Experimental Study on the Electrochemical Performance of PEMFC under Different Assembly Forces

Proton exchange membrane fuel cell(PEMFC)is of paramount significance to the development of clean energy.The components of PEMFC are assembled using many pairs of nuts and bolts.The assembly champing bolt torque is critical to the electrochemical performance and mechanical stability of PEMFC.In this paper,a PEMFC with the threechannel serpentine flow field was used and studied.The different assembly clamping bolt torques were applied to the PEMFC in three uniform assembly bolt torque and six non-uniform assembly bolt torque conditions,respectively.And then,the electrochemical performance experiments were performed to study the effect of the assembly bolt torque on the electrochemical performance.The test results show that the assembly bolt torque significantly affected the electrochemical performance of the PEMFC.In uniform assembly bolt torque conditions,the maximal power density increased initially as the assembly bolt torque increased,and then decreased on further increasing the assembly torque.It existed the optimum assembly torque which was found to be 3.0 N·m in this work.In non-uniform assembly clamping bolt torque conditions,the optimum electrochemical performance appeared in the condition where the assembly torque of each bolt was closer to be 3.0 N·m.This could be due to the change of the contact resistance between the gas diffusion layer and bipolar plate and mass transport resistance for the hydrogen and oxygen towards the catalyst layers.This work could optimize the assembly force conditions and provide useful information for the practical PEMFC stack assembly.

填充纳米氧化铝对氢化丁腈橡胶摩擦磨损行为的影响

以采油单螺杆泵定子常用材料氢化丁腈橡胶(HNBR)为研究对象,改性纳米氧化铝(Al2O3)为填充剂,实验研究了填充不同粒径氧化铝对橡胶材料的交联密度、耐原油溶胀性能和摩擦磨损性能的影响,并分析了Al2O3对HNBR材料的补强机理。结果表明,填充纳米氧化铝的HNBR材料的交联密度、耐原油溶胀性能均有所提高,且交联密度和耐原油溶胀性能随Al2O3粒径的减小而提高;摩擦磨损试验结果表明,填充纳米氧化铝后,HNBR材料的摩擦系数和体积磨损率降低,且摩擦系数和体积磨损率随着填充Al2O3粒径的减小而减小,即填充10 nm Al2O3的HNBR材料耐磨性较好。纳米氧化铝补强HNBR机理是填充Al2O3后形成了以Al2O3为交联点的交联网络以及Al2O3表面的不饱和基团自聚后形成的大分子链与HNBR分子链互穿缠绕形成类似互穿聚合物的网络结构。

镁离子对质子交换膜性能的影响

以质子交换膜(PEM)为研究对象,研究Mg^2+对PEM性能的影响。将PEM浸泡在3种不同浓度(100 mg/L,300 mg/L和500 mg/L)的MgSO4溶液中,测定污染前后PEM的离子交换容量(IEC)、结晶情况和热稳定性的变化,并利用衰减全反射傅里叶变换红外光谱和扫描电子显微镜研究了Mg^2+不同污染浓度和污染时间对PEM性能影响的机理。实验结果表明,随着Mg^2+浓度的增加,PEM的H+交换能力、结晶情况和热稳定性均变差,且PEM的化学损伤程度增加。尤其是经500 mg/L的Mg^2+溶液污染20 h后,PEM的IEC降低了59.7%,且其热降解速率增加了47.4%。Mg^2+对PEM性能影响可能的机理是,Mg^2+攻击PEM中的磺酸基团(-SO3H),与-SO3H上的H+进行交换反应生成了新的物质,同时损伤膜中的聚四氟乙烯(PTFE)骨架,使膜性能衰减。