操作条件对DMFC阴极电化学阻抗谱参数的影响

通过降低阴极催化剂载量强化了阴极氧还原反应的电化学极化, 测量了不同操作条件下直接甲醇燃料电池(DMFC)的极化曲线和交流阻抗谱,并提出了改进的等效电路模型LR(CR)(QR(LR))用以分析温度、空气流量和甲醇流量对DMFC阴极电化学反应和传质极化过程的影响. 研究结果表明, 提高工作温度会导致更多的甲醇渗透到阴极, 加大阴极氧气还原反应的电荷转移电阻; 只有采用大的空气流量,才会有效地防止水淹, 加大氧气向催化剂层的传质, 促进阴极反应的进行; 适当提高甲醇的流量可以促进阳极和阴极电化学反应的进行, 但是过高的甲醇流速可能会降低电极表面的温度, 加剧甲醇的渗透.

Effect of Operating Condition on Cathodic EIS Parameters in a DMFC

Optimization of direct methanol fuel cell(DMFC) temperature and flow rate can effectively prevent cathode "flooding",reduce the adverse effects of methanol crossover on cathode reaction,therefore,it is critical to improve the performance of DMFC.In this paper,we reduced the cathode catalyst loading to strengthen electrochemical polarization of DMFC cathode oxygen reduction reaction,and measured polarization curves and electrochemical impedance under different operating conditions.Moreover,an improved equivalent circuit model LR(CR)(QR(LR)) is built to fit the measured spectrum to analyze the effect of operating parameters such as temperature,air flow rate,methanol flow rate on the cathode electrochemical reaction and mass transfer polarization process of DMFC under the full cell conditions.The results show that: increasing temperature will lead to more methanol to permeate to the cathode,and increase the charge transfer resistance of cathodic oxygen reduction reaction;and only using the high air flow can effectively prevent cathode flooding,and improve oxygen mass transfer to the catalyst;appropriately increasing the flow of methanol can promote the electrochemical reaction of DMFC,but the excessive flow of methanol may lower electrode surface temperature,increase penetration of methanol,therefore adversely affect oxygen reduction reaction.