Fig. 3: In situ investigation of PMS activation behaviors over different catalysts.

a The reaction sequence of in situ Raman, first add ONP for a period of time and then add PMS. b Vibrational modes of different peaks in the Raman spectrum. c–e The shift of different peaks in the in situ Raman spectrum. f Schematic of the in situ Raman cell set-up. g, h The movement of the characteristic peak i of the in situ Raman spectra in all samples during the different reaction sequence.