Rappel Potentiel Chimique: Travail pour une transférer une molécule vers une phase Potentiel externe : Tout excès de charge se répartit à la surface d’une phase. Le potentiel généré par cet excès de charge s’appelle le potentiel externe Potentiel de surface : L’anisotropie des forces en surface résulte en la formation d’une couche dipolaire

Potentiel chimique de NaCl

Potentiel électrochimique : Contribution chimique Toutes les interactions courtes distance y compris les interactions électrostatiques : Travail électrique pour l’approche de la phase chargée : Travail électrique pour passer les dipôles de surface

Potentiel (électro)chimique Variation d’énergie interne: Variation d’énergie de Gibbs: Définition thermodynamique:

Potentiel électrochimique standard Partie indépendante de la concentration

Potentiel chimique réel Potentiel électrochimique quand l’excès de charge est nul. Partie intrinsèque à la phase du potentiel électrochimique, pour autant que le potentiel de surface soit indépendant de la phase,

Potentiel chimique d’un sel En développant Les termes électriques s’éliminent Coefficient d’activité Coefficient d’activité ionique moyen

Exemple MgCl2 Potentiel chimique : Coefficient d’activité : Coefficient stoechiométrique moyen :

Structure de bande

Solide Bande de conduction Bande de conduction Bande de conduction eV Bande de valence Bande de valence Bande de valence Isolant Semi-conducteur Métal

Statistique de Fermi-Dirac

Niveau de Fermi Potentiel électrochimique de l’électron HOMO à 0K Probabilité d’occupation = 1/2 Faible variation avec la température dans le cas d’un métal

Potentiel électrochimique de l’électron

Travail d’extraction Electron au repos dans le vide Potentiel Energie potentielle Niveau de Fermi Travail d’extraction Contribution chimique Potentiel électrochimique

Influence de la charge Electron au repos dans le vide Niveau de Fermi Métal chargé <0 Niveau de Fermi Métal chargé >0 Niveau de Fermi Métal non chargé

Travail d’extraction Métal eV Pt 5.4 Au 5.32 Pd 5.0 Os 4.83 Ru 4.80 K 2.30 Ba 2.35 Na 2.7 Ca 2.71 Li 3.1 métaux nobles métaux alcalins

Contact entre 2 métaux

Sonde de Kelvin

Quand le courant est nul Sonde de Kelvin Quand le courant est nul

Tension aux bornes d’un générateur : Sonde de Kelvin Tension aux bornes d’un générateur : Contact entre métaux :

Modification de surface Contact entre métaux : Avant Après Différence de la tension de compensation suite à la modification de surface:

Sonde de Kelvin à balayage

octaldecyltrimethoxysilane R1: ODS octaldecyltrimethoxysilane

–170 mV +50 mV

Enrico Fermi Enrico Fermi was born in Rome on 29th September, 1901, the son of Alberto Fermi, a Chief Inspector of the Ministry of Communications, and Ida de Gattis. He attended a local grammar school, and his early aptitude for mathematics and physics was recognized and encouraged by his father's colleagues, among them A. Amidei. In 1918, he won a fellowship of the Scuola Normale Superiore of Pisa. He spent four years at the University of Pisa, gaining his doctor's degree in physics in 1922, with Professor Puccianti. Soon afterwards, in 1923, he was awarded a scholarship from the Italian Government and spent some months with Professor Max Born in Göttingen. With a Rockefeller Fellowship, in 1924, he moved to Leyden to work with P. Ehrenfest, and later that same year he returned to Italy to occupy for two years (1924-1926) the post of Lecturer in Mathematical Physics and Mechanics at the University of Florence. In 1926, Fermi discovered the statistical laws, nowadays known as the «Fermi statistics», governing the particles subject to Pauli's exclusion principle (now referred to as «fermions», in contrast with «bosons» which obey the Bose-Einstein statistics).

Kelvin, Lord William Thomson (1824-1907) Scottish mathematician and physicist who contributed to many branches of physics. He was known for his self-confidence, and as an undergraduate at Cambridge he thought himself the sure "Senior Wrangler" (the name given to the student who scored highest on the Cambridge mathematical Tripos exam). After taking the exam he asked his servant, "Oh, just run down to the Senate House, will you, and see who is Second Wrangler." The servant returned and informed him, "You, sir!" (Campbell and Higgens, p. 98, 1984). Another example of his hubris is provided by his 1895 statement "heavier-than-air flying machines are impossible" (Australian Institute of Physics), followed by his 1896 statement, "I have not the smallest molecule of faith in aerial navigation other than ballooning...I would not care to be a member of the Aeronautical Society." Kelvin is also known for an address to an assemblage of physicists at the British Association for the advancement of Science in 1900 in which he stated, "There is nothing new to be discovered in physics now. All that remains is more and more precise measurement." A similar statement is attributed to the American physicist Albert Michelson. Kelvin argued that the key issue in the interpretation of the Second Law of Thermodynamics was the explanation of irreversible processes. He noted that if entropy always increased, the universe would eventually reach a state of uniform temperature and maximum entropy from which it would not be possible to extract any work. He called this the Heat Death of the Universe. With Rankine he proposed a thermodynamical theory based on the primacy of the energy concept, on which he believed all physics should be based. He said the two laws of thermodynamics expressed the indestructibility and dissipation of energy. He also tried to demonstrate that the equipartition theorem was invalid.