Importance of Surface IrO_xin Stabilizing RuO₂for Oxygen Evolution

Abstract

The high precious metal loading and high overpotential of the oxygen evolution reaction (OER) prevents the widespread utilization of polymer electrolyte membrane (PEM) water electrolyzers. Herein we explore the OER activity and stability in acidic electrolyte of a combined IrO/RuO system consisting of RuO thin films with submonolayer (1, 2, and 4 Å) amounts of IrO deposited on top. Operando extended X-ray absorption fine structure (EXAFS) on the Ir L-3 edge revealed a rutile type IrO structure with some Ir sites occupied by Ru, IrO being at the surface of the RuO thin film. We monitor corrosion on IrO/RuO thin films by combining electrochemical quartz crystal microbalance (EQCM) with inductively coupled mass spectrometry (ICP-MS). We elucidate the importance of submonolayer surface IrO in minimizing Ru dissolution. Our work shows that we can tune the surface properties of active OER catalysts, such as RuO, aiming to achieve higher electrocatalytic stability in PEM electrolyzers.

Trends in Activity and Dissolution on RuO2 under Oxygen Evolution Conditions: Particles versus Well-Defined Extended Surfaces

“…Such understanding corroborates our earlier work on the role of surface Ir in stabilising RuOx 18 and surface Ti on MnOx 39 , without compromising activity. Such work points to ample opportunities for engendering further improvements to the stability of oxygen evolution catalysts under acidic conditions.…”

“…Only oxides based on Ir 10,11 show reasonable activity and stability, even though they still corrode at low, yet appreciable rate [12][13][14][15] . Oxides based on Ru are more active but less stable than those based on Ir 14,[16][17][18][19] . RuO2 corrodes via the following reaction 20 :…”

Synthesis of Iridium Nanocatalysts for Water Oxidation in Acid: Effect of the Surfactant

“…To ensure a sustainable use of this precious metal, a careful design of the catalyst is needed . Much effort has been recently devoted to develop Ir‐based nanoparticulate catalysts to maximise the electrochemical activity per amount of Ir …”

Layered and two dimensional metal oxides for electrochemical energy conversion

“…In both acidic and basic media, RuO 2 and IrO 2 are considered the state-of-the-art materials for the OER reaction. [28][29][30][31] However, the high cost of these materials compared to other metals combined with their lack of abundance renders their widespread use in commercial devices uneconomical. 32,33 One should also note, another alternative way to potentially increase the efficiency of the HER is to couple this reaction with a thermodynamically more favourable reaction such as the Urea Oxidation Reaction (UOR).…”