lecture #1 of 17 - uci department of chemistry · 2019-04-11 · welcome to chem 248! the following...

1

Lecture #1 of 17

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 UCI chemistry

department, you will learn fundamental and applied physics and chemical engineering in this course.

Both chemists and non-chemists 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.

Therefore, 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

7 “labs” and deliver a presentation. This should be fun!

Our syllabus (continued): 8

9

● 8 weeks of discussion section (for 21 – 22 people… thus far)

Audit’ers – If you want to participate, please let me know

● Each section will (ideally) have 10(-ish) people in it that are split

into 5 groups of 2(-ish), because we have 5 potentiostats

● Each discussion class has an activity associated with it; a type-

written procedure will be made available the weekend prior to

the activity, and will include an assignment + up to ~2 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 readjust discussion sections now? Who canNOT

meet 1 – 3p on Mondays? What about 3 – 5p on Mondays?

Discussion classes are… actually hands-on (lab) activities!

10

Introduction and Review of

Electrochemistry

Chapter “0”

11

Looking forward… our review of Chapter “0”

● Cool applications

● Redox half-reactions

● Balancing electrochemical equations

● History of electrochemistry

● IUPAC terminology and Ecell = Ered – Eox

● Nernst equation and Common reference electrodes

● Standard and Absolute potentials

● Latimer and Pourbaix diagrams

● Calculating Ecell under non-standard state conditions

● Conventions

12Q: What processes occur in electrochemistry?

A: Spring, 2019: Those that occur when the electrochemical

potential of electrons in a solid influence, or are influenced

by, chemical reactions, including…

A: Winter, 2017: Those 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).

13

http://lmchromecorp.com/uncategorized/chrome-wheels-motorcycle-auto/

Example: Electroplating

Q: What processes occur in electrochemistry?




http://lmchromecorp.com/uncategorized/chrome-wheels-motorcycle-auto/

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/

16

Example: corrosion





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

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

17

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

19

MAYBE electrochemistry: 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

PROBABLY electrochemistry: photosynthesis in green plants





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

MAYBE Electrochemistry: Archaea photosynthesis





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.

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 presentation in pairs: 12 min max + 3 min for Q&A,

as 7 – 9 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 (2015 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

30



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…

33

From M3C: Oxidation and reduction

An oxidation-reduction, or “redox” reaction is one

in which one or more electrons are transferred.

34

Redox reactions

2NaCl(s)2Na(s) + Cl2(g)

35

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

36

CO2 (g) + 2H2O (l)CH4 (g) + 2O2 (g)-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, or not?

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

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

(A)

redox

(B)

(B)

not redox

(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-reactionsRedox reactions are often difficult to balance by inspection.

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

reactions don’t actually exist all that often… (read on)…

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

Method of 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

Method of half-reactions(under 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.

lecture #1 of 17 - uci department of chemistry · 2019-04-11 · welcome to chem 248! the following...

Documents