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

• Published in: Applied catalysis. B, Environmental Vol. 241; pp. 385 - 392
• Main Authors: Hamad, Hesham, Bailón-García, Esther, Maldonado-Hódar, Francisco J., Pérez-Cadenas, Agustín F., Carrasco-Marín, Francisco, Morales-Torres, Sergio
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2019
• Subjects: Band gap narrowing; Black titania; Oxygen vacancies; Synergetic effect; Visible light photocatalysts; Visible light photocatalysts; Oxygen vacancies; Synergetic effect; Black titania; Band gap narrowing
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2018.09.016

[Display omitted] •A new method has presented to synthesize reduced black TiO2 in mild conditions.•The material possesses an optimum band gap and visible light adsorption.•XPS reveals that Ti3+ is the main component at the surface of colored TiO2.•Orange G adsorption is improved by electrostatic interactions with the surface Ti3+.•An exceptionally high visible light photocatalytic activity is obtained under visible light. 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).