EPR spectroscopy of transformations of iridium(III) and iridium(IV) hydroxo complexes in alkaline media

Pankratov, D. А.; Komozin, P. N.; Kiselev, Yu. M.

doi:10.1134/s0036023611110210

Cited by 21 publications

(16 citation statements)

References 7 publications

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“…[51] In presence of ab ase, IrCl 6 2À ,w hich is aw ell-known outer-sphere oxidant, first reduces to IrCl 6 3À by water oxidation. [53] The subsequent hydrolysis of IrCl 6 3À is as low process occurring over days at room temperature (RT)and is still not completely understood with respectt ot he suspected formation of mixed-valence iridium oligomers. [53] The subsequent hydrolysis of IrCl 6 3À is as low process occurring over days at room temperature (RT)and is still not completely understood with respectt ot he suspected formation of mixed-valence iridium oligomers.…”

Section: Synthesis and Characterization Of Catalyst Support (Ato)mentioning

confidence: 99%

“…[52] This phenomenoni se videncedb yt he formation of O 2 bubbles and by the discoloration of the solution from redbrownt op ale yellowish, owing to the loss of the IrCl 6 2À ligand-to-metal charge-transfer bands (LMCT). [51,53,54] The MW treatmentg reatly accelerates this process while avoiding thermalt reatment under dry conditions, which would easily lead to the formation of crystalline IrO 2 . [51,53,54] The MW treatmentg reatly accelerates this process while avoiding thermalt reatment under dry conditions, which would easily lead to the formation of crystalline IrO 2 .…”

Section: Synthesis and Characterization Of Catalyst Support (Ato)mentioning

confidence: 99%

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High‐Performance Supported Iridium Oxohydroxide Water Oxidation Electrocatalysts

et al. 2017

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The synthesis of a highly active and yet stable electrocatalyst for the anodic oxygen evolution reaction (OER) remains a major challenge for acidic water splitting on an industrial scale. To address this challenge, we obtained an outstanding high-performance OER catalyst by loading Ir on conductive antimony-doped tin oxide (ATO)-nanoparticles by a microwave (MW)-assisted hydrothermal route. The obtained Ir phase was identified by using XRD as amorphous (XRD-amorphous), highly hydrated Ir oxohydroxide. To identify chemical and structural features responsible for the high activity and exceptional stability under acidic OER conditions with loadings as low as 20 μg cm , we used stepwise thermal treatment to gradually alter the XRD-amorphous Ir phase by dehydroxylation and crystallization of IrO . This resulted in dramatic depletion of OER performance, indicating that the outstanding electrocatalytic properties of the MW-produced Ir oxohydroxide are prominently linked to the nature of the produced Ir phase. This finding is in contrast with the often reported stable but poor OER performance of crystalline IrO -based compounds produced through more classical calcination routes. Our investigation demonstrates the immense potential of Ir oxohydroxide-based OER electrocatalysts for stable high-current water electrolysis under acidic conditions.

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Section: Synthesis and Characterization Of Catalyst Support (Ato)mentioning

confidence: 99%

Section: Synthesis and Characterization Of Catalyst Support (Ato)mentioning

confidence: 99%

High‐Performance Supported Iridium Oxohydroxide Water Oxidation Electrocatalysts

et al. 2017

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“…[21,26] In the intermediate KOH/Ir regime (4:1 KOH/Ir 7:1) only weaka bsorption features were observed, which corresponds to the formation of oligomeric Ir species resulting in ah igh synthesis yield (! [28] The wide array of proposed products highlightst he complexity of the oligomerization chemistry of hydrolyzed Ir species and ChemSusChem 2017ChemSusChem , 10,1958ChemSusChem -1968 www.chemsuschem.org 2017 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim suggestsg reat precaution when analyzing the composition of resultingp roducts. [21] It appears that the KOH/Ir ratio is acrucial parameter in optimizingt he synthesis yield of rare-earth Ir compounds produced by hydrolyzationo fh ydrolyzed Ir species.…”

Section: Uv/vismentioning

confidence: 99%

“…Oligomerization and condensation reactions are thus in competition with re-oxidation, leading to aw ide range of possible products.U nder basic conditions, authors have suggested the formation of binuclear oxo-bridged mixed oxidations tate Ir complexes [27] and even peroxo-bridged Ir III/IV oligomers. [28] The wide array of proposed products highlightst he complexity of the oligomerization chemistry of hydrolyzed Ir species and ChemSusChem 2017ChemSusChem , 10,1958ChemSusChem -1968 www.chemsuschem.org suggestsg reat precaution when analyzing the composition of resultingp roducts.…”

Section: Uv/vismentioning

confidence: 99%

Microwave‐Assisted Synthesis of Stable and Highly Active Ir Oxohydroxides for Electrochemical Oxidation of Water

et al. 2017

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Water splitting for hydrogen production in acidic media has been limited by the poor stability of the anodic electrocatalyst devoted to the oxygen evolution reaction (OER). To help circumvent this problem we have synthesized a class of novel Ir oxohydroxides by rapid microwave-asisted hydrothermal synthesis, which bridges the gap between electrodeposited amorphous IrO films and crystalline IrO electrocatalysts prepared by calcination routes. For electrode loadings two orders of magnitude below current standards, the synthesized compounds present an unrivalled combination of high activity and stability under commercially relevant OER conditions in comparison to reported benchmarks, without need for pretreatment. The best compound achieved a lifetime 33 times longer than the best commercial Ir benchmark. Thus, the reported efficient synthesis of an Ir oxohydroxide phase with superior intrinsic OER performance constitutes a major step towards the targeted design of cost-efficient Ir based OER electrocatalysts for acidic media.

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“…Little is known about the solution chemistry of iridium in an alkaline environment, although an EPR‐study states the formation of different iridium hydroxide species . First hydrothermal reactions explored the field of alkaline earth iridates under strong basic conditions, yielding the hydroxides BaIr(OH) 6 · H 2 O and Sr 2 Ir(OH) 8 , e.g .…”

Section: Introductionmentioning

confidence: 99%

Hydrothermal Synthesis, Crystal Structure Determination, and Magnetic Properties of a New Calcium Iron Iridium Hydrogarnet Ca₃(Ir_2–xFe_x)(FeO₄)_2–x(O₄H₄)_1+x with 0 ≤ x ≤ 1

Poddig

Hunger

Kamusella

et al. 2019

Zeitschrift anorg allge chemie

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The new calcium iron iridium hydrogarnet Ca 3 (Ir 2-x Fe x )(FeO 4 ) 2-x (H 4 O 4 ) 1+x (0 Յ x Յ 1) was obtained by hydrothermal synthesis under strongly oxidizing alkaline conditions. The compound adopts a garnet-like crystal structure and crystallizes in the acentric cubic space group I43d (no. 220) with a = 12.5396(6) Å determined at T = 100 K for a crystal with a refined composition Ca 3 (Ir 1.4 Fe 0.6 )(FeO 4 ) 1.4 (O 4 H 4 ) 1.6 . Iridium and iron statistically occupy the octahedrally coordinated metal position, the two crystallographically independent tetrahedral sites are partially occupied by iron. Hydroxide groups are found to cluster as hydrogarnet defects, i.e. partially substituting oxide anions around the empty tetrahedral metal * Prof. Dr. T. Doert E-Mail: thomas.doert@tu-dresden.de [a] 631 sites. The presence of hydroxide ions was confirmed by infrared spectroscopy and the hydrogen content was quantified by carrier gas hot extraction; the overall composition was verified by energy dispersive X-ray spectroscopy. The structure model is supported by 57 Fe-Mössbauer spectroscopic data evidencing different Fe sites and a magnetic ordering of the octahedral iron sublattice at room temperature. The thermal decomposition proceeds via three steps of water loss and results in Ca 2 Fe 2 O 5 , Fe 2 O 3 and Ir. Mössbauer and magnetization data suggest magnetic order at ambient temperature with complex magnetic interactions.

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EPR spectroscopy of transformations of iridium(III) and iridium(IV) hydroxo complexes in alkaline media

Cited by 21 publications

References 7 publications

High‐Performance Supported Iridium Oxohydroxide Water Oxidation Electrocatalysts

High‐Performance Supported Iridium Oxohydroxide Water Oxidation Electrocatalysts

Microwave‐Assisted Synthesis of Stable and Highly Active Ir Oxohydroxides for Electrochemical Oxidation of Water

Hydrothermal Synthesis, Crystal Structure Determination, and Magnetic Properties of a New Calcium Iron Iridium Hydrogarnet Ca₃(Ir_2–xFe_x)(FeO₄)_2–x(O₄H₄)_1+x with 0 ≤ x ≤ 1

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EPR spectroscopy of transformations of iridium(III) and iridium(IV) hydroxo complexes in alkaline media

Cited by 21 publications

References 7 publications

High‐Performance Supported Iridium Oxohydroxide Water Oxidation Electrocatalysts

High‐Performance Supported Iridium Oxohydroxide Water Oxidation Electrocatalysts

Microwave‐Assisted Synthesis of Stable and Highly Active Ir Oxohydroxides for Electrochemical Oxidation of Water

Hydrothermal Synthesis, Crystal Structure Determination, and Magnetic Properties of a New Calcium Iron Iridium Hydrogarnet Ca3(Ir2–xFex)(FeO4)2–x(O4H4)1+x with 0 ≤ x ≤ 1

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Hydrothermal Synthesis, Crystal Structure Determination, and Magnetic Properties of a New Calcium Iron Iridium Hydrogarnet Ca₃(Ir_2–xFe_x)(FeO₄)_2–x(O₄H₄)_1+x with 0 ≤ x ≤ 1