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Introduction to electrochemical systems

Introduction to electrochemical systems. Sähkökemian peruseet KE-31.4100 Tanja Kallio t anja.kallio@aalto.fi C213. CH 1. Introduction to electrochemistry. Electrochemical cell. l oad or measuring equipment. external circuit. load. electrodes. electrically charged species. medium. =.

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Introduction to electrochemical systems

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  1. Introduction to electrochemical systems Sähkökemianperuseet KE-31.4100 Tanja Kallio tanja.kallio@aalto.fi C213 CH 1

  2. Introduction to electrochemistry

  3. Electrochemical cell load or measuring equipment external circuit load electrodes electrically charged species medium = electrolyte + organic solvent ions water molecules molten salts ionic liquids complex ions membranes ceramics

  4. Electrochemical reaction electrode electrochemical reaction = heterogeneous redox reaction e- The rate of an electrochemical reaction depends on the potential of the electrode

  5. Redox-reactions in the cell I = nFr Q = It = nzF load Anode H2 2H+ + 2e- Eo= 0.00 V Cathode O2 + 4H+ + 4e- 2H2O Eo = 1.23 V counter electrode reference electrode auxillary electrode reaction of interest = working electrode Pt Pt acidic aqueous electrolyte H2SO4, HClO4, …

  6. Metal bonding, Fermi level and work function Fermi level P(E) = 1/2 Fermi Dirac distribution

  7. finnerorgalvapotential surfacepotential outerorvoltapotential Potential and voltage charge in vacuum faasi a

  8. Electrode potential, potential difference and voltage electrode solution solution electrode - unoccupied unoccupied Ef’ energy electrod potential Ef occupied states occupied states + 0 0.5 1 0 0.5 1 probability for finding an electron

  9. Electron transfer on the electrode a molecule in a solvent a molecule in a solvent electrode electrode unoccupied e- LUMO LUMO energy Ef’ e- Ef HOMO HOMO occupied states Ag+(aq) + e- Ag Ag+(aq) + e- Ag

  10. Potentialwindow

  11. Li4Ti5O7electrode for lithiunionbattery polarizability ideallynonpolarizable reactionrate ~  ultra capacitor ideallypolarizable reactionrate ~ 0

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