Hydrogen spillover phenomenon: Enhanced reversible hydrogen adsorption/desorption at Ta_2O_5-coated Pt electrode in acidic media

摘要

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 TaO_x/Pt surfaces. TaO_x/Pt electrodes were prepared by galvanostatic electrodeposition of Ta on Pt from LiF-NaF (60:40 mol%) molten salts containing K_2TaF_7 (20wt%) at 800℃ and then by annealing in air at various temperatures (200, 400 and 600℃). The thus-fabricated TaO_x/Pt electrodes were compared with the non-annealed Ta/Pt and the unmodified Pt electrodes for the hydrogen adsorption/desorption (H_(ads)/H_(des)) reaction. The oxidation of Ta to the stoichiometric oxide (Ta_2O_5) 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 H_(ads)/H_(des) reaction at TaO_x/Pt electrode. The extraordinary increase in the hydrogen adsorption/desorption at the electrode annealed at 600℃ is explained on the basis of a hydrogen spillover-reverse spillover mechanism. The hydrogen adsorption at the TaO_x/Pt electrode is a diffusion-controlled process.