Lecture #1 of 18 - UCI Department of Chemistryardo/echem/UCI-CHEM248... · Welcome to CHEM 248! The...
Transcript of Lecture #1 of 18 - UCI Department of Chemistryardo/echem/UCI-CHEM248... · Welcome to CHEM 248! The...
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1
Lecture #1 of 18
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2Welcome to CHEM 248!
The following thousands of slides were graciously given to us by (mostly) Prof. Penner.
Of course, I made (and will continue to make) changes and updates to them but most of
the focus was his idea, and not mine. Thus, if you like the course, please tell him.
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3
Helpful Pre-(non-)requisite Courses
ChemistryInorganic Chemistry
Thermodynamics
Quantum Mechanics
PhysicsGeneral Physics
Electricity & Magnetism
Condensed Matter (Solid-State) Physics
Chemical EngineeringTransport Phenomena
Materials Science and EngineeringTheory of Diffusion
Materials Physics
Welcome to CHEM 248!
The following thousands of slides were graciously given to us by (mostly) Prof. Penner.
Of course, I made (and will continue to make) changes and updates to them but most of
the focus was his idea, and not mine. Thus, if you like the course, please tell him.
![Page 4: Lecture #1 of 18 - UCI Department of Chemistryardo/echem/UCI-CHEM248... · Welcome to CHEM 248! The following thousands of slides were graciously given to ... Shall we sign up for](https://reader033.fdocuments.in/reader033/viewer/2022051307/5abad5d57f8b9a321b8c2788/html5/thumbnails/4.jpg)
Welcome to CHEM 248!
The following thousands of slides were graciously given to us by (mostly) Prof. Penner.
Of course, I made (and will continue to make) changes and updates to them but most of
the focus was his idea, and not mine. Thus, if you like the course, please tell him.
4
Hey look! Slide numbers.
Helpful Pre-(non-)requisite Courses
ChemistryInorganic Chemistry
Thermodynamics
Quantum Mechanics
PhysicsGeneral Physics
Electricity & Magnetism
Condensed Matter (Solid-State) Physics
Chemical EngineeringTransport Phenomena
Materials Science and EngineeringTheory of Diffusion
Materials Physics
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Our syllabus: 5
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6Our textbook:
Please make sure you have access to the second edition
(Purchase it if you will perform electrochemistry; it is a top resource.)
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7Electrochemistry:… where physics and chemistry meet; thus, we need to know our physics!
Textbook Resources (Section 1.6 in B&F)
(1) “Electrochemical Methods” (2nd ed.) by Allen J. Bard and Larry R.
Faulkner (UT, Austin), John Wiley & Sons, Inc., 2001.
(2) “Modern Electrochemistry” (3 volumes: 1, 2A, and 2B; 2nd ed.) by John
O’M. Bockris (TAMU), Amulya K. N. Reddy, et al., Springer, 2001.
(3) “Electrochemical Systems” (3rd ed.) by John Newman (UC, Berkeley)
and Karen E. Thomas-Alyea, John Wiley & Sons, Inc., 2004.
Electrochemistry is mostly physical analytical chemistry and as a close second is chemical
engineering and as a close third is materials physics. Thus, although this course is formally in the
chemistry department, you will learn fundamental and applied physics and chemical engineering in
this course. Both the chemist and non-chemist will be challenged. Electrochemistry requires a
strong working knowledge of thermodynamics, electrokinetics, and transport phenomena. Each of
these has its own course and not all in the same departments. This electrochemistry course is not a
required core course, but obviously will draw interest from a range of students with varying and
diverse backgrounds. So, some sections of the course will be very easy to some and challenging to
others, but together we can get through the course and the material. The way the course is
structured is two lectures and one hands-on discussion session per week for ten weeks. In addition
to discussion of electrochemical phenomena, you will also be given seminal literature publications
to peruse (~50) and you will perform 9 “labs” and deliver a presentation. This should be fun!
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Our syllabus (continued): 8
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● 7… 8… 9 weeks of discussion (for 16 people… so far)
Audit’ers – If you want to participate, please let me know
● Each section will have 8 people in it, and will be split into 4
groups of two, because we have 4 potentiostats
● Each discussion class has an activity associated with it that; a
type-written procedure will be made available the weekend prior
to the activity, and will include an assignment + 0 – 1 problems
● Assignments are not due every week, but in general are due
after two related 2-hour activities are performed (4 hr in total)
● We can “discuss” things during discussion too, or office hours
● Shall we sign up for discussion sections now? Who cannot
meet either 1 – 3p or 3 – 5p on Mondays?
Discussion classes are… actually hands-on (lab) activities!
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Introduction, Review, and
Overview
Chapters 1, 15, and 4
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Q: What’s in this set of lectures?
A: Introduction, Review, and B&F Chapters 1, 15 & 4 main concepts:
● Section 1.1: Redox reactions
● Chapter 15: Electrochemical instrumentation
● Section 1.2: Charging interfaces
● Section 1.3: Overview of electrochemical experiments
● Section 1.4: Mass transfer and Semi-empirical treatment of
electrochemical observations
● Chapter 4: Mass transfer
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12Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
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http://lmchromeplating.com/phoenix-chrome-wheel-plating-2
Example: Electroplating
Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
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http://en.wikipedia.org/wiki/Hall%E2%80%93H%C3%A9roult_process
Example: Aluminum extraction
Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
(Na3AlF6/Al2O3)
~1000 °C
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Prof. Zuzanna Siwy (UCI)
Example: ionic circuits
Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
http://www.physics.uci.edu/~zsiwy/
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Example: corrosion
Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
http://www.greenprophet.com/2012/11/energy-solar-rust-israel/
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http://sperchemical.com/Polyphosphate/Corrosion_Inhibition/corrosion_inhibition.html
Example: corrosion
Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
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http://auto.howstuffworks.com/fuel-efficiency/vehicles/lithium-ion-battery-car1.htm
Example: Li+ battery
Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
http://www.evworld.com/images/a123_csize.jpg
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Example: neuron signal transduction
Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
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http://newscenter.lbl.gov/2011/09/15/tracking-the-sun-iv/
NOT electrochemistry: pn-junction photovoltaic cell
Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
http://www.azom.com/article.aspx?ArticleID=3744
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Prof. Michael Grätzel
(EPFL)
Example: dye-sensitized solar cell
Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
Grätzel, Nature, 2001, 414, 338
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http://www.nrel.gov/hydrogen/proj_production_delivery.html
Dr. John Turner (NREL)
Example: photoelectrochemical water electrolysis (splitting)
Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
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+
23
http://en.wikipedia.org/wiki/Photosystem_IIhttps://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb2/part1/pentose.htm
Example: plant photosynthesis
Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
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http://en.wikipedia.org/wiki/Bacteriorhodopsin
Example: Archaea photosynthesis
Q: What is electrochemistry?
A: Any process involving the motion/transport of charge – carried
by entities other than unsolvated electrons and holes – through
phase(s), or the transfer of charge across interface(s).
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25
so we can already conclude that electrochemistry is...
… super cool!
… extremely diverse.
… at the heart of some very important, and still unsolved,
scientific and technological challenges.
… and consequently, an extremely active area of scientific
endeavor.
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26… wow, those were some neat applications…
… I wish I could learn more about all of them!
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27… wow, those were some neat applications…
… I wish I could learn more about all of them!
… Lucky you! … Lucky us!
● PowerPoint presentations: 10 min MAX, plus 2 min for Q&A,
as 5 – 8 slides emailed to me the day before the presentation
● One seminal and/or review publication (~70% of the time);
include background, where and when it is used, why it is useful,
and the nitty gritty of how it works; your main goal should be to
bridge information presented in the course to your topic,
and/or teach us something entirely new
● One recent publication (2013 or later) (~30% of the time); include
what the paper did, the major discovery, and how it works,
including at least one graph or plot or image or something!
… this, plus the discussion assignments, equal 60% of your course
grade, so take them seriously, but HAVE FUN!
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28Presentation… topics… include…
• fast electrochemistry (5.9.1)
• low conductivity electrochemistry (5.9.2)
• rotating (ring) disk electrochemistry (9.3, 9.4)
• electro-osmotic flow (9.8.1)
• electrochemical impedance spectroscopy (10.4)
• bulk (water) electrolysis (11, 11.5, 11.6)
• thin-layer electrochemistry (11.7)
• stripping analysis (11.8)
• coupled reactions / catalysis (6.6, 12, 12.3)
• modified electrodes (14, 14.5.2)
• electrochemical scanning tunneling microscopy (16.2)
• scanning electrochemical microscopy (16.4)
• spectroelectrochemistry (17.1, 17.2)
• in situ, in operando spectroscopy (17.3, 17.6)
• electrochemical quartz crystal microbalance (17.5)
• electro-generated chemiluminescence (18.1)
• aluminum extraction and processing
• bipolar electrochemistry
• electrodeposition / electroless deposition
• chlor-alkali process
• polymer-electrolyte fuel cells
• solid-oxide fuel cells
• batteries (acid/base; intercalation)
• redox flow batteries
• electrochemical supercapacitors
• (bio)sensors
• electrodialysis
• nanopore/nanorod ion conductors
… or propose your own to me… but I really do prefer these.
You will get one of your top 5 choices…
… more info to come later in the quarter
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Q: Explain cyclic voltammetry.
Course goal, i.e. best 2-hour-long final-exam question ever!
From syllabus
Evans, …, Kelly, J. Chem. Educ. 1983, 60, 290
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Q: Explain cyclic voltammetry.
Course goal, i.e. best 2-hour-long final-exam question ever!
From syllabus
Evans, …, Kelly, J. Chem. Educ. 1983, 60, 290
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Q: Explain cyclic voltammetry.
Course goal, i.e. best 2-hour-long final-exam question ever!
Evans, …, Kelly, J. Chem. Educ. 1983, 60, 290
From syllabus
Course philosophy
Theory/Experiments versus Technologies (me vs you)
I will teach the theory, history, and experimental specifics, and you will
teach the technologies, and real-world and academic state-of-the-art
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Q: What’s in this set of lectures?
A: Introduction, Review, and B&F Chapters 1, 15 & 4 main concepts:
● Section 1.1: Redox reactions
● Chapter 15: Electrochemical instrumentation
● Section 1.2: Charging interfaces
● Section 1.3: Overview of electrochemical experiments
● Section 1.4: Mass transfer and Semi-empirical treatment of
electrochemical observations
● Chapter 4: Mass transfer
… but first…
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From M3C: Oxidation and reduction
An oxidation-reduction, or “redox” reaction is one
in which one or more electrons are transferred.
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Redox reactions
2NaCl(s)2Na(s) + Cl2(g)
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Oxidation states
Covalent compound, different types of atoms: the
oxidation state equals the charge that would result if the
electrons were given to the most electronegative atom.
Covalent compound, same type of atoms: charge that
the compound would have if the electrons were divided
evenly among atoms of the same type.
Ionic compound: the oxidation state of an atom is equal
to its charge.
N2H4 (H2NNH2)
KCl
NH3 N:-3, H:+1
N:-2, H:+1
K:+1, Cl:-1
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36
CO2 + 2H2O2O2 + 8e–-20 -2
ZnCl2 (aq) + H2 (g)Zn (s) + 2HCl (aq)
0 +1 -1 +2 0-1
Closed shells mean…
… in general H (+1), O (-2), halides (-1), etc.
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37
2Mg (s) + O2 (g) 2MgO (s)
2 Mg 2 Mg2+ + 4 e-
O2 + 4 e- 2 O2-
Oxidation half-reaction
reactant (= reducing agent) loses e-
Reduction half-reaction
Reactant (= oxidizing agent) gains e-
0 0 2+ 2-
Oxidation and Reduction
Oxidizing agent (oxidant) molecule that gains electrons
Reducing agent (reductant) molecule that loses electrons
This reaction can be split into two half-reactions
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38Oh (silly) acronyms…
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39
Redox reactions
Cu2+ (aq) + 2Ag(s)Cu (s) + 2Ag+ (aq)
Cu(NH3)42+ (~aq)Cu2+ (aq) + 4NH3 (l)
(A)
(B)
(B)
(A)
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40
Redox reactions
ZnCl2 (aq) + H2 (g)Zn (s) + 2HCl (aq)
Zinc metal reacts with aqueous hydrochloric acid to form zinc
chloride in solution and hydrogen gas. Is this a redox
reaction? If yes, identify the oxidizing agent, the reducing
agent, and the substances being oxidized and reduced.
1. Write a balanced chemical equation (not always easy).
2. Assign oxidation states.
0 +1 -1 +2 0-1
3. Determine whether atomic oxidation states change. Yes
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41
Redox reactionsZinc metal reacts with aqueous hydrochloric acid to form zinc
chloride in solution and hydrogen gas. Is this a redox
reaction? If yes, identify the oxidizing agent, the reducing
agent, and the substances being oxidized and reduced.
4. Use the changes in oxidation state for each atom to
determine what is being oxidized and reduced.
Zn: 0 +2 oxidized, reducing agent
H: +1 0 reduced, oxidizing agent
Cl: -1 -1 spectator ion
ZnCl2 (aq) + H2 (g)Zn (s) + 2HCl (aq)
0 +1 -1 +2 0-1
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42
Half-reactions
Redox reactions are often difficult to balance by inspection.
Instead, we can use the method of half-reactions.
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43
Writing half-reactions
1. Assign oxidation states for each element in the
reactants and products.
2. Determine what is being oxidized, what is being
reduced, and how many electrons are transferred.
3. Write balanced half-reactions, using electrons as
reactants or products, as appropriate.
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44
Half-reactions
Each redox reaction can be separated into two half-
reactions, one for oxidation and one for reduction.
In half-reactions, electrons are written as reactants or
products depending on whether they are gained or lost.
CO2 (g) + 2H2O (g)CH4 (g) + 2O2 (g)
oxidation half-reaction
reduction half-reaction
CO2 + 8e–CH4
-4 +4
CO2 + 2H2O2O2 + 8e–-20 -2
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45Balancing Redox Equations
1. Write the unbalanced equation for the reaction in ionic form.
The oxidation of Fe2+ to Fe3+ by Cr2O72- (becomes Cr3+) in acid
solution?
Fe2+ + Cr2O72- Fe3+ + Cr3+
2. Separate the equation into two half-reactions.
Oxidation:
Cr2O72- Cr3+
+6 +3
Reduction:
Fe2+ Fe3++2 +3
3. Balance the atoms other than O and H in each half-reaction.
Cr2O72- 2Cr3+
Fe2+ Fe3+
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46Balancing Redox Equations
4. For reactions in acid, add H2O to balance O atoms and H+ to
balance H atoms.
Cr2O72- 2Cr3+ + 7H2O
14H+ + Cr2O72- 2Cr3+ + 7H2O
5. Add electrons to one side of each half-reaction to balance the
charges on the half-reaction.
Fe2+ Fe3+ + 1e–
6e– + 14H+ + Cr2O72- 2Cr3+ + 7H2O
6. If necessary, equalize the number of electrons in the two half-
reactions by multiplying the half-reactions by appropriate
coefficients.
6Fe2+ 6Fe3+ + 6e–
6e– + 14H+ + Cr2O72- 2Cr3+ + 7H2O
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47Balancing Redox Equations
7. Add the two half-reactions together and balance the final
equation by inspection. The number of electrons on both
sides must cancel.
6e– + 14H+ + Cr2O72- 2Cr3+ + 7H2O
6Fe2+ 6Fe3+ + 6e–Oxidation:
Reduction:
14H+ + Cr2O72- + 6Fe2+ 6Fe3+ + 2Cr3+ + 7H2O
8. Verify that the number of atoms and the charges are balanced.
14x1 – 1x2 + 6x2 = 24 = 6x3 + 2x3 + 7x0
9. For reactions in basic solutions, add OH– to both sides of the
equation for every H+ that appears in the final equation…
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48
Half-reactions(basic/alkaline conditions)
1. Use the half reaction method for acidic solution to
balance the equation as if excess H+ ions were present.
2. To both sides of the equation, add the number of
OH– ions needed to balance the H+ ions added in the
last step.
3. Form H2O on the side containing both H+ and OH–
ions, and cancel out the number of H2O molecules
appearing on both sides of the equation.
4. Check to make sure that the equation is balanced.