The effect of MgO coating on photocatalytic activity of SnO2 for the degradation of chlorophenol and textile colorants; the correlation between the photocatalytic activity and the negative shift of flatband potential of SnO2

Abstract

Abstract SnO 2 is a totally inactive photocatalyst for the degradation of 2-chlorophenol (2CP) and textile colorant Mercurochrome (MC) at acidic pH values, but shows feeble photocatalytic activity for the degradation of said pollutants at basic pH values. However, coating of a thin MgO layer on SnO 2 nanocrystalline particles transforms photocatalytically inactive SnO 2 to an active photocatalyst. A negative shift of the flatband (FB) potential of SnO 2 was observed with the increase of pH values and coating of a thin MgO layer on SnO 2 particles. Further we noticed the retardation of charge recombination on SnO 2 upon MgO coating and increase in pH values. Hence, the promoting effects of MgO layer on SnO 2 catalyst for the sensitized degradation of colorants and chlorophenol degradation in aqueous phase were assigned to both slow charge recombination and to the negative shift of FB potential.