Study On Preparation And Photocatalytic Hydrogen Production Performance Of Efficient Sulfide Heterojunction System

Solar-driven photocatalytic water splitting for hydrogen provides a new approach to solve the problems of fossil energy shortage and environmental contamination.Transition metal sulfides have become widely preferred catalysts for photocatalytic hydrogen production due to their excellent optical property,tunable electronic structure and abundant edge hydrogen production active sites.However,in the photocatalytic hydrogen production reaction,the mono transition metal sulfide is limited by the low photogenerated carrier separation efficiency,thus leading to inferior photocatalytic hydrogen production activity.By constructing a high-efficiency heterojunction system,compact hetero-interfaces are formed to provide rich fast channels for charge transfer,which in turn dramatically promotes the separation of carriers and significantly enhances the photocatalytic hydrogen production activity.Therefore,this paper aims at constructing high-efficiency sulfides heterojunction system by heterostructure construction and co-catalyst loading,which bringing a significant increase in photogenerated carrier separation capacity and ultimately achieves a noteworthy augment in the activity of photocatalytic water splitting for hydrogen.First,narrow-band-gap Zn In₂S₄ was selected as the photocatalyst,and the Zn In₂S₄@Ni₃S₂ transition metal sulfide co-catalyst/photocatalyst heterojunction was constructed by introducing transition metal sulfide co-catalyst of Ni₃S₂,which realized the embedded growth of co-catalyst and enhanced the photogenerated carrier separation and transport capacity of the system.On this basis,a Zn In₂S₄@Cu In P₂S₆ heterojunction system with 2D/2D structure was designed to achieve a significant improvement in the visible-light-driven photocatalytic hydrogen production capacity.In addition,this paper extended the transition metal sulfide co-catalyst loading technique to the wide-band-gap Nb₂O₅ semiconductor system,and constructed the transition metal sulfide/photocatalyst heterojunction system by loading CoS and ReS₂ co-catalysts on the surface of Nb₂O₅,which effectively improved the light absorption capacity and photogenerated carrier separation and migration efficiency of the photocatalyst.The specific contents of this paper are as follows:（1）A surfactant-assisted one-step hydrothermal method was employed to successfully prepare the embedded distributed Ni₃S₂@Zn In₂S₄ heterojunction system with simultaneous growth of the co-catalyst and the photocatalyst.Compared with the traditional surface loading method,the Ni₃S₂ co-catalyst was embedded inside and on the surface of Zn In₂S₄,which effectively reduce the hydrogen production barrier and promote the rapid charge migration from the inside to the surface,while exposing more active reaction sites,thus achieving an efficient visible-light-driven photocatalytic hydrogen production activity of 60μmol·h^-1.（2）The surfactant-assisted hydrothermal method was used to successfully fabricate the Zn In₂S₄@Cu In P₂S₆ photocatalyst with 2D/2D heterostructure.The construction of2D/2D heterojunction not just endows the hetero-interface with abundant carrier transfer pathways,but also provides a strong built-in driving force for carrier migration,ultimately achieving an excellent visible-light-driven photocatalytic hydrogen production performance of 76.2μmol·h^-1,which is 13 times higher than that of pure Zn In₂S₄(5.88μmol·h^-1).（3）A novel in-situ-vapor-phase growth method was employed to successfully prepare CoS@Nb₂O₅ nanosheets composite.The loading of CoS co-catalysts not only enhances the light absorption capacity of the system,but also increases the specific surface area and pore volume,which providing richer active sites for photocatalytic reaction.The transient absorption spectra and other experimental results show that the successful construction of CoS@Nb₂O₅ heterojunction effectively promotes the separation and migration of internal carriers,thus exhibiting a significantly enhanced photocatalytic hydrogen production,reaching 355μmol·h^-1,which is about 17.5 times higher than that of pure Nb₂O₅ nanosheets.（4）ReS₂ quantum dots@Nb₂O₅ nanosheets composite were prepared using an in-situ-vapor-phase growth method.The structural design of ReS₂ quantum dots not only improves the light absorption of Nb₂O₅ from the UV to the visible region,but also provides more active sites and charge transfer channels for the photocatalytic reaction.The transient absorption spectra and other experimental results demonstrated the more efficient photogenerated charge separation and transfer capability of the system,which ultimately achieves a significant increase in the photocatalytic hydrogen production activity of 182.5μmol·h^-1.