(Invited) Development of Ir-Based Electrocatalyst for Proton Exchange Membrane Water Electrolysis

PEMWE (proton exchange membrane water electrolysis) is one of the most prospective way to produce hydrogen without environmental damage. So far, various materials have been studied for more efficient water electrolysis. These studies have mainly focused on anode-side material since the over potential for the anode side reaction (H 2 O → 1/2O 2 + 2H + + 2e - ) is much higher than that of the cathode side reaction (2H + +2e - → H 2 ). Among various materials, iridium oxide (IrO x , IrO 2 ) is one of the most superior anode side material. As a company, which address PGM (platinum group metal) and their technologies, we have been developing the iridium-based catalyst for PEMWE. We have TEC77100, TEC77110 etc. as catalyst line-up for water electrolysis. TEC77100 is an amorphous-type iridium oxide catalyst with large surface area which reaches about 100 m 2 g -1 , whereas, TEC77110 is a crystalline (rutile) -type catalyst with high durability. The amorphous-type TEC77100 shows higher activity (–1.86 V@2A cm -2 , 50°C, measured in MEA with Nafion TM 115 membrane) than the rutile-type TEC77110 (–1.92 V@2A cm -2 , 50°C). In terms of durability, however, TEC77110 is superior to TEC77100. The degradation was suggested to be due to the crystallization of TEC77100 under water electrolysis condition. Except for these two types of catalyst, I’ll also introduce a catalyst to countermeasure cross leaking hydrogen in the anode side from the cathode side briefly. Figure 1