| AVS 55th International Symposium & Exhibition | |
| Energy Science and Technology Focus Topic | Monday Sessions |
| Session EN+SE+NS+SS-MoA |
| Session: | Hydrogen Storage |
| Presenter: | I. Zoric, Chalmers University of Technology, Sweden |
| Authors: | C. Langhammer, Chalmers University of Technology, Sweden I. Zoric, Chalmers University of Technology, Sweden S.T. Kelly, Stanford University B.M. Clemens, Stanford University B. Kasemo, Chalmers University of Technology, Sweden |
| Correspondent: | Click to Email |
Nanosized metallic particles may have advantageous hydrogen storage properties compared to the corresponding bulk material both in terms of sorption/desorption kinetics and in terms of storage capacity. In order to understand the physical principles behind the influence of nanosizing on hydrogen uptake/release properties, we have developed a novel localized surface plasmon resonance (LSPR) based optical hydrogen sensing scheme for nanoparticle storage systems. As model experiments we carried out measurements of the phase diagram and thermodynamic properties for supported Pd nanodisks, ranging in size from 30 nm to 300 nm. By monitoring the shift of the LSPR extinction peak upon hydrogen uptake/release as a function of hydrogen pressure, at different temperatures, we have mapped out a series of pressure-concentration (p-C) isotherm for a range of particle sizes. These optical studies are complemented by gravimetric studies using a quartz crystal microbalance (QCM). In the latter case the corresponding p-C isotherms were obtained by monitoring the frequency shifts when the Pd nanodisks were prepared on the QCM electrode and exposed to hydrogen environment at different temperatures. We have used Van’t Hoff plots (log of the isotherm plateau pressure, in the two-phase region, versus inverse plateau temperature), to obtain the enthalpy and entropy for hydride formation in Pd nanodisks of different sizes. Furthermore, we have used Sievert’s plots in the low hydrogen concentration limit (α-phase) to extract enthalpies and entropies of hydrogen dissolution. An excellent agreement was obtained for the corresponding thermodynamic variables obtained from LSPR sensing data and QCM data. Similarities and differences to the corresponding thermodynamic variables for bulk systems are discussed. In addition, we have carried out corresponding measurements with Mg nanoparticles “capped” with few nanometers of Pd to facilitate H2 dissociation. The “capping“ with a Pd layer circumvents the bottleneck associated with low dissociative sticking of hydrogen on Mg. Double plateau isotherms were obtained indicating initial onset of the mixed phase formation at low hydrogen pressure in Mg nanoparticle followed by a corresponding two phase onset in the Pd cap at higher pressure, characteristic for Pd nanoparticles at a given temperature. In addition, we also present the QCM and LSPR based studies of hydrogen uptake/release kinetics at different temperatures.