The applicability of electrochemistry to the physical ... · PDF fileThe applicability of electrochemistry to the physical, chemical and biological sciences ... • The Danish biochemist

Queensland University of Technology

CRICOS No. 00213J

The applicability of electrochemistry to the physical,

chemical and biological sciences

Anthony O’Mullane

School of Chemistry, Physics and Mechanical Engineering

QUT

Seminar, NanoES-3

Monday 28th September 2015

CRICOS No. 00213Ja university for the worldrealR

2

Background

PhDOrganic electronics

Localised

electrochemical

techniques

More electrochemistry


Electrochemistry –

Concerned with the interrelation of electrical and chemical

effects. Reactions involving the reactant – the electron.

Chemical changes caused by the passage of current

An electrochemical system is not homogeneous but is

heterogeneous (we use solid electrodes).

Broad Field : electroanalysis, sensors, energy storage and

conversion devices, corrosion, electrosynthesis, and metal

electroplating

What is electrochemistry?


According to Sawyer et al. (Electrochemistry for Chemists, 2nd ed.), "..chemical

questions amenable to treatment by electrochemistry include....“

• evaluation of solution thermodynamics

• standard potentials of oxidation-reduction reactions

• determination of the electron stoichiometry of oxidation-reduction

reactions

• evaluation of the heterogeneous electron-transfer kinetics and

mechanism

• determination of the effect of solvent and electrode material on

electron-transfer kinetics


• study of reaction and product absorption processes in relation

to heterogeneous catalysis

• study of pre- and post- chemical reactions associated with the

electron-transfer reactions preparation and study of unstable

intermediates

• evaluation of the valence of the metal in new compounds

• determination of the formulas and stability constants

• evaluation of M-X, H-X, and O-Y covalent bond formation

energies

• studies on the effects of solvent, supporting electrolyte, and

solution acidity on oxidation-reduction reactions


Electrochemistry

6

CE REF WE


Electrochemistry

7

Scaleable!


Electrorefining

The anode is electrochemically dissolved to liberate the

species of interest which is plated on to the cathode


Mixing Al2O3 with cryolite (Na3AlF6 –

mixture of NaF and AlF3) lowers the

melting point of the ore from 2050°C to a

mere 1000°C. This is due to all

components forming a homogeneous

phase which reduces the melting point.

A worker serves an electrolysis

furnace in the RUSAL aluminium

smelter in the Siberian city of

Krasnoyarsk (REUTERS/Ilya

Naymushin).


Other industrial electrochemical processes

The Chlor-Alkali industry is one of the largest chemical processes worldwide.

It involves the electrolysis of NaCl to produce NaOH and Cl2(g)

Anode: 2Cl− → Cl2 + 2e−

Cathode: 2H2O + 2e− → H2 + 2OH−

Overall: 2NaCl + 2H2O → Cl2 + H2 + 2NaOH

A membrane is used to avoid the reaction

between Cl- and OH- ions

Membrane allows Na+ ions to pass through but not Cl- ions

Nearly 55% of all specialty chemical products manufactured

require one of the chlor-alkali products as a precursor



Electrochemical production of organic compounds

The most successful organic electrosynthesis process that has been

commercialised is the manufacture of adiponitrile from acrylonitrile.

Adiponitrile is a key intermediate for the production of nylon 6, 6

polymers. I




Semiconductor industryCopper electrodeposition has become an extremely critical process

Intel statement:

Copper has replaced aluminum as an interconnect material due to lower resistivity and higher electromigration resistance.

While copper could be deposited by numerous methods, the major semiconductor manufacturers prefer the electrochemical route over CVD or sputtering due to the better electromigration performance and the rapid deposition rate.

Another added benefit of the copper electrodeposition process is its abilityto obtain superfill in dual-damascene structures (trenches) with varying sizes and feature densities. A robust gapfill chemistry, i.e., one which provides void-free super-fill, is central to the commercial implementation of the plating process



Can fabricate void-free gap-fill of metallic interconnects with high aspect ratio

Electrochimica Acta 52 (2007) 2891



Electroplating

Electroplating gives a cheap metal the look and the feel of an expensive metal at a very affordable cost.

Chrome plating is one of the most commonly used types of electroplating. Chromium is deposited onto a metal (usually steel or iron) which can then be finished into a shiny reflective coating. This coating also puts a physical barrier between a metal and the elements, so it is more resistant to wear. Chrome plating is used in automotive, furniture, and tools because of its resistance to wear and its shiny coating.

Chrome Discovered 1798, first successful electrolytic plating 1856, commercial utilization late 1920’s



Electroplating

Gold electroplating is the process of applying a thin layer of gold onto a desired metal material, usually that of copper or silver.

When gold electroplating is used on silver in the manufacturing of jewelry, a copper and nickel layer must be deposited onto the silver before the gold electroplating occurs (pre-treatment). The reason for this is that if no intermediate layer were provided the silver atoms would, over time, diffuse through the gold plating and cause tarnishing. The copper and nickel layers slow down this process.

Academy Award: electroplating of Oscar statuettes


Potential industrial electrochemical processes

Electrolysis of coal and other solid fuels. A simple reaction is oxidation of

C to CO2 at the anode.

At the cathode Hydrogen is produced.

However the previous reaction is not favoured (25%) and usually a

hydrogen rich coating is formed over the coal which can be represented

by the following

These coatings can be extracted with ethanol at 78ºC at ambient

pressure to release various chemicals and fuels.



Corrosion

Several types: pitting, crevice, weld decay, microbial,

stress corrosion cracking

Several protection strategies: coatings, cathodic

protection, anodization, sacrificial anode

CRICOS No. 00213Ja university for the worldrealR 21

Fuel cells – Proton Exchange Membrane Fuel Cell

(Nafion)


Dye Sensitised

Solar Cells

Electrochemistry reaction at

a thin Pt electrode


Biosensors

Glucose biosensor arguably has been the most successful



Glucose Biosensor

Signal

The reduced form of the mediator is reoxidized at the

electrode, giving a current signal (proportional to the

glucose concentration) while regenerating the oxidized

form of the mediator


Commercial sensor

Where the electrochemistry

happens

Each strip contains the printed working and

reference electrodes, with the working one

coated with the necessary reagents (i.e.,

enzyme, mediator, stabilizer, surfactant,

linking, and binding agents) and membranes


Ion selective electrodes

• Ion Selective Electrodes (ISE) are membrane

electrodes that respond selectively to ions in the

presence of others.

• These include probes that measure specific ions

and gases in solution.

• The most commonly used ISE is the pH probe.

• Other ions that can be measured include fluoride,

bromide, cadmium, and gases in solution such as

ammonia, carbon dioxide, and nitrogen oxide.


Principle of operation

• An ideal I.S.E. consists of a thin membrane across which only the intended ion can be transported.

• The transport of ions from a high conc. to a low one through a selective binding with some sites within the membrane creates a potential difference.

• Ion selective electrodes are selective rather than specific



Types of ion selective electrodes

• Glass membrane

Uses: Univalent cations such as H+, Na+, K+, NH4+ and

Ag+

• Liquid membrane

Uses: Cations and some anions such as Ca2+, Mg2+, Cu2+ and Cl-, ClO4

-, NO3-

• Solid state

Uses: anions such as F-, Cl-, Br-, I- and S2-


Advantages and disadvantages

Advantages:

The cost of initial setup to make analysis is relatively low.

The expense is considerably less than other methods,such as Atomic Adsorption Spectrophotometry or IonChromatography.

There are few matrix modifications needed to conductthese analyses. This makes them ideal for clinical use(blood gas analysis) where they are most popular;

Linear response: over 4 to 6 orders of magnitude ofanalyte

Non-destructive: no consumption of analyte

Non-contaminating

Short response time: in sec. or min. industrially useful

Unaffected by color or turbidity.


Advantages and disadvantages

• Limitations:

Precision is rarely better than 1%.

Electrodes can be fouled by proteins or other

organic solutes.

Interference by other ions.

Electrodes are fragile and have limited shelf life.

Electrodes respond to the activity of the

uncomplexed ion. So ligands must be absent or

masked.


Glass membrane electrodes

• Mechanism of response involves ion exchange

rather than an electron transfer reaction

• Not subject to interferences from other oxidising

or reducing agents in the solution of interest

• Responds rapidly and accurately

• Classic example is the pH electrode


Some history

• The history of measuring the acidity of liquids electrically

began in 1906 when Max Cremer in his studies of liquid

interfaces discovered that the interface between liquids could

be studied by blowing a thin bubble of glass and placing one

liquid inside it and another outside.

• It created an electric potential that could be measured.

• This idea was taken further by Fritz Haber (who invented the

synthesis of ammonia and artificial fertiliser) and Zygmunt

Klemsiewicz who discovered that the glass bulb (which he

named glass electrode) could be used to measure hydrogen

ion activity and that this followed a logarithmic function.

• The Danish biochemist Soren Sorensen then invented the

pH scale in 1909.


pH electrode

• A traditional pH measurement with a glass

electrode is the best known potentiometric ion

selective electrode (ISE)

• A thin glass layer with the composition 22%

Na2O, 6% CaO, 72% SiO2 is used

• Normal laboratory glass is unsuitable

• The glass must be hydrated with 50-100 mg H2O

per cm3 to function

• NB: There is no change in the inner solution and

there is no actual contact between inner and outer

solution for any potentiometric probe or sensor


Practical pH measurements

NB: Reference half cell can also with saturated calomel electrodeGalvanic cell

Ag | AgCl(s), HCl (0.1 M) | glass membrane | sample solution | Hg2Cl2(s), KCl(s) | Hg

CRICOS No. 00213Ja university for the worldrealR 37

Other sensors

Gas sensors – ethylene, carbon monoxide

Biological species : dopamine, uric acid, ascorbic acid

Organic/inorganic species: cations, anions, peroxide, hydrazine, peroxide etc….

Pt nanoparticles (NP) assembled in

poly(diallydimethylammonium chloride),

PDDA


Microrockets• A "microrocket" - that can propel itself through acidic

environments, such as the human stomach, without any

external energy source, opening the way to a variety of

medical and industrial applications.

• The microrocket is ultrafast -- it can move farther than

100 times its 0.0004-inch length in just one second.

J. Am. Chem.Soc. 2012, 134, 897−900


Magnetised

rockets for

functionality

J. Am. Chem.Soc. 2012, 134, 897−900

100 body lengths per second

Queensland University of Technology

CRICOS No. 00213J

Fundamental electrochemistry

• Need to understand electron transfer processes

• Examining electrochemistry at the nanoscale /

molecular scale

• Can fabricate materials at the nanoscale

• Characterise their electrochemical properties


WE

Electrolyte + analyte

Mechanistic information

Classic sensing

CE REF


Electrolyte + surface confined layer

Enzymes, proteins, SAMs

Corrosion, conducting polymers

Biosensing


RMIT University©2013 School of Applied Sciences 43

Change electrode material

Flat or nanostructured (electrodeposited)

Electrocatalysis, sensing

Photoelectrochemistry


RMIT University©2013 School of Applied Sciences 44

Change solvent

Electro – organic synthesis

Electrocrystallisation


Main ways of performing an experiment

Interfacial

methods

Static methods

(I = 0)

Dynamic

methods

(I > 0)

Potentiometry

(E)

Conductometry

(G = 1/R)

Controlled

potential

Constant

current

Based on Figure 22-9 in Skoog,

Holler and Crouch, 6th ed.

Coulometric

titrations

(Q = It)

Electro-

gravimetry

(m)

Amperometric

titrations

(I = f(E))

Voltammetry

(I = f(E))

Bulk methods

I = current, E = potential, R = resistance, G = conductance, Q = quantity of charge, t =

time, vol = volume of a standard solution, m = mass of an electrodispensed species


Cyclic voltammetry (CV)

• The most widely used electrochemical technique

• Simple to perform and extremely informative

• Principles

• Practical considerations

• Examples


Edc = Einitial + t

Initial potential

Switching potential

Switching potentialA = B + e-

Sweep rate


Classic example 1 electron oxidation process

Reversible process

The peak potential separation (Epa - Epc) is equal to 57 mV

The peak current ratio (ipa/ipc) is equal to 1 for all scan rates

The peak current increases linearly as a function of the square root of v

The peak current is proportional to concentration


Electrochemical cell

CE REF WE


Cell Design

– Electrodes (Working, Reference, Auxiliary)

• material

• geometry (available theory?)

• size

• location

– Quiescence- no adventitious stirring caused by

• Source of vibration - fumehoods

• gas flow through or over solution

• density gradients (electrochemically induced)

• temperature gradients

– Temperature Control

– Integrity (“air” tight; vacuum tight)

•

Solvent

Supporting Electrolyte (excess assumed)

Choose analyte concentration

selection and purification;

maximize relevant electro-

chemical window.


Additional chemical processes


Oxidation product unstableConsumed chemically to an electrochemically inactive species

Less oxidised product available for reduction

Example of an EC mechanism


Dopamine detection(important neurotransmitter)

EC mechanism


Implantable electrodes

Grahn, et al, Front. Neurosci., 25 June 2014

http://dx.doi.org/10.3389/fnins.2014.00169


Common interfering species

Ascorbic acid

Irreversible


Common interfering species

Uric acidIrreversible


How do we detect all 3 species at once?


Nanostructured surfaces – electrochemically made

AFM images of a)

electrodeposited

pyramidal, b)

rodlike,

c) spherical, and

(d) a sputtered

gold surfaces.


Separation of AA and UA

We observe here

electrocatalytic effects –

each electrochemical

reaction is catalysed to a

different extent – rates of

electron transfer are

different as well as the peak

positions – allows us to

resolve the processes


Chronoamperometric detection under stirring conditions – AA detection at 10

μM additions - electrode held at 0.0 V vs Ag/AgCl

Pyramids > Rods > Spheres : shape dependent electrochemistry


Heavy metal ion detection

Anodic stripping voltammetry



Anodic stripping voltammetry is a voltammetric method for quantitative

determination of specific ionic species.

Generally it is for the detection of metal ions in solution.

The analyte of interest is electroplated on the working electrode during a deposition

step, and oxidized (or stripped) from the electrode during the stripping step.

The current is measured during the stripping step. The oxidation of species is

registered as a peak in the current signal at the potential at which the species begins

to be oxidized.

The stripping step can be either

linear or pulse.


• Detection limits can be obtained by replacing the hanging

mercury drop electrode (HMDE) with a mercury thin film

electrode (MTFE). Here, a very thin film (usually a few atoms

thick) of mercury is electrolytically plated onto a solid

electrode - most often a carbon disk electrode.

• The mercury film forms an amalgam with the analyte of

interest, which upon oxidation results in a sharp peak,

improving resolution between analytes.

• Excellent technique for trace metal ion analysis. The

preconcentration step leads to low detection limits, typically

10-9 - 10-10 M.

• The stripping peak currents and peak widths are a function of

the size, coverage and distribution of the metal phase on the

electrode surface (Hg or alternate).



Can also get excellent results when you

use differential pulse voltammetry when

performing anodic stripping

Note the much smaller currents and good

baseline at such low currents (background

charging is removed – higher signal to

noise ratio


Current Research Areas

Electrochemical formation and

characterisation of nanostructured

electrocatalysts and catalysts

Au/Ag

Development of organic semiconductors

and composites for various applications

Investigation of Li metal electrodes

and SEI formation in ionic liquids Miscellaneous


66

• Li metal batteries using ionic liquids

• Electrochemical based methods to create metallic and

bimetallic nanostructured materials and their applications

• Liquid metal marbles – heavy ion sensing

– electrochemical driven actuation

– liquid metal pump

– catalysis


Lithium-Ion is the popular battery technology

• There is no lithium metal used in battery

fabrication

• Battery is fabricated with electrodes

capable of

intercalating lithium cation (e.g. graphite

anode)

• Li+ ions are the charge carrier, not

electrons

Why are they popular?

• Li-ion batteries are light, rechargeable

• No memory effect and long shelf life

– But this technology is becoming inadequate

The current lithium battery technologyLithium-Ion


lithium battery technologies have safety concerns

• Carbonate electrolytes are toxic and corrosive

… (and cheap)

• Carbonates have high vapour pressure

• Explosive under high charge or temperature

• Flammable

• Poor cycle life

There are several safety precautions in place to nullify

these issues

• Tear-away tabs

• Overcharging fuses

• Presure vents

• Shutdown Separators

• The problem• Safety costs the industry


– As the consumer uses more powerful devices

• Higher power output is required

• Greater energy capacity is required

• Efficient energy storage is required

– Possible solution is lithium metal

batteries

• Li-Air and Li-S solutions

• Both systems have inherent issues

• Both technologies share commonalities

– Lithium metal anode highly reactive

– Anode cycling instability

The future for batteries?Lithium-Air | Lithium-Sulphur


– Bruce et al. Nature Mater. 11, 19-29 2011

• A solution for the lithium anode problem• Room temperature ionic liquid electrolyte


– Tarascon, J-M. Armand, M. Nature 414, 359-367 2001



– A way to solve these issues is to use an RTIL

electrolyte

• Do away with most safety precautions

• Less weight/volume

– Can use lithium metal as the anode

• Li-ion (c.a. 150 - 180 W h/kg)

• Li-S (c.a. 450 – 650 W h/kg)

• Li-air (c.a. 10 000 - 11 000 W h/kg)

– Which RTIL is best suited?



There is a lot of misconception surrounding ionic liquids

Not all ionic liquids behave in the same fashion

• Common properties

– Low melting point (< 100°C)

– Viscous

– Low vapour pressure

• Variable properties

– Conductivity

– Flammability

– Thermal stability

– Liquid regions

– Electrochemical window

Ionic Liquids “designer solvents”They are not all the same…


• The SEI is formed in all lithium metal batteries

It is the direct result of the highly reactive nature of lithium

• Made up of breakdown products of electrolyte-metal interaction

• The SEI inhibits further reaction as a passivation layer

• A critical component in secondary lithium metal battery

technologies

– Determines cycle life

– Determines safety

• A rough/dendritic SEI can lead to short circuits

• A smoother SEI will allow long cycle life

Lithium+RTIL = solid-electrolyte interphase?or SEI for short


• The SEI is a complex species when formed in

carbonate electrolytes

Solid-electrolyte interphaseStill an issue

J. Yan et al. Electrochimica Acta 53 (2008) 7069–7078

Lithium fluoride

Lithium dioxide

Lithium carbonate

Lithium hydroxide

Lithium organic compounds

Insoluble oligoethers


Possible SEI mechanism

D. Aurbach et al, Solid State Ionics. 148 (2002) 405– 416


SEI Products

D. Aurbach et al, Solid State Ionics. 148 (2002) 405– 416


Process for SEI formation and pristine lithium data

SEI formation via chemical reaction pathwayDr. Andrew Basile, Dr. Anand Bhatt

Hexane polish

1 cm disks punchedDisks in electrolyte for

set time periods

1 2 1 8

7 Washed using DMC

FTIR

XRD

SEM

XPS

Lithium Metal Foil

40 50 60 70 80 90

Inte

ns

ity

2

Lithium Pristine

Quartz Substrate

* * * * *

Li(

1,1

,0)

Li(

2,0

,0)

Li(

2,1

,1)

Li(

2,2

,0)

Li(

3,1

,0)


SEI formation via chemical reaction with neat [C3mPyr][FSI]

Immediate breakdown of FSI- anion via S-N cleavage

Fluorine dissociates from •NSO2F2 radical to form LiF & LiSO2F

Oxygen then dissociates to form LiO•

species

LiO• species obtain H+ available from

cation breakdown: LiOH


• Lithium metal plates and

strips during the cycling of

a lithium metal battery.

• Both electrodes are lithium.

• Li|Li couple measured via

cycling.

• Current density (J) 0.1 mA

cm-2

• Galvanostatic, measuring

voltage response over time

(V-t plot)

Li|electrolyte|Li symmetrical cell


LiFSI and LiTFSI symmetrical cell cycling

Only LiFSI completed 5000 cycles

Similar cycling behaviour for both salts

– Salt anions are analogous (FSI- & TFSI-)

– Likely an IL affect (C3mpyr[FSI])

LiTFSI cell failure ca. 2000 cycles.

Voltage instability typical of dendritic growth shortly before cell failure.

At this region salt nature is believed to determine cycling behaviour at long cycle lifetimes.

Differing V-t profiles are dependant not only on salt nature but SEI formation.

LiFSI

LiTFSI


Pretreated symmetrical cell cycling

0.1 mA cm-2 & 1.0 mA cm-2

18 & 12 day SEI pretreatment

Symmetrical Li|electrolyte|Li

Hexane polish

1 cm disks punchedDisks in electrolyte for

set time periods

1 2 1 8

7 Washed using DMCCYCLING

Lithium Metal Foil

Will long term cycling be altered by chemical SEI pretreatment?



a

LiFSI

LiTFSI

LiPF6

LiAsF6



Li metal anode

Separator


Pretreated full battery cyclingLi|electrolyte|LiFePO4

Not treated

LiFSI

LiPF6

LiAsF6


86

Bimetallic nanostructured materials

Dr. Ilija Najdovski and Dr. Periasamy Selvakannan

• Wide variety of uses in electrocatalysis, heterogeneous catalysis,

sensing, optical and electronic applications

• Bimetallic surfaces and nanoparticles for (electro)-catalytic

applications have improved properties over their single metallic

counterparts.

• This is due to synergistic or fine tuning effects that can be observed

when metals are used in combination either as alloys or when phase

separated.

• By careful choice of composition, shape and size, improvements in

important properties such as activity, selectivity and stability can be

achieved

• Various methods are employed to fabricate bimetallic surfaces

• This talk outlines one approach – co-electrodeposition


Templated electrodeposition

Chapter 12Fabrication, Characterization and Thermal Properties of NanowiresBy Yang-Yuan Chen, Cheng-Lung Chen, Ping-Chung Lee and Min-Nan OuDOI: 10.5772/16941

Wang, J. Mater. Chem., 2008,18, 4017-4020


88

Electrodeposition of porous metallic surfaces

Substrate Substrate

Hydrogen bubbles Electrodeposited metal

SubstrateSubstrate SubstrateSubstrate

Hydrogen bubbles Electrodeposited metal

Hydrogen bubble templating – electrodeposit around a clean and transitory template

Cu one of

the 1st

examples

Nikolic, Liu,

Cherevko


Effect of the substrate on Cu deposition

Cu

Au

Pd

GC

Cu Au Pd

500 µm 5 µm


Some properties

1 M NaOH

1 M NaOH

HER


Application

Best surface was Cu deposited on Pd – 1.5 x 10-3 s-1

Note the Pd surface gave a value of 5 x 10-5 s-1

J. Electroanal Chem., 2014, 722-723, 95


92

Electrodeposition of porous bimetallic

surfacesCu/Pd system

Pore size

decreases

upon

increased Pd

loading


93

Cu/Pd system

Internal wall structure changes from dendritic to cube like crystallites


94

Free standing films can be achieved

0

2

4

6

8

10

12

14

16

18

0mM 5mM 10mM 15mM 20mM 50mM

Surface Pd (%)Bulk Pd (%)

930 931 932 933 934 935 333 334 335 336 337 338 339

Cu 2p3/2

5

4

3

2

Binding Energy [eV]

0.5eV

1

(a) (b)

5

4

3

Binding Energy [eV]

2

Pd 3d5/2

-0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2-0.4

-0.3

-0.2

-0.1

0.0

54

32

I [A

cm

-2]

E [V] vs Ag/AgCl

1

Chem. Eur. J., 2011, 17, 10058

Surface alloy formation

Hydrogen

evolution

catalyst


95

Electrodeposition of porous bimetallic

surfacesCu/Au system

b

c d

a

a b

c d

Microscale and nanoscale morphology is again dependent on the composition ratio


96

Cu/Au system

Nanoscale, 2012, 4, 6298

Cu/AuCu

Conversion of nitrophenol to

aminiophenol (precursor to

paracetamol)

30 ml of 1 mM nitrophenol in

3 min

Electrochemical

reduction of

nitrophenol

Rate is

dependent on

composition and

morphology


An interesting effect

When we electrodeposited Pd onto Cu we observed the following

Morphology is consistent with this approach

The voltammetry shows a Cu profile!

Cu on Pd Cu on Cu Pd on Pd


An interesting effect

When we electrodeposited Pd onto Cu we observed the following

Morphology is consistent with this approach

Cu on Pd Cu on Cu Pd on Pd


Not confined to Pd deposition on Cu

AAS Cu - Ag Cu - Au Cu - Pd

Bulk mol% 61 – 39 35 – 65 56 – 44


Why is there so much Cu in the sample?We propose cathodic corrosion of Cu

Mirkin demonstrated that Pt polarised at conditions of -1.0 V vs Ag/AgCl in 0.1 M KCl

containing oxygen resulted in dissolution of Pt (Langmuir 2013, 29, 1346-1350)

Kreizer and co-workers reported that copper oxidation/dissolution occurs under even

milder cathodic polarisation conditions (-0.40 to -0.70 V vs (SHE)) in acidic solution in

the presence of trace oxygen which is promoted by stirring of the electrode/interface

layer by bubbles of evolving hydrogen (Protection of Metals 2002, 38, 226-232)

The liberated Cu2+ species or adsorbed Cu+ads, Cu2+

ads are reduced to Cu


Evidence of oxidised Cu on the surface

(facilitated by the local alklaine conditions at

the deposit/solution interface)

No Cu2+ species were found in the

electrolyte after electrodeposition

Galvanic replacement very unlikely –

immersed under potential control – the

system is also at around -2.3 V which

makes this mechanism thermodynamically

impossible


Nitrophenol reduction

Part B shows that for Ag

deposited on Cu but with

some CuSO4 (2.5 mM)

added to the electrolyte

(1.5 M H2SO4 with 50 mM

AgNO3)

Rate constant of 5.1 min-1


103

Summary

• Simple method of synthesis

• Access a wide variety of metallic and bimetallic

compositions

• Effective catalysts and electrocatalysts

• High surface area

• Tri-metallic compositions are also possible


Part III: Liquid metal marbles

104

Liquid marble team RMIT

• Prof. Arnan Mitchell

• Prof. Kourosh Kalantar-zadeh

• Dr. Vijay Sivan

• Dr. Khashayar Khoshmanesh

• Dr. Nicky Eshtiaghi

• Phred Peterson

• Shi-Yang Tang

• Wei Zhang

• QUT

• Dr. Faegheh Hoshyargar

• Husnaa Khan

• Jessica Crawforf



105

• Concept based on liquid marbles – water drop covered in a

superhydrophobic coating

The liquid marble of cobalt chloride with

Teflon powder on the left changed colour

from pink to green after being exposed to

ammonia and amine gas (Shen, Chem.

Commun., 2010,46, 4734-4736)



106

• Concept based on liquid marbles – water drop covered in a

superhydrophobic coating

• These liquid marbles behave, to some degree, like solid

particles

• Their structural form is dominated by surface tension and so

exhibit a number of unique properties, including very small

contact area with surfaces leading to low friction rolling,

superhydrophobic interactions with other fluids and the ability to

be split or fused together with self-healing encapsulation layers

• Extend this to liquid metal marbles where a liquid metal is

used instead of water

• Explore their chemistry and uses


Liquid metal marbles

107

Liquid metal is galinstan - gallium (68.5%), indium (21.5%) and tin

(10%)

Galinstan coated with various amounts of 80 nm WO3

nanoparticles


Liquid metal marble based sensing –

heavy metal ions

108

Adv. Funct. Mater., 2013, 23, 137


Increase sensitivity using a surface immobilised

network of liquid marbles

Adv. Funct. Mater., 2014, 24, 3799


Liquid metal marble actuation

110

Uncoated: 15 V Coated: 6V

Nanoscale., 2013, 5, 5949


111

Uncoated: 15 V Coated: 6V

Nanoscale, 2013, 5, 5949


Liquid metal enabled pump

PNAS, 2014, 111, 3304



Liquid metal enabled pump

PNAS, 2014, 111, 3304

Flow rate = 5,400 µL min-1

Power consumption 13 mW

http://www.youtube.com/watch?v=TmDgOrNiOpE

http://www.youtube.com/watch?v=TmDgOrNiOpE


Conclusions

115

• Electrochemistry is at the heart of storage devices – batteries

• Electrochemical approaches offer significant versatility for the creation of a

variety of metallic nanostructures

• In conjunction with other techniques it can offer unique insights into the

properties of nanomaterials

• Can be used to actuate liquid metals in a controllable manner and detect

heavy metal ions in a highly sensitive and selective manner

• Applicability is widespread for the materials presented – electrocatalysis,

heterogeneous catalysis, mobile heavy metal sensors and many more!


116

AcknowledgementsElectrochemistry

group• Dr. Andrew Pearson

• Dr Blake Plowman

• Dr Ilija Najdovski

• Dr Andrew Basile

• Manika Mahajan

• Muhammad Abdelhamid

• Ali Balkis

• QUT• Dr. Faegheh Hoshyargar

• Md Abu Sayeed

• Husnaa Khan

• Jessica Crawford

• Rory Shortt

• Tenille Herd

Thank you

Funding

• Australian Research Council

• QUT

• Platform Technology Research Institute, RMIT University seed funding

• CSIRO

• AOARD

Liquid marble team

• Prof. Kourosh Kalantar-zadeh

• Prof. Arnan Mitchell

• Dr. Vijay Sivan

• Dr. Khashayar Khoshmanesh

• Shi-Yang Tang

• Wei Zhang

RMIT SASAssoc. Prof. Vipul BansalProf. Suresh Bhargava

Documents

The applicability of electrochemistry to the physical ... · PDF fileThe applicability of electrochemistry to the physical, chemical and biological sciences ... • The Danish biochemist