Improved utilization of IrOx on Ti4O7 supports in membrane electrode assembly for polymer electrolyte membrane water electrolyzer

Abstract

Recently, since the continuous rise in cost and scarcity of iridium, it is necessary to minimize the iridium-loading in the membrane electrode assembly (MEA) for large-scale green hydrogen production systems. In this study, IrOx/Ti4O7 catalysts were prepared to increase the utilization of IrOx in the MEA by evenly dispersing the structurally layered IrOx on Ti4O7 support via a modified simple solution-reduction method. Among the catalysts with various iridium/support ratios, the IrOx/Ti4O7(7:3) catalyst demonstrated the optimal balance of catalytic activity, catalytic stability, and corrosion resistance. IrOx/Ti4O7(7:3) catalyst demonstrated a higher mass activity of 372 mA mg-1 at 1.55 V, stable durability period of > 12 h under accelerated stability test (AST), and a low iridium dissolution rate of 0.078 ppbIr h-1. A single-cell test was further conducted using the IrOx/Ti4O7(7:3) catalyst to reveal its catalytic activity in the MEA. Consequently, the mass activity of the IrOx/Ti4O7(7:3) catalyst was found to increase by 139% in comparison to a black IrOx/None catalyst. Additionally, in the single-cell durability test (applied 1 A cm-2 for 50 h), the IrOx/Ti4O7(7:3) catalyst demonstrated a degradation rate of only 0.6 mV h-1 at 1000 A g-1 which can be estimated to have reasonable stability. Therefore, it is anticipated that the IrOx/Ti4O7(7:3) catalyst will reduce the amount of high-cost iridium in the MEA and will result in a low-cost and efficient polymer electrolyte membrane water electrolyzer system for large-scale hydrogen production.