IrxRu1-XO2 Electrocatalysts for PEM Water Electrolysis

Abstract

A potential method for storing energy from renewable energy sources into hydrogen is water electrolysis [1]. Direct electrochemical splitting of water is a non-polluting way to produce pure hydrogen and oxygen. Proton Exchange Membrane Electrolysis Systems have attracted great interest as a hydrogen production method. The combination of water electrolysers and fuel cells in coupled with renewable sources could provide an ideal green and efficient mode for future energy utilization systems. PEM water electrolysers offer various advantages [2] but the major disadvantage is the relatively high anodic overpotential for the oxygen evolution reaction (OER). Oxygen evolution occurs on noble metal electrodes but metal oxides like IrO2, RuO2, etc. are generally more active for oxygen evolution than metal electrodes [3]. However, issues like electrocatalyst stability and reduction of the catalyst loading are of great and continuous research interest. In this work, unsupported IrxRu1-xO2electrocatalysts, synthesized by the modified Adams fusion method, were evaluated as potential electrodes for water splitting. Complete physicochemical characterisation of the synthesised materials was performed regarding their structure, morphology, specific surface area as well as surface composition using X-ray Diffraction (XRD), BET analysis, High Resolution Transmission Electron Microscopy (HTTEM) and X-ray Photoelectron Spectroscopy (XPS). The electrochemical performance and stability of the prepared electrocatalysts, casted on glassy carbon (GC), were evaluated with repetitive cyclic voltammetry in a typical three-cell electrode configuration using 0.5 M H2SO4solution. Furthermore, the mixed oxides have been used as anodes in Nafion® based MEAs and evaluated in a PEM electrolysis cell. The results have shown that the synthesis method leads to the formation of rutile structure oxides with high surface area (90-127 m2/g) and nano-level particle size (5-7 nm). The stability of the mixed oxides during potentiostatic cycling has been proven remarkable, while the best performing MEA with an anode of Ir0.4Ru0.6O2 reached a current density of 320 mA/cm2at 1.7 V. The work is supported by the European Space Agency (ESA).