Development of Thin-Film Nanoporous Ruthenium Electrocatalysts Using Atom Probe Tomography

Abstract

Dealloying corrosion has been used to create high surface area nanoporous metals with promising catalytic properties towards alkaline water electrolysis [1], [2]. The selective dissolution of the less-noble metal from a solid-solution alloy results in a 3D open-pore, nanostructured substrate which is chemically rich in the more noble metal. Ruthenium, the cheapest Pt-group metal [3], has desirable catalytic properties for the hydrogen evolution reaction, however making nanoporous ruthenium (NPR) substrates by dealloying has been challenging due to its limited miscibility with Ag and Cu, compared to the more widely studied Au. Hence, the potential improvement of Ru catalytic properties through dealloying Ru-based systems remains unexploredIn this study, we use magnetron sputtering to make metastable, single-phase, Ag-Ru thin films, with the aim of electrochemically dealloying them to create uniformly NPR substrates. The impact of thin-film structures and chemistry on subsequent dealloying behaviors were investigated by integrating electrochemical measurements with high-resolution characterization techniques including atom probe tomography (APT), electron backscatter diffraction (EBSD), and scanning electron microscopy (SEM). Furthermore, we correlate the thin-film properties studied with the structure and chemistry of NPR formed during dealloying. Amongst the valuable insights attained, we reveal atomic-scale compositional fluctuations in as-deposited non-equilibrium Ag-Ru, that impact the nanoligament compositions in dealloyed nanoporous ruthenium. Finally, the electrocatalytic performance of different NPR substrates are reported for hydrogen evolution reaction. Thereby, advancing the development of novel Ru-based nanoporous electrocatalysts and outlining pathways for future guided optimization.[1] Erlebacher, J., Newman, C. & Sieradzki, K. Fundamental physics and chemistry of nanoporosity evolution during dealloying. RSC Nanosci. Nanotechnol. 11–29 (2012). doi:10.1039/9781849735285-00011[2] J. Tian et al., “Dealloying of an amorphous TiCuRu alloy results in a nanostructured electrocatalyst for hydrogen evolution reaction,” Carbon Energy, vol. 5, no. 8, Aug. 2023, doi: 10.1002/cey2.322.[3] Johnson Matthey Inspiring science, enhancing life. Available at: https://matthey.com/products-and-markets/pgms-and-circularity/pgm-management (Accessed: 18 December 2023).