Preparation And Research Of Cobalt Phosphide/zinc Selenide Photocatalysts For Splitting Water To Hydrogen

Recently,using photocatalytic semiconductors to convert abundant solar into hydrogen is one of the new technologies for developing new green energy.The key to photocatalytic hydrogen evolution is to choose the proper photocatalyst.Zn Se possesses diversified morphology,suitable band structure,and excellent stability.Compared with Cd Se,Zn Se with no toxic Cd,low price,and environmental friendliness is regarded as an ideal photocatalyst.To overcome the high recombination of electron and hole pairs,loading cocatalyst is an effective modification strategy.Cobalt phosphides are potential because of their high conductivity and significant improvement in photocatalytic reaction.In this paper,solvothermal method and organic liquid phase method were used to prepare Zn Se semiconductors in different morphology.The composites anchoring with cobalt phosphide were synthesized through in-situ growth and liquid phase approach,respectively.By summarizing all experiments and characterization,we studied the factors and mechanisms that cobalt phosphide leads to the enhancement in photocatalytic water splitting reaction.The following are the details of the research:（1）The preparation of 0D/0D Co₂P/Zn Se nanocomposites via an in-situ solvothermal method and the investigation of its photocatalytic properties and mechanism.Ultrafine 0D Co₂P nanoparticles were successfully grown onto irregular 0D Zn Se nanoparticles in an in-situ liquid phase way.The photocatalytic hydrogen evolution activity were tested under visible light.Co₂P exhibits no hydrogen production activity indicating the role of cocatalyst.The8.4%Co₂P/Zn Se composite shows the highest hydrogen evolution activity of2799μmol g^-1 h^-1,which is 4.2 times of pure Zn Se.Moreover,8.4%Co₂P/Zn Se composite reveals excellent stability in a 12-hour recycle test.Based on the results of photoelectrochemical properties and time-resolved fluorescence spectroscopy test,the behavior of photogenerated charge separation and transfer was analyzed.The Co₂P cocatalyst with high conductivity prompts the photocatalytic performance splitting water to hydrogen by improving the photogenerated carrier separation efficiency.（2）The preparation of 2D/0D Co_xP/Zn Se nanocomposites via a simple liquid phase method and the investigation of its photocatalytic properties and mechanism.The uniform and spherical 0D Zn Se nanoparticles were prepared by a simple organic solvothermal method using oleamine as the template solvent.Zn Se nanoparticles were anchored onto 2D Co_xP nanosheets through a liquid phase method,which formed a 2D/0D heterojunction structure.The hydrogen evolution activity of Co_xP/Zn Se composite photocatalysts was tested under visible light.The best hydrogen production performance of the composite was 2609μmol g^-1 h^-1,while the Co_xP content was 18%,which is7.37 times that of pure Zn Se.After an 18-hours test,Co_xP/Zn Se still maintains good stability.Combined with photoelectrochemical properties and time-resolved fluorescence spectroscopy test,a reasonably enhanced photocatalytic hydrogen mechanism was proposed.Co_xP not only promotes the transfer of photogenerated electrons from Zn Se to Co_xP for H⁺reduction reaction but also provides abundant active sites which are beneficial to capture electrons and protons for photocatalytic hydrogen evolution.