二氨基马来腈共聚合改性氮化碳光催化剂

利用二氨基马来腈(DMNA)与二聚氰胺(DCDA)的高温共聚合反应, 制备了石墨相氮化碳 (g-C₃N₄), 并通过X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱、透射电镜 (TEM)、氮气吸脱附实验 (N₂-sorption)、电子顺磁共振 (EPR)、紫外-可见漫反射光谱 (UV-Vis DRS) 和荧光 (PL) 光谱等表征手段,系统考察了共聚合改性对g-C₃N₄晶体结构、化学结构、能带结构、织构、光吸收性能和光催化性能等的影响.研究结果表明:共聚合改性后氮化碳材料仍保持石墨相晶体结构, 但其π电子的离域性增强, 并在催化剂表面产生异质结构, 进而提高了氮化碳在可见光区域的光吸收性能, 并促进了光生载流子的有效分离. 性能评价结果显示, DMNA改性的氮化碳在可见光下光催化产氢活性明显高于未改性的样品, 当DMNA用量为0.01g时, 催化剂的产氢速率最高, 达到45.0 μmol·h^-1, 为纯氮化碳样品的4.5倍.

Modification of Carbon Nitride Photocatalysts by Copolymerization with Diaminomaleonitrile

g-C₃N₄photocatalysts were synthesized by copolymerization of diaminomaleonitrile (DMNA) with dicyanodiamide (DCDA) at high temperatures. The effect of copolymerization on the crystal structure, chemical structure, band structure, texture, optical property and photocatalytic performance of g-C₃N₄ was studied by such characterization techniques as X-ray diffraction patterns (XRD), Fourier transformed infrared (FT-IR), transmission electron microscopy (TEM), nitrogen-sorption (N₂-sorption),electron paramagnetic resonance (EPR), UV-Vis diffuse reflectance spectra (UV-Vis DSR) and photoluminescence (PL) analyses. Results demonstrated that the graphitic-like layer packing structure of g-C₃N₄ remained unchanged after the modification; however the copolymerization with DMNA can efficiently extend the delocalizationof π-electrons and induce the formation of surface junctions, greatly enhancing the light-harvesting abilityof g-C₃N₄ in visible light region and promoting the separation of photogenerated charge carriers, respectively. Photocatalytic performance showed that all DMNA-modified samples presented an enhanced H₂ evolution activity under visible light irradiation. The optimized weight-in amount of DMNA is found to be 0.01g, by which the modified sample shows the highest hydrogen evolution rate of 45.0 μmol·h^-1. This value is 4.5 times as high as that of the unmodified carbon nitride sample.