Application Of Multidimensional Conductive Cocatalyst Materials In Photocatalytic Hydrogen Production

Hydrogen production from photocatalytic water splitting is one of the most promising technologies to solve future energy and environmental problems,where the key scientific issue is the design and development of efficient photocatalysts/systems.Studies have shown that the photocatalytic cocatalysts can promote the separation efficiency of photogenerated carriers and reduce the energy barrier of hydrogen evolution reaction（HER）,thus effectively improving the activity of photocatalytic decomposition of aquatic hydrogen.However,the practical application of noble metals in a large-scale photocatalytic HER is greatly restricted because of their high cost and scarcity.Therefore,developing highly active and stable and H₂ evolution cocatalysts based on earth-abundant elements is of great significance to promote the large-scale and practical application of photocatalytic water splitting technology for hydrogen production.In this research work,four kinds of photocatalysts/systems with visible light response,high efficiency and stability were designed and constructed.Using 0D 0D[Mo₃S₁₃]^2-nanoclusters,1D polyaniline nanowires（PANI NWs）,2D Ti3C2Tx nanosheets（Ti₃C₂T_x NSs）and layered VB₂ as new conductive cocatalyst materials,.Specific research results are as follows:（1）MoS₂ is one of the most promising materials to replace Pt,but its hydrogen-producing active site is limited to the S atom at the boundary site and its catalytic efficiency is not high.The[Mo₃S₁₃]^2-nanoclusters,as a derivative of MoS₂,have all three sulphur ligands as hydrogen-producing active sites and are,in addition,soluble in acidic solutions and very stable.In this work,0D[Mo₃S₁₃]^2-nanoclusters were used as hydrogen production catalysts and H₄Si W₁₂O₄₀(Si W₁₂)was used as a photosensitizer to design and construct an all-inorganic,quasi-homogeneous photocatalytic hydrogen production system.The experimental results show that the Si W₁₂/[Mo₃S₁₃]^2-system has a high catalytic conversion number（TON）of 922 based on[Mo₃S₁₃]^2-in the hydrogen production reaction within 6 h.The hydrogen production activity is 14 times that of MoS₂ and 1.7 times that of a-MoS_x.Thanks to the excellent physicochemical properties of the inorganic components,the activity of the system remained constant during stability tests of up to 36hours.The mechanism of the photocatalytic water splitting for hydrogen production was systematically studied by electrochemical characterization.In this work,efficient and stable hydrogen production was achieved through the design and construction of an efficient and stable quasi-homogeneous photocatalytic water splitting for hydrogen production system.This work provides a new idea for the construction of stable dye-sensitized photocatalytic hydrogen production system.（2）The MAPb I₃/PANI NWs composite catalyst with strong coupling interface was prepared by in-situ coupling of positive PANI NWs and negative CH₃NH₃Pb I₃（MAPb I₃）,which was used for hydrogen production by photocatalytic cracking of HI.Preparation of MAPb I₃/PANI NWs composite catalysts for photocatalytic cracking of HI to hydrogen.The experimental results showed that the photocatalytic hydrogen production rate of the composite catalyst under visible light drive（370≤λ≤780 nm）could reach 38.8μmol h^-1,which was 29 times higher than that of MAPb I₃.Electrochemical characterisation revealed that PANI NWs act as a hole transport medium and inhibit the complexation of photogenerated electron-hole pairs through hole migration out,thereby enhancing the photocatalytic hydrogen production activity.This work strengthens the complexation of MAPb I₃ with PANI NWs by forming a strong coupling interface through self-assembly,reduces the carrier migration resistance and improves the photocatalytic hydrogen production activity,providing a reference for the preparation of composite catalysts with a strong coupling interface.（3）The ultrathin Ti₃C₂T_x NSs with excellent conductivity,high specific surface area and good Fermi energy level is a high performance cocatalyst.The 2D Ti₃C₂T_x NSs were prepared by HF etching and ultrasonic exfoliation with MAPb I₃ in situ to prepare Ti₃C₂T_x NSs/MAPb I₃ composite catalysts for photocatalytic cracking of HI for hydrogen production under visible light（370≤λ≤780 nm）drive.The experimental results show that the MAPb I₃/Ti₃C₂T_x NS composite catalyst produces hydrogen at a rate of up to 63.6μmol h^-1,which is 43 times higher than MAPb I₃.In addition,no significant decrease in activity was observed during stability tests up to 120h.Study on the mechanism of photocatalytic hydrogen production showed that the excellent electrical conductivity of Ti₃C₂T_x NSs enhances the photocatalytic hydrogen production activity of MAPb I₃by increasing its photoelectron migration rate.This work enhances the efficiency of photocatalytic hydrogen production by rapidly transferring photo-generated electrons and thus achieving the separation of electron-hole pairs.（4）Studies show that V-based materials are the kind of potential photocatalytic hydrogen production cocatalyst materials.Currently,V-based cocatalyst materials such as VC and VN have been successfully applied in the production of hydrogen from photocatalytic water splitting,but VB₂ has not been reported in photocatalytic splitting water for production hydrogen.In this research work,VB₂ was used as the catalyst for hydrogen production.erythrosin B（ErB）as the photosensitizer and triethanolamine（TEOA）as the sacrificial reagent to construct a visible light（370≤λ≤780 nm）driven ErB-TEOA-VB₂ three-component photocatalytic hydrogen production system.The results of the photocatalytic hydrogen production experiments demonstrated that the hydrogen production rate in the ErB-sensitized system could reach 34μmol h^-1 and the catalytic conversion number（TON）based on ErB was as high as 17.The electrochemical characterisation confirmed that VB₂ is an efficient photo/electrocatalytic hydrogen precipitation catalyst and possesses excellent electrical conductivity.This work has successfully explored a novel cocatalyst that can be used in the field of photocatalytic hydrogen production,providing a reference for the exploration of new cocatalysts for hydrogen production in the future.