Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Photoelectrochemistry with the optical rotating disc electrode Part 4. Steady state and transient studies on colloidal US in the presence of solution phase photogenerated charge scavengers
AU - Boxall, C
PY - 2002/5/31
Y1 - 2002/5/31
N2 - Results are presented for the steady state and light-on transient photoelectrochemistry of two colloidal semi conductor/electron scavenger systems, US/Fe(CN)(6)(3-) and CdS/MV2+, studied with the optical rotating disc electrode (ORDE). Measurements with the ORDE allow calculation of values of 1.74 x 10(-9) and 3.12 x 10(-6) M s(-1) for the electrochemical rate coefficient for reduction of Fe(CN)(6)(3-) and MV2+, respectively, at the photoexcited particle surface. The difference in the values of k(ET) for the cationic and anionic scavenger species at the negatively charged CdS particles underlines the importance of the Coulombic interaction between particle and scavenger in determining the efficiency of particle-to-scavenger electron-transfer, ORDE measurements also indicate that the same Coulombic interactions are found to play an important role in determining the efficiency of the undesirable scavenger-to-particle back reaction, the reduced scavenger being oxidised by holes trapped at the particle surface. Importantly, the largest photocurrents are observed from the CdS/Fe(CN)(6)(3-) system which also has the lowest value for the rate coefficient for the scavenger-to-particle back reaction. The value of 0, the quantum efficiency for the photogeneration of electrons detectable by the ORDE, is found to increase upon the addition of either scavenger, However, the low values of phi observed (0.027 for the CdS/Fe(CN)(6)(3-) system, 0.02 for the CdS/MV2+ system) indicate that, even in the presence of an electron scavenger, the dominant processes within the particle are direct and indirect photogenerated electron-valence band hole recombination. (C) 2002 Elsevier Science B.V. All rights reserved.
AB - Results are presented for the steady state and light-on transient photoelectrochemistry of two colloidal semi conductor/electron scavenger systems, US/Fe(CN)(6)(3-) and CdS/MV2+, studied with the optical rotating disc electrode (ORDE). Measurements with the ORDE allow calculation of values of 1.74 x 10(-9) and 3.12 x 10(-6) M s(-1) for the electrochemical rate coefficient for reduction of Fe(CN)(6)(3-) and MV2+, respectively, at the photoexcited particle surface. The difference in the values of k(ET) for the cationic and anionic scavenger species at the negatively charged CdS particles underlines the importance of the Coulombic interaction between particle and scavenger in determining the efficiency of particle-to-scavenger electron-transfer, ORDE measurements also indicate that the same Coulombic interactions are found to play an important role in determining the efficiency of the undesirable scavenger-to-particle back reaction, the reduced scavenger being oxidised by holes trapped at the particle surface. Importantly, the largest photocurrents are observed from the CdS/Fe(CN)(6)(3-) system which also has the lowest value for the rate coefficient for the scavenger-to-particle back reaction. The value of 0, the quantum efficiency for the photogeneration of electrons detectable by the ORDE, is found to increase upon the addition of either scavenger, However, the low values of phi observed (0.027 for the CdS/Fe(CN)(6)(3-) system, 0.02 for the CdS/MV2+ system) indicate that, even in the presence of an electron scavenger, the dominant processes within the particle are direct and indirect photogenerated electron-valence band hole recombination. (C) 2002 Elsevier Science B.V. All rights reserved.
KW - photoelectrochemistry
KW - photocatalysis
KW - colloidal semiconductors
KW - cadmium sulphide
KW - AQUEOUS CDS COLLOIDS
KW - SEMICONDUCTOR PARTICLES
KW - THEORETICAL-ANALYSIS
KW - POLAROGRAPHY
KW - FEMTOSECOND
KW - VOLTAMMETRY
KW - SYSTEMS
KW - TIO2
KW - ELECTROCHEMISTRY
KW - PHOTOCHEMISTRY
U2 - 10.1016/S1010-6030(02)00065-5
DO - 10.1016/S1010-6030(02)00065-5
M3 - Journal article
VL - 148
SP - 375
EP - 386
JO - Journal of Photochemistry and Photobiology A: Chemistry
JF - Journal of Photochemistry and Photobiology A: Chemistry
SN - 1010-6030
IS - 1-3
ER -