Tuning the Morphology of Heterostructured Palladium/Magnetite Nanoparticles for Enhanced Catalytic Electro-oxidation of Formic Acid

Abstract

The present study explores the synthesis, characterization, and comparative electrocatalytic evaluation of heterofunctionalized palladium/magnetite (iron oxide) nanoparticles (Pd/IONPs) with diverse morphologies for formic acid (FA) oxidation to enhance catalytic activity. Various morphologies, including dumbbell, hybrid, branched, and core−shell-like structures were synthesized and characterized using transmission electron microscopy (TEM), selected area electron diffraction (SAED), and vibrating sample magnetometer (VSM). In addition, polyvinylpyrrolidone (PVP)-coated Pd nanobars were synthesized and used as a control catalyst to compare the performance of the heterostructured Pd/IONPs. The electrocatalytic activity of these particles was investigated via cyclic voltammetry (CV) to reveal structure−function relationships in heterogeneous catalysts. Among the different morphologies, branched Pd/octopod-shaped IONPs demonstrated superior catalytic activity and carbon monoxide (CO) poisoning tolerance in FA oxidation. This is attributed to the high-energy {113} facets in the arms of the IONP octopods, which facilitated the attachment of many Pd atoms and promoted a synergistic catalytic effect. The increased exposure of active sites on these facets enabled more efficient FA oxidation pathways, as evidenced by a higher ratio of anodic direct oxidation peak current density (I a1 ) to anodic indirect oxidation peak current density (I a2 ) and greater endurance against CO poisoning measured as the ratio of I a1 to cathodic direct oxidation peak current density (I b ). These findings highlight the critical role of NP morphology in catalyst design for advancing energy conversion and storage technologies.