亚氧化钛负载Pt、Pd和Pt-Tb催化剂对甲酸电氧化的催化性能研究
发布时间：2018-07-22 13:00
【摘要】：铂、钯及其合金催化剂在甲酸燃料电池中应用广泛,但作为传统载体的碳材料存在易腐蚀、易氧化等缺点,这在很大程度上限制了甲酸燃料电池的工作效率和性能。近年来,非碳载体材料逐渐受到人们广泛的关注。钛黑作为一种新颖的非碳载体材料,因其高的电导率和在酸性以及碱性环境中较好的抗腐蚀性、抗氧化性和稳定性,而有望成为甲酸燃料电池催化剂的候选载体。本论文以钛黑为载体分别制备了负载Pt、Pd以及Pt-Tb双金属催化剂,并研究了它们在甲酸电氧化过程中的催化性能。为关联催化剂结构与性能,采用X射线衍射(XRD)、透射电镜(TEM)、X射线光电子能谱(XPS)等测试手段对催化剂的组成、结构、形貌、晶粒大小及分布等物理化学性质进行表征;并运用循环伏安法(CV)、计时电流法(CA)、线性扫描法(LSV)以及CO溶出伏安法(CO stripping)等电化学方法研究了催化剂对甲酸的电化学性能。论文主要分为3个部分:第一部分:以钛黑、炭黑及TiO2为载体采用硼氢化钠还原法分别制备了Pt/Ti4O7、Pt/C和Pt/TiO2催化剂。接触角测试结果显示,Ti4O7的疏水性是导致Pt纳米粒子在Ti4O7载体上分散性不好,进而造成粒子团聚的一个重要原因。然而,以上3个催化剂对甲酸氧化的电化学测试结果表明,与Pt/C和Pt/TiO2催化剂相比,Pt/Ti4O7催化剂具有更高的催化活性和稳定性。除了由于Ti4O7自身的高电导率之外,Ti4O7载体具有“金属化”效应是另一个重要的原因。第二部分:采用硼氢化钠还原法制备了Pd/Ti4O7和Pd/C催化剂。TEM表征结果发现,Pd金属纳米粒子均匀的分散在各载体上。电化学测试结果显示,催化剂Pd/Ti4O7具有较高的电催化活性。用PDDA功能化载体钛黑之后,采用硼氢化钠还原法制备的Pd/PDDA-Ti4O7催化剂的电催化性能比Pd/Ti4O7催化剂的更高。XPS结果证实,PDDA的作用是通过增加Ti4O7载体的“金属化”效应,使得催化剂中金属态Pd的含量增加,从而显著改善了催化剂的活性。第三部分:以钛黑为载体采用硼氢化钠还原法合成了不同比例的Pt-Tb双金属催化剂。TEM结果显示,Pt-Tb纳米粒子在钛黑载体上的分散性好,且较均匀。电化学测试结果表明,20%Pt-2.5%Tb/Ti4O7催化剂对甲酸电氧化的催化活性较高,且其对移除CO中毒中间体的性能也较好。进一步研究表明,Tb的作用是能在更负的电位条件下促进II CO中毒中间体发生氧化反应,从而解除了贵金属Pt被占据的活性位点,缓解了催化剂中毒的现象,即可以解释为双功能机理。
[Abstract]:Platinum, palladium and its alloy catalysts are widely used in formic acid fuel cells, but the carbon materials used as traditional carriers are easy to corrode and oxidize, which limits the efficiency and performance of formic acid fuel cells to a great extent. In recent years, non-carbon carrier materials have been paid more and more attention. As a novel non-carbon carrier material, titanium black is expected to be a candidate carrier for formic acid fuel cell catalysts due to its high conductivity and good corrosion resistance, oxidation resistance and stability in acidic and alkaline environments. In this paper, supported PtPd and Pt-Tb bimetallic catalysts were prepared with titanium black as the carrier, and their catalytic properties in the process of formic acid electrooxidation were studied. The composition, structure, morphology, grain size and distribution of the catalyst were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The electrochemical properties of the catalyst for formic acid were studied by cyclic voltammetry (CV), chronoamperometry (CA), linear scanning voltammetry (LSV) and CO stripping. The thesis is mainly divided into three parts: in the first part, the Pt / Ti _ 4O _ 7N _ t / C and Pt / TIO _ 2 catalysts were prepared by sodium borohydride reduction method with titanium black, carbon black and TIO _ 2 as the support. The contact angle test results show that the hydrophobicity of Ti _ 4O _ 7 is one of the important reasons leading to the poor dispersion of Pt nanoparticles on Ti _ 4O _ 7 support and thus to the agglomeration of the particles. However, the electrochemical measurements of the oxidation of formic acid over the above three catalysts showed that the catalytic activity and stability of PtTi4O7 catalysts were higher than those of Pt / C and PT / TIO _ 2 catalysts. Besides the high conductivity of Ti _ 4O _ 7, the metallization of Ti _ 4O _ 7 carrier is another important reason. Part two: PD / Ti _ 4O _ 7 and PD / Ti _ 4O _ 7 and PD / C catalyst 路TEM were prepared by sodium borohydride reduction method. Electrochemical measurements showed that PD / Ti _ 4O _ 7 catalyst had high electrocatalytic activity. After using PDDA functionalized carrier titanium black, PD / PDDA-Ti _ 4O _ 7 catalyst prepared by sodium borohydride reduction method has higher electrocatalytic performance than PD / Ti _ 4O _ 7 catalyst. XPS results show that the effect of PDDA is by increasing the "metallization" effect of Ti _ 4O _ 7 support. The content of PD in the catalyst was increased, and the activity of the catalyst was improved significantly. The third part: Pt-Tb bimetallic catalyst with different proportion was synthesized by sodium borohydride reduction method with titanium black as the carrier. The results of TEM showed that the dispersion of Pt-Tb nanoparticles on titanium black was good and uniform. The electrochemical test results show that the catalytic activity of Tb- / Ti _ 4O _ 7 catalyst is higher for formic acid electrooxidation, and the catalytic activity for removing CO poisoning intermediates is better than that of Tb- / Ti _ 4O _ 7 catalyst. Further studies show that Tb can promote the oxidation reaction of II CO poisoning intermediates under more negative potential, thus removing the active sites occupied by noble metals Pt, and alleviating the phenomenon of catalyst poisoning. It can be explained as the mechanism of double function.
【学位授予单位】：河南师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;TM911.4
本文编号：2137544
[Abstract]:Platinum, palladium and its alloy catalysts are widely used in formic acid fuel cells, but the carbon materials used as traditional carriers are easy to corrode and oxidize, which limits the efficiency and performance of formic acid fuel cells to a great extent. In recent years, non-carbon carrier materials have been paid more and more attention. As a novel non-carbon carrier material, titanium black is expected to be a candidate carrier for formic acid fuel cell catalysts due to its high conductivity and good corrosion resistance, oxidation resistance and stability in acidic and alkaline environments. In this paper, supported PtPd and Pt-Tb bimetallic catalysts were prepared with titanium black as the carrier, and their catalytic properties in the process of formic acid electrooxidation were studied. The composition, structure, morphology, grain size and distribution of the catalyst were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The electrochemical properties of the catalyst for formic acid were studied by cyclic voltammetry (CV), chronoamperometry (CA), linear scanning voltammetry (LSV) and CO stripping. The thesis is mainly divided into three parts: in the first part, the Pt / Ti _ 4O _ 7N _ t / C and Pt / TIO _ 2 catalysts were prepared by sodium borohydride reduction method with titanium black, carbon black and TIO _ 2 as the support. The contact angle test results show that the hydrophobicity of Ti _ 4O _ 7 is one of the important reasons leading to the poor dispersion of Pt nanoparticles on Ti _ 4O _ 7 support and thus to the agglomeration of the particles. However, the electrochemical measurements of the oxidation of formic acid over the above three catalysts showed that the catalytic activity and stability of PtTi4O7 catalysts were higher than those of Pt / C and PT / TIO _ 2 catalysts. Besides the high conductivity of Ti _ 4O _ 7, the metallization of Ti _ 4O _ 7 carrier is another important reason. Part two: PD / Ti _ 4O _ 7 and PD / Ti _ 4O _ 7 and PD / C catalyst 路TEM were prepared by sodium borohydride reduction method. Electrochemical measurements showed that PD / Ti _ 4O _ 7 catalyst had high electrocatalytic activity. After using PDDA functionalized carrier titanium black, PD / PDDA-Ti _ 4O _ 7 catalyst prepared by sodium borohydride reduction method has higher electrocatalytic performance than PD / Ti _ 4O _ 7 catalyst. XPS results show that the effect of PDDA is by increasing the "metallization" effect of Ti _ 4O _ 7 support. The content of PD in the catalyst was increased, and the activity of the catalyst was improved significantly. The third part: Pt-Tb bimetallic catalyst with different proportion was synthesized by sodium borohydride reduction method with titanium black as the carrier. The results of TEM showed that the dispersion of Pt-Tb nanoparticles on titanium black was good and uniform. The electrochemical test results show that the catalytic activity of Tb- / Ti _ 4O _ 7 catalyst is higher for formic acid electrooxidation, and the catalytic activity for removing CO poisoning intermediates is better than that of Tb- / Ti _ 4O _ 7 catalyst. Further studies show that Tb can promote the oxidation reaction of II CO poisoning intermediates under more negative potential, thus removing the active sites occupied by noble metals Pt, and alleviating the phenomenon of catalyst poisoning. It can be explained as the mechanism of double function.
【学位授予单位】：河南师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;TM911.4
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