Electrochemistry

40 lessons, pages 3151–3190.

  1. Electrochemistry at University Level — From ideal Nernstian cells to real ions, real rates and real devices
  2. Chemical Potential of Ions in Solution — Activity, activity coefficients and the non-ideal chemical potential
  3. Mean Ionic Activity Coefficients — Why single-ion activities cannot be measured and how the mean is defined
  4. Ionic Strength — Weighting ion concentrations by the square of their charge
  5. The Ionic Atmosphere — Screening of a central ion by a diffuse cloud of counter-charge
  6. Debye Length and Charge Screening — The characteristic thickness of the ionic atmosphere and its dependence on ionic strength
  7. Deriving the Debye–Hückel Limiting Law — Poisson–Boltzmann linearisation and the energy of the ionic atmosphere
  8. Applying the Debye–Hückel Limiting Law — Calculating mean activity coefficients in dilute aqueous electrolytes
  9. Extended Debye–Hückel and Davies Equations — Finite ion size and empirical corrections at higher ionic strength
  10. Limits of Debye–Hückel Theory — Ion pairing, concentrated solutions and specific ion interactions
  11. Activity Effects on Solubility and Equilibria — The salt effect on sparingly soluble salts and weak-acid dissociation
  12. Activities in Cell Potentials — Extrapolating measured EMF data to obtain standard potentials
  13. The Electrical Double Layer — Helmholtz, Gouy–Chapman and Stern models of the electrode–solution interface
  14. Faradaic and Non-Faradaic Processes — Charge transfer across the interface versus double-layer charging
  15. Current as a Measure of Reaction Rate — Relating current density to the rate of an electrode reaction through Faraday's constant
  16. Overpotential and Its Sources — Activation, concentration and resistive contributions to overpotential
  17. Activation Barriers at Electrodes — How electrode potential shifts the Gibbs energy of activation
  18. The Transfer Coefficient — Symmetry of the energy barrier and the fraction of potential that drives reaction
  19. Exchange Current Density — Dynamic equilibrium at an electrode and the intrinsic speed of a couple
  20. The Butler–Volmer Equation — Net current as the difference of anodic and cathodic partial currents
  21. Low-Overpotential Behaviour and Charge-Transfer Resistance — Linearising Butler–Volmer near equilibrium
  22. Tafel Analysis — High-overpotential limits, Tafel slopes and extracting kinetic parameters
  23. Mass Transport to Electrodes — Diffusion, migration and convection as supply routes for reactants
  24. Limiting Current and Concentration Overpotential — The Nernst diffusion layer and the ceiling on current
  25. Mixed Kinetic and Transport Control — Combining charge-transfer and diffusion limits in one current–potential curve
  26. Electrocatalysis and the Hydrogen Evolution Reaction — Why electrode material changes exchange current by orders of magnitude
  27. Probing Electrode Kinetics Experimentally — Conceptual principles of voltammetry and impedance measurements
  28. Battery Fundamentals and Performance Metrics — Voltage, capacity, specific energy, power and coulombic efficiency
  29. Theoretical Capacity and Specific Energy — Calculating charge and energy stored per unit mass of active material
  30. Why Real Batteries Deliver Less — Internal resistance, overpotentials and the polarisation curve of a cell
  31. Discharge Curves and Rate Capability — How current, temperature and state of charge shape delivered energy
  32. Primary Cells: Zinc–Manganese Dioxide Chemistry — Electrode reactions in alkaline and zinc–carbon cells
  33. The Lead–Acid Battery — Sulfate-forming electrodes, charging reactions and sulfation
  34. Nickel-Based Rechargeable Cells — Nickel oxyhydroxide cathodes with cadmium and metal-hydride anodes
  35. Lithium-Ion Batteries: Intercalation Electrodes — Rocking-chair operation, graphite anodes and layered oxide cathodes
  36. Electrolytes and the Solid–Electrolyte Interphase — Electrochemical stability windows and passivating films in lithium-ion cells
  37. Battery Degradation and Safety — Capacity fade, lithium plating and the concept of thermal runaway
  38. Emerging Battery Chemistries — Sodium-ion, solid-state, lithium–sulfur and flow batteries
  39. Connecting Activity, Kinetics and Battery Design — Integrated problems linking non-ideality, overpotential and cell performance
  40. Electrochemistry: Unit Review — Consolidating Debye–Hückel theory, electrode kinetics and batteries