Structural optimization of TiO2 supported IrO2 catalyst for proton exchange membrane water electrolysis
Darius Hoffmeister, S.M. Finger, Ramesh Pokhrel, Andreas Körner, Birk Fritsch, Simon Thiele, Andreas Hutzler, Chuyen Van Pham
Abstract
Reducing the iridium loading in proton exchange membrane water electrolysis (PEMWE) is essential, and catalysts with a low iridium content are one viable approach to reach this goal. This study investigates a series of TiO 2 supported IrO 2 catalysts with three different TiO 2 support-particle sizes (3, 14, and 56 m 2 g −1 ) and three different iridium oxide contents (30, 50, and 70 wt%). We demonstrate that, for optimal iridium utilization, the nominal IrO 2 shell thickness should be maximized, which is readily achieved by employing low-surface area supports. Following this strategy, a TiO 2 @IrO 2 catalyst with 50 wt% IrO 2 is designed, whose single-cell performance exceeds a commercial reference catalyst (88 wt% IrO 2 ) by 43 mV at 2 A cm −2 at a low iridium loading of 0.1 mg Ir cm −2 . Furthermore, we find a strong correlation between powder conductivity measurements and single-cell high frequency resistance, underlining the importance of catalyst conductivity.