Phase- and Surface Composition-Dependent Electrochemical Stability of Ir-Ru Nanoparticles during Oxygen Evolution Reaction

Escalera‐López, Daniel; Czioska, Steffen; Geppert, Janis; Boubnov, Alexey; Röse, Philipp; Saraçi, Erisa; Krewer, Ulrike; Grunwaldt, Jan‐Dierk; Cherevko, Serhiy

doi:10.1021/acscatal.1c01682

Cited by 95 publications

(109 citation statements)

References 130 publications

(238 reference statements)

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“…For the uncalcined sample, a small drop in current is already observed at 1.45 V, which can be attributed to the dissolution of the catalyst. This agrees with previous investigations, ,− which showed much higher dissolution stability for the calcined sample. For both samples, a decrease in current is observed during the applied highest OER potentials (1.6 and 1.55 V, respectively), which is attributed to bubble accumulation on the electrode.…”

Section: Resultssupporting

confidence: 93%

“…The recorded dissolution rates showed a selective Ir dissolution under OER potentials, where integrated Ir dissolution values per OER potential hold were 3 orders of magnitude higher for uncalcined than for calcined IrO 2 FSP catalysts. This is in good agreement with previous reports that correlated higher stabilities under OER operation for IrO x -based materials with higher crystallinities induced by thermal treatment. ,, Interestingly, a steady-state in the Ir dissolution rates after the fifth MES cycle was found, regardless of the degree of calcination, which can be further understood by our recently proposed dissolution stability benchmarking metric: the stability number ( S -number, details in ref , cf. also Figure S17).…”

Section: Resultssupporting

confidence: 92%

“…This is in good agreement with previous reports that correlated higher stabilities under OER operation for IrO xbased materials with higher crystallinities induced by thermal treatment. 48,54,55 Interestingly, a steady-state in the Ir dissolution rates after the fifth MES cycle was found, regardless of the degree of calcination, which can be further understood by our recently proposed dissolution stability benchmarking metric: the stability number (S-number, details in ref 9, cf. also Figure S17).…”

Section: ■ Resultsmentioning

confidence: 63%

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Increased Ir–Ir Interaction in Iridium Oxide during the Oxygen Evolution Reaction at High Potentials Probed by Operando Spectroscopy

et al. 2021

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The structure of IrO2 during the oxygen evolution reaction (OER) was studied by operando X-ray absorption spectroscopy (XAS) at the Ir L3-edge to gain insight into the processes that occur during the electrocatalytic reaction at the anode during water electrolysis. For this purpose, calcined and uncalcined IrO2 nanoparticles were tested in an operando spectroelectrochemical cell. In situ XAS under different applied potentials uncovered strong structural changes when changing the potential. Modulation excitation spectroscopy combined with XAS enhanced the information on the dynamic changes significantly. Principal component analysis (PCA) of the resulting spectra as well as FEFF9 calculations uncovered that both the Ir L3-edge energy and the white line intensity changed due to the formation of oxygen vacancies and lower oxidation state of iridium at higher potentials, respectively. The deconvoluted spectra and their components lead to two different OER modes. It was observed that at higher OER potentials, the well-known OER mechanisms need to be modified, which is also associated with the stabilization of the catalyst, as confirmed by in situ inductively coupled plasma mass spectrometry (ICP-MS). At these elevated OER potentials above 1.5 V, stronger Ir–Ir interactions were observed. They were more dominant in the calcined IrO2 samples than in the uncalcined ones. The stronger Ir–Ir interaction upon vacancy formation is also supported by theoretical studies. We propose that this may be a crucial factor in the increased dissolution stability of the IrO2 catalyst after calcination. The results presented here provide additional insights into the OER in acid media and demonstrate a powerful technique for quantifying the differences in mechanisms on different OER electrocatalysts. Furthermore, insights into the OER at a fundamental level are provided, which will contribute to further understanding of the reaction mechanisms in water electrolysis.

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Section: Resultssupporting

confidence: 93%

Section: Resultssupporting

confidence: 92%

Section: ■ Resultsmentioning

confidence: 63%

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Increased Ir–Ir Interaction in Iridium Oxide during the Oxygen Evolution Reaction at High Potentials Probed by Operando Spectroscopy

et al. 2021

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“…Their effect on the dissolution should, therefore,b em ore thoroughly studied in future studies. [85] Ad issolution study by Jovanovic ět al. [86] on different iridium-based nanoparticles showed some discrepancyf rom the disk measurements carried out by Cherevko et al, [11,55] which was attributed to ap ossible particle size effect.…”

Section: Methodsmentioning

confidence: 99%

Inter‐relationships between Oxygen Evolution and Iridium Dissolution Mechanisms

et al. 2022

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Figure 1. a) Electrochemical oxide pathway. [13] Copyright 2016, John Wiley and Sons. b) Cationic redox mechanism proposed by Kçtz et al. [21] Copyright 1984, IOP Publishing. c) Scheme of the OER, including the formation of an OOH intermediate, as detected by Sivasankar et al. [24] Copyright 2011, AmericanC hemical Society.d )Schematic representation of O2pbands penetrating into Ir dorbitals and triggering an anionic redox process. [27] Copyright 2016, Springer Nature. e) OER scheme showing the formation of oxyl species, as aresult of hybridization of Ir and O orbitals, which are prone to nucleophilic attack by water and the formation of an OÀObond. [33] Copyright2 019, Elsevier.

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“…[ 83 ] Such Ir enrichment was found in an Ir x Ru 1‐ x O 2 catalyst after selective Ru dissolution, which stabilized the Ir x Ru 1‐ x O 2 nanoparticles. [ 84 ] In addition, the selective exposure of specific crystal planes of catalysts with lower energies can also protect the active sites and thus improve their stability. [ 39 ] In addition, charge redistribution helps improve the stability in IrRu catalysts.…”

Section: Acidic Oer Catalysts With Long‐term Stabilitymentioning

confidence: 99%

Low‐Dimensional Electrocatalysts for Acidic Oxygen Evolution: Intrinsic Activity, High Current Density Operation, and Long‐Term Stability

Liu

et al. 2022

Adv Funct Materials

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Water electrolysis can occur in alkaline, neutral, and acidic media. Neutral water electrolysis is environmentally friendly and suitable for microbial electrolysis, but is faced with problems of sluggish kinetics induced by the low concentration of adsorbed reactants on the catalyst surface and a large energy loss during the reaction. [4] In comparison, alkaline water electrolysis has a wider application due to the low cost and good stability of the catalysts but currently suffers from problems of a high ohmic resistance, sluggish kinetics, and a low current density. [5] Compared with neutral and alkaline water electrolysis, acidic water electrolysis such as a proton exchange membrane water electrolyzer (PEMWE) can reach a higher current density (>2 A cm -2 ) due to higher proton conductivity and lower ohmic resistance. In addition, PEMWE has the advantages of high purity H 2 production, a fast response speed and few side reactions. [6] In recent years, much effort has been devoted to acidic water electrolysis, but there are still several challenges for its large-scale applications. A major challenge is the poor performance at the anode, which requires high-performance catalysts to reduce the overpotential and improve the overall efficiency. [7] First, the intrinsic activity of acidic OER catalysts needs to be improved due to the sluggish four-electron-transfer kinetics of the OER compared with the two-electron-transfer hydrogen evolution reaction (HER), which needs to be improved. Second, most reported catalysts cannot reach high current density (>200 mA cm -2 ) and meet the requirements of industrial use. Third, the dissolution and peeling of the catalyst from the electrode in oxidative and corrosive OER conditions worsen their activity and stability, and thus limits the long-term use of these catalysts.OER occurs at the interface between a catalyst and an acidic electrolyte, where the absorption and desorption of the intermediates is crucial for the whole catalytic reaction. Therefore, it is important to control the absorption and desorption energy of intermediates to improve the overall reaction efficiency. [8] Low-dimensional materials including 0D (nanoparticles/ nanodots), 1D (nanorods/nanowires), and 2D (nanosheets/ nanoplates) have received much attention in the energy conversion field because of their high specific surface area, abundant active sites, tunable electronic structure, and possible different

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Phase- and Surface Composition-Dependent Electrochemical Stability of Ir-Ru Nanoparticles during Oxygen Evolution Reaction

Cited by 95 publications

References 130 publications

Increased Ir–Ir Interaction in Iridium Oxide during the Oxygen Evolution Reaction at High Potentials Probed by Operando Spectroscopy

Increased Ir–Ir Interaction in Iridium Oxide during the Oxygen Evolution Reaction at High Potentials Probed by Operando Spectroscopy

Inter‐relationships between Oxygen Evolution and Iridium Dissolution Mechanisms

Low‐Dimensional Electrocatalysts for Acidic Oxygen Evolution: Intrinsic Activity, High Current Density Operation, and Long‐Term Stability

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