(673g) Aqueous Formiate-Bicarbonate for Hydrogen Storage

Hydrogen is recognized as a crucial energy vector the next-future circular economy. Investigate new processes for sustainable hydrogen storage is fundamental to enable fast and capillary diffusion of H₂ technologies. However, at present, mature H₂ storage technologies, i.e. high-pressure and/or cryogenic liquid H₂, still present many limitations and safety issues, also affecting public perception and acceptance of H₂-powered devices. H₂ release and uptake through cyclic interconversion of formate/bicarbonate aqueous solutions (Figure) at near-ambient conditions is an intrinsically safe and easy-to-handle storage system. Preliminary energetic assessment suggest that the available catalysts could meet the requirements for mobile applications in the automotive sector with storage tanks in the range of 200 L, with an energetic efficiency of about 72%, improvable up to 90%, depending on reaction temperature and pressure. From a thermodynamic point of view the reaction can be easily shifted at near ambient conditions (T = 20-90 °C; P = 1-30 atm) by slightly changing the operating conditions. Most state-of-the-art catalysts are based on Pd supported on carbonaceous materials, prepared by wet impregnation followed by chemical reduction, using toxic and expensive chemicals. In this work, we investigate the possibility of preparing Pd-based catalysts by photo-deposition of Pd and Pd/Ag on different semiconductors for the hydrogen release step of reaction. The proposed technique is easy to run in situ, and could be used to selectively recover noble metals from e-waste and catalytic converters, in the framework of next-future circular economy.