Valorization of lignin biowaste into Schiff base copper(II) complex as a magnetically reusable electrocatalyst for...

This work describes a cost-effective and sustainable copper(II) complex as an electrocatalyst for the hydrogen-evolution reaction (HER) under alkaline and acid conditions. A magnetic lignin-supported tetrazole Schiff base copper(II) complex was incorporated into a carbon paste electrode (MLS@SchTet-Cu(II)/CPE) by a surface modification and cross-linking method. The catalytic HER of the MLS@SchTet-Cu(II)/CPE electrodes was analyzed by electrochemical techniques, including linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), chronopotentiometry (CP), and cyclic voltammetry (CV). The effects of solution pH and complex amount in the paste electrode on HER performance were evaluated. The results demonstrated that the MLS@SchTet-Cu(II) nanocomposite exhibits good electrocatalytic activity in both acidic and basic media. In particular, in 0.5 M H₂SO₄, the modified CPE electrode with 2.5 % MLS@SchTet-Cu(II) demonstrated an overpotential of 581 mV at 10 mA cm^-2 (η₁₀) and a Tafel slope of 258 mV dec^-1, surpassing the performance of both the bare and other modified CPEs. These findings highlight the potential of MLS@SchTet-Cu(II) as a promising candidate for sustainable HER catalysis.