Enhanced reversible hydrogen storage in palladium hollow spheres

Palladium has long been used as a hydrogen sponge because of its ability to store hydrogen under ambient conditions (room temperature and 1 bar pressure). However, Pd suffers from a low storage capacity. The current investigation pertains to the enhancement in the reversible hydrogen storage capacity of Pd, by using hollow sphere geometry. Additional storage is achieved in molecular form; thus utilizing a recently developed multi-mode storage strategy. Hollow spheres, which can be viewed as nanocontainers, have been synthesized using a chemical reduction method (outer diameter of similar to 300 nm and shell thickness similar to 20 nm). Pressure-composition-isotherms have been used to characterize the hydrogen storage capacity and to establish the reversibility of the process. A 54% enhancement in the reversible storage capacity (25 degrees C and 140 bar) is observed in the case of Pd hollow spheres as compared to that of bulk Pd and 70% with respect to that of nanoporous Pd. The outer and inner surfaces of the hollow sphere play contrasting catalytic roles in the absorption and desorption process.