Growth control and characterization of vertically aligned IrO2 nanorods

Chen, Reui-San; Huang, Ying‐Sheng; Liang, Ya-Min; Tsai, Dah–Shyang; Chi, Yun; Jia, Kai

doi:10.1039/b305602n

Cited by 81 publications

(100 citation statements)

References 33 publications

(32 reference statements)

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“…1. All the diffraction peaks of both the samples could be indexed to the standard diffraction data (JCPDS 15-0870), confirming the formation of pure rutile-type IrO 2 [29]. In particular, only two much broadened diffraction peaks are observed at 35°and 54°, corresponding to the supported IrO 2 of IrO 2 /KB sample (Fig.…”

Section: Resultsmentioning

confidence: 56%

Ultrafine IrO2 nanoparticle-decorated carbon as an electrocatalyst for rechargeable Li–O2 batteries with enhanced charge performance and cyclability

Guo

Yuan

et al. 2014

J Solid State Electrochem

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Ultrafine iridium (IV) oxide (IrO 2 ) nanoparticles are homogeneously distributed on the surface of porous Ketjenblack (KB) carbon (IrO 2 /KB) via one-step hydrothermal approach, and the resulting nanocomposite is investigated as an electrocatalyst for nonaqueous Li-O 2 batteries. Transmission electron microscopy confirms the high dispersion of ultrafine IrO 2 particles with an average particle size of 1.47 nm. The IrO 2 /KB electrode exhibits remarkable catalytic activity towards oxygen evolution reaction (OER) as indicated by the voltammetric measurements. And, the IrO 2 /KB electrode decreases the recharge overpotential by ca. 400 and 200 mV compared to the electrodes with pure KB and a mechanical mixture of KB and pre-synthesized IrO 2 , respectively. Li-O 2 battery with IrO 2 /KB achieves high-capacity retention and stable cyclability, maintaining a long cycle life for 70 cycles without sharp decay under a limited dischargecharge depth of 500 mAh g −1 (ca. 1100 mAh g C −1). X-ray diffraction and scanning electron microscope analysis reveal that this excellent rechargeability is based on the reversible formation and decomposition of toroid-shaped lithium peroxide. Therefore, the uniform distribution of ultrafine IrO 2 particles, with extraordinary OER catalytic activity, on KB carbon enables the IrO 2 /KB to be a promising electrocatalyst for Li-O 2 batteries.

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Section: Resultsmentioning

confidence: 56%

Ultrafine IrO2 nanoparticle-decorated carbon as an electrocatalyst for rechargeable Li–O2 batteries with enhanced charge performance and cyclability

Guo

Yuan

et al. 2014

J Solid State Electrochem

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“…Another broader feature at 65.5 eV is observed, which is higher than that of [Ir 4+ ] 4f 5/2 by 0.5 eV. The O 1s signal appears to be doublet, whose major peak at 531.2 eV is close to that of the IrO 2 nanorods at 531.6 eV [26] but higher than the standard IrO 2 at 530.5 eV [27]. These higher binding energies of Ir 4f and O 1s most likely indicate the presence of a higher oxidation state of Ir than +4 in the IrO x [m]-Au nanostructures.…”

Section: Resultsmentioning

confidence: 71%

Enhanced electrochemical evolution of oxygen by using nanoflowers made from a gold and iridium oxide composite

2012

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We report on the synthesis of a composite made from iridium oxide and gold that has a flower-like morphology. The ratio of iridium oxide to gold can be controlled by altering the concentrations of the metal precursors or the pH of the solution containing the reductant citrate. Scanning electron microscopy, transmission electron microscopy, Xray diffraction, X-ray photoelectron spectroscopy, and laser confocal micro-Raman spectroscopy were applied to characterize the structures of the nanoflowers, and a mechanism of their formation was deduced. The nanoflowers display an electrocatalytic activity in an oxygen evolution reaction (OER) that is significantly enhanced compared to bare iridium oxide nanoparticles. The highest turnover frequency for the OER of the new nanoflowers is 10.9 s −1 , which is almost one order of magnitude better than that of the respective nanoparticles. These attractive features are attributed to the high oxidation states of iridium in the nanoflowers which is caused by the transfer of electronic charge from metal oxides to gold, and also to the flower fractal structure which is thought to provide a much more accessible surface than suspensions of the respective nanoparticle.

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“…[ 20 ] At the same time, there are two doublets located at 63.1 and 66.2 eV, which are believed to be caused by the existence of higher-oxidation-state iridium. [ 21 ] This is also supported by the analysis of the O1s peak shown in Figure 2 f. The additional doublet peak is around 531.5 eV, which is ≈1 eV higher than the main peak located at 530.5 eV. Another evidence for excess oxygen (higheroxidation-state iridium) is that the quantitative analysis of the XPS peaks shows the atomic ratio of Ir and O in the fi lm is 21:79.…”

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confidence: 54%

Long‐Life, High‐Voltage Acidic Zn–Air Batteries

Manthiram

2015

Advanced Energy Materials

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electrolyte, which can be operated at room temperature, has rarely been reported. [ 11 ] The rechargeability of ZABs requires bifunctional catalytic activity of the air cathode: ORR and OER. The requirements for the active sites and electrochemical environment for ORR and OER are so different that it is very diffi cult to achieve high activity for both reactions within one material. For example, ORR prefers hydrophobic sites, which form a three-phase (solid catalyst, liquid electrolyte, and air) interface. In contrast, OER prefers hydrophilic sites to maximize the contact between the catalyst and the electrolyte. Recently, a "decoupled" design of bifunctional air electrodes has attracted much attention. [ 12 ] By dividing the ORR and OER functions into two different electrodes, which are optimized for ORR and OER respectively, high cell effi ciency as well as long cycle life could be achieved. However, the decoupled design has mainly been pursued with alkaline metal-air batteries, and no such design has been reported for acidic metal-air batteries.We report here AZABs with decoupled air electrodes, which is promising to eliminate the problems of conventional Zn-air batteries. The prototype AZABs are composed of a Zn-metal anode, an alkaline anode electrolyte, a NASICON-type Li-ion solid electrolyte (LTAP), an acidic phosphate buffer catholyte, and a decoupled IrO 2 thin fi lms grown onto a Ti mesh (IrO 2 @Ti) for OER and a commercial Pt/C catalyst on a gas diffusion layer (GDL) for ORR. The Li-ion solid electrolyte LTAP separates the alkaline anode electrolyte and the acidic catholyte and provides ionic channels. LTAP does not serve as a direct Zn 2+ -ion conductor, but as a Li + -ion "messenger" to achieve the charge balance on both sides of an AZAB. [ 13 ] The decoupled OER electrode is carbon-free and binder-free, ensuring good mechanical integrity in the high-voltage oxidizing environment. The decoupled ORR electrode is isolated during the high-voltage charge process, minimizing the problem of catalyst dissolution and oxidation. [ 14 ] During cell operation, a high discharge voltage close to 2.0 V could be achieved at a low current density. The acidic catholyte also eliminates the persistence problem of CO 2 ingression associated with alkaline electrolytes. In addition, the solid electrolyte provides the possibility of blocking Zn dendrite from reaching the cathode, greatly improving the battery safety. Moreover, although the soluble discharge product zincate will still form on the anode side, the solid electrolyte will keep the zincate in the anode chamber, decreasing the mass transport barrier and facilitating zincate reduction upon charge. The assembled AZABs achieve a high voltaic effi ciency of ≈81% at 0.1 mA cm −2 . The cell could also be cycled for hundreds of hours in the ambient air environment without signifi cant degradation. Figure 1 shows the discharge and charge mechanism of an AZAB based on an alkaline anode electrolyte and an acidic catholyte. During discharge, oxygen (O 2 ) from air diff...

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Growth control and characterization of vertically aligned IrO2 nanorods

Cited by 81 publications

References 33 publications

Ultrafine IrO2 nanoparticle-decorated carbon as an electrocatalyst for rechargeable Li–O2 batteries with enhanced charge performance and cyclability

Ultrafine IrO2 nanoparticle-decorated carbon as an electrocatalyst for rechargeable Li–O2 batteries with enhanced charge performance and cyclability

Enhanced electrochemical evolution of oxygen by using nanoflowers made from a gold and iridium oxide composite

Long‐Life, High‐Voltage Acidic Zn–Air Batteries

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