Biochar-Based Catalyst Derived from Corn Husk Waste for Efficient Hydrogen Generation via NaBH₄ Hydrolysis

Biochars from agricultural waste are sustainable and eco-friendly alternatives in catalyst development for hydrogen evolution. However, the use of these materials in hydrogen generation remains underexplored, and some fundamental aspects have not yet been addressed. Here, we synthesized cobalt-impregnated biochars derived from corn husk modified with CoCl₂ and employed them as catalysts in NaBH₄ hydrolysis. Characterization was made by FTIR, XRD, TGA, MEV, TEM and EDS. The incorporation of cobalt into biochar increased its thermal stability, made its surface rougher and more heterogeneous, and increased its crystallinity by the presence of CoCl₂ and Co₃O₄. The catalytic activity of the material depended on the content of impregnated cobalt and the NaOH and NaBH₄ concentrations in the medium. Biochar with a higher cobalt content exhibited superior catalytic activity (hydrogen generation rate (HGR) = 271.4 mL/(min·g) and E_a = 54.75 KJ/mol) under the best conditions at 25 °C (10% w/v NaOH, 5% w/v NaBH₄, and 0.05 g of biochar). The catalyst experienced deactivation after two usage cycles, attributed to the formation of Co(OH)₂ from CoCl₂ and Co₃O₄ on the biochar surface under highly basic conditions during the reaction, as well as the formation of borate. Despite this, the biochar structure remained intact after the reaction, demonstrating the robustness of this carbonaceous material as a support. These findings are essential for guiding future research on metallic catalysts supported on biochar derived from biomass pretreated with metal salts for hydrogen generation via NaBH₄ hydrolysis.