Ligand Effect-Induced Electronic Structure Manipulation of Media-Entropy Alloy for Remarkable Stability over 50,000 Cycles in Oxygen Reduction.

Modulating the "trade-off" between activity and durability of Pd-based alloys while eliminating the dissolution of the nonprecious metal element issue is highly significant for the advancement of commercializing anion-exchange membrane fuel cells (AEMFCs). Herein, by harmonizing composition and ligand effects and targeting the stability concerns of Pd-based alloys, we propose PdRhNi ternary medium-entropy-alloy (MEA) networks (PdRhNi ANs) as exceptionally efficient oxygen reduction reaction (ORR) electrocatalysts via ligand effect. The results of theoretical calculations provide compelling evidence that the ligand effect of Ni in PdRhNi ANs, which can endow an inductive effect to reshape the electronic configuration to induce a reduced energy barrier in the rate-determining steps, optimizes the adsorption energy of O-related intermediates and lowers the d-band center of metal species, collectively boosting the anti-CO capacity and the ORR efficiency. Consequently, the as-made PdRhNi ANs not only demonstrate significantly enhanced electrocatalytic properties with a half-wave potential of 0.85 V and excellent resistance to CO toxicity, in contrast to those of commercial Pt/C and binary counterparts, but also exhibit a negligible half-wave potential decline after 50,000 cycle stability examination. More excitingly, the homemade AEMFC with a PdRhNi AN air cathode delivers a higher power density of 109 mW cm, surpassing that of the PdRh AN-based battery, highlighting promising prospects for implementing MEA materials with ligand engineering in AEMFC environments.