12,000

We have over 12,000 students, from over 100 countries, within one of the safest campuses in the UK

93%

93% of Lancaster students go into work or further study within six months of graduating

Home > Research > Publications & Outputs > Photoelectrophoresis of colloidal semiconductor...
View graph of relations

« Back

Photoelectrophoresis of colloidal semiconductors. Part 2.—Transient experiments on TiO2 particles

Research output: Contribution to journalJournal article

Published

Journal publication date1991
JournalJournal of the Chemical Society. Faraday Transactions Part 2
Journal number21
Volume87
Number of pages10
Pages3547-3556
Original languageEnglish

Abstract

We report experimental data and a second-order kinetic model for the time dependence of photo-induced changes in electrophoretic mobilities of aqueous dispersions of TiO2 semiconductor particles when irradiated with photons of energy corresponding to greater than their band gap (ca. 3.2 eV), in the absence of hole and electron scavengers. This is the first time that (laser Doppler) electrophoresis has been used to obtain kinetic information, in this case for analysing photocatalytic processes relevant to solar energy harvesting for chemical synthesis/destruction.

The second-order rate constant for intra-particle electron-hole recombination, k(r') was determined as > 10(6) times greater than either the pseudo-first-order rate constants for charged surface site generation from holes and electrons, k'A and k'B, respectively; this indicates that recombination was a dominant process in determining the efficiency of surface charge generation in the absence of charge carrier scavengers. The rate constants for positive and negative ionic surface charge removal by electrons and holes k(e) and k(h), respectively, were ca. 1-20 m3 mol-1 s-1, and compare very closely with the value of k(r') indicating that these processes compete with direct electron-hole recombination. The quantum yield, phi, for hole/electron capture by oxidizable/reducible sites on the particle surface was in the range (5.2-7.9) x 10(6).