Transition metal dissolution control in Pt-alloy catalyst layers for low Pt-loaded PEMFCs for improving mass transfer
By Wang, Hong; Lin, Rui; Cai, Xin; Liu, Shengchu; Zhong, Di; Hao, Zhixian
Published in International Journal of Heat and Mass Transfer
2021
Abstract
The decrease of Pt loading in the cathode catalyst layer (CCL) for proton exchange membrane fuel cells (PEMFCs) is extremely desirable to reduce their expenses. Meanwhile, Pt-alloy electrocatalysts are attractive as cathode catalysts in the low Pt-loaded membrane-electrode assembly (MEA) due to their high catalytic activities and high Pt utilization. However, reducing the Pt loading of the CCL leads to high voltage drops. These voltage drops are comprehended to originate from the mass transportation resistance of O2 through the ionomer-platinum interface. Moreover, the contamination of the transition metal dissolution hinders the development of alloy catalysts. Here, a self-made PtNi/C catalyst is selected as the oxygen reduction reaction (ORR) catalyst, with a unique CCL structure is designed by constituting the two sub-layers. The object is to apply an easy design close to commercialized manufacture to alleviate MEA degeneration induced by Ni pollution. Cross-sectional investigations of these MEAs reveals that the special CCL structure effectively mitigates the dissolution of Ni. The effect of Ni contamination on oxygen transport resistance (OTR) is studied using the limited current method. After 10,000 cycles of accelerated stress test (AST), the traditional alloy CCL's local oxygen transport resistance has increased by 16.3%. In contrast, the dual structure design of the CCL has only raised by 4.4%. These newly obtained results will be used to tune PEMFCs activity and stability and provide direction for future Pt-alloyed scale applications.