Oxygen Evolution Durability on Zirconia Coated Precious Metal Oxide in Sulfuric Acid

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New Energy and Industrial Technology Development Organization, Japan (NEDO) has been publishing a fuel cell and hydrogen technology development roadmap since 2005, in order for industry, academia and government to share a long-term perspective on technology development. In the field of water electrolysis, a document outlining the technical issues to be addressed in order to formulate a roadmap was published in February 2023. The situation surrounding the technological development of hydrogen is changing rapidly, and NEDO has therefore formulated a roadmap for ‘Water electrolysis’ on March 2025 [1]. The ‘Water Electrolysis Technology Development Roadmap’ divides into two periods to achieve the direction of water electrolysis technology of Japan and to design the scenario how to obtain the market for water electrolysis equipment; First, the technological requirements will be established through demonstration fields (short-term, from around 2030), and then the technological research and development to reduce the cost of water production using by cheap clean power (medium-term, around 2040). In Japan, proton exchange membrane water electrolysis (PEMWE) with small size produced by Kobelco Eco-Solutions Corp have released already installed over 200 units for 25 years. In Kofu City in Yamanashi, Japan, the Komekurayama facilities has demonstrated the Power-to-Gas (P2G) system with PEMWE electrolyser of 1.5 MW capacity [2]. However, the conventional electrocatalysts for PEMWE use precious metal materials, and especially, the iridium oxide (IrO 2 ) is used as an anode. As the iridium is by-product of platinum, its resources are very poor. Moreover, it is reported that the low loading of IrO₂ easily causes the degradation under dynamic operation condition simulated variable renewable energies (VRE) [3]. From this point of view, the durability of anode against VRE should be required for “Green Hydrogen” production. We focused on zirconium dioxide (ZrO 2 ) which has high stability in acidic solution [4]. Moreover, we found that an oxide-based film which is formed by Atomic Layer Deposition (ALD) showed bi-functional effects on the electrocatalyst for the oxygen reduction reaction and oxygen evolution reaction (OER)[5]; it can reflect the electrochemical properties of the substrate, and it can also protect the consumption of the substrate. In order to apply for PEMWE, we have investigated the OER durability of IrO 2 or RuO 2 electrodes deposited with ZrO 2 using ALD against potential cycling. Figure 1 shows the potential cycling durability of ALD-ZrO 2 on IrO 2 with and without interlayer of TaO x (ZrO 2 /IrO 2 and ZrO 2 /IrO 2 /TaO x ). The result of IrO 2 without ALD-ZrO 2 and TaO x interlayer is also shown in Fig. 1. These results are IR -free data. The loading amount of Ir was constant at 1 mg cm -2 . The vertical axis is based on geometric current density ( i geo ) at 1.55 V vs RHE from slow scan voltammetry after potential cycling from 0 to 2.0 V with scan rate of 1 V s -1 . The ZrO 2 /IrO 2 and ZrO 2 /IrO 2 /TaO x have obviously higher durability than IrO 2 , and they have still shown certain i geo after 40 k potential cycling. From ICP-MS analysis, the solubilities of Ir in the ZrO 2 /IrO 2 and ZrO 2 /IrO 2 /TaO x were one-order lower than that in the IrO 2 after 40 k cycle. The ZrO 2 /IrO 2 /TaO x has the lowest rate of degradation against potential cycling, but it also showed lowest initial i geo . Therefore, the ZrO 2 /IrO 2 was useful for having both OER activity and durability against potential cycling. Reference https://www.nedo.go.jp/library/battery_hydrogen.html https://www.nedo.go.jp/content/100956601.pdf M. Alia, and G. C. Anderson, J. Electrochem. Soc. , 166 , F282 (2019). A. Ishihara, Y. Ohgi, K. Matsuzawa, S. Mitsushima, and K. Ota, Electrochim. Acta , 55 , 8005 (2010). K. Matsuzawa, S. Yamada, Y. Kohara and A. Ishihara, Abst. 244 th ECS Meeting , I01F-2077 (2023). Figure 1

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