Tailoring Pd Content for Optimal Stability in FeCoNiCu Multielement Alloy Electrocatalysts for Oxygen Evolution Reaction

Abstract

Multielemental alloy (MEA) based on earth-abundant 3d transition metals hold significant promise as low-cost electrocatalysts for the oxygen evolution reaction (OER), but their long-term stability under oxidative conditions remains a major challenge. In this study, we investigate the effect of palladium incorporation on the electrochemical performance and structural durability of FeCoNiCu alloy nanoparticles. Our previous finding that trace Pd addition significantly improves catalyst durability. In this study, we systematically synthesized a series of Pd–FeCoNiCu alloy with Pd contents ranging from 0.177 to 1.97 at.%. Advanced characterization techniques including inductively coupled plasma optical emission spectroscopy (ICP-OES), electron microscopy, synchrotron-based spectroscopy, and electrochemical measurements were employed to elucidate the correlation between composition, structure, and performance. Our findings reveal a highly non-linear dependence of catalyst performance on Pd content: an optimal range (0.336–0.389 at.%) enables long-range, d–d/sp orbital hybridization that delocalizes the local density of states (LDOS) of surrounding 3d metals, thereby suppressing oxidative dissolution. In contrast, higher Pd concentrations lead to Pd–Pd interactions, localize electronic perturbation, and accelerate degradation. This volcano-type correlation between Pd content and durability highlights a general strategy for engineering catalyst longevity via minimal noble-metal doping and spatially cooperative electronic modulation.