(244a) Investigation of Advanced Catalysts and Metal Oxide Supports Having Nanoporous Structures Towards Oxygen Evolution Reaction in Proton Exchange Membrane Water Electrolyzer

Recently, the proton exchange membrane water electrolysis (PEMWE) which can store excess electricity as a form of transportable hydrogen has been attracting great attention as a power-to-gas technology for sector coupling of renewable power and industrial, transportation, and heating [1]. Owing to the sluggish oxygen evolution reaction (OER) that can generate the oxygen and proton from the water and harsh reaction conditions like low pH and high voltage in the anode of the PEMWE, the precious metal oxide catalysts such as IrO₂ and RuO₂ should be applied in the membrane electrode assembly (MEA). However, there is a challenge to decrease the amount of the noble metal to the level of 0.01 g_Ir/kW [2] in the MEA to commercialize PEMWE at a GW scale. Thus, the catalysts for the OER, which are mainly iridium(Ir)-based composition, have been developed for improving the activity and stability through several approaches such as control of oxidation states [3], supported catalysts [4], and mixed metal oxides [5].

In this presentation, the effect of the porous structure generated inside the OER catalyst and the metal oxide support on the activity toward OER will be discussed. To produce a nanoporous structure, hard templates such as an ordered mesoporous silica (OMS) [5], a silica nanosphere [6], and a polystyrene nanosphere are adapted. For example, a three-dimensional mesoporous IrO₂/RuO₂ catalyst was prepared by sequential nano-replication using OMS and the Adams method [5]. The effects of the structural changes of the binary oxide catalyst on the OER activity were analyzed. As the second example, to generate the concave pore structure inside the OER catalyst, silica nanospheres of different sizes were used to induce the formation of the larger mesopores over 10 nm and macropores. The macarpore-dominat OER catalyst showed improved activity and stability. In addition, the generation of the porous structure inside the metal oxide support will be discussed to emphasize the benefit of this approach.

[1] IRENA “Innovation Landscape Brief: Renewable Power-to-Hydrogen”, International Renewable Energy Agency, Abu Dhabi, 2019 at www.irena.org/publications.

[2] M. Bernt, A. Siebel, H. A. Gasteiger, J. Electrochem. Soc., 165 (2018) F305.

[3] S. W. Lee, C. Baik, D.-H. Kim, C. Pak, J. Power Sources, 493 (2021) 229689.

[4] S. Zhao, A. Stocks, B. Rasimick, K. More, H. Xu, J. Electrochem. Soc., 165 (2018) F82.

[5] S. W. Lee, C. Baik, T.-Y. Kim, C. Pak, Catal. Today, 352 (2020) 39.

[6] C. Baik, S. W. Lee, C. Pak, Micropo. Mesopo. Mater., 309 (2020) 110567.