Faster H recovery in Pd nanoparticle layer based Gd switchable mirrors: size-induced geometric and electronic effects

An investigation of the effect of the nanoparticle size in the Pd overlayer on the hydrogen-induced changes in the Gd switchable mirrors is reported in the present study. Deposition of a 10 nm thick Pd overlayer consisting of nanoparticles of 9 nm size results in a large increase in optical and electrical contrast and a substantial decrease in response and recovery time in Gd switchable mirrors. This study shows that a uniformly-deposited nanoparticle catalytic layer is important for improving H recovery. These results have been explained in terms of the size-induced increase in surface area, lattice contraction, and shift of Pd d-band centroid. The results of the present study, specifically the observation of decrease in recovery time has important implications for hydrogen sensor, storage, and switching applications.