The Global Energy Challenge –
Towards an Age of Electrochemistry?
Michael Eikerling
Department of Chemistry, SFU
Summer Seminar Series on Climate Change, June 27, 2012
The Problem of Climate Change
1.  Understanding relationship between climate and chemistry
of atmosphere, biological matter, and oceans
2.
Predicting impact on climate of different infrastructures
for energy conversion and storage (“sources”, production,
transportation, consumption, efficiency of energy use)
“In every case, after a bit of discussion, the audiences have
agreed that energy is the single most important issue we face.”
R.E. Smalley (1996 Nobel Prize), MRS Bulletin 30 (2005) 413.
What is Energy?
D
-
Not trivial…
q  fundamental physical property of objects (like atom number, volume)
q  practical definition: ability of a system to perform work
q  different forms (kinetic, potential, thermal, chemical, nuclear, mass, …)
q  What can be measured? Changes in energy distribution (during process)
Can there be an energy crisis? è
Thermodynamics
è  fundamental laws that govern distribution and transformation of energy
U
-
Something familiar?
(1) You cannot win
è you can’t get something for nothing because
matter and energy are conserved (always)
(2) You cannot break even
è you cannot return to the same energy state
because entropy always increases
(3) You cannot get out of the game
è absolute zero of temperature is unattainable
C.P. Snow, English physicist and novelist
Foundations of Thermodynamics
Two main approaches:
phenomenology (observations) vs. formal machinery (mathematics)
Empirical laws (“laws of experience”)
THE ENERGY OF THE UNIVERSE IS CONSERVED.
THE ENTROPY OF THE UNIVERSE INCREASES.
q  relationships between macroscopic properties of matter
q  always obeyed – consistent with any observation
q  basis for powerful theoretical formalism (> 50,000,000 math. relationships)
q  set of rules with capabilities to predict …
… spontaneous direction of reaction or process
… equilibrium constant of reaction that has never been run
… how equilibrium constant depends on temperature
… state (fate) of matter
Thermodynamics
ALBERT EINSTEIN: “A theory is the more impressive the greater the
simplicity of its premises, the more different kinds of things it relates, and
the more extended its area of applicability. Therefore the deep impression
that classical thermodynamics made upon me. It is the only physical
theory of universal content which I am convinced will never be
overthrown, within the framework of applicability of its basic concepts.”
SIR ARTHUR EDDINGTON (1928): “…if your theory is found to be against
the Second Law of Thermodynamics, I can give you no hope; there is
nothing for it but to collapse in deepest humiliation.”
Global Energy – Estimates
Basic energy demand
è  2500 kcal per capita (average): 7.5 ž
1016
basic demand
consumption
J p.d.
Energy consumption
= avg.efficiency
(~5%)
è global (~ 86% from fossil fuels): 14 ž 1017 J p.d.*
Earth is a closed system (no exchange of matter with universe):
è only significant external source of energy is the SUN
è  energy from sun hitting the earth: 1.5 ž 1022 J p.d.
è  10000 times global energy consumption
è  photosynthesis (“biomass production”): < 1% efficient
è  currently used: stored sun (fossil fuels)
è  economic action predicated upon unlimited access to fossil fuels
* > 220 Millions of Barrels oil equivalent per day
Three-Course Recipe for Disaster
Increasing power demand: double by 2050, triple by
Finite resources:
peak in oil extraction2
21001
Miserable energy efficiency
of “developed” societies3,4
NOW
global
average
energy efficiency
~ 40%
1 D.G.
Nocera, Chem. Soc. Rev. 38 (2009) 13.
I.S. Nashawi et al., Energy Fuels 24 (2010) 1788.
3 G. Deutscher, The Entropy Crisis, World Scientific Pub., 2008.
4 V. Smil, Visions of Discovery, ch. 35, Cambridge Univ. Press, 2010.
2
~ 1%
A
Global Energy: Drivers of a Transition
Increasing power demand: double by 2050, triple by 21001
Finite resources:
peak in oil extraction2
Miserable energy efficiency
of “developed” societies3,4
q  energy is conserved quantity
q  issue: rate of entropy production3
è  fatal implications (climate, economy)
è  is CO2 the problem?
1 D.G.
Nocera, Chem. Soc. Rev. 38 (2009) 13.
I.S. Nashawi et al., Energy Fuels 24 (2010) 1788.
3 G. Deutscher, The Entropy Crisis, World Scientific Pub., 2008.
4 V. Smil, Visions of Discovery, ch. 35, Cambridge Univ. Press, 2010.
2
E
A
fi
w
Global Energy: Drivers of a Transition
Increasing power demand: double by 2050, triple by 21001
Finite resources:
peak in oil extraction2
Miserable energy efficiency
of “developed” societies3,4
A
d
b
A simple problem in thermodynamics:
Calculate rate of T increase (ΔT/year)
-  energy consumption rate: ~ 15 TW
-  use key theorem of thermodynamics
-  uncertainty: # of degrees of freedom
-  fundamental issue: large numbers!
1 D.G.
Nocera, Chem. Soc. Rev. 38 (2009) 13.
I.S. Nashawi et al., Energy Fuels 24 (2010) 1788.
3 G. Deutscher, The Entropy Crisis, World Scientific Pub., 2008.
4 V. Smil, Visions of Discovery, ch. 35, Cambridge Univ. Press, 2010.
2
A
Global Energy: Drivers of a Transition
Increasing power demand: double by 2050, triple by 21001
Finite resources:
peak in oil extraction2
Miserable energy efficiency
of “developed” societies3,4
è  reduce inefficient use
è  exploit abundant source(s)
è  develop efficient technologies
Re
So
im
gr
Po
An
è a case for electrochemistry
Towards an Age of Electrochemistry?
Evaluation of energy technologies:
EFFICIENCY v abundance of resources v infrastructural needs (costs)
main
asset
Electrochemical energy
conversion and storage
Characteristics:
q  diverse technologies: photoelectrochemistry, batteries, fuel cells, ...
q  compatible with conventional and renewable sources
q  complex materials and phenomena (interfaces, nanomaterials)
Prediction of a Technical Revolution
Energy conversion in combustion engines
¢ limited by Carnot efficiency
¢ unacceptable levels of atmospheric pollution
vs.
Electrochemical energy conversion
¢ direct generation of electricity
¢ highly efficient, silent, no pollution
Practical realization could take a long time!
Source: Friedrich W. Ostwald (1909 Nobel prize),
Z. Elektrochemie, Vol. 1, p. 122-125, 1894.
P
b
What is Electrochemistry?
Attempt 1: branch of thermodynamics
expand concepts of free energy, chemical potential, td. equilibrium
è additional state variable: electrostatic potential of a phase
Attempt 2: surface science with a joystick
heterogeneous systems (phases of matter, interfaces)
è additional parameter: applied voltage (potential difference)
Attempt 3: process-based
separation of electrons from reactant in interfacial reactions
q intermittent storage of electricity: capacitor, rechargeable battery
q electron transfer and recombination with ions: fuel cell, battery
Ba
Fu
What is an Electrochemical System?
q  glass of water – electrochemical perspective:
homogeneous dielectric medium, polarizable
Apply voltage: - capacitance (energy storage)
- dielectric response function
q  add ions to water – electrochemical perspective:
liquid electrolyte, activity of ions
Apply voltage:
- ion transport
- ionic conductivity
What is an Electrochemical System?
q  dip metal stripe into electrolyte – electrochemical/electrified interface
apply voltage: add/extract electrons from metal – charged state
è adsorption of molecules, dissolution/deposition of metal
è polarization of charge and ion redistribution at or near interface
è formation of electrochemical double layer
electrostatic potential
+
ϕ
+
+
+
+
+
+
+
+
metal
electrolyte
What is an Electrochemical System?
q  insert two metal stripes and connect them via cable – electrochemical cell:
apply voltage: current flux (electrons in metal, ions in electrolyte)
è galvanic cell (generate electrical power: battery, fuel cell)
è electrolytic cell
Electrochemical Energy Conversion: Principles
KEY SYSTEM: metal|electrolyte interface
è charge separation, charge transfer
ϕ
ϕ‡
ϕM
Metal
H
H
O
Solution
- +
- à
+
- à
+
- à
𝛅
-
ϕo
KEY PARAMETER: specific interfacial area
è design of nanostructured materials
DEFAULT: heterogeneous media
è transport and reaction
σ Helmholtz plane
nanostructured
thin film (3M)
S
Electrochemical Energy Conversion and Storage
Batteries, fuel cells, supercapacitors è complementary technologies
Ragone plot
W
dr
ele
So
Is
Co
Co
rate of discharge
è dynamics
available energy
è range
M. Winter et al, Chem Rev. 104 (2004) 4245.
Fuel Cell Technology: Versatility
portable
q  energy efficiency (range) q  power density (dynamics) q  fuel flexibility and scalability q  zero emission vehicle technology
mobile
stationary
q  durability and life=me q  rapid response to load changes q  wide range of opera=ng condi=ons
Blueprint for Electrochemistry?
low entropy input
Important distinctions –
biological energy conversion:
è  microscopic charge separation
è  much smaller power density
Charge separation;
water as source of electrons
Efficiency of photosynthesis: < 1%
Efficiency of photovoltaics: ~ 18% (Si)
è efficiency of H2 production: ~ 12%
Recombination of fuel with O2;
water production
Efficiency of respiration: up to 90%
Efficiency of fuel cell: ~ 60%
M. Hambourger et al., Chem. Soc. Rev. 38 (2009) 25.
Pr
ef
Bi
-m
-m
Electrochemical Processes: Unrivalled Efficiency
2 H2 + O2
ΔH = - Q
Direct H2 combustion
2 H2O
Electrochemical Processes: Unrivalled Efficiency
O2
2 H2
L
-
ΔH
Reversible electrochemical process (const. T, P)
2 H2O
Electrochemical Processes: Unrivalled Efficiency
4 eO2
2 H2
ΔG
4 H+
Reversible thermodynamic efficiency:
ηrev =
ΔH
ΔG
ΔS
= 1−T
ΔH
ΔH
2 H2O
TΔS
Electrochemical Processes: Unrivalled Efficiency
FCV
4 e-
Wrev
Anode
Cathode
2 H2
O2
Pt
ΔG =– Wrev
4 H+
Polymer Electrolyte Membrane
electrocatalysis
ΔH
separation & proton conduction
2 H2O
TΔS
Electrochemical Processes: Unrivalled Efficiency
Faster!
Qr Joule heating
FCV
Wout
4 e-
O2
2 H2
Qp Joule heating
Pt
kinetics Qa
– Wout
4 H+
kinetics Qc
– Qc
Irreversible processes (finite rate) è heat losses
Thermal efficiency:
ηirr = −
Wout Wout ΔG
=
⋅
ΔH Wrev ΔH
inefficiencies
– Qp
– Qr
2 H2O
– Qa
TΔS
Electrochemical Processes: Unrivalled Efficiency
Qr
FCV
Wout
4 e-
O2
2 H2
- Wout
Qp
Pt
load
Qa
4 H+
Qc
Ho
as
- Qirr
Increasing the load (rate or current) è
2 H2O
TΔS
Polymer Electrolyte Fuel Cells
Thermodynamic efficiency
ηrev =
ΔG
ΔS
= 1−T
ΔH
ΔH
H2/O2 cell:
ε th = 83%
Voltage efficiency
W
ΔG
ηirr ( j0 ) = out ⋅
Wrev ΔH
ε V (1 A cm-2 ) ≈ 60 − 65%
Power density
P el = j0 ⋅ E ( j0 )
P el ≈ 1.0 − 2.0 W cm-2
1
T
F
T
m
D
g
A
W
(
[
Scientific Challenges: Hierarchy of Scales
φ0
φ
‡
φM
MEA H +
-O
H
- OH
+
H
H H
H
OH O
O
- O+
+
H
-O
+
H
Solution
Pt
metal
Ļ
OHP
Fig. 1. Levels of the structural hierarchy involved in understanding, designing and optimizing an electrochemical system.
microscopic nanocomposite single cell with cell,
stack.
From
left to right: electrified
interface,
nanocomposite medium,
electrochemical
electrochemical interface mul.func.onal materials membrane-­‐electrode assembly (MEA) fundamental phenomena,
innovative materials, diagnostics
Merit function:
fuel cell stack fabrication, testing,
engineering optimization
“power density”
cost
at given lifetime
è materials, engineering, mass production, …
Polymer Electrolyte Fuel Cells
Thermodynamic efficiency
Chemistry
è simple water-producing reaction
ΔG
ΔS
ηrev =
= 1−T
Thermodynamics è unrivalled reversible efficiency!
ΔH
ΔH
Materials science è complex heterogeneous materials
H2/O2 cell: ε th = 83%
System design
è intricate coupling of phenomena
Operation
è current response vs. (load, conditions)
Voltage efficiency
ηirr ( j0 ) =
Wout ΔG
⋅
Wrev ΔH
ε V (1 A cm-2 ) ≈ 60%
Power density
P el = j0 ⋅ E ( j0 )
P el ; 1.0 − 2.0 W cm-2
Fuel Cell Vehicles: On Track – But …
Fuel cell vehicles: no scientific curiosity!
q  1000s of fuel cell vehicles (FCV) tested
q  remarkable progress (performance, cost)
q  firm commitment to commercialization
FCV
C
u
m
an
DOE Hydrogen Program
Record #10004, Sept 2010.
Fuel Cell Vehicles: On Track – But …
Fuel cell vehicles: no scientific curiosity!
q  1000s of fuel cell vehicles (FCV) tested
q  remarkable progress (performance, cost)
q  firm commitment to commercialization
FCV
q  investments into engineering have been success!
q  limitations at materials level persist:
è performance
è cost
è durability and lifetime
“In the rush to do something – to find technological solutions to
global scale problems – we should not forget that we must ultimately
understand them …”, Whitesides & Crabtree, “Don’t Forget LongTerm Fundamental Research in Energy”, Science 315 (2007) 796.
Ma
re