二氨基马来腈共聚合改性氮化碳光催化剂

Modification of Carbon Nitride Photocatalysts by Copolymerization with Diaminomaleonitrile

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(FTIR)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-VisDRS)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45.0μmol·h-1,为纯氮化碳样品的4.5倍.

g-C3N4 photocatalysts 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 （XRD） patterns,Fourier transformed infrared （FTIR）,transmission electron microscopy （TEM）,nitrogen-sorption （N2-sorption）,electron paramagnetic resonance （EPR）,ultraviolet-visble 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 delocalization of π-electrons and induce the formation of surface junctions,greatly enhancing the light-harvesting ability of 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 45.0μmol·h-1.This value is 4.5 times as high as that of the unmodified carbon nitride sample.