Superoxide-Triggered Luminol Electrochemiluminescence for Detection of Oxygen Vacancy in Oxides

Oxygen vacancy is known to act as a reactive center in oxides to produce radicals. Currently, X-ray photoelectron spectra (XPS) become a unique spectral tool for analyzing oxygen vacancy based on the differences in atomic number ratios between metal ions and lattice oxygen. In this work, it was found that the superoxide radical (O₂^•-)-luminol electrochemiluminescence (ECL) intensity linearly increases with increasing the oxygen vacancy concentrations of TiO₂ samples coated on the electrodes. An experimental study of the mechanism demonstrates that an increase in oxygen vacancy concentrations could lead to an increase in the generation of O₂^•-, resulting in an increase in the O₂^•--related luminol ECL signals. Accordingly, we have developed a rapid and simple O₂^•--luminol ECL platform to detect oxygen vacancy in TiO₂ samples, based on the relationship between O₂^•- generation and oxygen vacancy. The proposed ECL platform exhibits good reproducibility and stability through the parallel ECL measurements. Moreover, the feasibility is verified by analyzing the oxygen vacancy concentrations in different TiO₂ samples with varying the Co, Cr, Fe, and N doping concentrations. The oxygen vacancy concentrations obtained by the proposed ECL method could match well with those obtained by conventional XPS measurements. Our successful construction of the ECL platform will significantly promote the development of the oxygen vacancy detection in oxides and deepen the understanding of the relationship between oxygen vacancy and radicals.