전기화학1

전기화학1

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Unformatted text preview: 1 Introduction to Electrochemistry Electrochemistry Electrochemistry 1) Study of chemical changes caused by the passage of an electric current and the production of electrical energy by electrochemical reactions. galvanic Chemical Energy Electrical Energy electrolytic 2) Study of electron transfer reactions, i.e, reactions in which reduction and oxidation occur.- Oxidation : loss of electrons (Fe → Fe² ⁺ + 2e ⁻ )- Reduction : gain of electrons (2H ⁺ + 2e ⁻ → H ₂ ) 2 • Electrochemistry = Electron + Chemistry • Electrochemical system = electrodes + electrolyte electrode : material that gives or accepts electrons (electronic conductor) electrolyte : phase that conducts ions (ionic conductor) • Interface between electrode and electrolyte • Electrochemical reaction kinetics ( i = function of η ) i = dQ/dt η = E- E eq (E:electrode potential, E eq : equilibrium potential) Electrical Conductivity 3 The additional potential (beyond the thermodynamic requirement) needed to drive a reaction at a certain rate is called the overpotential . 1) η > 0, anodic current flows 2) η = 0, no current flows (at equilibrium potential) 3) η < 0, cathodic current flows Overpotential Fig. Electrode potential vs. current For a given electrochemical reaction, O + n e ↔ R Nernst Equation E = E o + (RT/nF) ln ( a O n O / a R n R ) = E o’ + (RT/nF) ln ([O] n O / [R] n R ) As a potential increases, the concentration of [O] increases ⇒ oxidation As a potential decreases, the concentration of [R] increases ⇒ reduction 4 Oxidation : removal of electrons from a species (anode : the electrode at which oxidation occurs) Reduction : addition of electrons to a species (cathode: the electrode at which reduction occurs) H 2 → 2H + + 2e- 1/2O 2 + 2H + + 2e- → H 2 O H 2 + 1/2O 2 → H 2 O Anode (fuel electrode) Cathode (air electrode) Overall ㅖ뜨 Proton Exchange Membrane Fuel Cell 5 Electrochemistry vs Chemistry Quantity Charge (Q) moles (N) Driving Force E rxn D G D G = - nFE rxn Reaction Rate...
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  • Spring '11
  • suh
  • Electrochemistry, Reaction, Electrochemical cell, Anode Electrolyte Cathode, (fuel electrode), Journal of Electroanalytical Chemistry § Journal of Applied Electrochemistry § Journal of Solid State Electrochemistry § Journal of the Korean Electrochemical Society, (air electrode)

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전기화학1

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