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

Abstract

Graphitic carbon nitride (g-C 3 N 4 ) 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-C 3 N 4 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-C 3 N 4 catalyst is essential for CO methanation reaction. The as-prepared Ni/g-C 3 N 4 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-C 3 N 4 as a catalyst support enhances the complete reduction of Ni species and CO desorption. This can be attributed to the role of g-C 3 N 4 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-C 3 N 4 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.

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“…The higher energy peak located at 855–856 eV may be associated with transitional Ni 2+/3+ species, likely present as oxide/oxyhydroxides. 30–33 As the Ni loading increases, the peak attributed to Ni 2+/3+ shifts toward a lower binding energy, whilst its relative intensity to the Ni 2+ peak decreases. With the increase in Ni deposit size, the relative sampling depth into the Ni deposits would differ accordingly, being able to reach closer to the core of smaller deposits.…”