C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course Succinct, to-the-point title: Connections between Dry & Wet Interfaces: An Intro to Electrochemistry for Students Familiar with UHV…in 30 minutes or less. C. Friesen Please interrupt whenever necessary

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course Explanation for NAN 546: April 09 This talk was given on 4/16/09 as a guest lecture to our NAN 546: Surfaces and Thin Films class This material is copyright of the Author, Dr Cody Friesen. All queries for use other than private study should be directed to him personally. Dr Venables' interest in this material is as a student of crystal growth. The phenomena of growth or evaporation in UHV, and growth or dissolution in solution are very similar, but the language is quite different, and so is some of the science, especially the importance of solvation in Electrochemistry. This talk explores some of these issues

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course The Vacuum-Solid Interface

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course Sputter deposition Sputtering occurs by: ~10s keV Ar+ ions -Fields of order ~100 kV/m -~99% of ejected atoms are not ionized. -Sputtered atoms have kinetic Energies of order s eV -Sputtered atoms have high “T” ~10 6 K while evaporated metal Atoms might be 0.1 eV or ~10 3 K

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course The Electrolyte-Solid Interface IHLOHL l l l Solvated ions Electrode surface 1-10 nm The double-layer region is: Where the truncation of the metal’s Electronic structure is compensated for in the electrolyte nm in thickness ~1 volt is dropped across this region… Which means fields of order V/m “The effect of this enormous field at the electrode- electrolyte interface is, in a sense, the essence of electrochemistry.” [1] [1] Bockris, Fundamentals of Electrodics, 2000

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course Sputtering vs. Electrochemical deposition… …As in-the “Power of Solvation” (say it with an evangelists flair!) -Sputtering results in ~100s eV atoms being generated -Electrochemical reactions usually involve ~1e*1V ~1eV -Keep in mind that this could correspond to the same net result: -stripping of atoms from one surface and depositing them on another -PVD: Simple/easy to define interface : Complex equipment -EC: Complex/difficult to define interface : Simplest possible equipment -PVD: Line-of-sight deposition, massive supersaturation EC: Surface-normal deposition, operating very close to equilibrium Each has its own advantages and challenges…

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course Take the case of Cu. Vapor/Solid: 300 kJ/mol heat of vaporization Boiling point: 2843 K Electrolyte/Electrode: Valency = 2 E o =340 mV vs. SHE Supersaturation: overpotential vs. partial pressure How do driving forces (  T vs.  V) compare in the two systems?

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course Supersaturation: overpotential vs. partial pressure

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course A few practical matters…

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course The Electrochemical Series & Electrochemical Phase Diagrams Pourbaix Diagrams

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course 3-electrode cells and potentiostats Feedback circuit Working Electrode Reference Electrode Counter Electrode

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course Cyclic voltammograms, etc… Current: “+” is oxidation or “anodic” current “-” is reduction or “cathodic” current Potential: positive is synonymous with anodic negative is synonymous with cathodic

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course Naming electrodes The colloquial use of “anode” and “cathode” can get confusing: -The anode is the *negative* electrode and the cathode is the *positive* electrode in a battery or fuel cell. -In an electrolyzer or other driven cell its just the opposite. However, the formal definition is clear: the anode is where the oxidation reaction occurs and the cathode is where the reduction reaction occurs VV M/M+ H+/ ½H 2

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course Butler-Volmer Equation: A Comment on Exchange Current Density C 2 > C

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course Surface excess quantities

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course Laplace pressure and Charge vs. the Lippmann Equation and Electrocapillarity PP Liquid Solid Laplace Lippman Liquid Solid

C. Friesen, 4_16_09, A guest lecture in John Venables’ Surfaces Course Electrocapillarity Mercury-Drop Pt & Ru D. C. Grahame, “Theory of Electrocapillarity”, Chem. Rev. 41, 441 (1947).