Modification Of Graphite-Phase Polymeric Carbon Nitride By Doping And Its Photoelectrichemical Performances

With the development of modern industry, energy crisis and environmental degradation become the major problems for humanity to solve in the 21 st century. As a clean, inexhaustible energy, the usage of solar energy has caught much attention. Recently, it has been revealed that as a new metal-free semiconductor graphite-phase polymer carbon nitride (GPPCN) not only has a strong absorption of visible light, but also shows advantages such as biocompatibility, chemical stability, thermal stability and controllable electronic structures, thus exhibiting a great prospect in the field of photovoltaics and photocatalysis.In this thesis, we designed and synthesized two composites based on GPPCN, and applied them to the photoelectric conversion in visible light with enhanced performances. The thesis includes the following two sections:1. Using dicyandiamide (DCDA) as the precursor and calcium carbonate as the template, porous melem was synthesized after being calcined to 400 ℃. Then, titanium dioxide nanoparticles were introduced the hole of porous melem through ultrasonic dispersion. After that, the mixture was calcined to 550 ℃, and porous GPPCN-titanium dioxide composite was finally formed. By scanning electron microscope, infrared-/ultraviolet-spectra, X-ray diffraction, and N2 absorption-desorption method, physicochemical properties of the composite were characterized and analyzed. Moreover, by adjusting the ratio of melem to titanium dioxide, or adding an additional electron mediator, the photoelectric conversion efficiency of the composite material can be enhanced up to 10 times.2. Bulk GPPCN was synthesized by thermal condensation of DCDA. Then, it was protonated using HCl of different concentrations. Due to an effective interaction between H+ and the lone pair electrons of nitrogen atoms, the place where hydrogen ions and chloride ion sit could be considered as the active sites for cooperating foreign functional components. Through further ion-exchange reaction, chloride ion could be replaced by chloroplatinic ion. After that, by adding reducing agent sodium borohydride, chloroplatinic ion was reduced into platinum nanoparticles, so as to achieve the controllable loading of platinum nanoparticles on GPPCN. By scanning electron microscope, transmission electron microscope, infrared-/ultraviolet- spectra, X-ray diffraction, and other methods, physicochemical properties of the composites were characterized in detail. As a result, GPPCN which was treated with 27.8% HCl has the best photocurrent response that was 4 times of the bulk one.