The Preparation Of Novel N-RGO/MnO₂ Composite And Its Properties About Electrochemical Detection Of Mercury

Heavy metal pollution has become a global problem,which has serious damage to the human being and ecological system.Hg(Ⅱ)is considered to be one of the most dangerous pollutants in the environment.Even at very low concentrations,it can cause harm to human health.The accumulation of Hg(Ⅱ)in the ecosystem can result in the contamination of drinking water and food products.The World Health Organization(WHO)has set the acceptable limit for drinking water Hg(Ⅱ)to 30.0 nM,thus achieving an important,accurate,rapid and sensitive detection of Hg(Ⅱ)is very important.Square wave voltammetry(SWV)technology has become one of the most powerful techniques in electrochemical analysis for detecting inorganic Hg(Ⅱ).In recent years,graphene and graphene-based nanocomposites have been used as electrochemical detection electrode modification materials because of their large specific surface area and high electrical conductivity in order to achieve effective detection of heavy metal mercury ions.It is also a research hotspot to modify graphene,such as introducing other elements such as N element to improve its electrochemical performance.Metal oxide MnO2 is an environmentally friendly and low cost material that has been widely studied in the fields of sensors,supercapacitors,batteries and electrochemistry.Therefore,we intend to introduce nitrogen into graphene and MnO2 composite to improve its detection performance in this topic.In this paper,two-dimensional nanomaterials are combined with electrochemical analysis techniques.Based on the graphene materials,non-metallic elemental nitrogen is doped into graphene and MnO2 composites for research,and nitrogen is doped into composite materials to increase the reactive sites and further improve the properties of the composite.N-RGO/MnO2 was modified on the surface of the electrode to construct the RGO/MnO2-GCE sensor and used to explore its electrochemical properties and to be used in the detection of heavy metal ions of divalent mercury.The main research content includes the following parts:(1)The graphene oxide was synthesized by the Hummers method,and then the graphitized graphene and the p-phenylenediamine water bath were chemically synthesized to prepare the graphitized material.N-RGO/MnO2 composites were synthesized by hydrothermal method using KMnO4 and aminated graphene as raw materials.The structure and morphology of the composites were characterized by XRD,XPS,SEM,TEM and other characterization techniques.The results show that nitrogen is successfully doped into the composite,and MnO2 attached to the graphene material isδ-type MnO2 with a large specific surface area.The composite exhibits a large specific surface area that provides a good basis for the subsequent electrochemical detection.(2)The prepared N-RGO/MnO2 nanocomposite was modified onto the surface of glass carbon electrode and applied to the electrochemical detection of Hg(Ⅱ)under the optimized experimental conditions.The experiment result shows that the modified electrode have a high electrochemical response to mercury ions,indicating that the sensor can achieve rapid and efficient detection of mercury ions with a detection sensitivity of 72.16μA/μM and a detection limit of 0.0414nM(3a method).The modified electrode exhibits a better stability and repeatability and can be used in actual water sample analysis.(3)According to the above work,N-RGO/CeO2 nanocomposite was also prepared by hydrothermal method.The electrochemical performance of the N-RGO/CeO2 nanocomposite is better,and the sensitivity is higher than that of the bare glass carbon electrode,the pure CeO2 and RGO/CeO2 modified electrode.The constructed electrode was found to possess a long-term stability and good repeatability in further analysis.In summary,the functionalized NH2-RGO materials are combined with MnO2 and CeO2 to obtain nanostructured composites,which provides a new idea for the design of nanomaterials.Hg(Ⅱ)detection was proposed by using a novel nano-sensitive interface of N-RGO/MnO2 and N-RGO/CeO2 composites.The preparation method of the material is simple,and the N element doping can strengthen the connection between the metal oxide and the graphene,thereby improving the charge separation rate and the electron transfer rate,increasing the active site,increasing the adsorption performance of the material,and enriching the research in the detection of heavy metal ions.