Oxygen evolution activity and stability of iridium in acidic media. Part 1. – Metallic iridium

Cherevko, Serhiy; Geiger, Simon; Kasian, Olga; Mingers, Andrea Maria; Mayrhofer, Karl Johann Jakob

doi:10.1016/j.jelechem.2016.04.033

Cited by 186 publications

(250 citation statements)

References 85 publications

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“…0.95 and 0.65 V RHE , respectively. These features can be assigned to the Ir(IV)/Ir(III) transitions that are typically observed in the CVs of hydrous or amorphous iridium oxides [5,33]. The double-layer charging current is also increased, which may indicate a slight increase in the electrode's surface area.…”

Section: Oxygen Evolution and Electrochemical Dissolution Of Ir 07 Smentioning

confidence: 86%

“…The prepared Ir 0.7 Sn 0.3 O 2-x thin film served as the working electrode in the scanning flow cell-inductively coupled plasma mass spectrometer (ICP-MS, NexION 300X, Perkin Elmer)-based setup SFC-ICP-MS, as described in [5,27]. All presented data are normalized to the geometric area of the working electrode (1 × 10 −2 cm 2 ) assuming low roughness of the sputtered films.…”

Section: Methodsmentioning

confidence: 99%

“…Electrode stability, however, should not be sacrificed. Considering acidic environments as the most promising ones, nowadays only Irbased anodes meet these strict requirements [4][5][6][7]. Scarcity and the high price of Ir, however, are serious hindrances in the way of its universal application.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Oxygen Evolution and Electrochemical Dissolution Of Ir 07 Smentioning

confidence: 86%

Section: Methodsmentioning

confidence: 99%

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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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“…These observations lead to two conclusions: 1) increasing the potential leads to a change in the dissolution mechanism which is independent of the catalyst loading and activity, and 2) the early onset and start of the severe dissolution rate at a fixed potential when exceeding 1.4 V RHE are independent of the OER activity. Thus, it seems possible to control the dissolution reaction independently of the OER activity of iridium‐based catalysts …”

Section: Following Degradation By Materials Characterization and In Smentioning

confidence: 99%

The Stability Challenges of Oxygen Evolving Catalysts: Towards a Common Fundamental Understanding and Mitigation of Catalyst Degradation

et al. 2017

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This Review addresses the technical challenges, scientific basis, recent progress, and outlook with respect to the stability and degradation of catalysts for the oxygen evolution reaction (OER) operating at electrolyzer anodes in acidic environments with an emphasis on ion exchange membrane applications. First, the term "catalyst stability" is clarified, as well as current performance targets, major catalyst degradation mechanisms, and their mitigation strategies. Suitable in situ experimental methods are then evaluated to give insight into catalyst degradation and possible pathways to tune OER catalyst stability. Finally, the importance of identifying universal figures of merit for stability is highlighted, leading to a comprehensive accelerated lifetime test that could yield comparable performance data across different laboratories and catalyst types. The aim of this Review is to help disseminate and stress the important relationships between structure, composition, and stability of OER catalysts under different operating conditions.

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“…However, the rather rough surface of the nanoparticles indicates the leaching of nanocatalysts. By studying the dissolution of iridium for OER in acidic media, Cherevko and Mayrhofer et al [48][49][50] considered that the existence of instable intermediates or mixture of crystalline and amorphous Ir oxide phases would cause the dissolution of iridium at a high positive potential. Herein, ICP-AES results in Table S6 indicate that obvious mass loss takes place during the constant potential treatment.…”

Section: Surface Effect Of Ir-pd Alloy Nanocatalysts For Oermentioning

confidence: 99%

Ir-Pd nanoalloys with enhanced surface-microstructure-sensitive catalytic activity for oxygen evolution reaction in acidic and alkaline media

et al. 2018

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Ir-based electrocatalysts have been systematically studied for a variety of applications, among which the electrocatalysis for oxygen evolution reaction (OER) is one of the most prominent. The investigation on surface-microstructure-sensitive catalytic activity in different pH media is of great significance for developing efficient electrocatalysts and corresponding mechanism research. Herein, shape-tunable IrPd alloy nanocrystals, including nano-hollow-spheres (NHSs), nanowires (NWs), and nanotetrahedrons (NTs), are synthesized via a facile one-pot solvothermal method. Electrochemical studies show that the OER activity of the Ir-Pd alloy nanocatalysts exhibits surface-microstructure-sensitive enhancement in acidic and alkaline media. Ir-Pd NWs and NTs show more than five times higher mass activity than commercial Ir/C catalyst at an overpotential of 0.25 V in acidic and alkaline media. Post-XPS analyses reveal that surface Ir(VI) oxide generated at surface defective sites of Ir-Pd nanocatalysts is a possible key intermediate for OER. In acidic medium, the specific activity of Ir-Pd nanocatalysts has a positive correlation with the surface roughness of NWs > NHSs > NTs. However, the strong dissociation of surface Ir(VI) species (IrO 4 2− ) at surface defective sites is a possible obstacle for the formation of Ir(VI) oxide, which reverses the activity sequence for OER in alkaline medium.

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Oxygen evolution activity and stability of iridium in acidic media. Part 1. – Metallic iridium

Cited by 186 publications

References 85 publications

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

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

The Stability Challenges of Oxygen Evolving Catalysts: Towards a Common Fundamental Understanding and Mitigation of Catalyst Degradation

Ir-Pd nanoalloys with enhanced surface-microstructure-sensitive catalytic activity for oxygen evolution reaction in acidic and alkaline media

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