Synthesis of Ru_xIr_1-xO₂ Anode Electrocatalysts for Proton Exchange Membrane Water Electrolysis

Abstract

Ru and Ir based materials were prepared by the thermal decomposition of polymeric precursor's method. The anode catalysts free from carbon substrate were obtained by tailoring the reaction process to avoid occurrence of CO2 formation during water electrolysis. Various Ir contents were added in the Ru catalytic compositions for improving the oxidation-resistance of RuO2 which was the best metallic oxide in H2O splitting. Their physical characterizations revealed the presence of agglomerates due probably to the heat treatment process consisting in the removal of organic carbon at 400 ºC. The prevalent existence of RuO2 and IrO2 in the anode materials was confirmed by XPS experiments and the electrochemical measurements enabled to show that RuxIr1-xO2 materials were more active towards water oxidation than IrO2 catalyst. The O2 evolution process started at 1.45 V with Ru0.9Ir0.1O2 in the anodic compartment of a 25 cm2 Proton Exchange Membrane Water Electrolyzer at 60ºC.

Iridium‐Based Catalysts for Solid Polymer Electrolyte Electrocatalytic Water Splitting

“…Therefore, the oxygen‐evolving activity and stability of Ir and Ru binary oxides are much higher than that of single Ir or Ru. Extensive research has been performed on Ir−Ru alloys and their oxides . Mixed oxides formed by RuO 2 and IrO 2 retain the useful properties of both components (high activity of RuO 2 and high stability of IrO 2 ).…”

“…Methods to form mixed Ru−Ir oxides fall into two categories: a direct and dry film formation approach (i.e., reactive spray deposition technology) or wet powder synthesis followed by an electrode formation step (i.e., thermal decomposition, hydrolysis method, Adams fusion, or a sol–gel method) . The mixed oxides may be composed of homogeneous solid solutions of Ru and Ir, or present as IrO 2 and RuO 2 separate phases …”

“…Along with increasing Ru content in Ir x Ru 1− x O 2 , the average particle size and crystallinity of the catalysts increased. Generally, Ir x Ru 1− x O 2 compounds are observed to be more active than that of IrO 2 and more stable than that of RuO 2 . The synthetic routes have a great influence on atomic mixing, surface segregation, and particle size.…”