Structral Modification Of Graphite-phase Polymeric Carbon Nitride And Its Photoelectrochemical Performances

Energy crisis has been one of the great challenges people face.In order to relieve the problem of energy crisis and the subsequent environmental pollution,it is highly anticipated to develop and take full use of clean energy.As a renewable energy,the solar energy can be used widely and effectively.Graphite-phase polymer carbon nitride(CN)has been recently studied as a metal-free semiconductor.Its major components are C and N which are very abundant on earth.Also,the CN assures unique electronic band structure and chemical stability,thus this metal-free semiconductor exhibits a broad application prospect in the field of photocatalysis and photoelectric conversion.In this thesis,a facile ball milling method was adopted to modify the bulk CN and the optimal conditions were also summarized.Three different size of CN were prepared by this way and applied in photoelectric conversion.Moreover,three alternative ways to prepare photoelectrode were provided in order to investigate the impact of film forming property,boundary effect and the selection of binders on photoelectrochemcial activity.The thesis includes the following two parts:1.The pristine bulk CN was prepared by calcination of DCDA to 550?.Then,three different ball milling methods were adopted to modify the bulk CN and the effect of milling time on the size of CN was investigated.The pristine and modified CN were characterized by scanning electron microscope,X-ray diffraction,N2 absorption-desorption and other optical spectroscopy.It was found the CN material prepared by wet milling with water and milling for three hours possessed the excellent photoelectrochemcial property.By this method,the whole process was not only simple but also ecologically friendly.2.The morphology modified CN was prepared by wet milling with water for three hours,and then separated through centrifugation as its difference in particle size.Three different size of CN were adopted as electrode materials,and three general ways of preparing CN photoelectrode are also presented and compared,including drop-casting of CN particles,further blending with Nafion or PEDOT-PSS as the binder.The influences of film forming property,loading amount and the selection of binding agents to the overall photoelectrochemcial activity were also investigated.As a result,when PEDOT-PSS acted as binder,CN particles with size of 0.5 ?m and an optimal loading amount(2.4 mg/cm2)were adopted,the as-prepared CN photoelectrodc had much superior photoelectrochemical activity,which was about eight times higher than that by bulk CN.Therefore,this study would not only pave the way for preparing CN photoelectrode of superior quality so as to promote CN materials to be better applied in solar fuel and sensing applications,but also provide a universal and simple way to prepare CN-based photoelectrode.