전기화학2

전기화학2

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1 Electrode Potential § A galvanic cell is a combination of two electrodes, and each one can be considered as making a characteristic contribution to the overall cell potential. § Although it is not possible measure the contribution of a single electrode, we can define the potential of one of the electrodes as zero and then assign values to others on that basis. § The specifically selected electrode is the standard hydrogen electrode (SHE) : Pt(s) / H 2 (g) /H + (aq, a=1), E o = 0 V at all temperatures. Standard Hydrogen Electrode (SHE)
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2 § At SHE, the electrode reaction is 2 H + + 2e H 2 and we assign its standard reduction potential to the value of 0.0 V. § To achieve the standard conditions, the activity of the hydrogen ions must be 1 and the pressure of the hydrogen gas must be 1 bar. (i.e., all components are at unit activity) § The standard potential (E o ) of another electrode is then measured by constructing a cell in which it is the right-hand electrode and the standard hydrogen electrode is the left-hand electrode. § The procedure for measuring a standard potential can be illustrated by considering a specific case, the copper electrode. H 2 → 2H + + 2e, E o = 0.0 V Cu 2+ + 2e → Cu, E o = ? H 2 + Cu 2+ → 2H + + Cu, E o = 0.340 V Is it spontaneous reaction ? If so, how about the reverse reaction? 2H + + Cu → H 2 + Cu 2+
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3 anode material cathode material
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4 § The reversible potential of an electrode with all the active materials in their standard states. § Usual standard states specify unit activity for elements, solids, 1 M
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전기화학2

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