Supported iridium oxide films in aqueous electrolytes

Charge injection dynamics as monitored by time-resolved differential reflectance spectroscopy

Youjiang Chen, Ping Shi, Daniel Alberto Scherson

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Dynamic aspects of the electrochemical charge-discharge of hydrated Ir oxide, IrOx (hyd), films in aqueous 0.5 M H2 SO4 have been investigated by simultaneous chronocoulometry and time-resolved, normal incidence (λ=633 nm) differential reflectance spectroscopy, ΔR/R. Experiments were performed by applying potential steps between two judiciously selected values to IrOx (hyd) films electrodeposited on smooth Au disk microelectrodes to reduce the overall time constant of the cell. The analysis of the results obtained revealed that the rate at which charge is injected into or released from the film, as determined from the chronocoulometric response, is faster than the rate at which Ir sites in the lattice undergo redox transitions, as monitored by ΔR/R. This behavior appears consistent with the relatively high electronic conductivity of IrOx (hyd), which allows for charge to be stored on the highly convoluted surface of this structurally disorganized material, i.e., strictly capacitive, a process that occurs in parallel and at much higher rates than changes in the oxidation state of the Ir sites, i.e., pseudocapacitive.

Original languageEnglish
JournalElectrochemical and Solid-State Letters
Volume11
Issue number6
DOIs
Publication statusPublished - 2008 Apr 24
Externally publishedYes

Fingerprint

Charge injection
Iridium
iridium
Electrolytes
Oxide films
oxide films
electrolytes
Spectroscopy
injection
reflectance
spectroscopy
Microelectrodes
Oxides
time constant
incidence
Oxidation
conductivity
oxidation
oxides
cells

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Materials Science(all)
  • Physical and Theoretical Chemistry
  • Electrical and Electronic Engineering
  • Electrochemistry

Cite this

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abstract = "Dynamic aspects of the electrochemical charge-discharge of hydrated Ir oxide, IrOx (hyd), films in aqueous 0.5 M H2 SO4 have been investigated by simultaneous chronocoulometry and time-resolved, normal incidence (λ=633 nm) differential reflectance spectroscopy, ΔR/R. Experiments were performed by applying potential steps between two judiciously selected values to IrOx (hyd) films electrodeposited on smooth Au disk microelectrodes to reduce the overall time constant of the cell. The analysis of the results obtained revealed that the rate at which charge is injected into or released from the film, as determined from the chronocoulometric response, is faster than the rate at which Ir sites in the lattice undergo redox transitions, as monitored by ΔR/R. This behavior appears consistent with the relatively high electronic conductivity of IrOx (hyd), which allows for charge to be stored on the highly convoluted surface of this structurally disorganized material, i.e., strictly capacitive, a process that occurs in parallel and at much higher rates than changes in the oxidation state of the Ir sites, i.e., pseudocapacitive.",
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T2 - Charge injection dynamics as monitored by time-resolved differential reflectance spectroscopy

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AU - Shi, Ping

AU - Scherson, Daniel Alberto

PY - 2008/4/24

Y1 - 2008/4/24

N2 - Dynamic aspects of the electrochemical charge-discharge of hydrated Ir oxide, IrOx (hyd), films in aqueous 0.5 M H2 SO4 have been investigated by simultaneous chronocoulometry and time-resolved, normal incidence (λ=633 nm) differential reflectance spectroscopy, ΔR/R. Experiments were performed by applying potential steps between two judiciously selected values to IrOx (hyd) films electrodeposited on smooth Au disk microelectrodes to reduce the overall time constant of the cell. The analysis of the results obtained revealed that the rate at which charge is injected into or released from the film, as determined from the chronocoulometric response, is faster than the rate at which Ir sites in the lattice undergo redox transitions, as monitored by ΔR/R. This behavior appears consistent with the relatively high electronic conductivity of IrOx (hyd), which allows for charge to be stored on the highly convoluted surface of this structurally disorganized material, i.e., strictly capacitive, a process that occurs in parallel and at much higher rates than changes in the oxidation state of the Ir sites, i.e., pseudocapacitive.

AB - Dynamic aspects of the electrochemical charge-discharge of hydrated Ir oxide, IrOx (hyd), films in aqueous 0.5 M H2 SO4 have been investigated by simultaneous chronocoulometry and time-resolved, normal incidence (λ=633 nm) differential reflectance spectroscopy, ΔR/R. Experiments were performed by applying potential steps between two judiciously selected values to IrOx (hyd) films electrodeposited on smooth Au disk microelectrodes to reduce the overall time constant of the cell. The analysis of the results obtained revealed that the rate at which charge is injected into or released from the film, as determined from the chronocoulometric response, is faster than the rate at which Ir sites in the lattice undergo redox transitions, as monitored by ΔR/R. This behavior appears consistent with the relatively high electronic conductivity of IrOx (hyd), which allows for charge to be stored on the highly convoluted surface of this structurally disorganized material, i.e., strictly capacitive, a process that occurs in parallel and at much higher rates than changes in the oxidation state of the Ir sites, i.e., pseudocapacitive.

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