Low Ir-Containing Materials As Anode Catalysts for PEM Water Electrolysis

The PEM electrolysis is based on the application of IrO 2 as anode catalyst. Until now, there is no real alternative for this electrocatalyst, since the highly acidic and oxidative conditions at the anode lead to rapid corrosion. 1-3 With steadily increasing energy consumption, the demand for iridium will exceed the available resources in a few decades. As a result, the price of iridium as well as the technologies based on it will continuously increase. An enhancement of PEM electrolysis capacities on a large scale can therefore only be realized in the long term if the application of iridium is significantly reduced. 4 Therefore, our research aims at reducing the iridium content of PEM anodes while maintaining catalytic activity and stability. In this work, two approaches to save iridium were applied. On the one hand the iridium content was reduced by supporting it, on the other hand an additional, readily available metal is incorporated that is protected from corrosion by the presence of iridium and at the same time assists the iridium in catalysis. So, bimetallic included low-loading Ir and different transition metal (Ru, Sn, and Ag) nanoparticles on titanium nitride (TiN) were synthesized by using a chemical reduction method and thermal treatment. Experimentally, a IrSnO x /TiN sample in 0.5 M H 2 SO 4 with an Ir loading of 0.05 mg Ir /cm 2 achieves a mass activity of over 450 A/g Ir at 1.6 V vs RHE and an overpotential of 297 mV at 10 mA/cm 2 . The investigation includes stability tests at constant current density of 10 mA/cm 2 and determination of impedance by electrochemical impedance spectroscopy (EIS). As result, a suitable anode material was successfully achieved, which exhibits a similarly good activity and stability values compared to the IrO 2 materials that have been used industrially so far, but with a significantly reduction of iridium to 24% of the usually applied amount. 1 C. Minke, M. Suermann, B. Bensmann, R.H. Rauschenbach, Int. J. Hydrog. Energy , 2021 , 46 , 23581-23590. 2 F. Scarpelli, N. Godbert, A. Crispini, I. Aiello, Inorganics, 2022 , 10 , 115. 3 J. Gao, Y. Liu, B. Liu, K.W. Huang, ACS Nano , 2022 , 16 , 17761-17777. 4 T. Reier, H. N. Nong, D. Teschner, R. Schlögl, P. Strasser, Adv. Energy Mater. , 2017 , 7 , 1601275.