Effects of thermal program on physicochemical properties and photocatalytic activity of g-C3N4 prepared by dicyandiamide pyrolysis

Graphitic carbon nitride (g-C3N4) can be prepared by the pyrolysis of dicyandiamide, and its properties and performance are greatly affected by the pyrolysis parameters. In this study, the effects of heating rate and pyrolysis time on the physicochemical properties and photocatalytic activity of the obtained g-C3N4 are systematically investigated, and the results are used to guide the controllable production of g-C3N4 in industry. The results show the heating rate has a significant impact on the pore structure, crystallinity, number of amino functional groups, and the stability of structure. The pyrolysis time mainly affects the texture and layer structure of g-C3N4 products. In addition, the polymerization pathways during the dicyandiamide pyrolysis are analyzed through in-situ TG-MS combined with XRD analysis, elucidating the process of dicyandiamide forming complete g-C3N4 products with high polymerization degree by polyaddition, polycondensation and rearrangement. This study provides useful reference strategies for the design of large-scale controllable industrial production of gC3N4 through pyrolysis of dicyandiamide.