Prospects of Making Nanoporous Ruthenium from Transition Metal-Ru Alloys

Dealloying of Ag-Au alloys is known to produce Au-rich, bicontinous, nanoporous layers [1-2]. The high functionality of nanoporous gold, demonstrated in a variety of applications [3-4], invites us to study the fabrication of other nanoporous metals of interest by exploiting corrosion processes. Recent studies have shown how the use of ruthenium, which is the cheapest Pt-group metal, for catalysis could be expanded from the classical example of CO oxidation [5], to other important reactions such as hydrogen evolution [6]. Although several porous/non-porous Ru-containing systems have been studied before [7-8], there remains a knowledge-gap with regards to the design and optimization of Ru-based catalysts. As a first step towards the development of nanoporous ruthenium by metal corrosion, this work shall focus on the design of binary transition metal-Ru systems. High resolution APT (atom probe tomography) studies of Ru-lean alloys (Fe-Ru and Ni-Ru) will assess the bulk microstructure of as-cast alloys and how it is affected by processing conditions [9]. Furthermore, pathways to inducing Ru-surface enrichment in different thermochemical environments (oxidative/inert/reductive) will be investigated by combined APT and XPS (X-ray photoelectron spectroscopy) [10]. The results of this study will provide guidance to making low-cost, high surface area nanoporous ruthenium catalysts by dealloying in acidic media. References [1] H. W. Pickering and P. R. Swann. Electron metallography of chemical attack upon some alloys susceptible to stress corrosion cracking, Corrosion, 1963, 19, 373t. [2] R.C. Newman. Dealloying, Shreir's Corrosion (fourth ed.), 2, Elsevier (2010), 801-809. [3] A.A. Vega, R.C. Newman. Methanol electro-oxidation on nanoporous metals formed by dealloying of Ag–Au–Pt alloys, Journal of Applied Electrochemistry, 2016, 46, 995-1010. [4] Y. Xue, J. Markmann, H. Duan, J. Weissmüller and Patrick Huber. Switchable imbibition in nanoporous gold, Nature Communications, 2014, 5, 4237. [5] N.W. Cant, P.C. Hicks and B.S. Lennon. Steady-state oxidation of carbon monoxide over supported noble metals with particular reference to platinum, Journal of Catalysis, 1978, 54, 372-383. [6] B. Lu, L. Guo, F. Wu, Y. Peng, J.E. Lu, T.J. Smart, N. Wang, Y.Z. Finfrock, D. Morris, P. Zhang, N. Li, P. Gao, Y. Ping and S. Chen. Ruthenium atomically dispersed in carbon outperforms platinum toward hydrogen evolution in alkaline media, Nature Communications, 2019, 10, 631. [7] T. Li, P.A.J. Bagot, E.A. Marquis, S.C.E. Tsang and G.D.W. Smith. Characterization of oxidation and reduction of Pt-Ru and Pt-Rh-Ru alloys by atom probe tomography and comparison with Pt-Rh, Journal of Physical Chemistry C, 2012, 116, 17633–17640. [8] M. Hakamada, J. Motomura, F. Hirashima and M. Mabuchi. Preparation of nanoporous ruthenium catalyst and Its CO oxidation characteristics, Materials Transactions, 53, 2012, 524-530. [9] L. Li, Z. Li, A.K. da Silva, Z. Peng, H. Zhao, B. Gault, D. Raabe. Segregation-driven grain boundary spinodal decomposition as a pathway for phase nucleation in a high-entropy alloy, Acta Materialia, 2019, 178, 1-9. [10] K. Schweinar, O. Kasian, R.L. Nicholls, C.R. Rajamathi, P. Zeller, M. Amati, L. Gregoratti, D. Raabe, M. Greiner, and B. Gault. An integrated workflow to investigate electrocatalytic surfaces by correlative X-ray Photoemission Spectroscopy, Scanning Photoemission Electron Microscopy and Atom Probe Tomography, Microscopy and Microanalysis, 2019, 25, 306–307.