Achieving Pt Coating-Free Anodes Using Double-Layered Catalyst Layer Structure for Polymer Electrolyte Membrane Water Electrolysis

Abstract

Achieving high-performance and cost-effective proton exchange membrane water electrolysis (PEMWE) necessitates a reduction in the use of precious group metals (PGMs) while maintaining electrolysis efficiency. However, commercial high-activity IrOx catalysts often fail to deliver optimal performance at low loadings because of electron transport problems caused by the natural oxide (TiOx) on the Ti porous transport layer (PTL) surface. This is because the high work functions of IrOx catalysts create Schottky barriers in the low-work-function TiOx, thereby deteriorating the electrical conductivity at the interface. The Pt coating is commonly employed as a protective layer; however, hundreds of nanometers of coating significantly increases the cost of the electrolyzer. To address this challenge, we propose a double-layered catalyst-layer (DL-CL) structure that enables the fabrication of Pt-coating-free anodes, with crystalline, low-work-function rutile IrO2 (R-IrO2) positioned at the PTL interface and highly active IrOx (HA-IrOx) positioned on the membrane side. The key advantage of the R-IrO2 layer over the Pt coating is its porous structure, which effectively prevents contact between HA-IrOx and TiOx with much lower loading (0.1 – 0.2 mg cm-2). The DL-CL minimizes the influence of TiOx on both performance and durability while enabling all PGMs to actively participate in the oxygen evolution reaction.