Oxygen Vacancy‐rich Anatase TiO2 Hollow Spheres Via Liquid Nitrogen Quenching Process for Enhanced Photocatalytic Hydrogen Evolution.

Development of novel methods to obtain highly active catalysts for photocatalytic hydrogen evolution is desired. This work reports a facile preannealing‐quenching strategy to synthesize oxygen vacancy‐rich anatase TiO2 hollow spheres. TiO2 hollow spheres are first synthesized via a versatile kinetics‐controlled coating method and then subjected to high temperature preannealing followed by rapid quenching in liquid‐nitrogen (−196 °C). The as‐quenched samples appear light grey suggesting the presence of abundant surface oxygen vacancies, which are subsequently confirmed by the comprehensive analyses of XRD, XPS and EPR spectra. The oxygen vacancies induced by quenching process are proved to have promoted the light adsorption and inhibited the recombination of photo‐induced charges for TiO2 hollow spheres, which obviously improve the photocatalytic performance of those samples. The results showed that the TiO2 hollow spheres quenched at 500 °C exhibited a robust stability and the most excellent photocatalytic performance for hydrogen evolution (413.5 μmol h−1) over other quenched samples and it displayed 1.51 times higher performance than that of samples normally cooled at 500 °C (273.7 μmol h−1). Herein, this liquid‐nitrogen quenching strategy presented here provides an effective route for the synthesis of high‐performance TiO2 for water splitting and have a promising prospect in the other application. It's a vacancy‐rich world! During the liquid‐nitrogen quenching process, the isolated O atoms on the TiO2 surface are partially frozen and lose the opportunity to return the crystallographic sites, leaving abundant oxygen vacancy on the surface. The oxygen vacancy‐rich TiO2 prepared via liquid‐nitrogen quenching exhibited outstanding advantages on photocatalytic H2 evolution. [ABSTRACT FROM AUTHOR]