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

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.