【作者】 郑振；

【导师】 李宁；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2013， 博士

【摘要】 氢气是一种重要的化工原料，而氢能更是作为新型的绿色能源受到了越来越多的关注。电解制氢的方式历史悠久，由于其无污染可再生的技术特点，近些年再次成为研究的热点，在电解制氢过程中阴极析氢材料扮演着重要的角色，设计和制备新型的阴极电解制氢电极能够降低电解制氢的析氢过电位，节约生产成本。本文采用了适用于大规模生产的电化学复合共沉积的方法，制备了新型的镍基CeO₂复合材料，制备过程采用了不同粒径的CeO₂复合颗粒，使用了扫描电子显微镜（SEM）、X射线衍射分析（XRD）、热重-差热分析（TG-DSC）、X射线光电子能谱分析（XPS）等手段对制备的复合电极材料进行了表征，并通过线性扫描、Tafel曲线分析、电化学阻抗谱分析等电化学分析手段对复合电极材料的电化学析氢活性和耐腐蚀性能等进行了研究，发现并考察了析氢过程中CeO₂与Ni及其合金之间的析氢协同效应。首先对电化学方法制备的Ni/CeO₂复合镀层进行了研究，其中CeO₂复合颗粒粒径分为微米级（5-10μm）和纳米级（10-30nm）。研究发现，Ni/CeO₂复合镀层的热稳定性良好，两种不同粒径CeO₂复合进入镍层后都提高了镍层的硬度和表面粗糙度，起到了细化Ni电结晶的作用，并且改变了Ni镀层的择优取向；微米CeO₂加入抑制了Ni沉积，而纳米CeO₂则降低了Ni沉积的极化；Ni/CeO₂复合镀层表现出良好的催化析氢活性，CeO₂的加入大幅度降低了镍表面析氢反应的电荷传递阻抗，提高了镍表面析氢反应的交换电流密度。当微米CeO₂浓度为15g/L时，得到的复合镀层的析氢交换电流密度为Ni层的70倍，将Ni表面析氢反应的整体阻抗值降低了30余倍；Ni/CeO₂复合镀层的析氢稳定性良好。研究结果认为复合镀层优异的析氢性能归因于CeO₂颗粒与Ni基体间形成了析氢协同效应，还原氢原子可以与具有空的d轨道和f轨道的二氧化铈更好地形成吸附氢原子。对Ni/CeO₂复合材料的耐蚀性研究表明，低复合量CeO₂复合镀层的耐蚀性较高。利用合金电沉积方法制备了Ni基合金/CeO₂复合材料，并对其析氢催化性能进行了研究。对Ni-S/CeO₂合金复合镀层的研究中发现，不同粒径CeO₂颗粒的复合可以提高Ni-S合金层中硫的含量，Ni-S/CeO₂合金复合镀层的析氢性能要优于Ni-S合金镀层，当微米CeO₂加入量为10g/L时，合金复合镀层的交换电流密度为Ni-S镀层的2.2倍，认为Ni-S/CeO₂复合镀层的析氢性能受复合镀层中硫含量和CeO₂与合金层间的协同效应共同影响。对Ni-Zn/CeO₂合金复合镀层的研究中发现，合金电沉积制备的Ni-Zn合金镀层由多种金属间化合物组成，Ni-Zn合金层本身具有较高的催化析氢活性，控制加入CeO₂的量可以进一步提高其的析氢活性，CeO₂的加入可以明显改变Ni-Zn合金层的微观结构和元素组成，通过研究加入CeO₂对合金电沉积中间产物的影响，结合Ni-Zn异常共沉积机理，解释了不同Ni-Zn/CeO₂复合镀层合金组分变化的原因。同时发现少量加入CeO₂颗粒可以提高Ni-Zn合金层的耐腐蚀性能。对Ni/CeO₂复合镀层的析氢动力学过程参数进行了计算，结果发现不同粒径的CeO₂的加入提高了镀层的比表面积，CeO₂的加入降低了Ni表面析氢反应的活化能，其中当微米CeO₂加入量为15g/L时，得到的Ni/CeO₂复合镀层的析氢反应活化能仅为20.69kJ mol-1，远低于Ni表面析氢反应的活化能；通过计算得到了Ni和不同Ni/CeO₂复合镀层表面析氢反应速率常数，并且得到了不同过电位下电极表面的吸附氢覆盖度，发现CeO₂的加入有利于还原氢原子的吸附，提高了稳态时Ni层表面的吸附氢原子的覆盖度，进一步验证了CeO₂与Ni层间的析氢协同效应。更多还原

【Abstract】 Hydrogen was mainly used as an important chemical raw material, and thehydrogen energy has received more and more attention as new green energycandidate. The method to get hydrogen by electrolysis was historic. Many studieswere focused on this electrolysis method recently, because of its clean andsustainable characteristics. Cathodic hydrogen evolution reaction （HER） materialsplayed an important role in this process. It was possible to improve the energyconversion efficiency and reduce cost by designing and preparing new cathodicHER electrodes. In this thesis, the electrochemical co-deposition method suitable toindustry application was employed; the new Ni-based CeO₂composite electrodematerials were prepared; the different sized CeO₂particles were used in theco-deposition process. The scanning electron microscopy （SEM）, X-ray diffraction（XRD）, thermo gravimetric and differential scanning calorimetry （TG-DSC） andX-rays photoelectron spectroscopy （XPS） were used to characterize the compositeelectrodes, the HER catalysis activity and corrosion resistance of the compositeelectrodes were studied by electrochemical analysis method, such as linearpolarization, Tafel curve analysis, and electrochemical impedance spectroscopy（EIS）. It was focused on the HER synergetic effects between CeO₂particles and theNi matrix.Firstly, Ni/CeO₂composite coatings were prepared by electrochemicaldeposition， using the micro-CeO₂（5-10μm） and nano-CeO₂（10-30nm） particles.The results showed the Ni/CeO₂composite coatings had a good thermal stability.The different sized co-deposited CeO₂particles can improve the hardness and thesurface roughness of the nickel coating, make the fining effect on the Nielectrocrystallization, and change the preferred orientation of the nickel coating. Themicro-CeO₂particles inhibited the nickel deposition, but the nano-CeO₂decreasedthe Ni polarization. A good HER catalysis activity can be observed on the Ni/CeO₂composite electrodes, i.e. the HER charge-transfer resistance on the Ni surfacedecreased and the HER exchange current density increased obviously with the CeO₂particles addition. When the micro-CeO₂concentration was15g/L, the HERexchange current density on the Ni/CeO₂composite was70times higher than thaton the Ni coating, meanwhile, the HER total resistance on the composite coatingwas30times lower than that on the nickel coating. And the composite electrodescan keep a good stability during the HER process. The good HER activity oncomposite coating can be attributed to the synergetic effects between CeO₂particles and the Ni matrix. The H atom reduced on the nickel surface can be adsorbed on theCeO₂particles which have empty d and f orbits. The result showed the low-contentCeO₂composite coating had a better corrosion resistance.And then, Ni-based alloy CeO₂composite coatings were prepared by alloydeposition method. HER activities on the alloy composite coatings were studied.During Ni-S/CeO₂composite coatings investigation, it was found that the additionof different sized CeO₂particles increased the sulfur content in the Ni-S alloycoatings. The HER activity on the Ni-S/CeO₂composite coatings was higher thanthat on the Ni-S alloy coating. When the micro-CeO₂concentration was10g/L, theHER exchange current density on the Ni-S/CeO₂composite was2.2times higherthan that on the Ni-S coating. It was considered the HER activity on the Ni-S/CeO₂composite coatings were affected by the sulfur content in the Ni-S alloy coating, thesynergetic effects between CeO₂particles, and the Ni-S alloy coating. DuringNi-Zn/CeO₂composite coating investigation, it was worth noting that the Ni-Znalloy was consisted by some intermetallic compound. The Ni-Zn alloy coatingshowed an instinctive high HER activity. However, the HER activity can be furtherimproved with a proper CeO₂content embedded. The addition of the CeO₂particlescan change the microstructure and element composition of the Ni-Zn alloy coating.According to the Ni-Zn anomalous co-deposition mechanism and the CeO₂influence on the intermediate in the Ni-Zn co-deposition, the alloy elementcomposition of the Ni-Zn/CeO₂composite coatings was explained. Meanwhile, thecorrosion resistance of the Ni-Zn alloy coating can be improved with a lower CeO₂particles content.At last, the parameters of HER kinetics on the Ni/CeO₂composite coatingswere calculated. The results showed different sized CeO₂particles addition canincrease the specific surface area of the Ni coatings, and decrease the HERactivation energy on the Ni surface. When the micro-CeO₂concentration was15g/L,the HER activation energy on the Ni/CeO₂composite coating surface was only20.69kJ mol-1, much lower than that on the Ni surface. The HER rate constants onthe Ni and Ni/CeO₂surface were calculated, and then the adsorbed hydrogen atomscoverage was obtained at different overpotential. It was found that the addition ofthe CeO₂particles can accelerate the adsorption of the reduced hydrogen atoms,increase the value of adsorbed hydrogen atoms coverage as the hydrogen evolutionwas stable. It further confirmed the synergetic effects between CeO₂particles andthe Ni matrix.更多还原