Enhancing the durability of Au-coated Ti porous transport layers (PTLs) with a thin Pt top layer for PEM water electrolyzer applications

Abstract

The porous transport layer (PTL) is an integral component of the proton exchange membrane water electrolyzer (PEMWE), ensuring the supply of water, electrical conduction, and the removal of produced oxygen. The applied positive potential and acidic nature of the proton exchange membrane (PEM) in the PEMWE lead to an acidic environment, which promotes the formation of passivated TiO_x on the surface of the Ti PTL. The limited conductivity of TiO_x results in an increase in contact resistance and cell voltage. The precious metal coatings prevent TiO_x formation, ensure low interfacial contact resistance (ICR), and provide long-term stability. In this work, a durable bilayer coated Ti PTL was prepared by applying a thin Pt sputtered coating onto Au-electroplated PTL. The bilayer coating of Au/Pt reduced the loading of precious metals to a low level (overall 0.14 mg cm⁻²) while exhibiting outstanding corrosion resistance and cell performance. The coated Pt layer with 0.06 mg cm⁻² loading on Au coated Ti PTL exhibited a stability number 50 times higher than that of Ti PTL coated with Au alone. The balanced residual shear stress at the Au/Pt interface assisted to improve the charge transfer resistance against acid based corrosive environment. Employing the TiH/Au/Pt-0.06 coating on the Ti-PTL, a PEMWE cell performance of 1.716 V at 2.0 A cm⁻² was achieved at 80 °C under ambient pressure.