The Research Of Cu₂ZnSnS₄ For Photocatalytic Hydrogen Production And Degradation Of Rhodamine B

Since the energy shortage and environmental pollution problems are getting moreand more serious,the development of new environmentally friendly energy get more and more attention of people.Now days,most photocatalysts used for hydrogen production are wide band gap materials,only ultraviolet and/or partial visible illumination can be used for water splitting due to their wide bang-gaps,thus cause low efficient utilization of solar irradiation.In order to improve the utilization of sunlight,development of narrow band gap photocatalytic materials with high stability and activity is eminent.The band gap of Cu₂ZnSnS₄ is about 1.5 eV,which matches with the solar spectrum,In addition,Cu₂ZnSnS₄possesses high absorption coefficient(>10⁴cm^-1)and low-toxicity elements,therefore Cu₂ZnSnS₄ may be used as next generation photocatalytic hydrogen production material.As an excellent semiconductor material,Cu₂ZnSnS₄ is well known and used in dye-sensitized solar cells and thin film solar cells area.As a kind of new emerging photocatalyst,the study of Cu₂ZnSnS₄ for photocatalytic hydrogen production is just getting started.Especially,the relationship between the separation and recombination of Cu₂ZnSnS₄ electron-hole pairs and light catalytic hydrogen production is rarely reported.Therefore,this thesis is mainly focused on photocatalytic hydrogen production and pollutant degradation of pure Cu₂ZnSnS₄,as well as the formation of Cu2ZnSnS4-CdS p-n heterostructurefor photocatalytic hydrogen production.Through in-depth study photogenerated carrier separation,transfer and recombination,we will obtain Cu₂ZnSnS₄ based photocatalyst with high hydrogen production performance.?1?Cu₂ZnSnS₄ nanoparticles were synthesized via a step hot-injection method using copper?II?chloride dihydrate,zinc oxide,tin???chloride pentahydrate,1-dodecanethiol and t-dodecanethiol as precursors,The obtained Cu₂ZnSnS₄ nanoparticles are wurtzite Cu₂ZnSnS₄with sizes of about 9 nm,which also possess high monodispersity and well crystallinity.After ligand exchange,Cu₂ZnSnS₄ transferred from oil phase to water phase,then used for visible light photocatalytic hydrogen production and Rhodamine B degradation under Xe lamp.Due to the high monodispersity and well crystallinity,Cu₂ZnSnS₄ showed relatively high photocatalytic performance.?2?Cu₂ZnSnS₄-CdS heterojunction nanoparticles were first synthesized via ion exchange and epitaxial growth method.Cu2ZnSnS4 is p-type semiconductor material,while CdS is n-type semiconductor material.By building p-n junction at Cu₂ZnSnS₄-CdS interface,a built-in electric field can be formed which may eliminate interfacial defect at the Cu2ZnSnS4surface.The p-n junction not only beneficial to photogenerated carrier transmission between Cu₂ZnSnS₄ and CdS,but also can effectively inhibit the recombination of electron-hole.By building the p-n junction,the Cu2ZnSnS4-CdS heterostructured nanoparticles shown almost15 times of photocatalytic hydrogen production performance than that of original Cu₂ZnSnS₄nanoparticles.