Electrochemical Detection Of Heavy Metal Ions In Water Based On Cobalt-iron Nanomaterials

With the promulgation of our policies to build a modernized country in an all-round way,industrialization has made rapid progress,but the environmental problems are also becoming more and more serious,protecting the environment has become very important,however,heavy metal ions pollution in environmental issues has become a matter of national concern,heavy metal ions can also cause serious harm to public health.At certain concentrations,it can cause serious damage to human health.Therefore,it is very important to establish monitoring means for heavy metal ions.However,electrochemical methods are widely used due to their convenience,sensitivity,and speed.With the development of nanotechnology,the use of nanomaterials to construct electrochemical sensing interfaces has been widely used in electrochemical detection.However,the mechanism of how nanomaterials act on the electrochemical sensing process is lacking,and the practical application value of the developed electrochemical sensors for heavy metals is very limited.Therefore,in this paper,cobalt-Fe-based nanomaterials are used as electrode modification materials to further study the mechanism between the sensitive interface of nanomaterials and the highly sensitive electrochemical behavior.The research work of this paper is as follows:（1）cobalt-iron composite oxide（CoFe₂O₄）nanospheres were synthesized by simple hydrothermal method and calcined at 300℃,400℃and 500℃respectively to adjust the concentration of oxygen vacancy.They were characterized by testing methods such as EPR,XPS,CV and EIS.A group of materials(CoFe₂O_4-X)with the best electrochemical properties were obtained.It was modified on a glassy carbon electrode to construct an electrochemical sensing interface.The square wave anodic stripping voltammetry（SWASV）was used to achieve highly sensitive detection of Pb（Ⅱ）.The sensitivity was 52.54μA/μM,and the detection limit（LOD）was 0.023μM.It was found that CoFe₂O_4-X showed a good sensing effect on Pb（Ⅱ）because its surface oxygen vacancy provided more catalytic active sites and efficient synergistic catalysis of bimetal.This work provides a new idea for the detection of heavy metal pollutants by adjusting the oxygen vacancy defect on the surface of nanomaterials to analyze and design the sensing interface.（2）Regular metal-organic framework ZIF-67 polyhedron was synthesized by simple experimental method.On this basis,Fe,N and C elements were added with potassium ferricyanide.Finally,cobalt-iron phosphide was obtained by phosphating（FeCoP/NC）.The physicochemical properties of FeCoP/NC/GCE were explored by means of SEM,TEM,XPS and other characterization methods,and the metal ions were modified on a glassy carbon electrode to construct an electrochemical sensing interface for electrochemical exploration.It was found that the detection sensitivity of FeCoP/NC/GCE to Pb（Ⅱ）was much higher than that of the other three heavy metal ions.The sensitivity was 66.58μA/μM,and the detection limit was 0.025μM,which was lower than the World Health Organization（WHO）safety standard for drinking water（0.048μM）.By exploring its action mechanism,it is found that FeCoP/NC has a good sensing effect on Pb（Ⅱ）because nitrogen doping carbon improves its electrical conductivity,and it has excellent selective adsorption of lead ions.This work provides a good design idea for the development of cobalt-iron phosphide and its application in the field of electrochemistry.