Sequential reactions toward a high-pressure H₂ generation from a mixture of sodium borohydride and formic acid

Chemical compression enables direct high-pressure hydrogen generation from chemical hydrogen storage materials in a closed system. By utilizing a water-soluble catalyst, this method achieves rapid formic acid (FA)-mediated sodium borohydride (SBH) hydrolysis, followed by FA dehydrogenation at moderate temperatures, using a mixture of SBH and FA. The sequential reactions facilitate simultaneous dehydrogenation of both carriers without mutual inhibition, resulting in impressive hydrogen pressures (650 bar) and storage capacities (4.22 wt % and 48.25 gH₂ L⁻¹) with minimal CO content. The exothermic SBH hydrolysis and endothermic FA dehydrogenation effectively enable heat-coupling reactions, enhancing overall process efficiency. Moreover, the study introduces a cost-effective SBH regeneration method, evaluating the closed hydrogen cycle's feasibility in SBH-FA chemical compression technology. Economic analysis demonstrates reduced compressor size and overall cost benefits at hydrogen fueling stations, making this innovative approach promising for fuel-cell-based electric vehicle refueling at 700 bars, with potential energy and cost savings.