Ortho-phenylenediamine-Pd Hybrid on Magnetic γ-Fe2O3 for Efficient Hydrogen Evolution Catalysis

Abstract

Hydrogen evolution reaction (HER) electrocatalysts that are both efficient and cost-effective are needed to support sustainable hydrogen production. In this study, a γ-Fe2O3/OPD/PdCl2 nanocomposite was synthesized and deposited onto a glassy carbon electrode. The material was prepared through stepwise functionalization of γ-Fe2O3 magnetic nanoparticles with o-phenylenediamine (OPD), followed by coordination with Pd (II). Structural analysis by FT-IR and XRD confirmed surface modification and Pd incorporation, while TEM images revealed a core-shell structure with an average particle size of about 35 nm. X-ray photoelectron spectroscopy verified Pd-N coordination and electronic interaction between Pd and the OPD-functionalized support, providing insight into the origin of the enhanced electrocatalytic activity. Magnetic studies showed reduced magnetization compared with pristine γ-Fe2O3, consistent with organic and metal loading. Electrochemical tests in 0.5 M H2SO4 demonstrated promising HER performance, with an onset potential of 65 mV (vs. RHE), and an overpotential of 269 mV at a current density of 10 mA cm-2. Durability was verified by stable activity over 1000 cycles and long-term chronoamperometry. Comparison with precursor materials indicated that both OPD functionalization and Pd sites contributed to improved catalytic activity. These findings suggest that γ-Fe2O3/OPD/PdCl2 is a stable and efficient Pd-based electrocatalyst and a potential alternative to Pt for water splitting applications.