碳化钼基质子交换膜燃料电池氢氧化阳极催化剂的研究

RESEARCH ON MOLYBDENUM CARBIDE-BASED HYDROGEN OXIDATION CATALYSTS OF PROTON EXCHANGE MEMBRANE FUEL CELL

邓成龙

11749102

硕士

材料学

李辉

2019-05-31

2019-07-10

哈尔滨工业大学

深圳

质子交换膜燃料电池（PEMFCs）具有零排放、能量转换效率高的优点，是化石燃料和传统电池强有力的替代品。然而，事实上PEMFCs仍然无法扩大规模实现产业化，高成本是PEMFCs发展的最大阻碍。随着阴极催化剂研究取得巨大进展，阳极催化剂研究停滞不前，阳极催化剂所占成本比例逐渐升高，阳极催化剂的高成本将成为燃料电池发展的主要阻碍。因此，亟需开发制备工艺简单、成本低廉、催化活性和稳定性高的阳极催化剂，以满足PEMFCs的大规模商用要求。碳化钼具有Pt类似的催化特性，与少量Pt复合成Pt-Mo2C复合催化剂时，不仅能大大降低Pt的使用量，还能保持高的催化活性和稳定性。本论文介绍了燃料电池阳极催化剂的研究现状及进展，主要研究了能够大幅降低Pt使用量的同时，保持高的催化活性和稳定性的碳化钼基PEMFCs氢氧化阳极催化剂的稳定可行的合成方法，并且分别探究了不同碳化钼基阳极催化剂氢氧化活性和稳定性提高的原因及机理。此外，还为高性能超低铂载量阳极催化剂的精确设计与合成提供了一种全新的思路。首先，探索了不同的氮掺杂Mo2C/C（Mo2C/NC）合成方法，确定了简便可行的合成路径，实现了BP2000碳黑载体的氮掺杂，得到了β-Mo2C的稳定纯相，合成了Mo2C/NC和4%Pt-氮掺杂Mo2C/C（Pt-Mo2C/NC）氢氧化阳极催化剂，并分别研究了其氢氧化反应催化活性和稳定性。4%Pt-Mo2C/NC阳极催化剂的Pt质量分数为3.42%，大幅降低Pt负载量的同时，得到了与商业化JM 20% Pt/C催化剂相近的氢氧化催化活性，1000圈CV扫描以后，LSV曲线的电流密度衰减较小，表现出良好的催化稳定性和耐久性，同时，其50cm2 MEA组装的单电池开路电压为0.956V，阳极Pt载量为0.012mg/cm2，最大功率密度为700mW/cm2。其次，探索了不同的氮掺杂Mo2C/CNT（Mo2C/CNT）合成方法，确定了简便可行的合成路径，实现了碳纳米管载体的氮掺杂，得到了β-Mo2C的稳定纯相，合成了Mo2C/CNT和4%Pt-氮掺杂Mo2C/CNT（Pt-Mo2C/NCNT）氢氧化阳极催化剂，并分别研究了其氢氧化反应催化活性和稳定性。4%Pt-Mo2C/NCNT阳极催化剂的Pt质量分数为3.26%，大幅降低Pt负载量的同时，得到了与商业化JM 20% Pt/C催化剂相近的氢氧化催化活性，1000圈CV扫描以后，LSV曲线的电流密度衰减极小，表现出十分优异的催化稳定性和耐久性，同时，其50cm2 MEA组装的单电池开路电压为0.956V，阳极Pt载量为0.012mg/cm2，最大功率密度为792mW/cm2。最后，经过催化剂形貌和结构的精确设计，通过简单的搅拌、程序升温还原法首次合成了氮掺杂HCS@Mo2C（NHCS@Mo2C）和氮掺杂HCS@Mo2C-4%Pt（NHCS@Mo2C-4%Pt）核壳结构氢氧化阳极催化剂，并分别研究了其氢氧化反应催化活性和稳定性。原位氮掺杂的空心碳球（NHCS）分布均匀、无团聚，粒径在200nm左右；粒径2-5nm左右的Mo2C、Pt颗粒均匀负载在空心碳球上。NHCS@Mo2C-4%Pt核壳结构氢氧化阳极催化剂的比表面积>450m2/g，Pt质量分数为3.80%，大幅降低Pt负载量的同时，展现出比商业化JM 20% Pt/C催化剂更好的氢氧化催化活性，1000圈CV扫描以后，LSV曲线的电流密度衰减极小，表现出十分优异的催化稳定性和耐久性，同时，其50cm2 MEA组装的单电池开路电压为0.955V，阳极Pt载量为0.012mg/cm2（DOE阳极Pt载量的1/4），最大功率密度为877mW/cm2，其性能可以媲美DOE报道的高Pt载量阳极催化剂MEA性能。

With the merits of zero emission and high efficiency, Proton exchange membrane fuel cells (PEMFCs) are considered to be a promising alternative to fossil fuels and conventional batteries. PEMFCs have already been commercialized and used in many fields. However, with the biggest obstacle of high cost, PEMFCs still cannot be extensive used. Nowadays, PEMFCs cathode catalysts have been reported in a large number of studies, with the accomplishment of reduced Pt loading. Unfortunately, the study on anode catalysts has been shelved for many years, which also affect the total Pt loading in fuel cells especially when the Pt loading on cathode has been reduced to a reasonable level. Therefore, there is an urgent demand on developing anode catalysts with simplified preparation processes, low cost, high catalytic activity and high stability to meet the market requirements. Mo2C has Pt-like HOR catalytic properties. When combined with a low Pt loading to form a Pt-Mo2C composite catalyst, it can not only greatly reduce the amount of Pt used, but also maintain high catalytic activity and stability. This thesis introduces the research status and progress of fuel cell anode catalysts. In our work, the stable and feasible synthesis methods of molybdenum carbide-based hydrogen oxidation catalysts of PEMFCs have been established which can greatly reduce the amount of Pt loading, and the reasons and mechanisms of catalytic activity and stability improvement of molybdenum carbide-based anode catalysts also have been explored respectively. Moreover, it provides a new way on the precise design and synthesis of ultra-low platinum loading anode catalysts.Firstly, different synthesis methods of Mo2C/NC have been explored, the nitrogen doping of BP2000 carbon black support was realized, Mo2C/NC and 4%Pt-Mo2C/NC anode catalysts have been synthesized by the suitable synthesis route. Their catalytic activities and stabilities for hydrogen oxidation reaction have been studied. The Pt mass fraction of 4%Pt-Mo2C/NC anode catalyst was 3.42%, which greatly reduced the loading of Pt, and obtained similar catalytic activity of hydrogen oxidation to that of commercial JM 20% Pt/C catalyst. After 1000 cycles of CV scanning, the current density of the LSV curve decays slightly, showing good catalytic stability and durability. At the same time, the open circuit voltage of 50cm2 MEA assembled single cell is 0.956V, its Pt loading of anode is 0.012mg/cm2, and its maximum power density is 700mW/cm2. Secondly, different synthesis methods of Mo2C/NCNT have been explored, the nitrogen doping of carbon nanotube support was realized, Mo2C/NCNT and 4%Pt-Mo2C/NCNT anode catalysts have been synthesized by the suitable synthesis route. Their catalytic activities and stabilities for hydrogen oxidation reaction have been studied. The Pt mass fraction of 4%Pt-Mo2C/NC anode catalyst was 3.26%, which greatly reduced the loading of Pt, and obtained similar catalytic activity of hydrogen oxidation to that of commercial JM 20% Pt/C catalyst. After 1000 cycles of CV scanning, the current density of the LSV curve decays negligibly, showing excellent catalytic stability and durability. At the same time, the open circuit voltage of 50cm2 MEA assembled single cell is 0.956V, its Pt loading of anode is 0.012mg/cm2, and its maximum power density is 792mW/cm2.Finally, through the precise design of the catalyst morphology and structure, nitrogen-doped HCS@Mo2C and nitrogen-doped HCS@Mo2C-4%Pt core-shell hydrogen oxidation anode catalysts have been synthesized for the first time by simple stirring and temperature programmed reduction. The catalytic activities and stabilities of NHCS@Mo2C and NHCS@Mo2C-4%Pt have been studied separately. The in-situ nitrogen-doped hollow carbon spheres are evenly distributed and without agglomeration, the particle size is about 200 nm. Mo2C and Pt particles with a particle size ~2-5 nm covered on hollow carbon spheres uniformly. The specific surface area of the NHCS@Mo2C-4%Pt core-shell anode catalyst is >450 m2/g, its Pt mass fraction is 3.80%, which greatly reduced the loading of Pt, and obtained better catalytic activity of hydrogen oxidation than that of commercial JM 20% Pt/C catalyst. After 1000 cycles of CV scanning, the current density of the LSV curve decays negligibly, showing excellent catalytic stability and durability. At the same time, the open circuit voltage of 50cm2 MEA assembled single cell is 0.955V, its Pt loading of anode is 0.012mg/cm2 (1/4 of DOE anode Pt loading), and its maximum power density is 877mW/cm2. Its MEA performance is comparable to that of high Pt loading anode catalyst reported by DOE.

质子交换膜燃料电池 氢氧化阳极催化剂 碳化钼 超低铂 氮掺杂 催化剂设计

PEMFCs Anode catalysts Molybdenum carbide Ultra-low platinum Nitrogen-doped Catalyst design

中文

联合培养

南方科技大学

邓成龙. 碳化钼基质子交换膜燃料电池氢氧化阳极催化剂的研究[D]. 深圳. 哈尔滨工业大学,2019.