Effect of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) on low-iridium catalyst layer for proton exchange membrane water electrolysis

Reducing iridium loading in membrane electrode assembly (MEA) without sacrificing electrochemical performance plays a critical role in lowering the cost of proton exchange membrane water electrolyzers. However, low Ir loading often results in insufficient percolation of IrO2 particles and high interfacial resistance between the catalyst layer and the porous transport layer, causing reduced electrochemical performance and long-term durability issues. Herein, a MEA incorporating the conductive polymers of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) as a binder and dispersant is investigated under 0.3 mgIr cm−2 loading. The zeta potential and morphological experiments confirm that the incorporation of PEDOT:PSS to the catalyst ink can improve the ink stability, reduce the catalyst particle size and create more pores in the catalyst layer. The MEA using a 1:1 ratio of PEDOT:PSS to Nafion achieves an enhanced current density of 1.68 [email protected] A cm−2 at 80 °C (vs. a MEA using Nafion only, 1.75 [email protected] A cm−2). The Raman results indicate that the PEDOT in the presence of Nafion exhibits a more conductive quinoid resonance structure than PEDOT. In situ durability testing of the MEA for over 800 h demonstrates a degradation rate of 48.7 μV h−1 at 1.0 A cm−2 and 80 °C.