Effective Enhancement of TiO2 Photocatalysis by Synergistic Interaction of Surface Species: From Promoters to Co-catalysts

The enhancement of TiO 2 -based catalyst activity by effect of surface species is analyzed in the photoelimination of toluene in a complex, ternary system having ceria and Mn-modified carbon nitride in contact with a major anatase phase. With a combination of kinetic and spectroscopic tools applied to the ternary system and corresponding binary/single references, this study delineated a method to quantitatively analyze the quantum yield or reaction rate through a strict measurement of the effect of each component of the ternary system in the generation of the active OH-related radical species of the reaction and the subsequent influence in photocatalytic observables. Using this procedure, the study allows elucidating the role and significance of the surface species in the reaction and, in particular, the important and unique role of a cationic Mn species in modifying the behavior of the carbon-containing species, a fact exclusively occurring in the ternary system and not in the corresponding parent binary/single ones. The method unveils a transformation of such surface species role from that of a promoter to that of a co-catalyst through the synergistic/cooperative interaction of all present phases at the catalyst and establishes a general scheme to measure and interpret the interaction of components in multicomponent photocatalysts.