Hydrogen diffusion in palladium nano-crystal film

Thin (less that 1 μm) and continuous palladium film was fabricated by brush plating. The topography and cross-sections of the film were characterized by atom force microscopy (AFM) and scanning electron microscopy (SEM). The results showed that there are no cracks and pinholes in the film. The film is made up of spherical nano-clusters. The size of most clusters is 20-30 nm. The hydrogen coefficient, DH, in the Pd film was measured by electrochemical stripping method in the Pd-H solid solution (α-phase) at the temperature ranging from 298 to 328 K. The DH is 1 order of magnitude smaller than that in the bulk. An equation is given to calculate the total charge due to hydrogen diffusion. The DH vs 1/T plots show that the film follows Arrhenius behavior, DH = D0 exp(- Ea/RT), with a activation energy larger than that in bulk Pd. The diffusion of hydrogen was suffered by the crystal interface.