A Simple Technique for the Measurement of H₂ Sorption Capacities

Abstract

An accurate (and low-cost) experimental technique has been developed to screen the effectiveness of an adsorbent in improving gas storage capacity within a pressurized vessel. Specifically, the capsule technique is shown to be effective in directly measuring the total H 2 contained within a pressurized vessel and can be used to evaluate the amount of gas in the free space and adsorbed on the solid, that is, a sorption isotherm. The capsule technique was benchmarked by measuring isotherm data for CH 4 on an activated carbon sample and was then subsequently evaluated for use with H 2 . The capsule data are in excellent agreement with the total storage capacities expected from calculations using equation of state information. In addition, H 2 isotherm data from the sorption capsule are found to be within 1% of values obtained from a more sophisticated differential pressure adsorption unit (DPAU). Conditions for when the adsorbent aids or hinders storage are also discussed in terms of the 2010 DOE H 2 storage targets.

Irreproducibility in hydrogen storage material research

“…A cruder approach to gravimetric measurement is to simply measure the change in weight of an isolated sample cell at the chosen hydrogen pressure. 56 Temperature-Programmed Desorption (TPD), or Thermal Desorption Spectroscopy (TDS), involves the application of a temperature ramp to a sample that has previously been exposed to H 2 , and the detection of the amount of hydrogen subsequently desorbed from the material, typically using a quadrupole mass spectrometer. [57][58][59] The quantification of the amount of hydrogen desorbed, in this case, requires calibration of the mass spectrometer signal.…”

Stability and hydrogen adsorption of metal–organic frameworks prepared via different catalyst doping methods

“…In certain cases, either the isotherms are not parallel or the calculated active catalytic sites exceed that expected from the total metal content of the material: these are signs of hydrogen spillover from the catalyst to the support [57]. Hydrogen spillover entails catalytic dissociation of molecular hydrogen on the catalyst followed by diffusion from the catalyst to its support, and has been reviewed for both catalytic applications [57,58] and as a means to increase the operative adsorption temperature of hydrogen storage [59][60][61][62]. Here we use hydrogen spillover as a means to assess whether active catalytic entities may diffuse from the catalyst to the MOF support, in order to ascertain whether the surface of the MOF has potential to participate in the chemical reaction.…”

Payne cell gravimetric measurements in polymer‐solvent systems for diffusion coefficients and isotherm data

“…Since it took only a short amount of time to obtain a steady‐state weight loss profile, only a small amount of solvent was lost from the system. Based on analyses described previously 29 , this amounted to a variation of 0.1% RP or a 0.05 mm Hg change in the driving force pressure.…”