Electrochemical Behaviours Research Of Mg,Mg-7.5Li-3.5Al And Mg-7.5Li-3.5Al-Y As Anode Material

Mg-air semi-fuel cell is a kind of metal semi-fuel cell with magnesium or magnesium alloys as anode.As an electrode,magnesium has the advantages of negative potential,high energy density,good discharge activity and low price.However,the magnesium electrode is still vulnerable to corrosion in practical application,and there will be "hysteresis effect","hydrogen evolution reaction" and "negative difference effect",which will lead to the decline of discharge performance.The discharge properties of magnesium are improved in two ways.One is to add other alloying elements into magnesium.The other is to add additives to the electrolyte.Potentiodynamic polarization,chronoamperometry,chronopotentiometry,electrochemical impedance spectroscopy,potential step chronoamperometry and weight-loss measurement are used to study three kinds of electrodes Mg,Mg-7.5Li-3.5Al and Mg-7.5Li-3.5Al-Y in simulated seawater(0.7 mol·L-1NaCl),and the morphology of the electrode after discharge is analyzed by SEM.It is found that the discharge activities of the three electrodes Mg,Mg-7.5Li-3.5Al and Mg-7.5Li-3.5Al-Y are enhanced successively.There is no "negative difference" effect in Mg-7.5Li-3.5Al and Mg-7.5Li-3.5Al-Y electrodes.The response of the three electrodes is good,but there is a certain degree of "hysteresis effect" at the beginning of discharge.The effects of electrolyte additives sodium dodecyl benzene sulfonate(C18H29NaO3S)and sodium stannate(Na2SnO3)on the discharge performances of the three electrodes are discussed.In the 0.7 mol·L-1NaCl containing different concentrations of additives,the concentration of additives that can improve the electrode performance to the greatest extent is selected by using potentiodynamic polarization,potentiostatic discharge.The optimal concentration of C18H29NaO3S corresponding to the Mg,Mg-7.5Li-3.5Al and Mg-7.5Li-3.5Al-Y are 1.0 mmol·L-1,1.0 mmol·L-1 and 0.8 mmol·L-1,respectively.The optimal concentration of Na2SnO3 corresponding to Mg,Mg-7.5Li-3.5Al and Mg-7.5Li-3.5Al-Y are 0.8 mmol·L-1,1.0 mmol·L-1 and 1.0 mmol·L-1,respectively.After adding the two additives,the discharge current density of the three electrodes increased,the self-corrosion velocity decreased,and the "hysteresis effect”of the electrodes was alleviated.However,there is still negative difference effect in Mg electrode.