The Study Of Graphene Modified ZnIn₂S₄ For Splitting Water To Hydrogen Under Visible Light

With the consumption of traditional fossil fuels, energy issues and environmental problems have become increasingly prominent. The development of new clean renewable energy has been very urgent. Photocatalytic decomposition of water is one of the most promising methods to effectively solve these problems. And, the key of producing hydrogen from water is how to prepare photocatalyst that is efficient, strong absorption of visible light and good stability. This article studied hydrogen production performance from water by using the most promising nanomaterials ZnIn₂S₄ which was modified by graphene and changing In content. Photocatalytic degradation of pollutants and hydrogen production performance from water had been researched at the same time by using optimal catalyst, and a series of meaningful results had been abtained. The main contents were as following:A series of ZnInxS4?x=1.6, 2.0, 2.3, 2.6, 2.9, 3.1? photocatalysts were synthesized via a facile hydrothermal method and characterized by various analytical techniques. With the increase of indium content, their crystal sizes decreased firstly and then increased and the variation of the specific surface area and total pore volume was exactly opposite, the absorption edges of ZnInxS4 photocatalysts shifted to longer wavelength, the separation efficiency of photogenerated electron-hole pairs increased firstly and then decreased. Additionally, the morphology of ZnInxS4 greatly depended on the contents of indium. The Pt-containing experimental results showed that photocatalytic hydrogen production rate increased firstly and then decreased with increase of indium content, when x=2.3, hydrogen production rate of catalyst reached its maximum and was 363 ?mol/?g·h?.A series of ZnIn₂S₄/graphene photocatalysts with different sizes were synthesized via an alcohol thermal method and characterized by various analytical techniques. Sizes?k? of the graphene could be separated by using differential centrifugation method and the different rotational speed that were below 2000 r/min, 2000-4000 r/min, 4000-6000 r/min, 6000-8000 r/min and 8000-10000 r/min could get different sizes which were 12-18 ?m, 7-12 ?m, 5-7 ?m, 3-5 ?m, 1-3 ?m, respectly. With the decrease of size, their crystal sizes decreased firstly and then increased and the variation of the specific surface area and total pore volume was exactly opposite, the absorption edges shifted to longer wavelength, the separation efficiency of photogenerated electron-hole pairs increased firstly and then decreased. Additionally, the morphology of ZnIn₂S₄/graphene greatly depended on the size of graphene. The Pt-free experimental results showed that photocatalytic hydrogen production rate increased firstly and then decreased with decrease of graphene size, when k=5-7 ?m, hydrogen production rate reached its maximum and was 40.85 ?mol/?g·h?.A series of ZnIn₂S₄/graphene photocatalysts with different loadings?0.05%, 0.1%, 0.2%, 0.5%, 1.0%, 2.0%? were synthesized via an alcohol thermal method and characterized by various analytical techniques. With the increase of graphene loading, the crystal sizes of ZnIn₂S₄/graphene photocatalysts decreased firstly and then increased and the variation of the specific surface area and total pore volume were exactly opposite, the absorption edges of ZnIn₂S₄/graphene photocatalysts shifted to longer wavelength, the separation efficiency of photogenerated electron-hole pairs increased firstly and then decreased. Additionally, the morphology of ZnIn₂S₄/graphene greatly depended on the size of graphene. The Pt-free experimental results showed that photocatalytic hydrogen production rate increased firstly and then decreased with increase of graphene loading, especially, when graphene loading was 0.2%, hydrogen production rate reached its maximum and was 40.85 ?mol/?g·h?, in Pt-containing condition, hydrogen production rate could reach 603 ?mol/?g·h?.With organic amine as sacrificial agent, hydrogen production performance from water was studied by using 0.2%-ZIS/G-?5-7 ?m? catalyst. The results showed that the hydrogen production rate reached maximum and was 1597 ?mol/?g·h? when the reaction conditions were that triethylamine acted as sacrificial agent, triethylamine concentration was 1 mol/L, pH=13, and the catalyst concentration is 1 g/L. In addition, experimental results that the sunlight acted as light source showed that the hydrogen production rate reached maximum and was 423 ?mol/?g·h? under the sufficient sunlight.