Carbon Monoxide Desorption and Reduction Studies of Graphitic Carbon Nitride Supported Nickel Catalysts for CO Methanation

Graphitic carbon nitride (g-C3N4) has attracted much attention due to its unique polymeric structure of carbon and nitrogen in the form of heptazine units. In this study, a nickel catalyst supported on graphitic carbon nitride was prepared by a facile impregnation method. Ni/g-C3N4 desorption and reduction behaviors with carbon monoxide (CO) were investigated by temperature-programmed desorption (TPD) and reduction (TPR). The chemisorption study of reduction and desorption behaviors of CO molecules on Ni/g-C3N4 catalyst is essential for CO methanation reaction. The as-prepared Ni/g-C3N4 catalyst was also characterized by X-ray diffraction (XRD), N-2 physisorption, and X-ray photoelectron spectroscopy (XPS). It was found that the utilization of g-C3N4 as a catalyst support enhances the complete reduction of Ni species and CO desorption. This can be attributed to the role of g-C3N4 support as a reducing agent for Ni, as well as its basicity owing to the richness of nitrogen functional group. The good performance of Ni/g-C3N4 catalyst towards CO methanation can be ascribed to the improvement in adsorption and activation of CO molecules on the active sites and the number of surface basic sites.