Circular economy approach to catalyst design: converting organic waste into synergistic metal-doped biochar electrocatalysts for sustainable hydrogen production through water electrolysis

The escalating global energy demand and mounting pressures from the accumulation of organic waste necessitate integrated strategies that simultaneously address waste management and clean hydrogen production. In this work, heterogeneous organic waste collected in Doha, Qatar, was converted into biochar and metal-functionalized biochar electrocatalysts (Cu/biochar, Ni/biochar, and bimetallic Cu-Ni/biochar) for alkaline hydrogen evolution via water electrolysis. The catalysts were synthesized by wet impregnation of mixed organic waste (date palm leaves, food waste, and agricultural residues) with Ni and Cu precursors, followed by pyrolytic carbonization at 500 degrees C under nitrogen, yielding well-dispersed metallic phases with total loadings of about 2.33 wt% Ni and 2.29 wt% Cu on the biochar framework. Comprehensive characterization using FTIR, Raman spectroscopy, TGA, XRD, and SEM-EDX confirmed successful metal incorporation, progressive modification of oxygen-containing surface groups, and a balanced carbon microstructure in the bimetallic material, which combines Ni-driven graphitization with Cu-induced defect generation. Electrochemical studies in KOH demonstrated that metal functionalization dramatically enhances the hydrogen evolution reaction (HER) activity relative to pristine biochar: CV and LSV measurements revealed up to 9-fold and 6-fold increases in current density, respectively, together with a substantial decrease in HER overpotential and Tafel slope for the Cu-Ni/biochar catalyst. Impedance, capacitance, and ECSA analyses further showed that the bimetallic Cu-Ni/biochar exhibits the lowest charge-transfer resistance and the highest electrochemically active surface area (4.31 cm & sup2;), consistent with improved charge-transfer kinetics and a hierarchically porous, highly accessible catalytic surface. Long-term chronoamperometry and post-stability polarization curves confirmed that Cu-Ni/biochar maintains a nearly constant current density and overlapping HER profiles over extended operation, evidencing excellent durability under alkaline electrolysis conditions. These findings demonstrate that synergistic Ni-Cu interactions on a waste-derived biochar scaffold provide an efficient, robust, and earth-abundant electrocatalyst for sustainable hydrogen production, offering a practical circular-economy route that transforms local organic waste streams into value-added materials for renewable energy technologies.