Durability Study of Anode Catalysts from Iridium-Based Titanium Supports in Polymer Electrolyte Membrane Water Electrolyzers

Abstract

Electrochemical water splitting has been recognized as one of the most promising methods for hydrogen production. Electrocatalysts are critical materials in water electrolysis. The sluggish reaction kinetics for the anode reaction, oxygen evolution reaction (OER), hinders the development of water electrolysis technology. Iridium-based material is an leading catalyst for OERs, but the high scarcity and high cost limit its application in polymer electrolyte membrane water electrolyzers (PEMWEs). Moreover, Ir dissolution during the OER operation is another limitation. Robust and effective support-based catalysts should be developed to reduce the catalyst loading and provide high durability in PEMWEs. Herein, we synthesized an OER catalyst of Ir deposited on Ti supports using a polyol reduction method. The Ir/Ti catalysts with different Ir loading were prepared and applied in the PEMWEs for performance evaluation. The cell performance (Figure 1A) with the optimized catalyst (Ir/Ti-50%Ir) exhibited better performance than the commercial IrO2 in the same low loading (0.1 mgIr cm-2) and very close current density (<10 mV difference) achieved at 4 A cm-2 as to the electrode with a high catalyst loading (0.4 mgIr cm-2). Accelerated stress tests (ASTs) performed between 2.0 V and 1.45 V were used to investigate the catalyst durability in the PEMWEs. Figure 1B shows a volcano shape for the correlation between degradation behavior and Ir percent in the catalyst. Our results, combined with the ex-situ characterization, provide a synthesis strategy for robust OER catalysts, and elucidate the catalyst degradation mechanism in the PEMWEs. Figure 1