Photoproduction of hydrogen: Potential dependence of the quantum efficiency as a function of wavelength

The quantum efficiencies (Q) of the photoelectrochemical oxygen evolution reaction on reduced TiO₂ in 0.1 N NaOH have been measured as a function of electrode potential and photon energy (E) over the range 3.2–4.0 eV. Maxima in the Q-E relations over the potential range ?0.4–+1.25 V NHE were observed and the maxima shifted towards lower photon energies as the potential became more positive. This trend can be interpreted in terms of the variation of the absorption coefficient with frequency.