Electrochemical Properties of Polycrystalline Tin Oxide

Elliott, David J.; Zellmer, David L.; Laitinen, Herbert A.

doi:10.1149/1.2407316

Cited by 106 publications

(51 citation statements)

References 14 publications

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“…The charge carrier concentrations were calculated for an electrode roughness factor equal to 1, and a static dielectric constant of 10, the value used by others in an analogous calculation for tin oxide electrodes. 34,35 These values for N are higher than published values 10,20 and attest to the electronic degeneracy of these films. From these estimates of charge carrier concentration, and our measurement of film thickness mentioned earlier, electron mobility was estimated to be ϭ 39 cm 2 V Ϫ1 s Ϫ1 and ϭ 2.8 cm 2 V Ϫ1 s Ϫ1 for films annealed at 600 and 750°C, respectively.…”

Section: Resultsmentioning

confidence: 63%

Electrochemical Properties of Nanocrystalline Cadmium Stannate Films

Valinčius

Reipa

Vilker

et al. 2001

J. Electrochem. Soc.

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Electrochemical properties of sol-gel nanocrystalline cadmium tin oxide electrodes ͑CTO͒ were investigated in 0.2 M potassium chloride buffered at pH 7.4 with phosphate. Films were found to be n-type degenerate semiconductors with charge carrier levels from 10 19 to 10 22 cm Ϫ3 depending on the thermal aftertreatment. X-ray diffraction analysis was used to reveal the appearance of the cubic cadmium stannate ͑Cd 2 SnO 4 ͒ phase at annealing temperatures above 600°C, and to indicate the extent of this dominant phase above 750°C. The flatband potential ͑E FB ,͒ of the film electrodes, as determined from capacitance measurements, was found to be around ϩ0.25 V at pH 7.4. Electrochemical activity toward ten redox processes in the range Ϫ0.45 V Ͻ E Ͻ 0.45 V was investigated, and standard electron transfer rate constants were estimated from ac impedance measurements. The dominant factor in the charge-transfer rate on CTO electrodes is the bulk film charge carrier concentration. It was found that the charge-transfer rates were dependent on the separation of the redox carrier formal potential (E o Ј͒ from the CTO flatband potential. The slowest rates ͑Ϸ10 Ϫ 5 cm s Ϫ1 ͒ were found for redox couples where E o Ј Ϸ E FB . For charge transfer from redox couples where E o Ј is away from E FB , the rates can be several orders of magnitude greater and it is thought that the density of states in the conduction band is rate limiting.Metal oxide electrodes such as tin oxide and indium oxide are used in a wide range of electrochemical applications including solar energy conversion and photovoltaic devices, flat panel displays, and biocatalytic redox transformations. 1-5 These electrodes have wide working potential windows in aqueous solutions. They are stable in acids and bases and have an additional advantage of transparency in the visible part of the optical spectrum. Their conductivity can be varied easily by doping with foreign atoms or varying synthesis conditions. It is not uncommon 6 to fabricate films with conductivity as high as 10 2 S/cm. However, on the nondegenerate semiconductor electrodes, redox processes occur with the transfer of the charge carriers to or from the conduction band or the valence band. Thus, in order to observe a significant redox rate, there exist certain conditions with regard to the alignment of the semiconductor band edge and redox couple potential. 7,8 In highly doped semiconductors, the restrictions regarding the alignment of the bandedge and the redox couple potential are not so strict because electron exchange with the solution may occur via tunneling. 7-9 From this perspective, new metal oxide materials with high charge carrier concentration might be interesting candidates for various electrocatalytic applications.Cadmium tin oxide ͑cadmium stannate, Cd 2 SnO 4 or CTO͒ is a wide bandgap (Ϸ2.1 to 2.9 eV͒ n-type semiconductor with high electrical conductivity ͑up to 1.33 ϫ 10 3 S/cm͒ and high transparency in the visible spectrum range. Nozik was the first who thoroughly investigated physical prop...

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Section: Resultsmentioning

confidence: 63%

Electrochemical Properties of Nanocrystalline Cadmium Stannate Films

Valinčius

Reipa

Vilker

et al. 2001

J. Electrochem. Soc.

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“…The choice of the antimony-doped tin oxide was suggested by its rather negative flat band potential (E fb ϭ Ϫ1.4 V vs. Ag͞AgCl) ensuring the excess positive charge in the potential range of interest (Ϫ0.5 to Ϫ0.9 V). Another important consideration was its reported resistance toward the adsorption of organic surfactants (24). We used traditional electrochemical (cyclic voltammetry, AC voltammetry) and spectroelectrochemical techniques (16,17) to characterize the interaction of Pdx with the tin oxide electrode in both the presence and absence of its CYP101 (P450cam) redox partner.…”

Section: Resultsmentioning

confidence: 99%

A direct electrode-driven P450 cycle for biocatalysis

Reipa

Mayhew²,

Vilker³

1997

Proc. Natl. Acad. Sci. U.S.A.

106

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The large potential of redox enzymes to carry out formation of high value organic compounds motivates the search for innovative strategies to regenerate the cofactors needed by their biocatalytic cycles. Here, we describe a bioreactor where the reducing power to the cycle is supplied directly to purified cytochrome CYP101 (P450cam; EC 1.14.15.1) through its natural redox partner (putidaredoxin) using an antimony-doped tin oxide working electrode. Required oxygen was produced at a Pt counter electrode by water electrolysis. A continuous catalytic cycle was sustained for more than 5 h and 2,600 enzyme turnovers. The maximum product formation rate was 36 nmol of 5-exo-hydroxycamphor͞nmol of CYP101 per min.

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“…The electron tunneling process at SnO2 electrodes in aqueous systems has been presented by Elliott et al (25) and reexamined by MSllers and Memming (26). According to the former study, the tunneling current prevails when the carrier concentration is larger than 3 X 101~ cm -~, and at 5.9 X l0 ~~ cm -3 the space charge barrier is completely transparent to electrons due to tunneling.…”

Section: Oxidation Of Cu(i) and Fe(ii)--thementioning

confidence: 94%

Some Redox Reactions on Semiconducting Tin Oxide Electrodes in Molten LiCl ‐ KCl Eutectic at 450°C

Laitinen

Uchida

Niki

1978

J. Electrochem. Soc.

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The electrode reactions of Eu (III)/Eu (II), Cr (III)/Cr (II), Cu (II)/Cu (I), Fe (III)/Fe (II), and Pt (IV)/Pt (II) redox couples have been studied using cyclic voltammetry at n-type semiconducting SnO2 electrodes in molten LiCI-KC1 eutectic at 450~ The highly doped oxide electrode is a stable indicator electrode usable at anodie potentials up to chlorine evolution. The redox couples examined are reversible at the tin oxide electrode, indicating no effect of electron depletion on the electron transfer kinetics. Electron tunneling through the space charge barrier takes place more easily in the high temperature melt system. For the oxidation of Cu(I) and Pt(II), which do not show diffusion controlled current peaks, an adsorption effect due to anionic bridge formation on the oxide covered with adsorbed chloride has been suggested.

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Electrochemical Properties of Polycrystalline Tin Oxide

Cited by 106 publications

References 14 publications

Electrochemical Properties of Nanocrystalline Cadmium Stannate Films

Electrochemical Properties of Nanocrystalline Cadmium Stannate Films

A direct electrode-driven P450 cycle for biocatalysis

Some Redox Reactions on Semiconducting Tin Oxide Electrodes in Molten LiCl ‐ KCl Eutectic at 450°C

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