Graphene oxide-P25 photocatalysts for degradation of diphenhydramine pharmaceutical and methyl orange dye

► Acidic character of GOP composites varied with the GO content and heat-treatments. ► The mesoporosity of the composites increases with GO wt. but not the microporosity. ► GO aggregates coated with P25 nanoparticles are stabilized with TiOC bonds. ► Optimization of the GO content is fundamental in the photocatalytic efficiency. ► The formation of reduced graphene oxide improves the photocatalytic performance.