Novel hydrogen storage properties of palladium nanocrystals activated by a pentagonal cyclic twinned structure

Researchers appear to have neglected a special form of crystallites, pentagonal cyclic twinning, in which an obvious two-dimensional lattice expansion exists leading to novel physical–chemical properties associated with the changes in geometric and electronic structures. Using the storage and release of hydrogen in Pd nanocrystals as a probe, we have found that icosahedral pentagonal cyclic twinned Pd nanocrystals had distinct hydrogen storage properties, due to the two-dimensional lattice expansions, quite different from those of the octahedral single crystalline counterpart. In addition, the two-dimensional lattice expansion in pentagonal cyclic twinned Pd nanocrystals causes a change in electronic structure, which results in novel catalytic properties involving in situ formation of PdH_x pentagonal cyclic twinned nanocrystals.