10 kW质子交换膜燃料电池电堆模拟工况下耐久性测试及衰减机理研究

Investigation of the performance degradation and mechanism for a 10 kW PEM fuel cell stack

质子交换膜燃料电池(PEMFC)的耐久性是影响其在交通领域实际应用的关键因素,尤其是在复杂的工况运行过程中,对PEMFC的耐久性更是严峻的考验.因此,掌握质子交换膜燃料电池的耐久性规律,了解清楚其性能衰减(尤其是膜电极的衰减)机理至关重要.基于此,本文对一台10 kW电堆进行长达2050 h的工况循环测试,发现经过工况循环测试后电堆的性能发生了明显的衰减,并获得了电堆性能衰减的特性及其规律.为了找出衰减的原因及机理,对工况测试前后电堆中膜电极(MEA)及其关键组件进行了分析,包括研究了催化层结构的变化、催化剂的铂颗粒大小及电化学活性比表面积(ECSA)的变化、气体扩散层结构的变化、电堆的阻抗(EIS方法测试)变化.分析结果表明,膜电极性能的衰减是电堆性能衰减最为关键的因素,膜电极经过长时间的工况循环之后,出现了程度不同的催化剂铂颗粒长大、铂的溶出及迁移及催化层结构的破坏,这些导致了膜电极性能的衰减及失效.本工作的成果对于进一步认识大功率质子交换膜燃料电池电堆衰减的规律及机理、提升燃料电池耐久性的研究将具有重要参考价值.

The durability of proton exchange membrane fuel cell(PEMFC)is a key factor affecting its practical application in the area of transportation,especially in the complex operating conditions.Therefore,improving the durability of PEMFC is very important,and it is essential to understand the performance degradation mechanism.In the PEMFC stack,the performance degradation of membrane electrode assembly(MEA)plays a decisive role in the performance degradation of the stack.Based on this opinion,we conduct a long-term cycling test for a 10 kW stack under a simulated operation conditions lasting for over 2,oo0 h.It is found that the performance of the stack has been attenuated obviously after the operating cycle test.The features and rule of the degradation have been analyzed.To find the reasons and mechanism for degradation,we carefully analyze the changes of the MEA and other components before and after the operating cycle testing,including the structure changes of the catalyst layer and the gas diffusion layer,the size changes of platinum nano-particles and electrochemistry surface area(ECSA)of the catalyst,the resistance changes of the stack(measured by EIS),etc.From the analysis results,it is found that the attenuation of MEA plays a crucial role for the degradation of stack.After a long-term testing,the size of the Pt particles grows larger,dissolution and migration of the Pt occur,the structure of the catalyst layer is destroyed and so on,all of which results in the degradation and fail of MEA and stack.The results of this work will be helpful to understand the attenuation rule and mechanism of large PEMFC stack,and it is meaningful for the researchers to improve the durability of PEMFC.