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

1

Lecture #1 of 18

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.

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!




Welcome to CHEM 248!




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

Our syllabus: 5

6Our textbook:

Please make sure you have access to the second edition

(Purchase it if you will perform electrochemistry; it is a top resource.)

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!

Our syllabus (continued): 8

9

● 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!

10

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

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?




14

http://en.wikipedia.org/wiki/Hall%E2%80%93H%C3%A9roult_process

Example: Aluminum extraction





(Na3AlF6/Al2O3)

~1000 °C

15

Prof. Zuzanna Siwy (UCI)

Example: ionic circuits





http://www.physics.uci.edu/~zsiwy/

http://www.physics.uci.edu/~zsiwy/

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Example: corrosion





http://www.greenprophet.com/2012/11/energy-solar-rust-israel/

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





18

http://auto.howstuffworks.com/fuel-efficiency/vehicles/lithium-ion-battery-car1.htm

Example: Li+ battery





http://www.evworld.com/images/a123_csize.jpg

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Example: neuron signal transduction





20

http://newscenter.lbl.gov/2011/09/15/tracking-the-sun-iv/

NOT electrochemistry: pn-junction photovoltaic cell





http://www.azom.com/article.aspx?ArticleID=3744

http://www.azom.com/article.aspx?ArticleID=3744

21

Prof. Michael Grätzel

(EPFL)

Example: dye-sensitized solar cell





Grätzel, Nature, 2001, 414, 338

22

http://www.nrel.gov/hydrogen/proj_production_delivery.html

Dr. John Turner (NREL)

Example: photoelectrochemical water electrolysis (splitting)





+

23

http://en.wikipedia.org/wiki/Photosystem_IIhttps://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb2/part1/pentose.htm

Example: plant photosynthesis





http://en.wikipedia.org/wiki/Photosystem_II

https://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb2/part1/pentose.htm

24

http://en.wikipedia.org/wiki/Bacteriorhodopsin

Example: Archaea photosynthesis





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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.

26… wow, those were some neat applications…

… I wish I could learn more about all of them!

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!

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

29

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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From syllabus


31




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

32

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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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.

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

38Oh (silly) acronyms…

39

Redox reactions

Cu2+ (aq) + 2Ag(s)Cu (s) + 2Ag+ (aq)

Cu(NH3)42+ (~aq)Cu2+ (aq) + 4NH3 (l)

(A)

(B)

(B)

(A)

40

Redox reactions


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

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


0 +1 -1 +2 0-1

42

Half-reactions

Redox reactions are often difficult to balance by inspection.

Instead, we can use the method of half-reactions.

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.

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

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+


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


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…

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.

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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