Copper salt impregnated biomass-derived microporous carbon for hydrogen storage

Biomass derived carbon is a promising class of sustainable porous materials for hydrogen storage. The natural vascular structure of plant biomass can potentially facilitate uptake and even dispersion of metal ions from aqueous solution, enabling activation during carbonisation. To test this hypothesis, we studied a one-step pre-activation approach for synthesis of microporous carbon using copper(ii) ions and kale plant stems as a model vascular biomass precursor. Thermogravimetric analysis (TGA) shows systemic changes in the mass loss profiles and increased residual inorganic content with higher CuCl₂ loading. Surface area analyses, Raman spectroscopy and transmission emission microscopy (TEM) demonstrate activation and localised structural ordering by the copper salt up to an optimal threshold. Nitrogen adsorption measurements confirmed the formation of ultramicroporous activated carbon, with a BET surface area of 385 m² g^-1 and total hydrogen uptake of 1.78 wt% at 50 bar and 77 K. An increase in porosity was observed with increasing metal-ion concentration. The findings highlight the pre-activation of vascular biomass precursors using metal ions as an effective strategy to create porous carbons, and the dual role of CuCl₂ in tailoring carbon structure and porosity, offering a combined sustainable route to prepare high-performance hydrogen storage materials from plant-based precursors.