Electronic modulation of palladium nanocatalysts supported on high-entropy spinel oxides for enhanced ethanol oxidation reaction

Abstract One of the key challenges in alkaline direct ethanol fuel cells (ADEFCs) is the sluggish kinetics of the anodic ethanol oxidation reaction (EOR) process. While mono-, bi-, and trimetallic catalysts have been employed to address this issue, high-entropy materials (HEMs) have attracted much attention as EOR electrocatalysts. Due to their multi-elemental compositions and unique high-entropy mixing states, HEMs offer tunable electrocatalytic activity and enhanced stability. These attributes arise from their intriguing quadruple effects: high entropy, lattice distortion, cocktail effect, and sluggish diffusion. Herein, we demonstrate, for the first time, the use of a high-entropy spinel oxide (CuMnFeNiCo) 3 O 4 , denoted HESOx, uniquely synthesized using a modified Pechini method for the electrocatalytic EOR. The HESOx was decorated with palladium nanoparticles with Vulcan carbon as a support to form Pd-HESOx/C electrocatalyst. After spectroscopic and microscopic characterization, the material was tested for EOR and showcased excellent electroactivity with a mass activity of 3486.5 mAcm −1 Pd , outperforming the commercial counterpart Pd/C (2 224.8 mAcm −1 Pd ) at a lower onset potential. The material also demonstrated excellent durability, retaining mass activity above 90% after 500 cyclic voltammetry scans and higher residual mass activity after 4 h of chronoamperometry. Density functional calculations revealed that Pd-HESOx/C reduces the energy barriers for both C–C bond cleavage and C–O coupling while facilitating easier removal of poisonous CO. Overall, the results indicate that Pd-HESOx/C holds promise to serve as a high-performing and durable anode material for alkaline direct ethanol fuel cells. Graphical Abstract