Preparation,modification And Photocatalytic Hydrogen Generation Performance Of TiO₂ Quantum Dots

TiO₂ quantum dots are favored by researchers in the field of photocatalysis because of their small size,large specific surface area,high surface atomic ratio,high electron mobility and good stability.In this paper,the micron-sized TiO₂ crystal precursors with mixed phases were firstly synthesized by a hydrothermal method.TiO₂ quantum dots were exfoliated from the as-obtained TiO₂ precursor through a modified ultrasonication process and their corresponding photocatalytic hydrogen generation performance was studied.To further improve the photocatalytic performance,TiO₂ QDs/MoS₂ nanosheets composite and TiO₂ quantum dots/TiO₂particles homojunction were constructed by hydrothermal treatment process,and their photocatalytic activity was systematically investigated.The main results of this work are presented as follows:（1）Micron-sized TiO₂ precursors with anatase and rutile mixed crystal phase were prepared by hydrothermal method.The particle size of as-prepared TiO₂ was～2μm and the proportion of anatase and rutile crystal forms are 77.7 wt%and 22.3 wt%,respectively.And the hydrogen production rate of TiO₂ precursor was 53.5μmol/（h·g）.（2）TiO₂ quantum dots were prepared from TiO₂ precursor via a modified ultrasonic exfoliation process.The average particle size of as-obtained quantum dots was 2-3.5 nm and the hydrogen production rate was 142.2μmol/（h·g）,which was 2.5 times higher than that of the TiO₂ precursor.（3）The photocatalytic hydrogen production performance of TiO₂ quantum dots was improved by applying the semiconductor-based MoS₂ nanosheets as cocatalyst.The TiO₂QDs/MoS₂ nanosheets composite photocatalyst constructed by hydrothermal method showed good photocatalytic hydrogen production performance and cycle stability.The hydrogen production rate was 435.16μmol/（h·g）,which was～3.1 times higher than that of the pristine TiO₂ quantum dots.（4）Due to the high matching rate of homogeneous crystal lattice,continuous chemical bonds can be formed between different band gaps,thus further improving the photocatalytic hydrogen production performance of TiO₂ quantum dots.TiO₂ quantum dots/TiO₂particles homojunction was constructed by a hydrothermal method.And the obtained photocatalyst exhibits excellent photocatalytic hydrogen production performance and cycle stability.The hydrogen production rate was 719.47μmol/（h·g）,which is～5.1 times than that of the pristine TiO₂ quantum dots.