Palladium nanoparticle functionalized conducting polymers for sensor applications

The development of low-temperature, flexible hydrogen sensors remains a key challenge in modern sensing technologies. Conducting polymers such as PEDOT:PSS offer advantages including solution processability, mechanical flexibility, and room-temperature operation; however, their intrinsic selectivity toward hydrogen is limited. In this work, palladium (Pd) nanoparticle functionalization of PEDOT:PSS thin films was systematically investigated to enhance hydrogen sensing performance through catalytic and interfacial electronic effects. Two fabrication strategies were explored: in-situ chemical reduction of PdCl₂ within the PEDOT:PSS matrix and electrochemical deposition of Pd onto pre-formed PEDOT:PSS films. The influence of Pd loading concentration and deposition cycles on electrochemical behavior and electrical properties was examined using cyclic voltammetry and Van der Pauw measurements, complemented by SEM, AFM, and KPFM characterization. In-situ reduced composites showed decreasing conductivity with increasing Pd loading, with optimal hydrogen-related response observed at 100 mM precursor concentration. Electrodeposited films exhibited well-defined hydrogen oxidation features and increasing Pd activity with deposition cycles, indicating superior catalytic efficiency. The sensing mechanism is attributed to hydrogen dissociation on Pd, formation of palladium hydride (PdHₓ), and modulation of the PEDOT:PSS hole concentration via interfacial work function shifts. Flexible Pd-PEDOT:PSS sensors demonstrated approximately 30% current variation under 5% H₂ exposure at room temperature, confirming the potential of this hybrid material system for efficient hydrogen sensing.