Effects of citrate concentration and pH on the electrochemical reduction process of Co（Ⅱ） were investigated by cyclic voltammetry（CV） and electrochemical impedance spectroscopy（EIS）. The results show that Co（...Effects of citrate concentration and pH on the electrochemical reduction process of Co（Ⅱ） were investigated by cyclic voltammetry（CV） and electrochemical impedance spectroscopy（EIS）. The results show that Co（Ⅱ） is reduced into two species which are free Co2＋ and [Co（C6H607）] in the solution composed of 0.05 mol/L CoS04·5H2O, 0.20 mol/L Na2SO4 and 0-0.40 mol/L C6H5O7Na3·2H2O in the pH range of 3-9. The reduction behavior depends on the pH of the solution. Co（H） is mainly reduced into the form of free Co^2＋ at pH 3 and into the form of [Co（C6H6O7）] at the pH range of 4-6 in citrate solution. The [Co（C6H6O7）] is first reduced to an intermediate state and then to Co°. Adsorption of the intermediate state exists on the surface of the electrode. Co（Ⅱ） is difficult to be reduced in the solution with the pH above 7, because the existing Co（Ⅱ）-citrate complex species [Co（C6H5O7）]- and [Co（C6H4O7）]2- are more difficult to be reduced than the hydrogen ion.展开更多
Electroreduction of Co(Ⅱ)to metallic cohalt in urea melt is irrevsible in one step.The transfer coeffi-cient of electrode reaction of Co(Ⅱ)+2e=Co(O)and the diffusion coefficient of Co(Ⅱ)were determined.The lanthanu...Electroreduction of Co(Ⅱ)to metallic cohalt in urea melt is irrevsible in one step.The transfer coeffi-cient of electrode reaction of Co(Ⅱ)+2e=Co(O)and the diffusion coefficient of Co(Ⅱ)were determined.The lanthanum can be inductively codeposited with cobalt. The contents of lanthanum in cobalt-lanthanum de-posts increase with the shift of electrode potential to the negative direction and the raise of La(Ⅲ)/Co(Ⅱ)mo-lar ratio in the melt. The cyclic voltammetry,open circuit potential-time curve after potentiostatic electrolysisand electron probe analyas were used.展开更多
基金Project(200800560002)supported by the Ph.D.Programs Foundation of Ministry of Education of China
文摘Effects of citrate concentration and pH on the electrochemical reduction process of Co（Ⅱ） were investigated by cyclic voltammetry（CV） and electrochemical impedance spectroscopy（EIS）. The results show that Co（Ⅱ） is reduced into two species which are free Co2＋ and [Co（C6H607）] in the solution composed of 0.05 mol/L CoS04·5H2O, 0.20 mol/L Na2SO4 and 0-0.40 mol/L C6H5O7Na3·2H2O in the pH range of 3-9. The reduction behavior depends on the pH of the solution. Co（H） is mainly reduced into the form of free Co^2＋ at pH 3 and into the form of [Co（C6H6O7）] at the pH range of 4-6 in citrate solution. The [Co（C6H6O7）] is first reduced to an intermediate state and then to Co°. Adsorption of the intermediate state exists on the surface of the electrode. Co（Ⅱ） is difficult to be reduced in the solution with the pH above 7, because the existing Co（Ⅱ）-citrate complex species [Co（C6H5O7）]- and [Co（C6H4O7）]2- are more difficult to be reduced than the hydrogen ion.
文摘Electroreduction of Co(Ⅱ)to metallic cohalt in urea melt is irrevsible in one step.The transfer coeffi-cient of electrode reaction of Co(Ⅱ)+2e=Co(O)and the diffusion coefficient of Co(Ⅱ)were determined.The lanthanum can be inductively codeposited with cobalt. The contents of lanthanum in cobalt-lanthanum de-posts increase with the shift of electrode potential to the negative direction and the raise of La(Ⅲ)/Co(Ⅱ)mo-lar ratio in the melt. The cyclic voltammetry,open circuit potential-time curve after potentiostatic electrolysisand electron probe analyas were used.
