Abstract

The production of hydrogen via acidic electrochemical water splitting is an important pillar towards more sustainability. The overall water electrolysis is hindered by the slow kinetics of the oxygen evolution reaction (OER). Therefore, the catalyst material for the anode still requires optimization. Hereby, we present two highly active OER catalysts, IrOx and Ir0.4Ru0.6Ox nanoparticles (NPs), prepared by a straightforward, surfactant-free, colloidal synthetic route.1 The metallic NPs are ~1.5 nm in diameter and were deposited on carbon Ketjen Black (CKB) as well as on antimony doped tin oxide (ATO) to investigate the active phase as well as potential influences of the support material. After the colloidal synthesis and supporting, the catalysts were activated, thus undergoing a particle growth of ~1 nm. Their performance was benchmarked in terms of activity and stability using our recently developed electrochemical flow cell called gas diffusion electrode (GDE) setup.2 This novel approach allows closing the experimental gap between the two most common methods, namely the rotating disk electrode (RDE) and the membrane electrode assembly (MEA). Independently from the support, Ir0.4Ru0.6Ox shows a higher activity towards OER than IrOx at three tested temperatures, i.e. 30, 40, 60 °C. The two different support materials were also compared, and it was found that independently from the material, NPs deposited on CKB showed slightly higher activity at low current densities (up to 40 mA mgIr -1). As expected, accelerated potentiostatic stability test reveals a rapid degradation of the IrOx/CKB, while IrOx/ATO and Ir0.4Ru0.6Ox/ATO exhibit similar stability than commercially available Ir black.[1] Francesco Bizzotto, Jonathan Quinson, Alessandro Zana, Jacob J. K. Kirkensgaard, Alexandre Dworzak, Mehtap Oezaslan, Matthias Arenz, Catal. Sci. Technol., 2019, 9, 6345-6356.[2] Johanna Schröder, Vladislav A. Mints, Aline Bornet, Etienne Berner, Mohammad Fathi Tovini, Jonathan Quinson, Gustav K. H. Wiberg, Francesco Bizzotto, Hany A. El-Sayed, Matthias Arenz, JACS Au, 2021, 1, 247-251. Figure 1

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