Improved catalytic wet peroxide oxidation of phenol over Pt-Fe2O3/SBA-15: Influence of platinum species and DFT calculations

Abstract

In this study, Pt-Fe2O3, Pt, and Fe2O3 catalysts supported on SBA-15 were prepared for catalytic wet peroxide oxidation (CWPO) of phenol at low temperatures. Pt-Fe2O3/SBA-15 and Pt/SBA-15 had higher H2O2 decomposition rates at 20 °C compared with that of Fe2O3/SBA-15, which is representative of a conventional CWPO catalyst. Although H2O2 was decomposed at a higher rate by Pt/SBA-15 than Pt-Fe2O3/SBA-15, Pt/SBA-15 barely exhibited any phenol removal activity. Meanwhile, Pt-Fe2O3/SBA-15 showed a superior phenol removal activity, indicating that Pt-Fe2O3/SBA-15 efficiently utilizes H2O2 for the CWPO reaction. To establish a correlation between the H2O2 decomposition activity and the phenol removal activity, characterization of the catalysts and density functional theory (DFT) calculations were conducted. TEM, XPS, and H2-TPR verified that Fe2O3 affected the state of the impregnated Pt via metal-support interactions, which enabled the formation of Pt4+ species in the Pt-Fe2O3/SBA-15 catalyst. DFT calculations revealed that PtO2 can selectively generate OH radicals, while Pt converts OH radicals into H2O via further reactions. As predicted by DFT calculations, EPR spectra demonstrated that OH radicals were formed by Pt-Fe2O3/SBA-15 but not by Pt/SBA-15. In conclusion, Pt4+ species in the Pt-Fe2O3/SBA-15 catalyst via interactions between Pt and Fe2O3 led to highly efficient phenol removal with H2O2.