Design,Synthesis And Hydrogen Evolution Of A New Transition Metal Molybdate Composite Photocatalyst

Hydrogen is an ideal carrier,which has the advantages of renewable ability,high energy release and no pollution,etc.Photocatalytic decomposition of water to produce hydrogen as a clean way of hydrogen production is the focus of people’s research.Photogenic electrons and holes in photocatalysts compound rapidly,resulting in low photocatalytic efficiency,and because of the high price of precious metals co-catalysts,the production is scarce,which is not suitable for sustainable development.Therefore,it is an important route for the development of photocatalytic hydrogen evolution technology to study the photocatalytic hydrogen evolution materials which have high efficiency of hydrogen evolution and can replace precious metals.The main content of this paper:the modification of catalyst and the optimization of hydrogen production conditions.The morphology,chemical states of surface elements,optical properties,physical properties and separation of electrons and holes were studied.Finally,the electron transfer mechanism during hydrogen production is explored.The main work is as follows:1.Synthesis and hydrogen production of dye-sensitized transition metal molybdate composite photocatalyst（1）based on the hydrothermal synthesis of NiMoO₄ nanorods,with in situ deposition by load amorphous CoS materials,The preparation of a kind of good photocatalytic performance type-Ⅱheterojunction CoS/NiMoO₄composite catalyst,effectively promote the light carrier separation.Further studies showed that the unique monoclinal structure and stable octahedral coordination structure of rod NiMoO₄could realize rapid electron transfer,and the disordered amorphous CoS,due to its good magnetic permeability,established a stable internal electric field with NiMoO₄,so that the hydrogen yield of composite catalyst could reach 67.6μmol·h^-1,3.23 times that of pure NiMoO₄.（2）In the dye sensitization system,in order to solve the problem that photocatalyst hydrogen production rate decreases due to degradation in the dye sensitization system,the NiCo P/NiMoO₄heterogeneous junction composite catalyst with bimetallic phosphates was synthesized by hydrothermal method in combination with the structural characteristics of NiMoO₄,so as to realize the rapid transmission of photocarriers at the interface of the heterogeneous junction.Further experiments show that the efficiency of sensitizers and cavitation sacrificial agents in the dye sensitization system is greatly improved,and the efficiency of charge separation and electron transfer is significantly improved,so as to achieve a good hydrogen evolution effect.The hydrogen yield of the compound catalyst with optimal activity was up to61.4μmol·h^-1,which was 2.93 times that of NiMoO₄.2.Synthesis and hydrogen production of amorphous CoS modified CdS nanoparticlesDue to the high plasticity of CdS,the composite catalyst CCS with special crystal morphology was synthesized by in-situ deposition of amorphous CoS.The favorable effect of disordered amorphous CoS load on electron transport is emphasized.The high conductivity of amorphous CoS can realize the effective separation of photogenerated electrons,which proves that the excellent synergistic effect between amorphous CoS and CdS is the main factor to improve the photocatalytic activity.The hydrogen production rate of the composite catalyst was up to 2.01 mmol·g^-1·h^-1,6.3times that of pure CdS.This study provides a new method for the design of highly efficient hydrogen evolution cocatalyst for amorphous-based nanostructures.