Synthesis of graphitic carbon nitride by directly heating sulfuric acid treated melamine for enhanced photocatalytic H_2 production from water under visible light

摘要

Herein we report the synthesis of graphitic carbon nitride (g-C_3N_4) by directly heating sulfuric acid treated melamine precursor. Thermoanalytical methods (TG-DSC) in combination with XRD, XPS and elemental analysis were used to characterize the condensation steps of the precursor. The TG-DSC curves clearly show significant difference in thermal behavior between the treated and untreated melamine. The sublimation of melamine during condensation was significantly suppressed by treating melamine with sulfuric acid. The decomposition of melamine sulfuric acid and the condensation of melamine occur simultaneously. The N/C ratio of the prepared carbon nitride (1.53) is slight higher than that of the ideal crystal g-C_3N_4 (1.33), indicating the incomplete condensation of amino groups in the material. The XPS and elemental analysis show that there is no sulfur residue in the final product. The sample synthesized from sulfuric acid treated melamine shows relatively higher BET surface area. The photocatalytic performance of the as prepared carbon nitride was evaluated under visible light irradiation (λ > 420 nm). The photocatalytic H_2 production rate on sample synthesized from sulfuric acid treated melamine is 2 times higher than that on sample synthesized from untreated melamine.