As an efficient potential hydrogen storage and conversion system, hydrogen electrosorption and evolution mechanisms in Pd-based metallic glass thin films (MGTFs) are investigated. In this study, thin films of 55 nm thickness were deposited by dc magnetron sputtering. The amorphous structure of MGTFs and the atomically smooth interface between the MGTF and substrate were confirmed by transmission electron microscopy, whereas the compositiondependent surface roughness was obtained via atomic force microscopy. The shifts in the broad diffraction maxima for the Si and Cu additions were evaluated by X-ray diffraction. The Pd thin film (PdTF) and MGTF working electrodes were chronoamperometrically saturated in 0.5 M H 2 SO 4 solution. The formation of palladium hydride (PdH x ) in the MGTFs was investigated by X-ray photoelectron spectroscopy. Cyclic voltammograms were subsequently recorded (between −0.2 and 1.4 V) at sweep rates of 0.02 V s −1 . Electrochemical impedance spectroscopy of MGTFs and PdTF was performed in full spectrum including sorption, desorption, and evolution of hydrogen in a conventional three-electrode configuration. Electrochemical circuit modeling provided the relationship between the composition-dependent hydrogen evolution and H absorption/adsorption processes. The adsorption capacitance parameter Y ad corresponding to αand β-hydride formation in the case of Pd 0.79 Si 0.16 Cu 0.05 MGTF is ∼5 times higher than that of the crystalline Pd thin film which is in line with the decrease in the charge-transfer resistance R ct . Addition of Cu disturbs the symmetry of the glass formers, leading to remarkable changes in interfacial hydrogen bonding and diffusion of hydrogen into sublayers. Compared to other Pd-based micron-sized materials, our findings show excellent volumetric hydrogen storage capacity 4 times higher than that of the traditional counterparts of several microns, and 50% higher than the Pd thin films of the same thickness, together with high tunable capacitance, charge-transfer resistance, and diffusivity depending on the glass-forming characteristics of the nanosized MGTF.

Nanostructured metallic glass films (NMGF) can exhibit surface and intrinsic effects that give rise to unique physical and chemical properties. Here we report a facile synthesis and electrochemical, structural, and morphologic characterization of Pd-Au-Si based MGs of ~50 nm thickness supported on Si/SiO2. Impressively, the maximum total hydrogen charge stored in Pd-Au-Si nanofilm is equal to that in polycrystalline Pd films with 1 µm thickness in 0.1 M H2SO4 electrolyte. The same NMGF has a volumetric desorption charge that is more than eight times and 25% higher than that of polycrystalline PdNF and Pd-Cu-Si NMGF with the same thickness supported on Si/SiO2, respectively. A significant number of nanovoids originated from PdHx crystals, and an increase in average interatomic spacing is detected in Pd-Au-Si NMGF by highresolution TEM. Such a high amount of hydrogen sorption is linked to the unique density fluctuations without any chemical segregation exclusively observed for this NMGF.

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