| The Ag/AgCl composite electrode has been widely used in the field of ocean electromagnetic field detection due to its advantages of high exchange current density,low polarization,low impedance and constant potential.However,natural seawater contains a variety of ions,such as Br-,I- and other interfering ions.In particular,the presence of Br- will seriously affect the structure and electrical properties of the single composition of Ag/AgCl composite electrode.Therefore,the electrochemical performance of Ag/AgCl reference electrode was optimized through the doping of AgBr.Firstly,the preparation process of AgBr powder with small particle size and even distribution was studied,and then the influence and mechanism of AgBr and Ag on electrochemical performance of the electrode were emphatically investigated.1.AgBr powders were prepared by coprecipitation method,hydrothermal synthesis method and solid phase ball-milling method,respectively.The experimental results showed that the micromorphology of AgBr powders obtained by different preparation methods varied greatly.Among them,the AgBr particles were prepared by coprecipitation method with polyhedral shape and good dispersibility,but the particle size distribution is not uniform and the particle size ranges from 1?m to 7?m.The AgBr powder prepared by hydrothermal synthesis method at 140? presented spherical particles with uniform particle size and good dispersibility,but the particle size was relatively large,and the average particle size was 7?m.The AgBr powder prepared by solid phase ball-milling method is usually spherical,and its particle size is between 3?m to 4?m.According to the requirements of electrode preparation,the AgBr powder obtained by solid phase ball-milling method with small and uniform particle size was selected as raw material powder for the preparation of electrode.2.Composite Ag/AgCl/AgBr electrodes with different AgBr dopants and different amounts of Agwere prepared by traditional ceramic process.The electrical performance of the electrode was tested by means of potential step method and electrochemical workstation.The AC impedance of Ag/AgCl/AgBr electrode and the kinetic parameters of electrode reaction were calculated by analog circuit.The relationship between the internal microstructure and electrochemical polarization properties was analyzed.The mechanism of electrochemical noise and its influence on the measurement performance of the electrode are also discussed.The results showed that with the increase of AgBr content,the porosity and specific surface area of the electrode increased gradually,then the increase decreased and tended to be flat.The electrode exchange current density was increased and the degree of electrochemical polarization was decreased.The electrode has the characteristics of resistance and capacitance at the same time.When the doping amount of AgBr was 0.3 times that of AgCl,the noise of Ag/AgCl/AgBr electrode was reduced to 4.29×10-9 V/?Hz,and the fluctuation of the electrode was controlled within 0.025 mV,and the 24 h stability of the electrode was the best.When the doping amount of AgBr was determined,the porosity,exchange current density and specific surface area of Ag/AgCl/AgBr electrode increased first and then decreased with the increase of the amount of Ag,while the degree of electrochemical polarization decreased first and then increased.When Ag:AgX was 1.0:1,the noise of the electrode was reduced to 2.62×10-9 V/?Hz,and the fluctuation of the Ag/AgCl/AgBr electrode was kept within 0.047 mV,and the best 24 h stability of the electrode was achieved. |
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