1. What is Electrochemistry?
1.1. Electrochemistry is any process involving motion of charge
1.2. This process must have the charge carried by entities other than unsolved electrons and holes
1.3. Variety of interfacial electrochemical techniques
1.3.1. Control current (i.e. potentiometry, chronoamperometry)
1.3.2. Control voltage (i.e. voltammetry, coulometry)
2. Redox Reactions
2.1. Involvement of electron transfers
2.2. Composed of half cells
2.3. Written out with specified notation
2.3.1. | Phase boundary || Salt bridge
2.3.2. (i.e.) Electrode 1 | Solution 1 || Solution 2 | Electrode 2
2.4. Measuring standard reduction potential
2.4.1. Beneficial to use a standard hydrogen electrode (SHE) to measure standard reduction potential
2.4.2. Standard reduction potential: The potential of a reversible cell or half-cell when all species are at standard states
2.5. Spontaneity (Delta G)
2.5.1. (Delta G) = -nFE
2.5.1.1. (Delta G) = Gibbs free energy of reaction
2.5.1.2. n = Number of electron transfers for reaction
2.5.1.3. F = Faraday constant (96,485 C/mol)
2.5.1.4. E = Electromotive force
2.5.2. If Ecell > 0, than the reaction (from the left to right half electrodes) is spontaneous
2.5.3. Electrons move toward the positive electrical potential
2.5.4. If Delta G < 0 (spontaneous), cell is a Galvanic Cell
2.5.5. If Delta G > 0 (non-spontaneous), cell is an Electrolytic Cell
3. Electrode Potential
3.1. Half cell potential can be calculated for each half cell reaction from the Nernst Equation
3.1.1. E = E0 - (RT/NF)ln(ared/aox)
3.1.2. ared = activity product of reduced side
3.1.3. aox = activity product of oxidized side
3.2. E0', known as the formal potential, can be used in the Nernst Equation to directly use concentration the calculations, rather than using activity
4. Electrodes
4.1. The reaction of one electrode is studied (with one half cell reaction). This particular electrode is called the working electrode.
4.1.1. Active electrode: electrode metal is part of half reaction
4.1.2. Inactive electrode: electrodes are only means of moving electrodes
4.1.2.1. Instead, the reagents of solution are involved in half-reactions
4.2. Reference electrode: the electrode against the potential of working electrode is measured
4.2.1. Ideally, reference electrodes should not contaminate the solution. Additionally, they should have invariant potential and zero impedance.
4.2.2. Common reference electrodes
4.2.2.1. Saturated calomel electrode (SCE)
4.2.2.2. Silver-silver chloride electrode (Ag/AgCl)
4.2.2.3. Mercury-mercurous sulfate electrode (Hg/Hg2SO4)
4.3. Polarizable vs. Non-Polarizable electrodes
4.3.1. Polarizable: behaves like a capacitor, where the charge accumulates on electrode
4.3.2. Non-Polarizable: the charge leaks out of the electrode, instead of the charge accumulating on the electrode surface
5. Current, charge, and moles
5.1. Cathodic current: electrode is a cathode, solution species is reduced, electrodes go from electrode to species in solution
5.2. Anodic current: electrode is anode, solution species is oxidized, electrodes go from species in solution to electrode
5.3. Relating Coulombs to Moles
5.3.1. Q = nFN
5.3.1.1. Q = charge
5.3.1.2. n= Number of electrons transferred per reaction
5.3.1.3. N = moles of reaction
5.3.1.4. F = Faraday constant