Green preparation of reusable Pd@magnetic lignosulfonate nanocomposite for hydrogen evolution reaction in all pHs

In this study, palladium nanoparticles (Pd NPs) were successfully synthesized and supported on a cost-effective, eco-friendly magnetic lignosulfonate matrix using Hibiscus Rosasinensis L. leaf extract as a natural reducing and stabilizing agent (Pd@Fe₃O₄-lignosulfonate). The magnetic lignosulfonate prevented the aggregation of Pd NPs, enhanced the active surface area, and improved the hydrophilicity of the modified carbon paste electrode (CPE), thus boosting hydrogen production efficiency. The Pd@Fe₃O₄-lignosulfonate was incorporated into the CPE at different weight percentages (1.5, 2.5, 5, 10, and 15 %), and employed as an efficient electrocatalyst for the hydrogen evolution reaction (HER) across all pH conditions (0.5 M H₂SO₄, 1 M NaOH, and phosphate buffer at pH 7). Electrochemical techniques such as linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and chronopotentiometry (CP) were employed to assess the catalyst's performance. Optimal hydrogen generation was achieved at 10 wt% Pd@Fe₃O₄-lignosulfonate/CPE, yielding an overpotential of -239 mV (vs. RHE) at a current density of 10 mA. cm^-2 and a Tafel slope of -62 mV. dec^-1 under acidic conditions. This work positions the low-loaded Pd NPs on magnetic lignosulfonate as a viable alternative to traditional noble metal catalysts, contributing to advancements in green chemistry and sustainable energy solutions.