SURFACE CHARACTERIZATION OF COBALT TETRAPHENYLPORPHYRIN MODIFIED GLASSY CARBON ELECTRODE BY XPS

Surface structure of the glassy carbon surface modified with cobalt tetraphenyl-porphyrin (CoTPP) by thermal-treatment has been studied by XPS, DTA and TG. During the thermal treatment a bond can be formed between the glassy carbon surface and TPP. Therefore the stability of electrode for the catalysis of dioxygen reduction is improved. Upon thermal treatment at 600 degrees C, FWHM of Co(2p(2/2)) is broadened, the reason is due to overlapping of peaks of multiple states, the spin orbit separation between Co (2p(1/2)) and Co (2p(3/2)) increases to 15.5-16.3eV, which indicated a change from low spin divalent states, the kinetic energy of Co L3VV Auger line and Auger parameter also increase. These changes of central cobalt ion provide a suitable redox potential for Co(III)/Co(II) which is related to the activity for catalysis of dioxygen reduction.