The Study On The Electrochemical Sensing Property Of Low-Dimensional Materials Supported Metal Nitrogen-Doped Carbon Single Atom Electrocatalysts

The metal nitrogen-doped carbon electrocatalysts（M-N-C）exhibit high metal utilization efficiency,unique coordination environment,excellent catalytic performance,and good chemical stability.M-N-C has been widely used in different catalytic reactions and energy conversions,but it is rarely used in electrochemical sensors.Metal-organic frameworks（MOFs）have the advantages of large specific surface area,high porosity,and adjustable structure.Moreover,MOFs with metal sources,nitrogen sources,and carbon sources can be used as precursors to synthesize M-N-C by pyrolysis.The M-N-C not only has advantages of MOFs,but also has the characteristics of single atom catalysts.In addition,low-dimensional nanomaterials have become hot topics of physics,chemistry,materials science,and other disciplines due to their distinct physical and chemical properties as well as the potential application values,which have been widely used as electrode material in sensors.Low-dimensional nanomaterials with good conductivity and large specific surface area are advantageous to support catalysts with good dispersion and high utilization rate as supports.Based on this,M-N-C materials with different metal centers and morphologies were synthesized by high-temperature pyrolysis using MOFs as the precursors in this study,and the low-dimensional nanomaterials were used as their supports.The morphology and structure of the materials were characterized by various techniques.The electrochemical catalytic sensitization characteristics and electrochemical sensing performance regulatory mechanisms of the prepared sensing materials were investigated.And a series of electrochemical sensing platforms were fabricated for the highly sensitive detection of environmental and food contaminants,which could be used for accurate analysis of real samples.The main contents are as follows:1.MOF-assisted spatial confinement and ionic substitution strategies were employed to synthesize Ru single atoms riveted with nitrogen-doped porous carbon（Ru-N-C）through one-step pyrolysis of Ru-doped zeolitic imidazole frameworkand-8.Thanks to the hierarchical porous structure and sunstantial Ru-N₄ sites in the carbon supporter,this catalyst exhibited excellent electrochemical sensing characteristics.The tow-dimensional graphene oxide nanosheets were introduced to support Ru-N-C catalysts,which further enhanced the electrochemical activity and promoted the interface interaction between the electroactive surface area and target molecules.The experiment results showed that the graphene oxide supported Ru-N-C composite could be used for sensitive and simultaneous detection of m-phenylenediamine,o-phenylenediamine,and aniline,with linear ranges of 0.8-65,0.5-30,and 0.5-75μmol/L,respectively.And the detection limits were obtained as 0.092,0.24,and 0.37μmol/L for m-phenylenediamine,o-phenylenediamine,and aniline,respectively.2.Novel hollow nitrogen-doped carbon polyhedrons（HNCPs）,featuring atomically dispersed Zn species,have been designed and fabricated through a topo-conversion strategy by utilizing metal-organic frameworks with hierarchical pores as precursors.The Zn@HNCPs achieved efficient electrocatalytic oxidation of two sulfonamides including sulfaguanidine（SG）and phthalyl sulfacetamide（PSA）,by taking advantage of the high intrinsic catalytic activity from Zn-N₄ sites and the superior diffusion from the hierarchical porous nanostructures.Impressively,the further combination of Zn@HNCPs with two-dimensional titanium（Ⅲ）carbide（Ⅱ）（Ti₃C₂T_x）MXene nanosheets exhibited enhanced bifunctional electrocatalytic performance for the simultaneous monitoring of SG and PSA,in which MXene showed fast kinetics,large sorption,and unique electronic structure.As a result,the detection limits of SG and PSA are 2.6 and 8.5 nmol/L,respectively,lower than some other techniques and state-of-art electrochemical methods for their analysis.Moreover,the electrocatalysts demonstrated promise for quantification of SG and PSA in aquatic products with standard addition recovery ranging from 91.5 to 104%.Our insights and findings can serve as guidelines for developing highly active electrocatalysts for next-generation food analysis sensors.3.In this work,the W single atom catalysts supported on MOF-derived N-doped carbon was firstly synthesized,which has high reactivity and good stability when used as electrode material.The two-dimensional conductive MOF Cu₃（HHTP）₂was then obtained at room temperature using 2,3,6,7,10,11-hexahydroxytriphenylene hydrate（HHTP）as the coordinating linker and Cu（II）as the metal node.Various analytical techniques including electron microscope,X-ray diffraction,X-ray photoelectron spectroscopy,Raman spectrum,N₂ adsorption-desorption,and electrochemical methods were used for morphological observation and electrochemical performance tests to clarify the electrocatalytic activity and sensing capability of the sensitizing materials.The two-dimensional Cu₃（HHTP）₂ and W-N-C were layer-by-layer modified on the surface of templated graphene filtered paper electrode to fabricate a paper-based electrochemical sensor platform for the detection of carbendazim.The synergistic effect of the two materials significantly improved the current response signal and detection sensitivity of carbendazim.The detection limit of carbendazim was 1.8 nmol/L（S/N=3）.Moreover,the paper based electrochemical sensor could be successfully applied for the quantitative analysis of carbendazim in cabbage,lake water,soil and strawberry samples.4.The integrated electrode array template was constructed on the hydrophobic tape by laser engraving technique,and the Mn and N codoped single wall carbon nanotube electrode（Mn-N-SWNTPE）array was obtained by template-filtered method,which realized the simple and low-cost preparation of paper electrode array.Pt-N-C single atom catalyst derived from Pt@ZIF-8 was modified on the working electrode region to further enhance the electrocatalytic activity of Mn-N-SWNTPE.This electrode showed enhanced electrochemical responses for the electrochemical oxidation of two pesticide fungicides including fenhexamid and pyrimethanil.The type of electrolytes,the thickness of electrode material,and the accumulation time were optimized,respectively.The detection limits of fenhexamid and pyrimethanil were 1.0 and 3.0 nmol/L,respectively.The carbon-based electrode array constructed in this work has potential application value in the fabrication of portable paper-based electrochemical sensors with advantages of simplicity,low cost,and rapidness,which is expected to achieve rapid and highly sensitive real-time analysis in complex samples.