Changes in the redox state of iridium oxide clusters and their relation to catalytic water oxidation: radiolytic and electrochemical studies

Nahor, Gad S.; Hapiot, Philippe; Neta, P.; Harriman, A.

doi:10.1021/j100155a024

Cited by 73 publications

(83 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Alternatively, the hydroxyl radicals may react directly with the compact IrOx film underlying the hydrous oxide, causing new IrOx to form, similar to what is normally achieved by cycling to high potentials. This latter explanation would be in agreement with reports of IrOx formation via the irradiation of Ir salt solutions, resulting in the production of hydroxyl radicals [65],…”

Section: Enhanced Irox Film Growth At Low H 2 0 2 Concentrationssupporting

confidence: 93%

Hydrogen Peroxide Detection at Electrochemically and Sol‐Gel Derived Ir Oxide Films

et al. 2004

View full text Add to dashboard Cite

Ir oxide (IrOx) films, formed electrochemically on bulk Ir metal (Ir/IrOx) and also on sol‐gel (SG) derived non‐silica based nanoparticulate Ir, have been studied as material useful for the detection of hydrogen peroxide, with possible application as a glucose biosensor. H2O2 reduction and oxidation on Ir/IrOx and SG‐derived IrOx films, deposited on various substrates such as Pt, Ir and GC, have been compared to the H2O2 behavior at the bare substrate. It was found that H2O2 reduction proceeds on the underlying electrode substrate, while H2O2 oxidation is independent of the nature of the substrate, therefore occurring via the IrOx film. The reactivity of IrOx towards H2O2 oxidation is similar to that seen at Pt, although IrOx has the additional advantages of excellent stability, insensitivity to common interfering substances, biocompatibility and a linear range of detection, up to at least 12 mM H2O2. At micromolar concentrations of H2O2, a second mode of detection, involving the catalyzed growth of IrOx films at Ir substrates, can be employed. These two methods of H2O2 analysis (oxidation/reduction and enhanced IrOx growth) can also be employed for glucose detection using IrOx‐based glucose biosensors.

show abstract

Section: Enhanced Irox Film Growth At Low H 2 0 2 Concentrationssupporting

confidence: 93%

Hydrogen Peroxide Detection at Electrochemically and Sol‐Gel Derived Ir Oxide Films

et al. 2004

View full text Add to dashboard Cite

show abstract

“…During photolysis, the color of the catalyst also gradually changes from blue to white. Because the blue color of IrO 2 (cit) nanoparticles is attributed to a d-d transition of Ir 4+ , 31 this optical change indicates a change of the Ir 4+ oxidation state. Photobleaching can be ruled out, because disappearance of the blue color is permanent.…”

Section: Resultsmentioning

confidence: 99%

“…The absorption is caused by the IrO 2 (cit) nanoparticles (inset in Figure 3), 28 suspensions of which appear deep blue due to a Ir 4+ d-d transition. 31 The spectra for Pt-APS-[Ca 2 Nb 3 O 10 ] with grown or deposited Pt nanoparticles have a broad absorption at 380-580 nm that gives the material a brown appearance. The same color is also observed in the citrate-stabilized Pt sol that served as the starting material in the Pt coupling reaction (inset in Figure 3).…”

Section: Introductionmentioning

confidence: 99%

A Building Block Approach to Photochemical Water-Splitting Catalysts Based on Layered Niobate Nanosheets

et al. 2008

View full text Add to dashboard Cite

We present a modular approach to the synthesis of nanostructured catalysts for photochemical splitting of water into hydrogen and oxygen. The catalysts are built from exfoliated, semiconducting niobate nanosheets derived from the layered perovskite HCa 2 Nb 3 O 10 . The latter is a catalyst for photochemical evolution of hydrogen from water under UV irradiation. After chemical modification with 3-aminopropyltrimethoxysilane (APS), IrO 2 or Pt particles can be attached to the nanosheets to produce various two-component nanostructures that were fully characterized with transmission electron microscopy and ultraviolet and infrared spectroscopy. Cyclic voltammetry was used to determine the onset potentials for O 2 and H 2 evolution. At pH ) 14, the observed values are in the range +0.61 to +1.24 V (NHE, water oxidation) and -1.36 to -1.62 V (NHE, water reduction). Under UV irradiation, all catalysts evolve hydrogen from water without any sign of deactivation for 5 h. The highest quantum efficiency of 3.49% is observed for a structure with Pt directly grown onto the nanosheets. No O 2 is evolved, which we attribute to the adsorption of O 2 to the catalyst surface. For Pt-[HCa 2 Nb 3 O 10 ], this process starts to shut down H 2 evolution after 9 h of constant irradiation, but the activity can be restored to >60% by evacuating the catalyst dispersion and purging it with Ar. Catalysts assembled from preformed citrate-coated Pt nanoparticles are slightly less active for H 2 evolution and so are catalysts that use the linker aminoethyl-aminoundecanetrimethoxysilane (AEAUS) instead of APS. The activity of IrO 2 -APS-[Ca 2 Nb 3 O 10 ] is lowest among two component catalysts, near the activities of the pure or APSmodified nanosheets. On the basis of XPS data, IrO 2 in this catalyst undergoes photochemical reduction to Ir(0) upon UV irradiation.

show abstract

“…Nahor and coworkers' investigation found that after the initial IrO x cluster is oxidized to Ir 4+ , further oxidation of the cluster leads to oxidation of water to O 2 . 20 On the basis of the experiments, we investigated the hydrolysis reaction of (IrO 2 ) n (n = 1−5) nanoclusters. Reactions with two H 2 O molecules have been studied because one O 2 molecule is produced by oxidizing two H 2 O molecules.…”

Section: Methodsmentioning

confidence: 99%

Theoretical Study of Structure, Stability, and the Hydrolysis Reactions of Small Iridium Oxide Nanoclusters

Zhou

Yang

2012

J. Phys. Chem. A

View full text Add to dashboard Cite

ABSTRACT:The geometric structures and relative stabilities of small iridium oxide nanoclusters, Ir m O n (m = 1−5 and n = 1−2m), have been systematically investigated using density functional theory (DFT) calculations at the B3LYP level. Our results show that the lowest-energy structures of these clusters can be obtained by the sequential oxidation of small "core" iridium clusters. The iridium-monoxide-like clusters have relatively higher stability because of their relatively high binding energy and second difference in energies. On the basis of the optimized lowest-energy structures of neutral and cationic (IrO 2 ) n (n = 1−5), DFT has been used to study the hydrolysis reaction of these clusters with water molecules. The calculated results show that the addition of water molecules to the cationic species is much easier than the neutral ones. The overall hydrolysis reaction energies are more exothermic for the cationic clusters than for the neutral clusters. Our calculations indicate that H 2 O can be more easily split on the cationic iridium oxide clusters than on the neutral clusters.

show abstract

Changes in the redox state of iridium oxide clusters and their relation to catalytic water oxidation: radiolytic and electrochemical studies

Cited by 73 publications

References 0 publications

Hydrogen Peroxide Detection at Electrochemically and Sol‐Gel Derived Ir Oxide Films

Hydrogen Peroxide Detection at Electrochemically and Sol‐Gel Derived Ir Oxide Films

A Building Block Approach to Photochemical Water-Splitting Catalysts Based on Layered Niobate Nanosheets

Theoretical Study of Structure, Stability, and the Hydrolysis Reactions of Small Iridium Oxide Nanoclusters

Contact Info

Product

Resources

About