Self-Optimized Ligand Effect in L1<sub>2</sub>-PtPdFe Intermetallic for Efficient and Stable Alkaline Hydrogen Oxidation Reaction
Tonghui Zhao, Guangjin Wang, Mingxing Gong, Dongdong Xiao, Yi Chen, Tao Shen, Yun Lu, Jian Zhang, Huolin L. Xin, Qing Li, Deli Wang
Abstract
It is of paramount importance to explore high efficient and stable electrocatalysts toward anodic hydrogen oxidation reaction (HOR) in anion exchange membrane fuel cells. Herein, a new class of ternary (Pt0.9Pd0.1)3Fe intermetallic is developed with excellent performance toward alkaline HOR. Specifically, the Pd-substitution facilitates the formation of L12-Pt3Fe intermetallic at a lower annealing temperature. Electrochemical analysis and density functional theory calculations indicate that the in-situ formed interstitial alloying PdHx during the electrochemical cycle widens the d-band structure of (Pt0.9Pd0.1)3Fe and shifts downward the d-band center toward the Fermi level. The optimized ligand effect from PdHx gives rise to the encouraging activity for alkaline HOR. Meanwhile, a step-by-step monitoring technique and ex situ CO-stripping voltammetry jointly demonstrate that ordered atoms’ arrangement of (Pt0.9Pd0.1)3Fe intermetallic contributes to stabilize the local coordination environment and enables the maintenance of the ligand effect from the in situ formed Fe/Fe(OH)x heterostructure. Negligible decay in electrochemical surface areas of (Pt0.9Pd0.1)3Fe intermetallic after a given accelerated durability test confirms the significant advantage in stability over Pt3Fe alloy. This work sheds light on the significance of ligand effects optimization and real-time tracing of the catalytic process to the structure–activity relationship establishment and subsequent catalyst designs.