Chemistry

DANILO DINI

In accordance to the first two Dublin descriptors, at the end of the course the student will have the knowledge of the following five points:

a) the mechanisms at the basis of electrical conduction in the different types of materials (ionic, electronic and mixed conductors) and the factors that control this phenomenon;
b) the phenomena that originate the electrochemical double layer;
c) the thermodynamics and the working principle of the electrochemical devices
d) kinetic factors that control the passage of electrical current in an electrochemical device;
e) electrochemical analysis of the phenomena of corrosion

The student will use the concepts grasped during the course of electrochemistry to realize electrochemical experiments for fundamental studies or for routine research.

The course has also the finality of developing the communication skills of the student (fourth Dublin descriptor). This is realized through questions during classes and in the final exam.

1-Calculation of the current and current density passing through an electrode with semi-spherical shape when 15 ms have passed in case:
a) the electron transfer process is monoelectronic
b) the process is anodic
c) the diffusion coefficient of the redox active species is 8*10^-5 cm^2 s^-1
d) the concentration of the redox active species in the bulk is 0.1 M
e) the electrode radius is 10^-5 m


2- Calculation of the radius of the ionic cloud in an electrolyte composed of NaCl when
a) salt molality is 0.1m
b) solvent density is 1000 Kg m^-3
c) the dielectric constant of the solvent is 80
d) the temperature is 300 K

3- Calculation of the electrical potential at the distance 0.2 nm from the electrode/electrolyte interface when
a) the electrical potential at the electrode surface is 1.5 V
b) the electrical potential of the solution is -1.2 V
c) the diamter of the solvation shell in correspondence of the IHP is 1 nm

For the calculation consider the double layer model of Helmholtz

Knowledge of general chemistry, physical chemistry, mathematics and physics of the electromagnetic fields

FOUNDATIONS AND DEFINITIONS
Ions, electrolytes and quantization of charge. Transition from electronic to ionic conductivity in an
electrochemical cell. Electrolysis cells and galvanic cells. Faraday’s laws. Systems of units.

ELECTRICAL CONDUCTIVITY AND INTERACTIONS BETWEEN IONS
Fundamentals; empirical laws of electrolyte conductivity. Ionic mobility and Hittorf transport. The
Debye-Hueckel-Onsager theory of conductivity. Properties of weak electrolytes. The concept of activity
from the electrochemical viewpoint.

ELECTRODE POTENTIALS AND DOUBLE-LAYER STRUCTURE
Electrode potential; overvoltage. EMF and maximum useful energy from electrochemical reactions.
Reference electrodes; electrochemical series; electrocapillary effect. PZC. Double layer models according
to Helmholtz, Gouy-Chapman and Stern.

ORIGIN OF ELECTRICAL CURRENT
Charge flux and overpotential; e-transfer and the activated complex model. Butler-Volmer equation and
its approximations (high field, or low field). Concentration overvoltages and other potential drops in a
cell. Diffusion: trasnsient, steady-state, planar, spherical., microelectrodes. Adsorption phenomena,
surface diffusion, electrocrystallization.

GALVANIC CELLS AND INDUSTRIAL APPLICATIONS
Fundamentals; electrolysis, separators, membranes. Electrosynthesis and electrocatalysis. Metal and
semiconductor electrodeposition (nano-structures as well). Water treatment, electrophoresis,
electrodialysis. Batteries and accumulators (examples); fuel cells and applications.

CORROSION
Thermodynamics: Pourbaix diagrams. Electrochemical kinetics of corrosion. Examples.

ELECTROCHEMISTRY (2nd Edition) by Hamann, Hamnett e Vielstich-Wiley VCH (531 pages)

Review and research articles about specific topics of the course. The articles are chosen among those having a prevailingly didactic character

The course of Electrochemistry is taught through the explanation of the various topics presented in PowerPoint slides

The course of Electrochemistry is offered within one semester. The frequency is two lessons per week. Every lesson has a duration of two hours.

The student is evaluated through a written exam. The exam consists in the explanation of the concepts presented during the course. In doing so, the student uses only pen and paper. The exam lasts 3 hours and half. The number of questions is three. It is strictly forbidden the use of computer, laptop, textbooks, smartphones, notes and slides of the course. The student has to indicate his/her name on each sheet of the test.

Models for the description of the electrochemical double layer
Equation of Butler-Volmer
Ionic cloud in electrolytic soloutions
Mass transport phenomena in electrochemistry and related kinetics equations

• testo : ELECTROCHEMISTRY (Hamann-Hamnett-Vielstich)