Preparation Of ZnIn₂S₄ And Its Photocatalytic Hydrogen Evolution Properties Under Visible Light

The semiconductor-based photocatalytic water spitting for hydrogen production is an effective measure to transform solar energy to hydrogen energy. ZnIn₂S₄ is a new promising material of chalcogenide for photocatalytic hydrogen production from water decomposition, which has a good visible-light harvesting, high photochemical stability and outstanding electrical and optical properties. In this thesis, we carried out a series of research works, which mainly concentrate on the preparation, formation mechanism and photocataltic hydrogen production performance of ZnIn₂S₄ photocatalyst. The main contents are divided into following two parts:1、In the case of triethanolamine as complexing agent and template agent, the hexagonal phase ZnIn₂S₄ photocatalysts were synthesized by chemical precipitation method using ZnSO4·7 H2 O,In₂（SO₄）3·6 H₂O and thioacetamide as raw materials,which are composed of a number of different sizes sheet aggregates,and the effect of adding amount of triethanolamine on its morphology, structure and optical absorption properties and photocatalytic hydrogen activity was investigated. With the increasing amount of triethanolamine, UV visible absorption edge of samples exhibited systematic blue shift. When the adding amount of triethanolamine is 2.0 mmol, the prepared sample ZIS-2.0 has the best photocatalytic hydrogen produciton activity of water-splitting and good stability. In 0.5 mol/L triethanolamine aqueous solution system（pH=13.0）, the average rate of hydrogen evolution over 0.5wt%Pt/ZIS-2.0reached 1290μmol/h·g.2、The hexagonal phase ZnIn₂S₄ photocatalysts were prepared by sodium hydroxide-assisted low temperature water bath method,and the effect of adding amount of sodium hydroxide on its composition, structure and and photocatalytic hydrogen performance was studied. The formation mechanism of the samples was also analyzed. The results showed that adding the sodium hydroxide can affect composition, morphology, optical properties and photocatalytic properties of the prepared sample in synthesis process. After adding sodium hydroxide, In³⁺ can form complexes with hydroxyl ions, leading to the relative concentration ratio of Zn²⁺/In³⁺in solution becomes larger, which affects the composition of the synthetic samples.When the adding amount of sodium hydroxide is 6.0 mmol, the prepared sample ZIS-6.0 has the best photocatalytic hydrogen produciton activity of water-splitting and good stability. The main reason can be attributed to a small amount of Zn2+incorporated into the crystal lattice of ZnIn₂S₄ and located at the In3+ position, which resulting ZnIn₂S₄ conduction band position become more negative and have a stronger thermodynamic driving force for water reduction.