Low-coordinated surface sites make truncated Pd tetrahedrons as robust ORR electrocatalysts outperforming Pt for DMFC devices
Xiaoling Wang, Jingwei Li, Xiaotong Yang, Fengling Zhao, Yongfei Li, Daliang Zhang, Li‐Yong Gan, Kexin Yao, Qiang Yuan
Abstract
Developing highly stable and active non-Pt oxygen reduction reaction (ORR) electrocatalysts for power generation device raises great concerns and remains a challenge. Here, we report novel truncated Pd tetrahedrons (T−Pd−Ths) enclosed by {111} facets with excellent uniformity, which have both low-coordinated surface sites and distinct lattice distortions that would induce “local strain”. In alkaline electrolyte, the T−Pd−Ths/C achieves remarkable ORR specific/mass activity (SA/MA) of 2.46 mA·cm−2/1.69 A·mgPd−1, which is 12.3/16.9 and 10.7/14.1 times higher than commercial Pd/C and Pt/C, respectively. The T−Pd−Ths/C also exhibits high in-situ carbon monoxide (CO) tolerance and 50,000 cycles durability with an activity loss of 7.69% and morphological stability. The rotating ring-disk electrode (RRDE) measurements show that a 4-electron process occurs on T−Pd−Ths/C. Theoretical calculations demonstrate that the low-coordinated surface sites contribute largely to the enhancement of ORR activity. In actual direct methanol fuel cell (DMFC) device, the T−Pd−Ths/C delivers superior open-circuit voltage (OCV) and peak power density (PPD) to commercial Pt/C from 25 to 80 °C, and the maximum PPD can reach up to 163.7 mW·cm−2. This study demonstrates that the T−Pd−Ths/C holds promise as alternatives to Pt for ORR in DMFC device.