Studies On Photocatalytic Hydrogen Production From Dyes Sensitized G-C₃N₄ Modified By Non-noble Metal Cocatalyst

The photocatalytic hydrogen production by water splitting has attracted worldwide attention due to the shortage of energy and the environmental pollution, however, it is a great challenge to establish stable, efficient and affordable heterogeneous photocatalytic systems for H₂ production from water splitting today. New semiconductor g-C₃N₄, as a metal-free layed visible-light photocatalyst, is the most employed in photocatalytic research at present because of its high thermal and chemical stability as well as rich and cheap building elements.However, pristine g-C₃N₄ band gap energy?Eg=2.7 eV? is too wide to absorb longer wavelength visible light. In addition, its photocatalytic activity is relatively low due to electron-hole recombination.Dye-sensitization is regarded as the most effective way to increase the ability of photocatalyst response to visible light. And it can widen g-C₃N₄ response to visible light range and improve its absorption of visible light intensity. Being loaded with non-noble metal cocatalyst can effectively reduce the overpotential, thus improve the photocatalytic activity.In this thesis, photocatalytic hydrogen production using xanthene dyes sensitized a new type of semiconductor g-C₃N₄ modified by non-noble metal under visible light irradiation was studied and the whole work is composed of the following two parts:?1?. g-C₃N₄ was prepared by pyrolysis of urea at 600 °C respectively. Layer MoS₂ was synthesized by hydrothermal method with sodium molybdate and thioacetamid.Few layer of MoS₂ was stripped ultrasonicly in DMF. MoS₂-g-C₃N₄ was prepared by a simple immersion method with g-C₃N₄. The photocatalytic activity for hydrogen evolution from aqueous triethanolamine solution under visible light irradiation???420 nm? was evalulated using Erythrosin B?EB? as the sensitizer. And 6 wt %Mo S₂-g-C₃N₄ exhibits the highest sensitization activity which is as 138 times as g-C₃N₄.It was found that the higher activity can be ascribed to loaded-cocatalyst MoS₂ which can effectively play an important role, promote the separation of the carriers, lower electron-hole recombination rate and reduce the overpotential.?2?. g-C₃N₄ was prepared by pyrolysis of urea at 600 °C respectively. The photocatalytic activity for hydrogen evolution from aqueous triethanolamine solution under visible light irradiation???420 nm? was evalulated using Eosin Y?EY? as the sensitizer and CoSx as cocatalyst. And 5 wt % CoSx-g-C₃N₄ exhibits the highest sensitization activity which is as 28.6 times as g-C₃N₄. It was found that the higher activity can be ascribed to loaded-cocatalyst CoSx which can effectively play an important role and reduce the overpotential.