Thermodynamic explanation of the universal correlation between oxygen evolution activity and corrosion of oxide catalysts

Binninger, Tobias; Mohamed, Rhiyaad; Waltar, Kay; Fabbri, Emiliana; Levecque, Pieter; Kötz, R.; Schmidt, Thomas J.

doi:10.1038/srep12167

Cited by 356 publications

(408 citation statements)

References 36 publications

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“…11 An intimate correlation between structural changes of the metal oxide and the onset of OER has been explained recently by the direct evolution of lattice oxygen (LOER) that is thermodynamically favoured under OER conditions. 12 Presented in Figure 10 are iridium EXAFS spectra for the IrO 2 -TiO 2 catalyst in k-space and in R-space which were recorded in situ within 1 min acquisition time at an electrode potential of 1.3 V RHE . The quality of the EXAFS data is reflected in Figure 10a, which shows that reliable data could be collected up to k ≈ 12 Å −1 .…”

Section: Resultsmentioning

confidence: 99%

“…Such information is crucial in order to understand the catalytically active state and the degradation properties of the metal oxide catalyst under OER conditions. [10][11][12][13] Electrochemical cells for in situ X-ray spectroscopy studies of electrocatalysts have been published based on a PEFC-type design with a non-liquid polymer electrolyte. [14][15][16][17] Although for PEFC-related catalyst investigations such setups are advantageous, their use remains restricted to available polymer electrolytes.…”

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confidence: 99%

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Electrochemical Flow-Cell Setup for In Situ X-ray Investigations

Binninger

Fabbri

Pătru

et al. 2016

J. Electrochem. Soc.

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109

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An electrochemical three-electrode flow-cell is presented for in situ small-angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS) experiments in transmission mode at synchrotron X-ray sources. The cell also allows for in situ XAS performed in fluorescence mode. Constant experimental conditions, even under moderate gas evolution, are provided by the electrolyte flow with controlled gas saturation. A special configuration of working and counter electrode, respectively, yields low residual ohmic resistance in three-electrode measurements that enables the study of thick porous electrodes of active high surface area materials. The cell proved its functionality and reliability in two studies: First, an in situ anomalous SAXS experiment for the high-potential degradation properties of a Pt/IrO 2 -TiO 2 catalyst for the oxygen reduction reaction at polymer electrolyte fuel cell cathodes; and second, an in situ XAS study of the electronic state of Ir centers inside an IrO 2 -TiO 2 catalyst under oxygen evolution conditions. © The Author Modern research in electrocatalysis makes extensive use of in situ X-ray techniques that provide information about the structure and the electronic state of catalyst materials under electrochemical potential control. The reason for this is the limited, merely indirect information about the state of the catalyst that can be deduced from purely electrochemical testing like cyclic voltammetry (CV) which often does not allow for an unambiguous interpretation of the data. In order to develop an understanding at a more fundamental level, additional information is required about the potential-dependent state of electrocatalyst materials that can be provided by synchrotron-based techniques like X-ray scattering or X-ray absorption spectroscopy.One example is the investigation of polymer electrolyte fuel cell (PEFC) Pt cathode catalyst degradation. Different mechanisms have been proposed for the loss of electrochemically active Pt surface area (ECSA) that occurs most severely at transient high-potential spikes during PEFC start and stop.1,2 Processes like agglomeration of primary Pt particles due to migration or carbon support corrosion, Pt loss due to dissolution, and growth of primary Pt nanoparticles due to dissolution/redeposition cycles have been considered 3,4 and quantified for different operation conditions and electrochemical environments. The most common technique applied for this purpose is transmission electron microscopy (TEM), which has the convenient advantage that changes of the Pt nanoparticle structure can be directly visualized, especially with the use of identical location TEM (IL-TEM).5 Although successfully demonstrated, 6 in situ TEM remains limited to certain electrochemical systems. Whereas the strength of TEM lies in the direct imaging of individual catalyst particles, it is challenging to extract quantitative statistical information about the entire catalyst sample from TEM analysis. Finally, the distinction of Pt nanoparticles from the support material p...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Electrochemical Flow-Cell Setup for In Situ X-ray Investigations

Binninger

Fabbri

Pătru

et al. 2016

J. Electrochem. Soc.

Self Cite

109

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“…In this case, an increase in Ir content on the surface results in adsorption of oxygen-containing radicals mainly on Ir active sites and an increase in overpotential and Tafel slope of OER. Taking into account the parallelism between OER and dissolution, 59,66 the amount of dissolved Ir should increase with Ir content (Fig. 4b).…”

Section: Discussionmentioning

confidence: 99%

On the Origin of the Improved Ruthenium Stability in RuO₂–IrO₂Mixed Oxides

Kasian

Geiger

Stock

et al. 2016

J. Electrochem. Soc.

114

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High oxygen evolution reaction activity of ruthenium and long term stability of iridium in acidic electrolytes make their mixed oxides attractive candidates for utilization as anodes in water electrolyzers. Indeed, such materials were addressed in numerous previous studies. The application of a scanning flow cell connected to an inductively coupled plasma mass spectrometer allowed us now to examine the stability and activity toward oxygen evolution reaction of such mixed oxides in parallel. The whole composition range of Ir-Ru mixtures has been covered in a thin film material library. In the whole composition range the rate of Ru dissolution is observed to be much higher than that of Ir. Eventually, due to the loss of Ru, the activity of the mixed oxides approaches the value corresponding to pure IrO 2 . Interestingly, the loss of only a few percent of a monolayer in Ru surface concentration results in a significant drop in activity. Several explanations of this phenomenon are discussed. It is concluded that the herein observed stability of mixed Ir-Ru oxide systems is most likely a result of high corrosion resistance of the iridium component, but not due to an alteration of the material's electronic structure. Renewable primary energies such as solar energy, wind energy and ocean energy receive more and more attention and are increasingly installed around the world.1-3 It is anticipated that renewables will eventually replace traditional fossil fuel-burning and nuclear power plants. However, intermittent power supply of renewables means that energy needs to be buffered. Thereby, hydrogen produced by water electrolysis is considered as an ideal energy carrier to adjust the balance between the generation of power by renewable primary energy and energy demand for end-use.3-5 Currently, acidic proton exchange membrane water electrolysis (PEMWE) is considered as a promising technology for this purpose. However, the widespread use of PEMWE is hindered by high capital costs, low efficiency, and shortages related to performance deterioration with time. 6 In this connection the nature of electrocatalysts and the procedure of their production and application conditions play a critical role. Materials used as electrocatalysts must be as active as possible to improve efficiency, while at the same time they need to be stable to maintain this efficiency throughout the lifetime of the electrolyzer. This is especially critical for materials catalyzing the anodic oxygen evolution reaction (OER), because of the detrimental positive potential and highly corrosive acidic environment. Only a few catalysts are able to withstand these harsh conditions, while providing sufficient activity, conductivity and mechanical stability. In fact, only iridium oxide anodes are proven to provide the required longevity of operation. On the other hand, ruthenium shows the highest electrocatalytic activity toward this reaction. 7,8 During the last decades, the electrochemical and surface properties of anodes based on these metals and their oxides we...

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“…In contrast, for heterogeneous catalysts, the OER is believed to proceed via four consecutive proton‐coupled electron transfer (PCET) steps, with the metallic center serving as active site (Supporting Information, Figure S1) 8. Nevertheless, the recent findings that surface oxygen can also act as active site on the surface of OER electrocatalysts bolsters the idea that a mechanism enlisting continuous bond‐breaking and ‐formation can be at play on the surface of some catalysts,9, 10, 11 eventually leading to their instability under oxidative conditions 12, 13, 14. Interestingly, amorphous structures lie at the frontier between heterogeneous and homogeneous catalysts but the exact nature of the active site as well as their interaction with the adsorbed water molecules remain unclear.…”

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Chemical Recognition of Active Oxygen Species on the Surface of Oxygen Evolution Reaction Electrocatalysts

et al. 2017

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Owing to the transient nature of the intermediates formed during the oxygen evolution reaction (OER) on the surface of transition metal oxides, their nature remains largely elusive by the means of simple techniques. The use of chemical probes is proposed, which, owing to their specific affinities towards different oxygen species, unravel the role played by these species on the OER mechanism. For that, tetraalkylammonium (TAA) cations, previously known for their surfactant properties, are introduced, which interact with the active oxygen sites and modify the hydrogen bond network on the surface of OER catalysts. Combining chemical probes with isotopic and pH‐dependent measurements, it is further demonstrated that the introduction of iron into amorphous Ni oxyhydroxide films used as model catalysts deeply modifies the proton exchange properties, and therefore the OER mechanism and activity.

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Thermodynamic explanation of the universal correlation between oxygen evolution activity and corrosion of oxide catalysts

Cited by 356 publications

References 36 publications

Electrochemical Flow-Cell Setup for In Situ X-ray Investigations

Electrochemical Flow-Cell Setup for In Situ X-ray Investigations

On the Origin of the Improved Ruthenium Stability in RuO₂–IrO₂Mixed Oxides

Chemical Recognition of Active Oxygen Species on the Surface of Oxygen Evolution Reaction Electrocatalysts

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Thermodynamic explanation of the universal correlation between oxygen evolution activity and corrosion of oxide catalysts

Cited by 356 publications

References 36 publications

Electrochemical Flow-Cell Setup for In Situ X-ray Investigations

Electrochemical Flow-Cell Setup for In Situ X-ray Investigations

On the Origin of the Improved Ruthenium Stability in RuO2–IrO2Mixed Oxides

Chemical Recognition of Active Oxygen Species on the Surface of Oxygen Evolution Reaction Electrocatalysts

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On the Origin of the Improved Ruthenium Stability in RuO₂–IrO₂Mixed Oxides