| Nowadays, the photocatalysis technique is considered to be one of the most promising techniques for solving the global energy crisis and environmental pollution. Ti O2 becomes the most extensively researched photocatalyst due to its low cost, nontoxicity and long-term stability. However, its large band gap energy of 3.2 e V and the high recombination rate of electron-hole pairs seriously restricted the practical application of Ti O2. Therefore, it is of great significance to develop new visible-light-responsive photocatalysts by enhancing light harvesting and reducing the recombination rates of the photoinduced electron-hole pairs.In this paper, two kinds of photocatalyst with efficient photocatalytic performance under visible-light irradiation were synthesised. One is ultrathin nanosheets g-C3N4/Ti O2 composites and the other is heterostructured g-C3N4/Ag-Ti O2 composites, which were devided into two parts:The first part: ultrathin g-C3N4 nanosheets modified Ti O2 photocatalyst have been successfully synthesized via a simply sonochemical approach, and thoroughly characterized. The photocatalytic activities were evaluated by degrading Rhodamine B dye. The g-C3N4/Ti O2 composites exhibited much higher photocatalytic activities than pure Ti O2. Moreover, the catalysts retained good stability and the photodegradation efficiency hardly changed after five cycles, which was attributed to the synergistic effects, including enhanced the absorption of visible light and the separation efficiency of photogenerated electrons and holes. In addition, a possible mechanism for the photodegradation process was proposed on the basis of active species scavenging experiments.The second part: Ag loaded Ti O2(Ag-Ti O2) was prepared through photodeposition procedure. And then g-C3N4/Ag-Ti O2 composites with close interfacial contactions among Ag, Ti O2 and g-C3N4 were facilely fabricated with calcination and thoroughly characterized. As the deposited Ag nanoparticles played the important roles as an electron-conduction bridge and surface plasmon resonance effect, Ag modification feasibly improved the separation efficiency for photoinduced electron-hole pairs and enhanced visible-light response. Furthermore, due to the further enhanced separation for photogenerated charges resulted from the existed build-in electric field of heterojunction and the superposed light response from hybridization of Ti O2 and g-C3N4, g-C3N4/Ag-Ti O2 composites exhibited remarkably improved photocatalytic activities for degrading Rhodamine B dye compared with pristine Ti O2 and g-C3N4 and single-component modified photocatalysts. Additionally, g-C3N4/Ag-Ti O2 catalyst retained excellent stability even after five recycles. |
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