Contents of Today S.J.T.U. Phase Transformation and Applications Review previous Nernst equation Pourbaix diagrams Concentration cells Oxygen pressure determination etc. Fuel cell SJTU Thermodynamics of Materials Springl2008©X.J.Jin Lecture 11 Electrochemistry Il
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Springl 2008 © X. J. Jin Lecture 11 Electrochemistry II Contents of Today Review previous Nernst equation Pourbaix diagrams Concentration cells Oxygen pressure determination etc. Fuel cell
判断过程的方向 S.J.T.U. Phase Transformation and Applications 定温定压的体系 (AG)t.p<0 表示自发 (AG)t. =0表示平衡 (AG).p>0 表示不自发 △G)n,n>W'表示不可能进行 在定温定压条件下，一个自发过程发生时，系统的Gbbs自 由能总要减少，当减少到不能再减少时，系统即达平衡， 这是系统的Gibbs自由能应为极小值 SJTU Thermodynamics of Materials Springl2008©X.J.Jin Lecture 11 Electrochemistry Il
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Springl 2008 © X. J. Jin Lecture 11 Electrochemistry II 判断过程的方向 定温定压的体系 (ΔG) , pT < 0 表示自发 (ΔG) , pT = 0 表示平衡 (ΔG) , pT > 0 表示不自发 (Δ ) , pT > WG ' 表示不可能进行 在定温定压条件下，一个自发过程发生时，系统的Gibbs自 由能总要减少，当减少到不能再减少时，系统即达平衡， 这是系统的Gibbs自由能应为极小值
Review previous S.J.T.U. Phase Transformation and Applications Electrochemicali电化学 Electrochemical cell电化学电池 Electrode电极 Electrolyte电解液 ● Oxidation氧化/anode阳极 ● Reduction还原/cathode阴极 ● Electrical work电功 e Electromotive force(emf)电动势 ·Faraday constant法拉第常数96480C.mo1 ·Half-cell reaction半电池反应 SJTU Thermodynamics of Materials Springl2008©X.J.Jin Lecture 11 Electrochemistry Il
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Springl 2008 © X. J. Jin Lecture 11 Electrochemistry II Review previous • Electrochemical电化学 • Electrochemical cell 电化学电池 • Electrode 电极 • Electrolyte 电解液 • Oxidation 氧化 / anode 阳极 • Reduction 还原 / cathode 阴极 • Electrical work 电功 • Electromotive force (emf) 电动势 • Faraday constant 法拉第常数 96480 C.mol-1 • Half-cell reaction 半电池反应
Calculation of Cell Voltage(2) S.J.T.U. Phase Transformation and Applications W=-EZF W1-2=-(p2-41) △G=-EzF (42-功)=E △G°=-E°zF E:the voltage of the cell Z:the number of moles of electrons transferred for the chemical equations as written The relationship between the electrical potential of a cell and the change in Gibbs free energy between the reactants and products SJTU Thermodynamics of Materials Springl 2008( X.J.Jin Lecture 11 Electrochemistry Il
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Springl 2008 © X. J. Jin Lecture 11 Electrochemistry II Calculation of Cell Voltage (2) = −EzFW =Δ −EzFG zFEGo o −=Δ E: the voltage of the cell Z: the number of moles of electrons transferred for the chemical equations as written The relationship between the electrical potential of a cell and the change in Gibbs free energy between the reactants and products W − = − φ −φ1221 )( Q φ −φ12 )( = E
Half-cell Reactions (2) S.J.T.U. Phase Transformation and Applications Table 6.1 Standard Oxidation Potentials Electrode Reaction at 298 K E(V) △G°=-E°zF Acid Solutions Li→Li*+e 3.045 K→K++e 2.925 Cs→Cs++e 2.923 E0>0 Ba→Ba2++2e 2.90 Operate Ca→Ca2++2e 2.87 NaNa +e 2.714 Mg→Mg2++2e 2.37 VG0<0 spontaneously Al→A13++3e 1.66 Zn→Zn2++2e 0.763 Fe→Fe2++2e 0.440 C2+→Cr3++e 0.41 Cd→Cd++2e 0.403 Reference point Sn→Sn2++2e 0.136 Pb→Pb2++2e 0.126 The standard hydrogen electrode Fe→Fe2++3e 0.036 H2→2H++2e 0.000 Cut→Cu2++e -0.153 Cu→Cu2++2e -0.337 Which have a zero voltage when 2I→12+2e -0.5355 Fe2+→Fe3++e -0.771 Ag→Ag++e -0.7991 the reactant,hydrogen and Hg→Hg2++2e -0.854 2Br→Br2(I)+2e -1.0652 product,hydrogen ions,are in C1-→Cl2+e -1.3595 Source:W.M.Latimer,The Oxidation States of the Ele- their standard states (1 mol /L) ments and Their Potentials in Aqueous Solutions,(2nd ed.,Prentice-Hall,Englewood Cliffs.NJ.1952). SJTU Thermodynamics of Materials Springl2o08©X.J.Jin Lecture 11 Electrochemistry ll
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Springl 2008 © X. J. Jin Lecture 11 Electrochemistry II Half-cell Reactions (2) 0 0 E > 0 0 G <∇ Operate spontaneously Reference point The standard hydrogen electrode Which have a zero voltage when the reactant, hydrogen and product, hydrogen ions, are in their standard states (1 mol / L). zFEGo o −=Δ