Pt/C催化剂长时间ORR过程性能衰减的机理

Research on Performance Decay Mechanism of Pt/C Catalyst in Long‑Term ORR Test

燃料电池的成本、性能和耐久性是决定其商业化的核心问题。燃料电池性能下降的主要原因是在其运行过程中催化剂的老化或瞬态时的电化学活性面积的损失,这些损失主要来自催化剂中金属的溶解和碳载体的腐蚀,这种连续不可逆的过程会大大缩短燃料电池的使用寿命。为探究此问题,基于硫酸刻蚀的碳载体制备了20%(质量分数)的Pt/C催化剂,形貌表征测试可知其分散均匀、粒径尺寸均一,被认为是进行长时间氧还原反应(ORR)稳定性测试的优异材料。接下来通过不同循环伏安(CV)圈数的ORR稳定性测试方法来观察其性能衰减情况,并利用一系列的物理表征:透射电子显微镜(TEM)、高分辨电子显微镜(HRTEM)、X射线光电子能谱(XPS)和拉曼光谱仪(Raman)进一步直观解析其衰减机理。报道了Pt/C催化剂稳定性衰减的原因主要来自于Pt粒子的溶解、团聚、氧化和迁移以及碳载体的腐蚀的现象。本研究解析了燃料电池在运行过程中稳定性受影响的来源,为设计高稳定性的商业ORR催化剂提供了参考。

In proton exchange membrane fuel cells,cost,performance and durability are important issues that are need to be resolved before commercialization.The main reason for fuel cell performance degradation during operation is the loss of electrochemical surface area during long-term aging or transient.These losses mainly come from the degradation of the catalyst metal and the corrosion of the carbon support.This is a continuous and irreversible process that will greatly shorten the service life of the fuel cell.In order to explore this problem,20%(mass fraction)Pt/C catalyst is prepared based on carbon carrier etched by sulfuric acid.The morphology characterization test shows that it is uniformly dispersed and uniform in particle size,which is considered as an excellent material for long-term oxygen reduction(ORR)stability test.Next,the ORR stability test method with different cyclic voltammetry(CV)cycles is used to observe its performance degradation,and a series of physical characterizations,e.g.transmission electron microscopy(TEM),highresolution electron microscopy(HRTEM),X-ray photoelectron spectroscopy(XPS)and Raman spectroscopy(Raman),are used to further intuitively analyzed the attenuation mechanism.It is reported that the reasons for the degradation of the stability of Pt/C catalysts are mainly from the dissolution,agglomeration,oxidation and migration of Pt particles and the corrosion of carbon supports.This study elucidates the source of the impact on the stability of fuel cells during operation,and provides a reference for designing high-stability commercial ORR catalysts.