Design And Synthesis Of Co-Based MOF/Graphene Composites And Their Water Splitting Performance

The rapid development of the global economy has caused serious energy crisis and environmental problems.The development of efficient and green renewable new energy has become the only way for human beings to achieve sustainable development.As one of the most promising new energy sources,hydrogen energy has high research and application value in energy conversion.Among them,the use of electrolytic water to produce hydrogen has the advantages of high product purity,no pollution,and simple operation.In the process of water electrolysis,the kinetic process of anodic reaction（OER）is slow,which limits the efficiency of the whole water electrolysis reaction.Therefore,the preparation of OER electrocatalysts with low cost,high catalytic activity and high stability is the key to the practical application of electrolytic water technology.Cobalt-based compounds show good OER catalytic performance,but they face some problems,such as poor conductivity and insufficient exposure of active sites.In view of the above problems,in this paper,the OER performance of Co-MOF was studied,and GO-Co-MOF,RGO-Co Ni-MOF and other composites were further designed and constructed.The structure,morphology and electrochemical properties of the composites were studied.The specific research of this paper is as follows.:（1）The lamellar Co（OH）₂was synthesized by a natural precipitation method with no stirring,and the effects of alkali source type,delivery method and dosage on the structure of Co（OH）₂were explored.Co（OH）₂was used as a sacrificial template to guide the growth of cobalt-based MOF materials.The obtained Co-MOF has a specific surface area of 965.19 m²g^-1,which is a microporous material with good electrochemical oxygen evolution performance.（2）Graphene oxide（GO）was selected as the carbon source,and Co-MOF was anchored on GO under the assistance of diethylenetriamine（DETA）.The Co-MOF particles in GO-Co-MOF are evenly distributed on graphene oxide to form a good MOF-graphene transmission network.GO-Co-MOF was used for electrocatalytic OER,showing good electrochemical activity and stability.The composite was heat treated at different temperatures.The experimental results show that the performance of RGO-Co-MOF is the best when the heat treatment temperature is 300℃.When the current density is 20 m A cm^-2,the overpotential is only 464 m V.The heat treatment makes the crystal form of the composite better,the stability is stronger,and the OER performance is improved.（3）Ni source was doped into GO-Co-MOF materials to synthesize composites with different Co Ni ratios.The LSV test results show that when the Co Ni ratio is 1.2:0.8,the sample has the highest electrochemical activity,and the initial overpotential is only 384 m V.GO-Co Ni-MOF was heat treated at 300℃.The results showed that the electrochemical properties of all samples were improved compared with those before heat treatment.The RGO-Co_1.2Ni_0.8-MOF with a Co Ni ratio of 1.2:0.8 can achieve a maximum current density of 300 m A cm^-2.Through BET test,it is found that RGO-Co_1.2Ni_0.8-MOF has micropores,mesopores and macropores.The rich hierarchical pore structure is beneficial to obtain a larger specific surface area and improve the electrocatalytic performance of OER.