Extremely fast hydrogen absorption/desorption through platinum overlayers

• Hydrogen sorption kinetics can be ultimately enhanced by two-dimensional platinum deposits.
• Hydrogen absorption in platinized Pd is faster than hydrogen evolution at Pt.
• Pt monolayers on Pd are stable even after hundreds of hydrogen sorption cycles.
• Electrosorption currents approach 1000 mA cm−2 in 3 M sulphuric acid.
• Diffusion coefficient of hydrogen have been determined for thin Pd films.

The hydrogen electrosorption in thin palladium films (50–1000 nm) was investigated at palladium electrodes covered with platinum overlayers. The results for this model system show that the rates of the hydrogen sorption/desorption are orders of magnitude higher for platinized samples with respect to pure palladium. 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 Pd layers. Diffusion coefficient, DH, determined in EIS, is two orders of magnitude higher than that previously reported for thin palladium films and approaches DH for bulk palladium. The system stability after hydrogen absorption was assessed and the sorption mechanism was discussed. Surprisingly high durability of the platinized palladium enables its use in a variety of applications where fast and selective response in the presence of hydrogen is required.