Enhancement of photoelectrochemical activity by Ag coating on black TiO2 nanoparticles

Abstract

This work reports the effect of Ag coating on black TiO2 nanoparticles for photoelectrochemical activity. Black TiO2 nanoparticles were synthesized in a vacuum and an ambient atmosphere at low temperatures. Ag nanoparticles were then coated on the black TiO2 using a wet-chemical method. Decreased bandgap energy of 1.89 and 2.28 eV was achieved for the black TiO2 nanoparticles synthesized in vacuum and air, respectively, along with the increase in visible light absorption. The reduced bandgap energy and black color were attributed to the formation of surface oxygen vacancies, which lead to a crystalline core/amorphous shell structure. The visible light absorption was further enhanced by Ag coating, which resulted in the enhancement of photoelectrochemical activity by 7.87 and 9.39 times compared to that of black TiO2 nanoparticles synthesized in vacuum and air, respectively. The possible mechanism for this enhancement in the photoelectrochemical activity of the Ag-coated black TiO2 is explained.