Open-circuit photopotential characterization of photoelectrochemical activities of Au-modified TiO2 nanorods

Abstract

The open circuit potential (OCP) of a semiconductor electrode can be used to quantify the transient photopotential (Ep), which represents wavelength-dependent charge accumulation and relaxation kinetics of a photoelectrode. Here OCP responses of a plasmonic Au@TiO2 nanorods (NRs) photoelectrode can be quantified without causing electrochemical corrosion of Au. The photogenerated charge accumulation kinetics data based on the wavelength-dependent growth rates of |Ep| can resolve the plasmonic effects on photoelectrochemistry (PEC) of Au@TiO2 NRs. Data fitting with Kohlrausch-Williams-Watts (KWW) stretched exponential kinetics model illustrates the complex charge relaxations at the Au/TiO2 Schottky contact, from which long relaxation lifetimes with broad lifetime distributions can be obtained. This is attributed to the abundant deep defects in the nanostructure TiO2, which has been strongly confirmed by reducing the oxygen vacancies using a post-thermal annealing treatment. Single-particle dark-field scattering (DFS) spectrum is measured with a tunable wavelength light source to support visible light activities of PEC characteristics of Au@TiO2 NRs. Light scattering spectra of >200 single Au@TiO2 NRs particles are collected to compare directly with PEC responses of OCP of the ensemble Au@TiO2 NRs.