Highly Active and Stable Iridium Pyrochlores for Oxygen Evolution Reaction

Abstract

Proton exchange membrane water electrolysis (PEMWE) is a promising technology for electricity-to-fuel conversion which allows for direct production of hydrogen from water. One of the key problems limiting widespread implementation of PEMWE into energy systems is the sluggish kinetics of the anodic process: the oxygen evolution reaction (OER). Additionally, state-of-the-art OER materials contain large amounts of low abundant noble metals (Ru, Ir), and therefore, development of low-cost, highly active and stable OER catalysts remains an important challenge. We developed a synthetic approach to the iridium pyrochlores−complex oxides of iridium with reduced content of the noble metal as compared to IrO 2 . The materials were synthesized from molten sodium nitrate (Adams fusion method) at moderate temperatures (500−575 °C) and consist of highly crystalline iridium pyrochlore nanoparticles with surface areas of up to 40 m 2 g −1 , which is a significant improvement compared to the traditional high temperature solid-state synthesis. Electrochemical measurements in acidic media showed that yttrium and bismuth pyrochlore catalysts possess high OER activity approaching the activity of state-of-the-art IrO 2 nanoparticles. High intrinsic activities and stability behavior of yttrium iridium catalysts were correlated with the formation of the highly active IrO x surface layer due to leaching of the Y 3+ cations into the electrolyte solution, revealed both experimentally and computationally using density functional theory calculations.

Ruthenium Oxide Nanosheets for Enhanced Oxygen Evolution Catalysis in Acidic Medium

“…[6,7] In an acidic environment, however, only a limited number of OER catalysts are known to operate in a stable way. This has already led to the development of several single-phase and multiphase oxides such as double perovskites Ba 2 MIrO 6 (M = Y, La, Ce, Pr, Nd, and Tb), [10] pyrochlores Y 2 Ir 2 O 7 , [11] [12] The fabrication of highly active and robust hexagonal ruthenium oxide nanosheets for the electrocatalytic oxygen evolution reaction (OER) in an acidic environment is reported. [8] While iridium oxides are more robust, ruthenium oxides exhibit better performance.…”

Free‐Sustaining Three‐Dimensional S235 Steel‐Based Porous Electrocatalyst for Highly Efficient and Durable Oxygen Evolution

“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] However,t he efficiencyo ft his methodi sm ainly restricted by the sluggish anodic oxygen evolution reaction (OER), the rate-limitings tep for overall water splitting, which involves four sequential proton-coupled electron-transfer steps and the formation of an oxygenoxygen bond. [30,31] However, scarcity,h igh acquisition costs, and poor performance over long-term OER measurements in alkaline solution hamper their suitability for widespread practical applications. [30,31] However, scarcity,h igh acquisition costs, and poor performance over long-term OER measurements in alkaline solution hamper their suitability for widespread practical applications.…”

Nanopolyaniline Coupled with an Anticorrosive Graphene as a 3D Film Electrocatalyst for Efficient Oxidation of Toluene Methyl C−H Bonds and Hydrogen Production at Low Voltage

“…However, the electrochemical technique has proved to be of limited applicability due to lack of efficient electrode materials. Most of the reported electrode materials are precious metals (e.g., platinum, gold) and noble metal oxides (e.g., IrO x and RuO x ); however, they afford low efficiency . The use of earth‐abundant elements as electrocatalysts for oxidation reactions is a research hot topic .…”