微觀磁場促進燃料電池內(nèi)氧傳遞和還原反應速度研究
發(fā)布時間：2018-09-08 20:39
【摘要】：低成本與長壽命兼顧問題,是制約燃料電池商業(yè)化的瓶頸問題,改進目前使用的Pt/C催化劑是降低成本與提高壽命的關(guān)鍵,利用氧氣具有順磁性、氮氣逆磁性的特點,將鐵磁性的磁粉與Pt/C催化劑共同負載于燃料電池的陰極,利用磁場促進氧的傳遞,這是提高燃料電池催化反應區(qū)氧濃度、降低燃料電池陰極活化極化和濃差極化的一種有效方法。 利用電化學三電極體系、旋轉(zhuǎn)圓盤玻碳電極、鋅空電池(ZAFC)和質(zhì)子交換膜燃料電池(PEMFC),在電磁場和磁粉的微磁場環(huán)境下,研究了磁對氧傳質(zhì)的作用效果；并分別采用球磨法-原位聚合、溶膠凝膠-原位聚合、高溫焙燒法制備了Nd2Fe,4B/PANI、 Fe3O4/PANI、Nd2Fe14B/C磁性材料,對以上材料和市售的50%Pt-5%Co/C催化劑在電化學體系中對氧的傳質(zhì)作用進行了研究。研究結(jié)果表明： (1)磁場強度與氧傳質(zhì)擴散系數(shù)、電荷傳遞系數(shù)和氧電化學還原反應電流的變化具有正相關(guān)性,磁場強度增大,氧傳質(zhì)擴散系數(shù)和電荷傳遞系數(shù)提高,并且雙電層電容增大、傳荷電阻下降、氧電化學還原反應電流提高； (2)在微磁場中,分子擴散、湍流削弱、抵消微磁場對氧分子的磁性吸引力,導致氧傳質(zhì)擴散系數(shù)和電荷傳遞系數(shù)降低,氧電化學還原速度下降； (3)微磁場垂直工作電極表面時,有利于順磁性氧分子在Pt/C催化劑表面的有序傳質(zhì)和反磁性H2O分子在電極表面的移除； (4)本文所制備的三種磁粉相比較,磁性能Nd2Fe14B/C≈Nd2Fe4B/PANI Fe3O4/PANI,材料均表現(xiàn)為鐵磁性； (5)增加磁粉負載量,磁性顆粒所提供的磁場源增多,磁性ZAFC或PEMFC的放電性能持續(xù)增大,且均高于非磁性ZAFC或PEMFC;在磁粉負載量高于臨界值,繼續(xù)增加磁粉負載量,磁性顆粒對氧傳遞通道的阻滯和磁性顆粒之間的磁相互作用增強會導致磁性燃料電池的放電性能下降； (6) Nd2Fe14B/C陰極負載密度0.40mg cm-2,放電電壓0.20V,磁性PEMFC的放電電流較非磁性PEMFC提高39.87%。 (7)施加外磁場,Pt-Co/C催化劑在電極載體表面取向并固定,不同磁性顆粒的易磁化軸取向一致,這種取向負載的Pt-Co/C催化劑有可能使Pt的氧還原催化優(yōu)勢晶面更多的暴露,提高了催化劑的氧還原催化活性。
[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，
本文編號：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，
本文編號：2231636
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