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 Springl2006©X.J.Jin Lecture 11 Electrochemistry Il
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Springl 2006 © 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 Springl2006©X.J.Jin Lecture 11 Electrochemistry Il
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Springl 2006 © 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 Springl 2006( X.J.Jin Lecture 11 Electrochemistry Il
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Springl 2006 © 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 (φ2-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 2006 ©X.J.Jin Lecture 11 Electrochemistry Il
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Springl 2006 © X. J. Jin Lecture 11 Electrochemistry II Calculation of Cell Voltage (2) = −EzFW =Δ −EzFG zFEGD D −=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 Springl2oo6©X.J.Jin Lecture 11 Electrochemistry ll
Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Springl 2006 © 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). zFEGD D −=Δ