Ru/C type ammonia synthesis catalysts are known to be poisoned by hydrogen. In order to elucidate a mechanism for hydrogen poisoning, H2 adsorption and spillover on Ru based ammonia synthesis catalysts were investigated. Supported Ru catalysts and Na promoted Ru catalyst were prepared by incipient wetness impregnation of Ru(NO)(NO3)3 on SiO2, SBA-15, CNT and Vulcan supports. Dispersion value of the catalysts was determined via H2 chemisorption and Transmission Electron Microscopy (TEM) characterization techniques. Over SBA-15 support, the dispersion of the catalyst determined by two different characterization techniques were in agreement. On the other hand, over CNT and SiO2 supports dispersion measured by TEM characterization method was higher than H2 chemisorption method. H2 chemisorption measurements performed over extended periods of time were used to determine the spilled over hydrogen amounts over Ru/Vulcan and Na-Ru/Vulcan catalysts at 375 torr and 10 torr H2 pressure at room temperature. By using H2 uptake data measured for extended periods of 6 &ndash / 24 hours, diffusion coefficient of hydrogen species over Vulcan support was calculated assuming a point source diffusion mechanism. Coefficient of diffusion for Ru/Vulcan and Na-Ru/Vulcan was found as 1.39 x 10-14 cm2/sec and 1.23 x 10-14 cm2/sec, respectively at 375 torr. Similarly, at 10 torr, diffusion coefficients of Ru/Vulcan and Na-Ru/Vulcan catalysts were determined as 1.51 x 10-15 cm2/sec and 1.81 x 10-15 cm2/sec, respectively.

Indiana University-Purdue University Indianapolis (IUPUI) / Based on plane wave DFT calculation, we carried out micro level investigation of hydrogen storage in nanoporous silicon (npSi). One quarter of a hexagonal pore with Palladium catalyst placed at the surface has been studied for hydrogen dissociation, spillover, bond hopping, and diffusion for both single catalyst atom and small catalyst cluster consisting of multiple catalyst atoms. All the DFT computations were done in one of the biggest research supercomputer facilities of the world, Big Red II. We opted ABINIT, an open source DFT tool for our computations. Our calculation revealed low dissociation, spillover, and bond hoping energy barrier. The energy required to be provided from external sources to fully recharge the storage medium from a gaseous source at a completely empty state has also been evaluated. Hydrogen diffusion along the inner surface of the pore as a means of bond hopping and the possibility of quantum tunneling, a low temperature phenomena used to spontaneously go over an otherwise less likely high energy barrier have been studied as well. Using these micro level parameter values evaluated from the DFT study, the performance of any potential hydrogen storage material can be compared to a set of characteristics sought in an efficient storage media. Thus, the micro scale feasibility of this novel npSi material based hydrogen storage technology was studied as a part of a STTR Phase I project.