Researches On Electrodeposition Of Magnesium From Ionic Liquids

Magnesium is the most promising metal in twenty-first Century due to its light weight,natural abundance,widely distribution and active chemical character;Magnesium alloy has superior features of light weight,corrosion resistance and impact resistance,which is widely used in automobile industry,military-industry and other fields.At present,the main industrial method to produce magnesium is Pijiang method,but it is labor-intensive and not environmentally friendly,which goes against the basic national policies of our country.Ionic liquids have the characteristics of extremely low vapor pressure,wide electrochemical window,liquidity at room temperature,designability,etc.,which open up a new path for low-temperature electrodeposition.Recently,there are few studies on the ionic liquid-electrodeposition of metal magnesium.It is found that the preparation process of deep eutectic solvent?DES?is simple,and relatively unresponsive with water.Most of them are biodegradable and cost-effective.In this context,three kinds of suitable DES systems have been used to study the electrodeposition of magnesium.?1?ChCl-urea-MgCl₂·6H₂OA series of DES of ChCl-urea-MgCl₂·6H₂O were synthesized.Urea was used as an additive to improve the electrochemical performance of Mg electrolyte and the quality of Mg deposition layer.The effect of urea is to improve the quality of the deposition layer by changing the hydrogen bond and coordination form of the electroactive species of the system,instead of adsorbing on the surface of the electrode.Combined with calculation,we explored the existence of electroactive ingredient of urea-MgCl₂·6H₂O ionic liquids in the system such as[MgCl?urea?₂]¹⁺,[MgCl?H₂O??urea?]¹⁺,[Mg?H₂O??urea?₂]²⁺,and speculate the deposition mechanism of the system.In ChCl-urea?mole ratio 1:1?-MgCl₂·6H₂O,at a constant-potential deposition for 1 h,a Mg-deposited layer was obtained but not dense enough.?2?2-Chloroacetamide-MgCl₂·6H₂OThe 2-Chloroacetamide-MgCl₂/6H₂O of different mole ratio was synthesized,and the conductivity of the system was measured.Using a 1:0.8 molar ratio of DES,the current-time curve remains above 10 mA after deposition for 1h at 80°C and-1.3V.The morphology of the deposited layer was observed by SEM,which is flat and smooth.The content of Mg in EDS is high,indicative of the successful electrodeposition of Mg.Due to the rapid oxidation of the test,XRD only detects the diffraction peaks of MgO.The structure of the system was analyzed by FTIR and Raman to explore the electroactive species of the system.?3?Acetamide-MgCl₂·6H₂OThe acetamide-MgCl₂/6H₂O of different mole ratio was synthesized,and the conductivity of the system was measured.After deposition in DES with a molar ratio of 1:1.3 at 80°C and-1.8 V for 1 h,the morphology of the deposited layer was observed by SEM,which is flat and smooth.The deposited layer was also characterized by EDS and XRD.