Electrochemistry Flashcards
What is a galvanic cell?
A galvanic cell consists of two half-cells, each containing an electrode immersed in an electrolyte solution, connected by a salt bridge. The salt bridge allows ions to flow, completing the circuit.
What does a galvanic cell do?
Galvanic cells convert chemical energy into electrical energy through spontaneous redox reactions.
What is an electrolytic cell?
An electrolytic cell consists of two electrodes immersed in an electrolyte solution with an external power source required to drive the redox reactions.
What does an electrolytic cell do?
Electrolytic cells convert electrical energy into chemical energy through non-spontaneous redox reactions.
What is a reference electrode?
The electrode with a stable and well-known electrode potential which serves as a reference point against which the potentials of other electrodes are measured.
What is a working electrode?
The electrode at which the reaction of interest occurs. We vary the potential of this electrode to control the reaction and monitor the resulting current. The material of the electrode tends to be inert to ensure that the electrolyte does not react with it.
What is a counter electrode?
The electrode at which the counter-reaction occurs. It completes the electrical circuit in the cell by balancing the charge added or removed by the working electrode.
Often made of inert materials like platinum, gold, or carbon
Should have a larger surface area compared to the working electrode to ensure that the reactions occurring at the counter electrode do not limit the processes at the working electrode
What is the point of using inert ions in an electrolyte solution?
Inert ions are less reactive than the solvent over a wide potential range to allow redox reactions to be studied within these potential limits.
Describe the Helmholtz description of an electrical double layer.
When the electrode charge (σ) is -ve, assumed +ve ions formed layer at electrode surface, held by -ve potential
Gives required potential profile for reaction to occur i.e. no potential outside ion layer
Doesn’t account for the randomising effect of the thermal motion of the solvent
If kT large, thermal energy may overcome force holding ions to electrode surface, leading to a partially filled in layer, residual charge outside Helmholtz layer
What is the Stern layer?
The compact layer of counter-ions (to charge of electrode surface), ions specifically adsorbed onto electrode surface
What is the Gouy-Chapman layer?
Diffuse layer – ions distributed according to balance between electrostatic attraction and thermal motion
What is a potential window?
The range of potentials that can be applied to the system w/out breaking down the background electrolyte.
What is the depletion zone?
The region near the electrode surface where the concentration of the electroactive species is lower than the bulk concentration due to the consumption or generation of these species during the electrochemical reaction.
