1.1 Fundamentals of Electrochemistry

Electrochemistry explores the connection between electrical and chemical changes. It's all about electron transfer between chemical species, covering both spontaneous and non-spontaneous reactions. This field has wide-ranging applications, from batteries to corrosion prevention.

At its core, electrochemistry revolves around electron transfer. Reduction gains electrons, while oxidation loses them. These processes occur simultaneously in redox reactions, with oxidation at the anode and reduction at the cathode. Understanding this is key to grasping electrochemical concepts.

Introduction to Electrochemistry

Scope of electrochemistry

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• Branch of chemistry studying the interrelation of electrical and chemical changes
• Focuses on processes and reactions involving electron transfer between chemical species
• Encompasses the study of both spontaneous (galvanic cells) and non-spontaneous reactions (electrolytic cells)
• Wide range of applications
  • Energy storage and conversion devices (batteries, fuel cells)
  • Electrochemical sensors and biosensors
  • Electrochemical synthesis and manufacturing (electrolysis, electroplating)
  • Corrosion science and prevention

Electron transfer in electrochemistry

• Fundamental process underlying electrochemical reactions
• Involves the movement of electrons from a reducing agent (reductant) to an oxidizing agent (oxidant)
• Reduction gains electrons by a chemical species
• Oxidation loses electrons by a chemical species
• Redox reactions involve the transfer of electrons
  • Oxidation and reduction occur simultaneously in a redox reaction
  • Oxidation occurs at the anode (negative electrode)
  • Reduction occurs at the cathode (positive electrode)

Electrochemical Cells

Components of electrochemical cells

• Electrodes conduct electricity and allow electron flow
  • Anode where oxidation occurs (negative electrode)
  • Cathode where reduction occurs (positive electrode)
• Electrolyte conducts electricity through ion movement
  • Aqueous solution containing dissolved ions or molten salt
  • Allows charge transfer between electrodes
• Salt bridge or porous membrane connects two half-cells
  • Maintains electrical neutrality by allowing ion passage between half-cells
  • Prevents mixing of electrolyte solutions in half-cells
• External circuit (wires) allows electron flow between electrodes

Electricity-chemical reaction relationship

• Electrochemical cells convert chemical energy into electrical energy and vice versa
  1. Galvanic (voltaic) cells generate electricity from spontaneous redox reactions (batteries, fuel cells)
  2. Electrolytic cells drive non-spontaneous redox reactions with an external power source (electrolysis of water, electroplating)
• Electrical quantities in electrochemical systems
  • Potential difference (voltage) drives electron transfer, measured in volts (V)
    • Standard electrode potential ($E^0$) is the half-cell potential under standard conditions (1 M concentrations, 1 atm pressure, 25℃)
  • Current is the rate of electron flow, measured in amperes (A)
    • Faraday's laws of electrolysis relate charge transferred to the amount of chemical change
  • Resistance opposes electric current flow, measured in ohms ($\Omega$)