Low-temperature sorption of hydrogen by porous carbon material containing palladium nanoclusters
Sorption of hydrogen isotopes of composite nanostructured carbon material containing palladium clusters with an average size of 3-5 nm was studied in the temperature range of 8-290 K. It was shown that the total sorbed hydrogen highly depends on the method of producing the composite and accounts for 2-4.5 % of the mass of the sample. It was allocated two processes with characteristic times differing more than an order of magnitude in the kinetics of hydrogen sorption and desorption by a composite. The relatively fast process seems to be consistent filling hydrogen molecules in the cavities of the carbon matrix, and longer process - hydrogen diffusion into the crystal lattice of palladium nanoclusters. There were two temperature zones in the samples in temperature dependences of the diffusion coefficients of deuterium in composite: above 60 K, the activation energy diffusion in a sample containing palladium nanoclusters was more than two times higher values obtained for a pure carbon matrix. Below 60K diffusion coefficient of deuterium in a pure carbon matrix had practically no temperature dependences, while in the case of deuterium diffusion into palladium nanoclusters, the change the nature of the temperature dependence was observed at a lower temperature (~ 30 K), and below this temperature, the activation energy decreased about an order of magnitude. Ke