A rechargeable and portable hydrogen storage system grounded on soda water

The bicarbonate-formate (HCO₃⁻ – HCO₂⁻) interconversion provides a promising cycle for a conveniently accessible hydrogen storage system via reversible dehydrogenation and hydrogenation processes. Existing catalytic systems often use organic solvents, tedious optimization as well as manipulation of pH values, solvent, pressure and various additives. Herein, we present an operational, robust, safe and cost-effective catalytic system for hydrogen storage and liberation. We have established a unique catalytic system with two different solid organometallic assemblies (NHC-Ru and NHC-Ir) that facilitate the reversible transformation between sodium formate and bicarbonate in aqueous solutions collaboratively and efficiently. Notably, the NHC-Ru catalyst is privileged for the hydrogenation of sodium bicarbonate, whereas the NHC-Ir component enables the dehydrogenation of sodium formate, all in a single reaction vessel. What sets this system apart is its simplicity. The H₂ discharging and recharging is simply regulated by heating the mixture with or without H₂. Remarkably, this process requires no extra additives or supplementary treatments. Moreover, the reversible hydrogen storage system is durable and can be reused for over 30 cycles without a discernible decline in activity and selectivity. The strategic paradigm in this study shows significant practical potential in hydrogen fuel cell applications.