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 (E_p), 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 |E_p| 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.