Fig. 8: The high-resolution XPS spectra of the fresh and used MBZ.

a The high-resolution XPS spectra of the MBZ for Ba 3d before and after the first application. b The high-resolution XPS spectra of the MBZ for S 2p before and after the first application. c, d The high-resolution XPS spectra of the MBZ for Mo 3d before and after the first application.