Exceptionally Fast Hydrogen Absorption and Desorption through Platinum Overlayers
The hydrogen electrosorption in thin palladium films (50-1000nm) has been investigated at electrodes covered with platinum overlayers. The highest absorption kinetics have been observed for Pd electrodes fully covered with 1 – 3 platinum monolayers. By means of electrochemical impedance spectroscopy (EIS) we have shown that the process is diffusion limited at platinized samples. Diffusion coefficient, DH, determined in EIS, is two orders of magnitude higher than that previously reported for thin palladium films and approaches DHfor bulk palladium. The approach provides insight into the mechanism of hydrogen absorption and the process of hydrogen transport in metals-hydrogen systems.
Surprisingly high stability of the platinized palladium enable its use in heterogeneous catalysis, hydrogenation reactions, or hydrogen purification. It should be stressed that palladium has already been proven to serve as an efficient catalyst to facilitate hydrogen insertion into other metal hydrides. Therefore, another set of potential applications is related to hydrogen storage or sensing systems, where fast and selective reaction in the presence of hydrogen is required.