Synthesis of TixOy nanocrystals in mild synthesis conditions for the degradation of pollutants under solar light

Abstract

Black TiO2 is capable to absorb the entire or part of the visible spectrum improving, a priori, the photoactivity under solar irradiation. Nevertheless, black TiO2 materials have not been able to demonstrate the expected photocatalytic activity in visible light due to the presence of a large number of recombination centers. In addition, high temperatures or pressures (>400 °C, 20 bar) are required for the conventional synthesis and alternative methods have high energy costs which limit the capability for mass production. In this report, a novel controlled hydrolysis method has been developed to synthesize reduced black TiO2 in mild conditions of temperature (180 °C) and pressure (8 bar). The synergetic effect of the stabilization of small crystal sizes, strong visible light absorption, band gap narrowing, Ti3+ defects or oxygen vacancies concentration, improved surface area and pollutant-surface interactions, significantly enhances the photocatalytic activity in the degradation of organic pollutants (Orange G) under visible light (almost totally degraded at 40 min).