Magnetron-Sputtered Thin-Film Catalyst with Low-Ir-Ru Content for Water Electrolysis: Long-Term Stability and Degradation Analysis

Abstract

Proton Exchange Membrane Water Electrolyzers (PEM-WEs) are entering the phase of commercial mass production. However, the issue of an iridium catalyst for the anode remains. This work presents an iridium-ruthenium-based catalyst (25% Ir = 158 µg cm-2, 75% Ru) prepared as a thin film on the surface-enhanced-anode of PEM-WE via magnetron sputtering. Using a strictly practical single-cell approach, without any iR corrections, we show its excellent activity – 1 A cm-2 at 1.606 V, 80 °C, and stability – 1.3 µV h-1 at 1 A cm-2 for 500 hours. Together with a purely Ir-based catalyst (158 µg cm-2), we subject it to a massive electrochemical and material analysis, showing that the thickness and interconnectivity are essential for the catalyst’s stability. This conclusion is based on results from single-cell galvanostatic measurements, Potential Electrochemical Impedance Spectroscopy (PEIS), Scanning Electron Micrsocopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), and Energy Dispersive X-ray spectroscopy (EDX). Consequently, we believe that magnetron sputtering is currently the most perspective method for preparing low-Ir-loading catalysts. Compared to the nanoparticle approach, it allows the creation of very thin films with unprecedented interconnectivity.