On the nature of Cr species on MCM-41 obtained by a one step method and their enhanced photocatalytic performance under visible radiation. New insights by a combined techniques approach

Abstract

MCM-41 materials modified with several Cr/Si molar ratios by a direct incorporation method and thenwith Ti by impregnation, were characterized by different instrumental techniques. In order to developnew photocatalysts that uses more efficiently solar light, the aim of this work was to evaluate the directincorporation method to synthesize Cr-modified MCM-41. The synthesized solids were tested as pho-tocatalysts for the Acid Orange 7 (AO7) degradation in aqueous solution. The catalysts with Si/Cr molarratios of 60 and 40 led to AO7 degradations higher than 70% after the Ti loading. Thus, it could be con-firmed that the direct incorporation method of Cr in the synthesis gel favored the high dispersion of theactive species of Cr6+making them accessible to interact with Ti species. Finally, the presence of Ti iscrucial to achieve a better use of the radiation due to the synergistic effect with the Cr species besidesavoiding the loss of this metal to the reaction medium.