High Performance Photocatalysts Based On π-conjugated Carbon Materials And Structrue-property Relationship

Based on the traditional UV-type photocatalyst and π-conjugated carbon material, chemical adsorption method, the heating reflux method, photo-reduction method and high temperature polycondensation method was used for prepared photocatalysts. The production and enhancement mechanism of activity, stability, morphology, size, crystal structure were systematically investigated. The ability of electron-hole transfer, free radicals and the main active species were characterized by photoelectrochemical, spectroscopy, electron spin resonance, and capture experiment in detail. Therefore, designing novel photocatalysts with high photocatalytic efficiency, visible-light response and high stability is of great importance for photocatalysis research. This work would provide some idea of synthesis for g-C3N4and carbon-based materials.A surface hybrid method was developed by using conjugated-π materials, which would enhance the transportation and the separation of photocarriers. The optimum photocatalytic activity of ZnO1-x/graphene-1.2wt%under visible and UV light was4.6and1.2times as that of ZnO1-x, the efficiency of ZnWO4/graphene-0.2wt.%was about7.1and2.3times as that of ZnW04, respectively. The photocorrosion of ZnO1-x and ZnW04was successfully inhibited by graphene hybridation. The enhancement of photocatalytic activity in ZnO1-x/graphene was attributed to the the synergistic effect between graphene and ZnOi-x for high separation efficiency of electron-hole pairs mainly resulting from the promotion of HOMO orbit of graphene and the Oi" defect level of ZnO1-x. The visible activity was originated from the OH and·O2, which were formed by photosensitization of graphene in ZnW04/graphene. The enhancement of UV light activity was attributed to the high separation efficiency of photoinduced electron-hole pairs resulting from the promotion of HOMO orbit of graphene.There may be existed more surface defects of g-C3N4after thermal condensation reaction, therefore, for purpose of eliminating the surface defects, the controlled transformation of g-C3N4from nanoplates to nanorods was realized by a simple reflux method. This is the first report on systhesis of g-C3N4nanorods structure with no template. The photocatalytic activity and the photocurrent response of g-C3N4nanorods were about1.5and2.0times as that of g-C3N4nanoplates, respectively. The formation mechanism of g-C3N4from nanoplates to nanorods was demonstrated that g-C3N4nanoplates undergo a possible exfoliation and regrowth process and a rollingmechanism of lamellar structure, which is responsible for elimination the surfacedefects. The enhancement of activity was attributed to increasement of active latticeface and elimination of surface defects. Based on defects and hanging bond on thesurface of g-C3N4, there may be easy to form the coordination effect with Ag andheterojunction with C60. Thus, Ag@C3N4core-shell structures and C60/C3N4compositeswere prepared and both of the photocurrent response is about4.0times as that of pureg-C3N4. The enhancement of activity may be ascribed to SPR effect of Ag andπ-conjugative interaction of C60, which were favorable for charge separation and lightadsorption. This work would put the research about regulation of g-C3N4structure to adeeper level, and have guidance for preparing special morphology of g-C3N4.