Phase- and Surface Composition-Dependent Electrochemical Stability of Ir-Ru Nanoparticles during Oxygen Evolution Reaction
Daniel Escalera-López,Steffen Czioska,Janis Geppert,Alexey Boubnov,Philipp Röse,Erisa Saraçi,Ulrike Krewer,Jan-Dierk Grunwaldt,Serhiy Cherevko +8 more
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In this paper, the phase-dependent stability of welldefined IrxRu1−xO2 NPs prepared by flame spray pyrolysis under dynamic operating conditions was investigated.Abstract:
The increasing scarcity of iridium (Ir) and its rutile-type oxide (IrO2), the current state-of-the-art oxygen evolution reaction (OER) catalysts, is driving the transition toward the use of mixed Ir oxides with a highly active yet inexpensive metal (IrxM1−xO2). Ruthenium (Ru) has been commonly employed due to its high OER activity although its electrochemical stability in IrRu mixed oxide nanoparticles (IrxRu1−xO2 NPs), especially at high relative contents, is rarely evaluated for long-term application as water electrolyzers. In this work, we bridge the knowledge gap by performing a thorough study on the compositionand phase-dependent stability of welldefined IrxRu1−xO2 NPs prepared by flame spray pyrolysis under dynamic operating conditions. As-prepared NPs (IrxRu1−xOy) present an amorphous coral-like structure with a hydrous Ir-Ru oxide phase, which upon post-synthetic thermal treatment fully converts to a rutile-type structure followed by a selective Ir enrichment at the NP topmost surface. It was demonstrated that Ir incorporation into a RuO2 matrix drastically reduced Ru dissolution by ca. 10-fold at the expense of worsening Ir inherent stability, regardless of the oxide phase present. Hydrous IrxRu1−xOy NPs, however, were shown to be 1000-fold less stable than rutile-type IrxRu1−xO2, where the severe Ru leaching yielded a fast convergence toward the activity of monometallic hydrous IrOy. For rutiletype IrxRu1−xO2, the sequential start-up/shut-down OER protocol employed revealed a steady-state dissolution for both Ir and Ru, as well as the key role of surface Ru species in OER activity: minimal Ru surface losses (<1 at. %) yielded OER activities for tested Ir0.2Ru0.8O2 equivalent to those of untested Ir0.8Ru0.2O2. Ir enrichment at the NP topmost surface, which mitigates selective subsurface Ru dissolution, is identified as the origin of the NP stabilization. These results suggest Ru-rich IrxRu1−xO2 NPs to be viable electrocatalysts for long-term water electrolysis, with significant repercussions in cost reduction.read more
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Molecular insight in structure and activity of highly efficient, low-Ir Ir-Ni oxide catalysts for electrochemical water splitting (OER)
Tobias Reier,Zarina Pawolek,Serhiy Cherevko,Michael Bruns,Travis Jones,Detre Teschner,Sören Selve,Arno Bergmann,Hong Nhan Nong,Robert Schlögl,Karl Johann Jakob Mayrhofer,Peter Strasser +11 more
TL;DR: This study highlights a novel, highly active oxygen evolution catalyst and provides novel important insights into the structure and performance of bimetallic oxide OER electrocatalysts in corrosive acidic environments.
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Stability and deactivation of OER electrocatalysts: A review
TL;DR: In this paper , the authors discuss the correlation between OER activity and stability, methodologies and experimental techniques to study the stability and deactivation as well as the deactivation mechanisms, together with factors influencing stability.
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Essentials of High Performance Water Electrolyzers – From Catalyst Layer Materials to Electrode Engineering
Chuyen Van Pham,Daniel Escalera-López,Karl Johann Jakob Mayrhofer,Karl Johann Jakob Mayrhofer,Serhiy Cherevko,Simon Thiele,Simon Thiele +6 more
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Increased Ir–Ir Interaction in Iridium Oxide during the Oxygen Evolution Reaction at High Potentials Probed by Operando Spectroscopy
Steffen Czioska,Alexey Boubnov,Daniel Escalera-López,Janis Geppert,Alexandra Zagalskaya,Philipp Röse,Erisa Saraçi,Vitaly Alexandrov,Ulrike Krewer,Serhiy Cherevko,Jan-Dierk Grunwaldt +10 more
TL;DR: In this article, the structure of IrO$2}$ during the oxygen evolution reaction (OER) was studied by operando X-ray absorption spectroscopy (XAS) at the Ir L$3}$-edge to gain insight into the processes that occur during the electrocatalytic reaction at the anode during water electrolysis.
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