Xu Huang,Yiwen Zhang,Zhi Liang,Yingfeng Zhao,Huiwen Yuan,Mingyang Li,Fengping Peng,Wei Wang
In this paper, a series of isotype heterojunction photocatalysts with urea-derived g-C 3 N 4 (CNU) as the core and cyanamide-derived g-C 3 N 4 (CNC) as the shell are reported. A much thinner CNC shell which can protect the CNU core from thermal etching and determines the light absorption is beneficial to improve the photocarrier transfer and separation efficiency, pore volume, and the overall crystalline degree of the most active CNU/CNC2 core–shell isotype heterojunction photocatalyst for rhodamine B (RhB) degradation. Contrast experiments confirm that the electron-derived oxidant species (⋅O 2 − ) play key roles in driving the RhB degradation.
Graphical Precursors and blessings : A precursor-engineering strategy coupled with a microwave molten-salt process is developed to synthesize g-C 3 N 4 with an isotype triazine/heptazine-based g-C 3 N 4 heterojunction as a photocatalyst for the hydrogen evolution reaction (HER) under visible light illumination. The promising HER activity is attributed to the composition and microstructure, efficient separation of electron–hole pairs, broadened photo-absorption edges, and narrowed band gaps. A precursor-engineering strategy coupled with a microwave molten-salt process (PE-MWMS) is developed to synthesize graphitic carbon nitride (g-C 3 N 4 ) with an isotype triazine/heptazine-based g-C 3 N 4 heterojunction as a photocatalyst for the hydrogen evolution reaction (HER) under visible light illumination. Four hybrid precursor combinations—thiourea/melamine, thiourea/dicyandiamide, urea/melamine, and urea/dicyandiamide—are used to synthesize g-C 3 N 4 heterojunctions by the PE-MWMS process. Control experiments indicate that the precursor components and microwave treatment have a great effect on the HER performance of the g-C 3 N 4 samples. Samples synthesized with the optimal molar ratios of thiourea/melamine (2:1), thiourea/dicyandiamide (2:1), urea/melamine (3:1), and urea/dicyandiamide (3:1), exhibit the highest HER rates of 3135, 2519, 2844, and 2565 μmol g −1 h −1 , respectively. The amounts of heptazine and triazine units in the g-C 3 N 4 samples can be easily adjusted by changing the ratios of the hybrid precursors and play a decisive role in improving the photocatalytic HER activity. Because of the unique composition and microstructure, the efficient separation of electron–hole pairs, the broadened photo-absorption edges, and the narrowed band gaps, the as-obtained triazine/heptazine-based g-C 3 N 4 nanostructures exhibit promising activity for HER application.
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