微观磁场促进燃料电池内氧传递和还原反应速度研究
发布时间：2018-09-08 20:39
【摘要】：低成本与长寿命兼顾问题,是制约燃料电池商业化的瓶颈问题,改进目前使用的Pt/C催化剂是降低成本与提高寿命的关键,利用氧气具有顺磁性、氮气逆磁性的特点,将铁磁性的磁粉与Pt/C催化剂共同负载于燃料电池的阴极,利用磁场促进氧的传递,这是提高燃料电池催化反应区氧浓度、降低燃料电池阴极活化极化和浓差极化的一种有效方法。 利用电化学三电极体系、旋转圆盘玻碳电极、锌空电池(ZAFC)和质子交换膜燃料电池(PEMFC),在电磁场和磁粉的微磁场环境下,研究了磁对氧传质的作用效果；并分别采用球磨法-原位聚合、溶胶凝胶-原位聚合、高温焙烧法制备了Nd2Fe,4B/PANI、 Fe3O4/PANI、Nd2Fe14B/C磁性材料,对以上材料和市售的50%Pt-5%Co/C催化剂在电化学体系中对氧的传质作用进行了研究。研究结果表明： (1)磁场强度与氧传质扩散系数、电荷传递系数和氧电化学还原反应电流的变化具有正相关性,磁场强度增大,氧传质扩散系数和电荷传递系数提高,并且双电层电容增大、传荷电阻下降、氧电化学还原反应电流提高； (2)在微磁场中,分子扩散、湍流削弱、抵消微磁场对氧分子的磁性吸引力,导致氧传质扩散系数和电荷传递系数降低,氧电化学还原速度下降； (3)微磁场垂直工作电极表面时,有利于顺磁性氧分子在Pt/C催化剂表面的有序传质和反磁性H2O分子在电极表面的移除； (4)本文所制备的三种磁粉相比较,磁性能Nd2Fe14B/C≈Nd2Fe4B/PANI Fe3O4/PANI,材料均表现为铁磁性； (5)增加磁粉负载量,磁性颗粒所提供的磁场源增多,磁性ZAFC或PEMFC的放电性能持续增大,且均高于非磁性ZAFC或PEMFC;在磁粉负载量高于临界值,继续增加磁粉负载量,磁性颗粒对氧传递通道的阻滞和磁性颗粒之间的磁相互作用增强会导致磁性燃料电池的放电性能下降； (6) Nd2Fe14B/C阴极负载密度0.40mg cm-2,放电电压0.20V,磁性PEMFC的放电电流较非磁性PEMFC提高39.87%。 (7)施加外磁场,Pt-Co/C催化剂在电极载体表面取向并固定,不同磁性颗粒的易磁化轴取向一致,这种取向负载的Pt-Co/C催化剂有可能使Pt的氧还原催化优势晶面更多的暴露,提高了催化剂的氧还原催化活性。
[Abstract]:Low cost and long life are the bottleneck problems that restrict the commercialization of fuel cell. Improving the Pt/C catalyst used at present is the key to reduce the cost and increase the life. The utilization of oxygen has the characteristics of paramagnetism and nitrogen demagnetization. The ferromagnetic magnetic powder and the Pt/C catalyst are co-loaded on the cathode of the fuel cell, and the oxygen transfer is promoted by the magnetic field, which increases the oxygen concentration in the catalytic reaction zone of the fuel cell. An effective method to reduce cathode activation polarization and concentration polarization of fuel cell. The effect of magnetic field on oxygen mass transfer was studied by using electrochemical three-electrode system rotating disk glassy carbon electrode zinc empty cell (ZAFC) and proton exchange membrane fuel cell (PEMFC),) in the environment of electromagnetic field and magnetic powder micromagnetic field. Nd2Fe,4B/PANI, Fe3O4/PANI,Nd2Fe14B/C magnetic materials were prepared by ball milling in situ polymerization, sol gel in situ polymerization and calcination at high temperature. The mass transfer of oxygen from the above materials and commercial 50%Pt-5%Co/C catalysts in electrochemical system was studied. The results show that: (1) there is a positive correlation between magnetic field intensity and oxygen mass transfer coefficient, charge transfer coefficient and oxygen electrochemical reduction current. The magnetic field intensity increases, and oxygen mass transfer diffusion coefficient and charge transfer coefficient increase. With the increase of the double layer capacitance, the charge transfer resistance decreases and the oxygen electrochemical reduction current increases. (2) in the micromagnetic field, the molecular diffusion and turbulence weaken, which counteracts the magnetic attraction of the micromagnetic field to the oxygen molecule. The oxygen mass transfer diffusion coefficient and charge transfer coefficient decrease, and the oxygen electrochemical reduction rate decreases. (3) when the micromagnetic field is perpendicular to the surface of the working electrode, It is advantageous to the ordered mass transfer of paramagnetic oxygen molecules on the surface of Pt/C catalyst and the removal of diamagnetic H2O molecules on the electrode surface. (4) compared with the three magnetic powders prepared in this paper, the magnetic properties of Nd2Fe14B/C 鈮，
本文编号：2231636
[Abstract]:Low cost and long life are the bottleneck problems that restrict the commercialization of fuel cell. Improving the Pt/C catalyst used at present is the key to reduce the cost and increase the life. The utilization of oxygen has the characteristics of paramagnetism and nitrogen demagnetization. The ferromagnetic magnetic powder and the Pt/C catalyst are co-loaded on the cathode of the fuel cell, and the oxygen transfer is promoted by the magnetic field, which increases the oxygen concentration in the catalytic reaction zone of the fuel cell. An effective method to reduce cathode activation polarization and concentration polarization of fuel cell. The effect of magnetic field on oxygen mass transfer was studied by using electrochemical three-electrode system rotating disk glassy carbon electrode zinc empty cell (ZAFC) and proton exchange membrane fuel cell (PEMFC),) in the environment of electromagnetic field and magnetic powder micromagnetic field. Nd2Fe,4B/PANI, Fe3O4/PANI,Nd2Fe14B/C magnetic materials were prepared by ball milling in situ polymerization, sol gel in situ polymerization and calcination at high temperature. The mass transfer of oxygen from the above materials and commercial 50%Pt-5%Co/C catalysts in electrochemical system was studied. The results show that: (1) there is a positive correlation between magnetic field intensity and oxygen mass transfer coefficient, charge transfer coefficient and oxygen electrochemical reduction current. The magnetic field intensity increases, and oxygen mass transfer diffusion coefficient and charge transfer coefficient increase. With the increase of the double layer capacitance, the charge transfer resistance decreases and the oxygen electrochemical reduction current increases. (2) in the micromagnetic field, the molecular diffusion and turbulence weaken, which counteracts the magnetic attraction of the micromagnetic field to the oxygen molecule. The oxygen mass transfer diffusion coefficient and charge transfer coefficient decrease, and the oxygen electrochemical reduction rate decreases. (3) when the micromagnetic field is perpendicular to the surface of the working electrode, It is advantageous to the ordered mass transfer of paramagnetic oxygen molecules on the surface of Pt/C catalyst and the removal of diamagnetic H2O molecules on the electrode surface. (4) compared with the three magnetic powders prepared in this paper, the magnetic properties of Nd2Fe14B/C 鈮，
本文编号：2231636
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