Effect of the Ag–CeO2 interaction and the nature of pore structure on the catalytic activities of different Ag–CeO2/mesoporous-SiO2 catalysts on the reduction of 4-nitrophenol

Photocatalytic reduction of 4-nitrophenol is one of the important waste-utilization techniques that transform toxic para-nitrophenol to useful chemicals, such as 4-aminophenol. The photosensitive nature of silver nanoparticles, Ce3+/Ce4+ redox systems of CeO2 and mass transport ability of different mesoporous SiO2 materials can be combined to design effective catalysts for the catalytic reduction of 4-nitrophenol to 4-aminophenol. Therefore, The Ag and CeO2 particles were impregnated on mesoporous SiO2 supports of different pore structures (KIT-6 = ordered interlinked pores, TUD-1 = irregular type pores) and were utilized to reduce 4-nitrophenol by NaBH4 reductant in the photocatalytic route. The catalytic reaction results revealed the superiority of Ag–CeO2/KIT-6 catalysts (rate constant = 0.008 s−1) compared to Ag–CeO2/TUD-1 catalysts (rate constant = 0.002 s−1) due to the pore blockage resistance capacity of the interlinked chanels of KIT-6 support and the formation of Ag2O–CeO2 p–n heterojunctions in the catalyst. Moreover, the Ag–CeO2/KIT-6 showed optimum activity among many other reported catalysts in terms of the normalized rate constant and turnover frequency.