Enhancement of Interfacial Hydrogen Interactions with Nanoporous Gold-Containing Metallic Glass

• Published in: ACS applied materials & interfaces Vol. 13; no. 36; pp. 42613 - 42623
• Main Authors: Sarac, Baran, Ivanov, Yurii P, Micusik, Matej, Karazehir, Tolga, Putz, Barbara, Dancette, Sylvain, Omastova, Maria, Greer, A. Lindsay, Sarac, A. Sezai, Eckert, Jürgen
• Format: Journal Article
• Language: English
• Published: American Chemical Society 15-09-2021; Washington, D.C. : American Chemical Society
• Subjects: Energy, Environmental, and Catalysis Applications; Engineering Sciences; Materials; gold; metallic glass; palladium; electrochemical hydrogen; transmission electron microscopy; X-ray photoelectron spectroscopy; equivalent circuit model; thin films
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.1c08560

Contrary to the electrochemical energy storage in Pd nanofilms challenged by diffusion limitations, extensive metal–hydrogen interactions in Pd-based metallic glasses result from their grain-free structure and presence of free volume. This contribution investigates the kinetics of hydrogen–metal interactions in gold-containing Pd-based metallic glass (MG) and crystalline Pd nanofilms for two different pore architectures and nonporous substrates. Fully amorphous MGs obtained by physical vapor deposition (PVD) co-sputtering are electrochemically hydrogenated by chronoamperometry. High-resolution (scanning) transmission electron microscopy and corresponding energy-dispersive X-ray analysis after hydrogenation corroborate the existence of several nanometer-sized crystals homogeneously dispersed throughout the matrix. These nanocrystals are induced by PdH x formation, which was confirmed by depth-resolved X-ray photoelectron spectroscopy, indicating an oxide-free inner layer of the nanofilm. With a larger pore diameter and spacing in the substrate (Pore40), the MG attains a frequency-independent impedance at low frequencies (∼500 Hz) with very high Bode magnitude stability accounting for enhanced ionic diffusion. On the contrary, on a substrate with a smaller pore diameter and spacing (Pore25), the MG shows a larger low-frequency (0.1 Hz) capacitance, linked to enhanced ionic transfer in the near-DC region. Hence, the nanoporosity of amorphous and crystalline metallic materials can be systematically adjusted depending on AC- and DC-type applications.