Chapter 7 Electrochemistry 87.12 Basic principal and application of electrolysis
Chapter 7 Electrochemistry §7.12 Basic principal and application of electrolysis
87.12 Basic principal and application of electrolysis Inert Oxidation of species in anode solution A nodic reaction Active dissolution Active Passivation and conversion anode Electrolysis reaction Anodization reduction of species in solution cathodic reaction reduction of oxide/conversion layer
Anodic reaction cathodic reaction Active dissolution Passivation and conversion Anodization Inert anode Active anode Oxidation of species in solution reduction of species in solution reduction of oxide/conversion layer Electrolysis reaction §7.12 Basic principal and application of electrolysis
87.12 Basic principal and application of electrolysis 1. Cathode reaction: discharge potential For liberation of metal, the overpotential is usually very low, and the reversible potential can be used in stead of irreversible potential 0.799V For evolution of gas, the overpotential is relatively large, PeAg*/Ag therefore, the overpotential should be taken into consideration 0.337V pe Cu2+/Cu Ag, Cu, H, and Pbzt will liberates at 0. 799 V;0.337 V: 0.000 0.000 V;-0126 V, respectively without consideration of P H*/H overpotential -0.126 Overpotential of hydrogen liberation on Cu is 0.6 V, on Pb P Pb+/pb is 1.56V
For evolution of gas, the overpotential is relatively large, therefore, the overpotential should be taken into consideration. Ag+ , Cu2+ , H+ , and Pb2+ will liberates at 0.799 V; 0.337 V; 0.000 V; -0.126 V, respectively without consideration of overpotential; Overpotential of hydrogen liberation on Cu is 0.6 V, on Pb is 1.56 V 0.337 V ⊖ Cu2+/Cu -0.126 ⊖ Pb2+/Pb 0.799 V ⊖ Ag+ /Ag 0.000 ⊖ H+ /H2 For liberation of metal, the overpotential is usually very low, and the reversible potential can be used in stead of irreversible potential. 1. Cathode reaction: discharge potential §7.12 Basic principal and application of electrolysis
87.12 Basic principal and application of electrolysis 1. Cathode reaction--residual concentration Potential sweep and residual concentration a(Pb2+)=33×10-49 a(Cu2)=22×1016 a(Ag+)=15×108 0.799V 0.337V 0.126V 1.56V The liberation order and the residual concentration of the ions upon negative shift of potential of cathode
a(Ag+ ) = 1.510-8 0.799 V a(Cu2+) = 2.210-16 0.337 V a(Pb2+) = 3.310-49 -0.126 V -1.56 V The liberation order and the residual concentration of the ions upon negative shift of potential of cathode Potential sweep and residual concentration 1. Cathode reaction—residual concentration §7.12 Basic principal and application of electrolysis
87.12 Basic principal and application of electrolysis 1. Cathode reaction 2)Application 1)Separation of metal 2)Quantitative and qualitative analysis(polarography) 3)Electroplating of single metal and alloy 4)Electrolytic metallurgy(Al, Ti, Mn) 5)Electrorefining of metal(Cu) 6)Electrosynthesis(Aniline
2) Application 1) Separation of metal 2) Quantitative and qualitative analysis (polarography) 3) Electroplating of single metal and alloy 4) Electrolytic metallurgy (Al, Ti, Mn) 5) Electrorefining of metal (Cu) 6) Electrosynthesis (Aniline) 1. Cathode reaction §7.12 Basic principal and application of electrolysis