Compositionally Tuned PdZn Nanoparticles for Enhanced Electrocatalytic Activity toward the Ethanol Oxidation Reaction

The sluggish kinetics of the ethanol oxidation reaction (EOR), coupled with the high cost and low stability of catalysts, pose a critical bottleneck for the development of direct ethanol fuel cells (DEFCs). Here, Vulcan XC-72 supported highly dispersed PdZn nanoparticles with tunable compositions (PdZnx/C) are synthesized via a facile liquid-phase reduction. The Zn incorporation induces a volcano-type dependence of catalytic activity on the ratio of Zn/Pd, with PdZn0.5/C showing the optimal performance. Specifically, PdZn0.5/C exhibits a mass activity 2.8 times higher than that of Pd/C and a lower Tafel slope (113.3 mV/dec), indicating enhanced reaction kinetics. The results of XRD and XPS reveal lattice contraction and a positive shift in Pd 3d binding energy, confirming that Pd-Zn interaction effectively modulates both the crystalline and electronic structure of Pd. This modification optimizes the adsorption of ethanol, reaction intermediates and OH(ads) species, thereby facilitating the EOR process. Consistently, the apparent activation energy of PdZn0.5/C (18.8 kJ/mol) is significantly lower than that for Pd/C (23.7 kJ/mol), confirming a reduced reaction energy barrier. Besides, PdZn0.5/C shows superior catalytic stability to Pd/C after 3000 s of long-term current testing. These results highlight the effectiveness of Pd-Zn interactions in enhancing both activity and stability of Pd-based catalysts for ethanol oxidation.