| In recent years,more and more attentions have been paid to the impact of nitrogen pollutants on the environment.Therefore,it is particularly important to developrapid,sensitiveandaccuratemethodsfor the determination of nitrogen pollutants in environ-mental samples.The electrochemical detection methods based on metal nanomaterials chemically modified electrodes have attracted wide attention in the field of environmental nitrogen pollutants detection due to its unique advanteges.At present,many positive progresses have been made in these efforts.However,on the one hand,how to immobilize metal nanomaterials on the surface of the base electrode,and make it has special morphology and goode interface binding stability to impove the sensitivity and reproducibility of the sensor is still one of the key issues in this filed.On the other hand,how to assemble multi active components on the sensing interface in order to improve the electrocatalytic activity of the sensor still needs futherresearch and exploration.In this thesis,the application of metal nanomaterials and their carbon-based composites in the nitrogen environmental pollutants electrochemical sensing have been reviewed carefully.Based on this,a multi-walled carbon nanotube suppoted nickel-iron double hydroide electrode,a multi-walled carbon nanotube suppoted nickel-cobalt double hydroide electrode,and a porous platinum/multi-walled carbon nanotubes composite film modified electrode had been prepared respectively by using direct electrochemical procedure.Furthermore,these electrodes had been applied to the electrochemical sensing of urea,hydrazine and ammonia,respectively.The main contents of the full text are as follows:1.Basedonthe high electrochemical oxidation activity of nickel-based oxide and hydroxide to urea,a nickel-iron doble hexacyanoferrate（Ni-Fe HCF）wasfirstly deposited on the surface of carbon nanotubes by direct electrochemical method.After electrochemical derivatization in alkaline condtion,amulti-waleedcarbon nanotube supported nickel-cobalt bimetallic hydroxide electrode（Ni（OH）2-Fe（OH）3/MWCNTs/CCE）was obtained.The results showed that,firstly,the Ni（OH）2-Fe（OH）3 can be conveniently loaded on the surface of MWCNTs by this method.Secondly,a porous structure interfacewasobtained by introducing MWCNTs,which improved the conductivity and interface permeability.In addition,the electrocatalytic activity of Ni（OH）2was furtherly improved by introducing Fe（OH）3.With thesynergic action of thess factor,the electrode showed better analytical performance for the determination of urea.Under the optimized conditions,the linear range of amperometric determination of urea was 5.0×10-6-2.8×10-3 mol·L-1.The detection limit was 3.6×10-6mol·L-1（3Sb）,with the sensitivity of 54.3μA·(mmol·L-1)-1(765μA·(mmol·L-1)-1·cm-2).Compared with other nickel-based sensors,the electrode had the advantages of high sensitivity,wide linear range and good stability in the detection of urea.2.A Co-Ni bimetallic hydroxide/multi-walled carbon nanotube composites（Co（OH）2-Ni（OH）2/MWCNTs）with controllable morphology and uniform particle size distribution was prepared by electrochemical in-situ derivatization of polynuclear metal hexcyanoffate.The electrocatalytic oxidation activity of the electrode for hydrazine was studied carefully.The results showed that the introduction of carbon nanotubes was conducive to obtain the interface of porous Co-Ni bimetallic oxide composite nano materials,and improved the conductivity and interface permeability.The introduction of bimetallic hydroxide improved the catalytic activity of the electrode.By optimizing the experimental conditions,the detection limit of hydrazine by amperometric method was 7.0×10-8 mol·L-1（3Sb）.The sensitivity was up to 297μA·(mmol·L-1)-1(4183μA·(mmol·L-1)-1·cm-2).The linear range was 2.0×10-7-1.5×10-3 mol·L-1.Compared with other reported similar electrodes,the electrode exhibited the characteristics of simple preparation procedure,low detection limit and high sensitivity.3.Based on the underpotential deposition of Pb on the surface of Pt,amulti-walled carbon nanotubes supported porous Pt nanoparticle composites was prepared by in-situ underpotential electrodeposition-electrochemicaldealloying method.Its electro-catalytic oxidation activity for ammonia under alkaline conditions was studied carefully.The results showed that,on the one hand,a porous Pt nanostructure with smaller particle size and more uniform distributionwas obtained by in-situ underpotential deposition-electrochemical dealloyingtechnique.On the otherhand,the introduction of carbon nanotubes provided a good carrier for the loading of Pt particles and enhanced the conductivity and permeability of the interface.Under the combined action of the above factors,the material showed high catalytic activity for the electro oxidation process of ammonia.On this basis,the concentration of ammonia nitrogen in water was determinedby differential pulse voltammetry（DPV）with the detection limit was 5.2×10-7 mol·L-1(8.8×10-3 mg·L-1,3Sb).The linear range is 1.0×10-6-1.0×10-4mol·L-1(the sensitivity is 52μA·(mmol·L-1)-1)and 1.0×10-4-2.0×10-3mol·L-1(the sensitivity is 26μA·(mmol·L-1)-1).Compared with other Pt-based sensors,the electrode showed the advantages of high sensitivity,wide linear range and good stability in the detection of ammonia in water. |
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