Preparation And Optimization Of Cobalt-copper-based Nanocomposite Catalysts And Their Electrocatalytic Oxygen Evolution Performance

With the development of industrial economy,researcher pay more and more attention to the usage of sustainable and renewable energy,Through the development of clean,recyclable and other properties,new energy can become a substitute for fossil fuels.Among them,hydrogen energy has received the most attention because of its high efficiency and environmental protection,and the production of hydrogen from electrolyzed water with zero carbon emissions is one of the most environmentally friendly options.In the electrolyzed water reaction,the cathode hydrogen evolution half reaction requires only small external energy,while the oxygen evolution half reaction（OER）at the anode requires a huge overpotential to achieve the transport of four protons/electrons and high activation energy form O=O.Therefore,the low-cost and efficient OER catalyst has an irreplaceable role in hydrogen energy research.Among many OER catalysts,transition metal composites with spinel structure become one of the best candidate materials due to their excellent combination valence state and abundant active sites.Based on cobalt-copper-based nanomaterials that have not been extensively studied,this thesis has been mainly focused on inexpensive,highly active,and stable electrochemical oxygen evolution catalysts through effective recombination and morphological control mechanism.The specific research is as follows:1.In order to further explore the effect of micro-morphology on the performance of the catalyst,it was prepared by a one-step solvothermal method under the condition that only the types of solvents（methanol,water,ethanol,ethylene glycol,and polyethylene glycol）were changed and other conditions were the same.There are five different morphologies of copper cobaltate/reduced graphene oxide（CuCo₂O₄/rGO）composite materials（rose-like,sheet-like,granular,film-like and chrysanthemum-like）.By characterizing and analyzing the electrochemical performance of each catalyst,the optimal rosette morphology was determined.Finally,the formation of different morphologies and the principles that caused different degrees of electrochemical performance are discussed.2.In order to avoid the negative effect of the electrode binder on the conductivity and catalytic activity of the catalyst,explore a macroscopic substrate material that can be directly used as an electrode.The graphene oxide（GO）self-polymerizes to form a graphene aerogel with a three-dimensional macroscopic shape,and a CuCo₂O₄ nano-array is directly grown on its internal structure.By changing the reaction temperature,needle spherical CuCo₂O₄nanoarray and sheet spherical CuCo₂O₄ nanoarray were grown on the graphene aerogel skeleton,and obtained copper cobaltate array/graphene aerogel CuCo₂O₄/GA)composite materials are directly used as working electrodes without adding any binder.The successful synthesis of these composite aerogel materials with two different structures was demonstrated by various characterization methods.Finally,the OER performance was tested by electrochemical testing methods,and the mechanism of excellent catalytic performance of the three-dimensional skeleton and uniformly distributed nanoarrayswere also studied.3.Inspired by the patchwork of artificial turf,planting in a smaller area can make the lawn grow in one direction and make the lawn more uniform.For the first time,we have defined the growth position and direction of a copper copper sulfide（CuCo₂S₄）nanoarray by plating a polyaniline（PANI）grid layer on a nickel foam to obtain a self-supporting layered electrode material.The nitrogen species derived from the PANI building block acts as a bridging site for binding to metal ions,which provides a strong coupling effect for the in-situ growth of CuCo₂S₄.At the same time,the network structure of PANI divides the growable position into smaller pieces,and the narrow fence structure limits the growth space and size of CuCo₂S₄,and guides the growth of CuCo₂S₄ perpendicular to the plane,and finally obtains a complete and structured CuCo₂S₄ layer.Composite material.The composition and structure of the copper sulfide copper/polyaniline/nickel foam（CuCo₂S₄/PANI/NF）composites were characterized,and the OER performance was tested and discussed.Finally,the principle of excellent hierarchical structure catalytic performance was obtained.