ni-W合金镀层。分别以纳米二氧化硅微球、纳米聚苯乙烯微球以及氢气泡为模板,采用无机模板移除电沉积法,有机模板移除电沉积法以及气泡模板法制备了多孔Ni-W合金电极,结果表明：采用无机模板移除电沉积法和有机模板移除电沉积法制备多孔Ni-W合金电极,虽然方法可行,但作为析氢电极用于电解水制氢,该电极的效果不佳；采用气泡模板法制备多孔Ni-W合金电极时,发现在高的阴极电流密度下,虽然可以获得多孔结构的镀层,但是不易获得多孔Ni-W合金电极。2、探讨了在柠檬酸体系中主要组份及工艺参数对电沉积Ni-Mo合金的成分、表面形貌以及电催化析氢活性的影响,得出电沉积Ni-Mo合金的最佳配方和工艺参数,获得Ni的质量分数为64.49%,Mo的质量分数为35.51%的光亮Ni-Mo合金镀层。采用溶胶凝胶-表面活性剂法制备出平均粒径为510nm的二氧化钛颗粒,采用原位合成法成功地制备出直径为200-500nm,比表面积达573m2/g,孔体积为1.19cm3/g,介孔孔径为3.2nm的纳米多级孔Ti-SiO2颗粒,采用同样的方法成功地制备出直径为200-800nm,比表面积达396m2/g,孔体积为1.37cm3/g,介孔孔径在3.3nm的纳米多级孔Al-SiO2颗粒。分别以纳米TiO2颗粒,纳米多级孔Ti-SiO2颗粒和纳米多级孔Al-SiO2颗粒作为复合粒子,制备出Ni-Mo复合电极,通过析氢极化曲线比较每种复合粒子浓度对复合电极电催化析氢活性的影响,结果表明：镀液中纳米Ti02、纳米多级孔Ti-SiO2和纳米多级孔Al-SiO2的浓度分别为4g/L,2g/L和2g/L时,复合电极的电催化析氢活性达到最佳值。在最佳复合粒子浓度的条件下,比较三种复合粒子对复合电极电催化析氢活性的影响,结果表明：三种Ni-Mo合金复合电极的电催化析氢活性比Ni-Mo合金电极都要好,其中纳米多级孔Ti-SiO2/Ni-Mo复合电极电催化析氢活性最好,纳米多级孔Al-SiO2/Ni-Mo复合电极次之,纳米Ti02/Ni-Mo复合电极最差。3、探讨了在柠檬酸体系中主要组份及工艺参数对电沉积Ni-Co合金的成分和电催化析氢活性的影响,得出电沉积Ni-Co合金的最佳配方和工艺参数,得到Ni的质量分数为62.25%,Co的质量分数为37.75%的Ni-Co合金镀层。采用模板溶解法制备出尺寸大约为70nm,球壳厚度为10nm左右,且空心球内外壁呈现多级孔结构,比表面积达896m2/g,孔体积达1.30cm3/g的空心纳米多级孔硅氢化合物颗粒,利用硅氢键的还原性,成功地在纳米多级孔硅氢化合物上负载贵金属Pd,通过TEM图表征发现：Pd纳米颗粒分布在纳米多级孔硅氢化合物颗粒的内部和表面上,内部Pd纳米颗粒的粒径大约为3nm,表面上Pd纳米颗粒的粒径为10-30nm左右,且没有破坏其内部的空心结构,得到纳米多级孔Pd-SiO2颗粒,以该纳米多级孔颗粒为复合粒子,制备出纳米多级孔Pd-SiO2/Ni-Co复合电极,通过对Ni-Co合金电极和纳米多级孔L Pd-SiO2/Ni-Co复合电极的电催化析氢性能进行研究,结果表明：Ni-Co合金的电催化析氢活性比纯镍要好得多,并随着合金镀层中Co含量的增加,电极电催化析氢活性不断增强,当镀液中纳米多级孔Pd-SiO2颗粒浓度为1.8g/L时,纳米多级孔Pd-SiO2/Ni-Co复合电极的电催化析氢活性最好。通过TEM图表征发现：Pd纳米颗粒分布在纳米多级孔硅氢化合物颗粒的内部和表面上,内部Pd纳米颗粒的粒径大约为3nm,表面上Pd纳米颗粒的粒径为10-30nm左右,且没有破坏其内部的空心结构,得到纳米多级孔Pd-SiO2颗粒,以该纳米多级孔颗粒为复合粒子,制备出纳米多级孔Pd-SiO2/Ni-Co复合电极,通过对Ni-Co合金电极和纳米多级孔Pd-SiO2/Ni-Co复合电极的电催化析氢性能进行研究,结果表明：Ni-Co合金的电催化析氢活性比纯镍要好得多,并随着合金镀层中Co含量的增加,电极电催化析氢活性不断增强,当镀液中纳米多级孔Pd-SiO2颗粒浓度为1.8g/L时,纳米多级孔Pd-SiO2/Ni-Co复合电极的电催化析氢活性最好。4、系统探讨了各种工艺参数对电沉积Ni-Mo-Co合金的成分和电催化析氢活性的影响,确定出在柠檬酸体系中电沉积Ni-Mo-Co合金的最佳配方和工艺参数,得到Ni的质量分数为35.10%,Mo的质量分数为50.15%,Co的质量分数为14.75%的光亮Ni-Mo-Co合金镀层。通过对不同组分的Ni-Mo-Co合金电极的电催化析氢性能进行比较,结果表明：随着合金镀层中Mo和Co含量的增加,合金电极的电催化析氢活性逐渐增大；通过比较纳米多级孔Pd-SiO2/Ni-Mo-Co复合电极、纳米多级孔Ti-SiO2/Ni-Mo-Co复合电极以及Ni-Mo-Co合金电极的电催化活性,结果表明：纳米多级孔Ni-Mo-Co复合电极的电催化析氢性能比Ni-Mo-Co合金电极要好,且纳米多级孔Pd-SiO2/Ni-Mo-Co复合电极的电催化析氢活性比纳米多级孔Ti-SiO2/Ni-Mo-Co复合电极要好,降低析氢过电位分别为80mV和60mV。更多还原

【Abstract】 Abstract:Hydrogen energy is a kind of clean renewable energy which has many prominent merits such as rich in resources and easy to store up. Because of the exhaustion of the fossil fuels and the environmental crisis, people have paid more attention to it. The main method to prepare hydrogen on a large scale is water electrolysis. In order to decrease cathode overpotential for reducing energy consumption, it’s of momentous significance to research new cathode eleetrode materials which have lower hydrogen-evolution overpotential and high catalytic activity. There are two important factors that can affect the catalytic activity of the hydrogen-evolution materials:energy factors and geometry factors. So there are two main methods can be taken to prepare cathode materials for hydrogen evolution which own high catalytic activity. One is to search for a new kind of catalytic materials of high catalytic activity so as to improve electrocatalytic activity of the electrode itself. The other is to inerease the actual specific surface area of the electrode, namely to amplify the electrode surface roughness which can decrease the true current density of the electrode surface in the course of electrolysis reaction so as to reduce the cathode overpotential. In this thesis, nanoporous nickel alloys composite electrodes were prepared by electrodeposition technique and characterized every electrode by SEM, EDS and XRD, and also analysised the electrochemical properties of hydrogen evolution reaction in25wt%KOH solution. The achievement will provide theoretic and technical support for water electrolysis with low energy, promote the development of the water electrolysis technique for hydrogen production. The main research contents are listed as following:1. Ni-W alloy coatings were prepared by electrodeposition technique in citric acid system. The influence of the main technical parameters on the compositions and surface quality of Ni-W alloy coatings were investigated, the bright Ni-W alloy coatings with W25.78wt%and Ni74.22wt%were obtained. The results showed that porous Ni-W alloy electrodes were obtained by removing templates electrodeposition methods, the inorganic templates were nano silica microspheres, the organic templates were nano polystyrene microspheres, the bubble templates were hydrogen bubbles. The methods of removing inorganic and organic templates electrodeposition for preparing porous Ni-W alloy electrodes were feasible, but the hydrogen evolution electrodes for electrolyzing water were ineffective. The electrodes with porous structure were obtained by bubble template electrodeposition method at high current density but the content of W in the Ni-W alloy coatings was too little, so it was difficult for obtaining porous Ni-W alloy electrodes using this method.2. Ni-Mo alloy coatings were prepared by electrodeposition technique in citric acid system. The influence of the main technical parameters on the compositions, surface morphology and the electrocatalytic activities for hydrogen evolution of Ni-Mo alloy coatings were investigated, the bright Ni-Mo alloy coatings with Mo35.51%wt%and Ni64.49wt%were obtained. Nano TiO2particles with average diameter510nm were prepared by Sol gel-surfactants. Nano hierarchically porous Ti-SiO2and Al-SiO2particles were prepared by using in-situ method. The diameter of Ti-SiO2particles were from200nm to500nm, specific surface area was573m2/g, pore volume was1.19cn3/g and mesopore size was3.2nm. The diameter of Ti-SiO2particles were from200nm to800nm, specific surface area was396m/g, pore volume was1.37cm/g and mesopore size was3.3nm. Nano hierarchically porous Ni-Mo composite electrodes were prepared with nano TiO2particles, nano hierarchically porous Ti-SiO2and Al-SiO2particles as composite particles respectively. The influence of the concentration of composite particles on the electrocatalytic activities of Ni-Mo composite electrodes for hydrogen evolution were investigated by polarization curves, the results showed that the electrocatalytic activities of Ni-Mo composite electrodes for hydrogen evolution reached the optimal values when the concentration of nano TiO2particles, nano hierarchically porous Ti-SiO2and Al-SiO2particles were4g/L2g/Land2g/L respectively. The influence of the three composite particles on the electrocatalytic activities of Ni-Mo composite electrodes for hydrogen evolution were investigated when the concentration of nano TiO2particles, nano hierarchically porous Ti-SiO2and Al-SiO2particles were4g/L,2g/Land2g/L respectively, the results showed that the electrocatalytic activities of Ni-Mo composite electrodes for hydrogen evolution were better than that of Ni-Mo alloy electrodes, and the electrocatalytic activity of nano hierarchically porous Ti-SiO2/Ni-Mo composite electrode for hydrogen evolution was the best in the three Ni-Mo composite electrodes, that of nano hierarchically porous Al-SiO2/Ni-Mo composite electrode and nano TiO2/Ni-Mo composite electrode were second and third, respectively.3. Ni-Co alloy coatings were prepared by electrodeposition technique in citric acid system. The influence of the main technical parameters on the compositions and the electrocatalytic activities of Ni-Co alloy coatings for hydrogen evolution were investigated, the bright Ni-Co alloy coatings with Co37.75%wt%and Ni62.25wt%were obtained. Nano hierarchically porous hydridosilica particles were prepared by dissolving template. The diameter of nano hierarchically porous hydridosilica hollow microspheres were about70nm, the thickness of hollow microspheres were obout10nm, the specific surface area was896m/g and pore volume was1.30cm/g. Precious metal Pd were successfully load on the nano hierarchically porous hydridosilica hollow microspheres due to the reductibility of silicon hydrogen bonds. The nano hierarchically porous Pd-SiO2particles with hollow structure were analyzed by TEM, the results showed that Pd nanoparticles were distributed in the internal and on the surface of nano hierarchically porous hydridosilica hollow microspheres, the diameter of Pd nanoparticles were about3nm in the internal of nano hierarchically porous hydridosilica hollow microspheres, and the diameter of Pd nanoparticles were from10nm to30nm on the surface of nano hierarchically porous hydridosilica hollow microspheres. Nano hierarchically porous Pd-SiO2/Ni-Co composite electrodes were prepared with nano hierarchically porous Pd-SiO2particles as composite particles. The influence of the concentration of composite particles on the electrocatalytic activities of Pd-SiO2/Ni-Co composite electrodes for hydrogen evolution were investigated by polarization curves, the results showed that the electrocatalytic activities of Pd-SiO2/Ni-Co composite electrodes for hydrogen evolution reached the optimal value when the concentration of nano hierarchically porous Pd-SiO2particles was1.8g/L. The influence of the different components on the electrocatalytic activities of Ni-Co alloy electrodes for hydrogen evolution were investigated, the results showed that the electrocatalytic activities of Ni-Co electrodes for hydrogen evolution were better than that of Ni electrode, and gradually increased with increase in the content of Co in the Ni-Co alloy coatings.4. Ni-Mo-Co alloy coatings were prepared by electrodeposition technique in citric acid system. The influence of the main technical parameters on the compositions and the electrocatalytic activities of Ni-Mo-Co alloy coatings for hydrogen evolution were investigated, the bright Ni-Mo-Co alloy coatings with Ni35.10wt%, Mo50.15wt%, and Co14.75wt%, were obtained. The influence of the different components on the electrocatalytic activities of Ni-Mo-Co alloy electrodes for hydrogen evolution were investigated, the results showed that the electrocatalytic activities of Ni-Mo-Co alloy electrodes for hydrogen evolution were gradually increased with increase in the content of Co and Mo in the Ni-Mo-Co alloy coatings. The electrocatalytic activities of nano hierarchically porous Pd-SiO2/Ni-Co composite electrode, nano hierarchically porous Ti-SiO2/Ni-Co composite electrode and Ni-Mo-Co alloy electrode for hydrogen evolution were investigated, the results showed that the electrocatalytic activity of nano hierarchically porous Pd-SiO2/Ni-Co composite electrode for hydrogen evolution was better than that of Ti-SiO2/Ni-Mo composite electrode, and the electrocatalytic activity of Ni-Mo-Co composite electrodes were better than that of Ni-Mo-Co alloy electrode, the over-potential of hydrogen evolution of nano hierarchically porous Pd-SiO2/Ni-Co and Ti-SiO2/Ni-Co composite electrode decreased80mV and60mV respectively,which were relative to that of Ni-Mo-Co alloy electrode.更多还原