直接液体燃料电池催化剂设计与催化过程研究
文献类型：学位论文
| 作者 | 姚世魁 |
| 学位类别 | 博士 |
| 答辩日期 | 2015-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 中国科学院长春应用化学研究所 |
| 导师 | 邢巍 |
| 关键词 | 直接液体燃料电池 电催化 Pd/C 催化剂 Pt/C |
| 中文摘要 | 直接液体燃料电池是通过电化学反应将燃料中的化学能直接转化为电能的发电装置，其能量转换效率高，发电过程环境友好。成本和性能仍然是制约直接液体燃料电池大规模商业化的两个突出问题，而阳极催化剂的活性及稳定性对此起着至关重要的作用。本论文将针对直接液体燃料电池阳极催化剂的电催化过程，关注催化过程中对催化性能起关键作用的组分与结构，探究催化剂的组成结构与性能的关系，采用不同制备方法调控催化剂结构，实现高性能催化剂的理性设计，主要研究内容如下： 1. 胶体沉淀法用于直接甲醇燃料电池Pt纳米催化剂的可控制备 通过胶体沉淀法制备了均匀地分散在碳载体上具有窄粒度分布的Pt纳米颗粒。Pt纳米粒子的大小与粒径分散度可以简单地通过调整 (NH4)2WO4的浓度来控制。当采用0.5 mmolL-1(NH4)2WO4作为保护剂时制备出最小尺寸为3 nm 的Pt纳米粒子。电化学测试结果表明采用胶体沉淀法所制备的Pt / C催化剂具有优良的催化活性和稳定性。其中，0.5 mmol.L-1 (NH4)2WO4条件下制得的Pt/C催化剂在循环伏安测试中的峰电流和和计时电流测试3600 s时的活性分别达到商业Pt/C的1.24和1.78倍。 2. 化学吸附的CO作为原位还原剂制备用于甲酸电氧化的亚单层Pd @Pt/C核壳催化剂 催化反应通常在催化剂的表面进行，为了提高贵金属的利用率，双金属材料的理想结构是所有用于催化的贵金属原子分散在催化剂的表面。我们提出以Pt基底上单层化学吸附的CO作为还原剂原位还原制备亚单层Pd的方法。实验结果表明采用吸附态的CO作为原位还原剂可以用于在Pt基底上制备载量由化学计量学精确控制的高分散的Pd亚单层。原位还原所制备的Pd@Pt/C催化剂同时实现了Pd的利用率和Pt催化HCOOH氧化直接途径选择性的提高。该原位还原方法简单易行，有望广泛用于制备高金属利用率的核壳结构催化剂。 3. 基于PdO的甲酸电氧化催化剂现场制备 催化剂制备和使用中不可避免存在奥斯瓦尔德熟化过程，造成催化剂团聚和性能下降。我们提出在催化现场制备催化剂能最大限度减小制备过程的奥斯瓦尔德现象，从而得到高性能催化剂。根据以上思路，我们由PdO/C现场制备了用于甲酸电氧化的Pd/C催化剂。现场制备的催化剂在透射电子显微镜表征中表现出了更小的粒径和更均匀的分散，表明奥斯瓦尔德熟化过程得到了有效抑制。该催化剂同样表现出了更高的电化学比表面积、质量比活性和电池性能，有望在直接甲酸燃料电池中得到应用。 4. TiO2对直接甲酸燃料电池Pd/C催化剂的促进作用研究 我们采用不同方法将TiO2引入甲酸Pd/C催化剂，TiO2的加入能够明显减小Pd纳米颗粒粒径提高其分散性。同时XPS表征表明TiO2与Pd之间存在强烈的相互作用。以上特性使TiO2的Pd/C催化剂对甲酸电氧化表现出更高的活性、稳定性与寿命。TiO2的加入方式对TiO2-Pd之间的作用强弱有直接影响，并同时/进一步影响催化剂的结构和性能，其中TiO2与Pd结合后负载至活性炭之上的样品表现出了最优异的性能。 5. 电化学方法考察甲酸电氧化过程的关键问题 我们采用循环伏安和多步计时电流对甲酸电氧化过程的尚存在争议的几个关键问题进行了研究：采用多步计时电流发现导致甲酸失活的毒化物种带负电；考察了PdO在催化过程中的作用，明确了二价Pd本身不能作为甲酸电氧化催化剂，提出了可能的助催化机理，并观察到过量二价Pd对Pd催化活性的抑制作用。 |
| 英文摘要 | Direct liquid fuel cells are energy generating devices can covert the chemical energy in fuel directly into electrical by electrochemical reaction with high energy efficiency and environmentally friendly power generation process. However, cost and performance is still two main issues that restricted the large-scale commercialization, while the activity and stability of anode catalysts plays a key role. The main content of this thesis is focused on the electro-catalytic process of anode catalysts, exploring the structure-activity relationship as well as understanding the effect of key composition, to achieve high-performance catalysts using different preparation methods. The main contents are as follows: 1. Controllable Synthesis of of Pt nanocatalyst by colloid-precipitation method for DMFC Highly dispersed Pt nanoparticles with narrow size distribution supported on carbon was prepared by colloidal precipitation. Both the particle size and the particle size distribution of the Pt nanoparticles can be easily controlled by adjusting the (NH4)2WO4 concentration. Pt nanoparticles with mean size of 3 nm was prepared when using 0.5 mmol L-1 (NH4)2WO4 as protective agent. The electrochemical test results showed that Pt nanoparticles obtained by colloid-precipitation method exhibited excellent catalytic activity and stability, while the Pt/C catalyst stabilize by 0.5 mmolL-1 (NH4)2WO4 showed 1.24 and 1.78 times as high as the commercial Pt/C for the peak current and stable current, respectively. 2. Pd@Pt/C fabricated using chemisorbed CO as in-situ reductant for formic acid electrooxidation To improve the utilization of the noble metal, the ideal structure is a bi-metallic materials of all atoms for the catalytic noble metal is dispersed in the catalyst surface as the catalyst reaction is usually carried out on the surface of catalysts. We proposed that sub-monolayer Pd on Pt substrate can be prepared using chemisorbed CO as in-situ reductant. Experimental results showed that highly dispersed Pd activity sites on Pt with loading precisely controlled by the amount of adsorbed CO in the in-situ reduction. Pd@Pt/C catalyst prepared by in situ reduction showed both enhanced Pd utilization and improved selectivity of direct way on Pd for HCOOH electrooxidation. The in-situ reduction method synthetic method can be expected for preparation of the core-shell-like bimetallic structure with ultra high novel metal utilization for catalysis. 3. Pd/C nanoparticles by in-situ synthesis for formic acid electrooxidation and study on the role of Pd valence for formic acid electrooxidation. Oswald ripening process is inevitable in both the preparation and catalytic process, resulting agglomeration and performance degradation. We proposed that Oswald ripening can be minimized by preparing catalysts in-situ. Based on the above ideas, we in-situ prepared Pd/C catalyst from PdO/C for formic acid oxidation. TEM test showed a smaller particle size and more uniform dispersion for the in-situ prepared catalyst, indicating that Ostwald ripening process had been effectively suppressed. The catalyst also showed a higher electrochemical surface area, specific activity and fuel cell performance, is expected to be used in the direct formic acid fuel cell. 4. Promotion effect of TiO2 on Pd/C for direct formic acid fuel cell We introduced TiO2 to Pd/C catalyst using different methods. TEM results showed that the addition of TiO2 can significantly enhance the Pd dispersion and reduce the particle size. XPS results showed that there is a strong interaction between TiO2 and Pd. Pd / C catalyst with TiO2 for formic acid electro-oxidation exhibited higher activity, stability and durability for formic acid electrooxidation. More importantly, the prepare method directly influence the intensity of effect between TiO2 and Pd is, and/or further affect the structure and properties of the catalyst. The catalyst that combined TiO2 and Pd before loading to activated carbon |
| 语种 | 中文 |
| 公开日期 | 2016-05-03 |
| 源URL | [http://ir.ciac.jl.cn/handle/322003/64470]  |
| 专题 | 长春应用化学研究所_长春应用化学研究所知识产出_学位论文 |
| 推荐引用方式 GB/T 7714 | 姚世魁. 直接液体燃料电池催化剂设计与催化过程研究[D]. 中国科学院长春应用化学研究所. 中国科学院研究生院. 2015. |
入库方式： OAI收割
来源：长春应用化学研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。