Oxygen and hydrogen evolution reactions on Ru, RuO 2 , Ir, and IrO 2 thin film electrodes in acidic and alkaline electrolytes: A comparative study on activity and stability

Cherevko, Serhiy; Geiger, Simon; Kasian, Olga; Kulyk, Nadiia; Grote, Jan-Philipp; Savan, Alan; Shrestha, Buddha Ratna; Merzlikin, Sergiy Vasil ́ović; Breitbach, Benjamin; Ludwig, Alfred; Mayrhofer, Karl Johann Jakob

doi:10.1016/j.cattod.2015.08.014

Cited by 1,110 publications

(943 citation statements)

References 89 publications

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“…For example, for electrodes containing 20 and 80 at.% of Ir, the rate of Ru dissolution during transient conditions is 32 and 5 times higher than the Ir dissolution rate, respectively. The data on dissolution of individual RuO 2 and IrO 2 are in agreement with previously obtained results on the stability of pure oxides prepared by different methods, 7,[59][60][61] as well as Ru and Ir based DSA. 58,62 A similar trend in the dependence of the dissolved amount of Ir and Ru on the ratio between the elements was observed during anodic polarization at 1 mA cm −2 (Fig.…”

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confidence: 91%

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

Kasian

Geiger

Stock

et al. 2016

J. Electrochem. Soc.

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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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supporting

confidence: 91%

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

Kasian

Geiger

Stock

et al. 2016

J. Electrochem. Soc.

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114

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“…Several explanations can be given for this phenomenon. As shown in Fig.1 [40]. Additionally, the poor catalytic activity of the as-prepared Ir 0.7 Sn 0.3 O 2-x means that a higher overpotential is required to achieve the same current density.…”

Section: Discussionmentioning

confidence: 98%

Using Instability of a Non-stoichiometric Mixed Oxide Oxygen Evolution Catalyst As a Tool to Improve Its Electrocatalytic Performance

et al. 2017

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Owing to their superior electrocatalytic performance, non-stoichiometric mixed oxides are often considered as promising electrocatalysts for the acidic oxygen evolution reaction (OER). Their activity and stability can be superior to those of the state-of-the-art IrO 2 catalysts, although the exact nature of this phenomenon is not yet understood. In the current work, a Ir 0.7 Sn 0.3 O 2-x thin-film electrode is taken as a representative example for a thorough evaluation of OER activity of the non-stoichiometric oxides. Complementary activity and stability analysis of Ir 0.7 Sn 0.3 O 2-x electrodes is achieved using a setup based on an electrochemical scanning flow cell and ICP-MS. The obtained ICP-MS data presents an unambiguous proof of the preferential dissolution of the less noble Sn from the mixed oxide during OER. While less than a monolayer of Ir is dissolved after a prolonged electrolysis of 1400 min during which its dissolution rate drops to near zero, the amount of Sn lost is ten monolayers. The latter finding is confirmed by XPS analysis, which besides showing Ir surface enrichment also indicates a gradual transformation of Ir 0 to Ir III species. This transition is beneficial for electrode activity, as the overpotential for OER at j = 5 mA cm −2 was decreasing up to 300 mV. The increase in electrode activity is attributed to several mechanisms including generation of Ir III active sites and overall surface area increase. A generalized description of OER catalysis by Ir-based materials is given, including data from the current work as well as from other Ir-based mixed oxides, such as Ir-Ru-O and Ir-Ni-O.

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“…In contrast, IrO2 (Furuya) showed no hysteresis in the voltammogram, and reached the steady-state current instantly after the potential step, suggesting that crystalline IrO2, such as IrO2 (Furuya) as shown in Figure S1, is electrochemically stable. The higher activity of IrO2 (Alfa Aesar) compared to IrO2 (Furuya) may stem from the presence of lower valent iridium, since Ir(III) is considered more active than Ir(IV) [12] for OER. Against potential cycles, however, catalysts containing Ir(III) are generally regarded as being less stable [12], although that trend is not seen in this short potential holding test.…”

Section: Electrochemical Propertiesmentioning

confidence: 99%

“…The higher activity of IrO2 (Alfa Aesar) compared to IrO2 (Furuya) may stem from the presence of lower valent iridium, since Ir(III) is considered more active than Ir(IV) [12] for OER. Against potential cycles, however, catalysts containing Ir(III) are generally regarded as being less stable [12], although that trend is not seen in this short potential holding test.…”

Section: Electrochemical Propertiesmentioning

confidence: 99%

“…For stabilities, ruthenium metal and oxides are regarded as unstable, since ruthenium forms volatile RuO4. Iridium, in contrast, does not form a volatile product, but can be dissolved as an ion, especially when the catalyst is electrochemically redoxable IrOx (x < 4), which is more OER active [12]. Moreover, those two elements are among the scarcest (much scarcer than platinum) [13], and their usage will be an obstacle for wide distribution of water electrolyzers.…”

Section: Introductionmentioning

confidence: 99%

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Assessing the Potential of Co-Pt Bronze for Electrocatalysis in Acidic Media

2018

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An electron-conducting mixed oxide, Co-Pt bronze was synthesized and examined as a candidate for a highly durable electrocatalyst for both the polymer electrolyte fuel cells and electrolyzers. The motivation of this study comes from the fact that this material has not been studied as an electrocatalyst in acidic media, although past studies showed a high electronic conductivity and a high corrosion resistance. Co-Pt bronze without metallic Pt was obtained by solid-state synthesis and hot aqua regia rinsing. The OER activity was found to be among the highest as a material without Ir and Ru in acidic media, and it showed extremely high electrochemical stability in the OER potential range. Its oxygen reduction reaction (ORR) was obtained after potential cycles down to the hydrogen region, which formed a thin Pt metallic layer over the oxide. While its specific activity was not more than that of pure platinum nanoparticles, its durability against the potential cycles was much higher.

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Oxygen and hydrogen evolution reactions on Ru, RuO 2 , Ir, and IrO 2 thin film electrodes in acidic and alkaline electrolytes: A comparative study on activity and stability

Cited by 1,110 publications

References 89 publications

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

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

Using Instability of a Non-stoichiometric Mixed Oxide Oxygen Evolution Catalyst As a Tool to Improve Its Electrocatalytic Performance

Assessing the Potential of Co-Pt Bronze for Electrocatalysis in Acidic Media

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Oxygen and hydrogen evolution reactions on Ru, RuO 2 , Ir, and IrO 2 thin film electrodes in acidic and alkaline electrolytes: A comparative study on activity and stability

Cited by 1,110 publications

References 89 publications

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

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

Using Instability of a Non-stoichiometric Mixed Oxide Oxygen Evolution Catalyst As a Tool to Improve Its Electrocatalytic Performance

Assessing the Potential of Co-Pt Bronze for Electrocatalysis in Acidic Media

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

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