Influence of cobalt species on the catalytic performance of Co-N-C/SiO2 for ethylbenzene oxidation

Abstract

In this paper, cobaltporphyrin is used as a precursor to synthesize carbon nitrides with metal active sites supported on silica spheres by heat treatment (i.e. M-N-C/SiO₂). The catalytic performance of M-N-C/SiO₂ for ethylbenzene oxidation has been investigated and techniques such as N₂ adsorption/desorption isotherm, NH₃-TPD, HRTEM, STEM mapping and X-ray photoelectron spectroscopy (XPS) are employed to explore the active sites for ethylbenzene oxidation. XPS results show that cobalt compounds, such as CoO_x and metallic Co, as well as cobalt nitrides, such as Co-N_x, are formed after the pyrolysis of cobaltporphyrin. However, according to the NH₃-TPD experiment, Co-N_x may be the primary active site. When Co-N_x is poisoned by KSCN, the significant loss of catalytic activity further proves and verifies that Co-N_x instead of CoO_x is the primary active site of M-N-C/SiO₂ for ethylbenzene oxidation.