Oxygen vacancy enhanced photostability and activity of plasmon-Ag composites in the visible to near-infrared region for water purification

Abstract

Solid solution of BiOBr and BHO (BiO(OH)0.06Br0.94) with abundant oxygen vacancies was supported on Ag/AgBr using precipitation and deposition–precipitation methods. The photocatalyst showed high and stable photocatalytic activity for the degradation of chlorophenols and azodyes in water under visible to NIR light irradiation without any release of Ag+, which came from visible-excited AgBr and the SPR of Ag NPs in the visible and NIR region. The different interfacial charge-transfer processes were verified on the basis of cyclic voltammetry analyses and all experimental information. The conduction band (CB) electrons of photoexcited AgBr reacted with the adsorbed oxygen forming O2•−, while the valence band (VB) holes of AgBr were transported the VB of BiO(OH)0.06Br0.94 to oxidize organic pollutants or H2O to •OH. The plasmon-induced electrons from Ag NPs transferred to the CB of AgBr reacting with the adsorbed oxygen to O2•−, while the electrons trapped on the oxygen vacancies of BiO(OH)0.06Br0.94 transferred to Ag NPs recombining with the plasmon-induced holes, inhibiting the release of Ag+, and the resulted VB holes of BiO(OH)0.06Br0.94 oxidized organic compound. These interfacial charge transfers evidenced the high photoactivity and photostability of BiO(OH)0.06Br0.94/Ag/AgBr.