Adsorption equilibrium and charge/discharge characteristics of hydrogen on MOFs

摘要

For obtaining relevant information about the development of hydrogen storage materials from metal organic frameworks (MOFs), MIL-101(Cr) was selected and synthesized for analyzing the adsorption equilibrium and characteristics of charge and discharge. The specific surface area, pore size distribution (PSD) of the sample were determined by 77.15 K nitrogen adsorption data. Isotherms of hydrogen adsorption on the sample were volumetrically measured at 77.15 K and 87.15 K, 0-100 KPa and 0-6 MPa. Henry law constants and Toth equation were respectively used to determine the isosteric heat of adsorption. A 3.2 L conformable vessel, which can meet the fuel consumption of 7.5 kW PEMFC under typical working condition for about 10 min, was designed and undergone charge and discharge tests at ambient temperature and 77.15 K under the flow rate 10-50 L.min(-1). Results show that the limit isosteric heat of adsorption on the sample is 7.368 kJ.min(-1), while the mean Isosteric heat determined by the Toth potential function is 2.925 kJ.min(-1). Results also reveal that, at 77.15 K, the ratio of hydrogen released is 80%, 79.4%, 77.2% and 76.1% at the flow rate of 20-50 L.min(-1); while at 301.15 K, the ratio is 85.1%, 85.0% and 82.3% with corresponding flow rate 10-30 L.min(-1). It suggests that the storage amount and the characteristics of charge/discharge on hydrogen-MIL-101(Cr) system at cryogenic temperature can meet the fuel requirements of the fuel cell.