Hydrogen spillover phenomenon: Enhanced reversible hydrogen adsorption/desorption at Ta2O5-coated Pt electrode in acidic media

The current study is concerned with the preparation and characterization of tantalum oxide-loaded Pt (TaOx/Pt) electrodes for hydrogen spillover application. XPS, SEM, EDX and XRD techniques are used to characterize the TaOx/Pt surfaces. TaOx/Pt electrodes were prepared by galvanostatic electrodeposition of Ta on Pt from LiF–NaF (60:40 mol%) molten salts containing K2TaF7 (20 wt%) at 800 °C and then by annealing in air at various temperatures (200, 400 and 600 °C). The thus-fabricated TaOx/Pt electrodes were compared with the non-annealed Ta/Pt and the unmodified Pt electrodes for the hydrogen adsorption/desorption (Hads/Hdes) reaction. The oxidation of Ta to the stoichiometric oxide (Ta2O5) increases with increasing the annealing temperature as revealed from XPS and X-ray diffraction (XRD) measurements. The higher the annealing temperature the larger is the enhancement in the Hads/Hdes reaction at TaOx/Pt electrode. The extraordinary increase in the hydrogen adsorption/desorption at the electrode annealed at 600 °C is explained on the basis of a hydrogen spillover–reverse spillover mechanism. The hydrogen adsorption at the TaOx/Pt electrode is a diffusion-controlled process.