Water oxidation by P25 TiO2 photoanodes in acidic solution

P25 TiO2 photoanodes are used to photo-oxidise water in two different acids, 0.5 M H2SO4 and 1 HClO4. In the former acid, linear sweep voltammogram, LSV, appears exhibit photocurrent waves, whilst only one latter. H2SO4, recorded LSV coupled with a low faradaic efficiency (0.58) for photooxidation of O2, fO2, significant level persulfate, fS2O8 = 0.12, shows that electrochemical kinetics not simply those oxidation. HClO4, high fO2 value (0.91) suggest is due Photo-induced absorption spectroscopy, PIAS, measurements made using photoanode reveal steady state absorbance change, ΔAbsss, associated steady-state concentration surface accumulated holes, [h+]ss, which varies with: (i) monitoring wavelength, peak at ca. 500 nm, (ii) applied potential, flattening off 0.7 V vs Ag/AgCl. PIAS measurements, concomitant transient (TC) on polarised 1.3 v Ag/AgCl, show oxidation second order respect surface-accumulated, photogenerated have calculated turnover frequency 19 s−1, under sun irradiation. This first reported example use PIAS/TC probe photoelectrochemical exhibited by mesoporous semiconductor derived from powder, significance such discussed briefly.