| The consumption of fossil energy and the harm to the environment promote the development of clean and green energy?hydrogen energy,solar energy,wind energy,etc.?to reduce the waste in the process of energy use.The cathodic hydrogen evolution?HER?and anodic oxygen evolution?OER?reactions of water splitting are important parts of energy storage?hydrogen energy?and conversion?waste reduction?.The HER of water electrolysis is one of the important ways to prepare high purity hydrogen,the OER is not only one of the hub-reactions of water electrolysis,but also one of the important hub-reactions of fuel cell and metal air cell.At present,the commercialized Pt?20%Pt/C?and Ir/Ru O2 have better performance of HER and OER respectively,but the shortage of resources,expensive price and poor stability are the important factors that hinder the large-scale commercialized application.In recent years,it has been found that transition metal composites exhibit certain catalytic ability,excellent stability and low price.In view of this,on the basis of simple and low-cost synthesis process,a variety of transition metal composite materials were prepared,including transition metal oxides,sulfides,phosphates,etc.,and the activity and mechanism of electrocatalytic reaction were analyzed in depth.As the supported catalyst needs to be coated with electrode technology and the addition of binder such as Nafion or PTEE,and resulting in complex process and increased cost.So a series of self-supporting electrode materials designed in this paper can be used as catalyst,which can reduce the cost of electrode preparation,at the same time,the self-supporting materials can fully expose the structural advantages of the materials and improve the catalytic efficiency.1.Synthesized a transition metal sulfide catalyst for hydrogen evolution.Commercial nickel foam is used as template and reaction raw material to prepare Mo S2/Ni S layered heterostructure by one-step hydrothermal method.In the process of obtaining Mo S2/Ni S,the content of layered Mo S2 nanosheets and the thickness and length of Ni S nanorods were controlled by adding different proportion of Mo sources.Because the heterogeneous structure can fully expose the active sites of catalysis,the layered structure of Mo S2 and Ni S has synergistic effect and rich valence state.Obtained the good HER performance,the overpotential of 84.1m V(10m A·cm-2),and the slope of Tafel was only 76.9 m V·dec-1.2.It mainly produces a defective Co,Mo oxide and studies its application in oxygen evolution?OER?.Firstly,the carbon fiber cloth after acid treatment is immersed in the hydrothermal reactor containing Co,Mo precursor to synthesize water of crystallization.The cobalt molybdate nanosheets array father is uniformly loaded on the carbon fibers,and the Co Mo O4 nanosheets is obtained by removing crystal water at temperature of 400?in the oven.In view of the strategy of material surface modification to optimize performance,it is an effective way to improve catalyst activity to provide defects on catalyst surface.Through the atmospheric pressure plasma jets?APPJs?in the Ar/0.1%water vapor mixture,the intrinsic micro-defects appeared on the surface of Co Mo O4 nanosheets.This special wet-air pressure plasma treatment exposed heterogeneous porous defect sites,formed more active sites involved in the reaction,promoted the reaction mechanism of intermediate products?M-OH/MO-OH?,and improved the kinetic rate of OER machanism.3.In order to develop the next generation of electrolyzed water catalyst,it is necessary to obtain a high performance catalyst material with hydrogen evolution and oxygen evolution simultaneously.In view of,the advantages of the study of Co and Mo oxides has found that good performance have been developed by adjusting the morphology and intrinsic characteristic.So,Co-Mo-P can be doped into the structure of Co-Mo-O by doping strategy,which can not only provide rich chemical state,but also the hybridization improves the electron coupling with the lattice.So,the Co-Mo-P complex was obtained by doping phosphide at 350?,and the overpotential of the catalyst as HER catalyst was only51.2 m V(10 m A·cm-2)for HER,which was close to the theoretical kinetic process of Tafel.At the same time,The lower overpotential of 353 m V(10m A·cm-2)was obtained as an oxygen evolution catalyst,also the Tafel slope was only 55.2 m V·dec-1.During the stability test for 20 hours and 3000 CV cycles also has excellent stability.The overpotential of total hydrolysis obtained as the anode and cathode of electrolytic water is only 1.603V(10m A·cm-2),which is an excellent electrocatalyst for water spilitting.The above three chapters mainly design the heterostructure,manufacture the intrinsic defects,surface morphology modification and material modification methods.develop a series of transition metal catalysts,including the transition metal oxides?TMOs?,sulfides?TMSs?and phosphides?TMPs?to modify the performance of transition metals.At the same time,explain the mechanism of the material in the catalytic process,high stability and low internal resistance loss,provide a way for further development of hydrogen energy and fuel cell research in the future,so as to promote the progress and development of energy. |
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