Novel Materials for
Renewable Energy
Hongjie Dai
Department of Chemistry, Stanford University
Fuel cells
Harvest solar, wind, hydro energies for
- Electricity
- Batteries for energy storage
- Make H2 fuel, …
Hydrogen fuels
Clean Energy for a Sustainable Future
Electrocatalysts and Novel Batteries
H+H2 O2
OH-
e-e-
• High activity and fast speed.
• Durable.
• Low cost; non-precious metal based
H. Wang et. al.,
Chem. Rev., 2013
Y. Liang et. al., JACS
(perspective), 2013
M. Lin et. al., Nature, 2015
• Low cost, active and
stable electrocatalysts.
• Water to H2 with high
efficiency/low voltage.
• Develop new battery
concepts.
Growth of Materials on NanoCarbon for Energy Storage
and Electrocatalysis
H+H2 O2
OH-
e-e-
• High activity and fast speed.
• Durable.
• Low cost; non-precious metal based
(H. Wang et. al., Chem.
Rev., 2013)
[Y. Liang et. al., JACS
(perspective), 2013]
Nucleation and Growth of Inorganic Materials on
Oxidized Nano-Carbon
• Nucleation step: metal ions binding to COOH groups on GO or CNT. • Growth step: the degree of graphene oxidation affects morphology. • Nanoparticles grown are electrically wired up to carbon. • Covalent coupling between nanoparticle and carbon observed. • A series of covalently coupled hybrid materials for energy applications.
Precursor Free particles
B
nucleation/growth on oxygen functional groups
on nano-carbon
Traditional: free particles + carbon black (or CNTs)
‘Strongly coupled hybrid’
Or ‘covalent hybrid’ of
inorganic/nano-carbon
• Excellent electronic coupling for high activity
• Excellent stability for high durability
Growth of Oxides, Hydroxides, Phosphates,
Sulfides… on Graphene & Nanotubes
MoS2
10 nm
graphene
Co3O4
LiMn0.75Fe0.25PO4
graphene
Graphene Ni(OH)2
100nm
7
Electrocatalysts for High Efficiency Electrolysis
-0.4 0.0 0.4 0.8 1.2 1.6 2.0
HER
Cu
rre
nt
De
ns
ity
Potential (V vs RHE)
OER
1.23 V
Over-
potential
A theoretical voltage of 1.23 V
Multi-proton/electron transfer
(Large overpotential)
The best catalysts (~1.5-1.6 V)
(Pt for HER / IrO2 for OER)
2H2O O2+4H++4e- OER:
4H++4e 2H2 HER:
Need cheap and scalable
electro-catalysts
with high activity and durability
Industrial catalyst (> 1.8-2.0 V)
(Ni for HER / Stainless steel for
OER)
MoS2 Grown on Graphene Oxide for Hydrogen Evolution
Electrocatalyst (HER) in Acids
Free growth
Without GO
Growth on GO
(Y. Li et al., JACS, 2011)
(f)
(d)
(e)
(a) (b)
(c)
-0.4 -0.3 -0.2 -0.1 0.0-30
-25
-20
-15
-10
-5
0
Cu
rre
nt
De
ns
ity
(m
A/c
m2
)
Potential (V vs RHE)
1x oxCNT
2x oxCNT
4.5x oxCNT
without CNT
0.5 M H2SO
4
a
-0.5
-0.4
-0.3
-0.2
-0.1
Pt(111)Fe0.9Co0.1S2(110)FeS2(110)
EH
EH2
Ab
so
rpti
on
en
erg
y (
eV
)
c
b
• Growth on CNT is critical
• FeS2 affords suitable adsorption energy for H.
• Co doping lower the kinetic energy barrier by promoting H-
H bond formation on two adjacently adsorbed Hads.
FeS2 Doped with Co Grown on CNTs for HER in Acids
(D. Y. Wang, et al, C. J. Chen, B. J. Hwang, H. Dai, JACS, 2015)
10
NiFe Layered Double Hydroxide (LDH) for OER in Base
-0.4 0.0 0.4 0.8 1.2 1.6 2.0
HER
Cu
rre
nt
De
ns
ity
Potential (V vs RHE)
OER
1.23 V
Over-
potential
4OH- 2H2O+O2+4e- OER:
Fe3+ Cation Ni2+ Cation
Charge-balancing anion
LDH structure
Gong, M. et al, J. Am. Chem. Soc., 2013, 135, 8452-8455
• NiFe LDH grown on carbon nanotubes
11
NiFe-LDH Grown on CNTs:
More Active and Durable Than Ir
~ 240 mV overpotential @ 10 mA /cm2
Tafel slope of 31 mV/decade in 1 M KOH
Gong, M. et al, J. Am. Chem. Soc., 2013, 135, 8452-8455
Gratzel group:
• NiFe LDH is both OER and HER active.
• Can be used for solar driven electrolysis efficiently
with perovskite solar cells
13
Hydrogen Evolution Reaction (HER) Electrocatalysis
-0.4 0.0 0.4 0.8 1.2 1.6 2.0
HER
Cu
rre
nt
De
ns
ity
Potential (V vs RHE)
OER
1.23 V
Over-
potential
2H2O 2OH-+H2+2e- HER:
• HER is important to
o Alkaline water
electrolysis
o Chloralkali catalysis
• Nickel (Ni) has been widely
used
• Lower activity than Pt
Pt
14
O Ni
C Ni+O Ni+O+C
Gong, M. et al. Nature Comm., 2014, 5, 4695
Ni@NiO Grown on CNT for HER in Base
• Ni-NiO interfaces are highly active for HER
• Onset over-potential ~ 0 volt
Ni-NiO HER + NiFe LDH OER:
~ 1.5 V Water Splitting
Thermodynamic limit = 1.23 V
Compared to 2V:
~ 25% energy saving
Ming Gong, et al.,
Nature Comm.
With Dr. Wu Zhou
S. Pennycook,
Oakridge
Latest: A Highly Stable Ni-NiO-Cr2O3 HER Catalyst (Ming Gong, et al., Angew Chemie, 2015; with ITRI + Prof. BJH)
0 10 20 30 40 5050
100
150
Cu
rre
nt
Re
ten
tio
n (
%)
Time (hour)
without Cr2O
3
with Cr2O
3
-0.4 -0.3 -0.2 -0.1 0.0-100
-80
-60
-40
-20
0
Cu
rre
nt
De
ns
ity
(m
A/c
m2)
Potential (V vs RHE)
CrNN + Ni powder
Pt/C
0 20 40 60 800
50
100
150
200
250C
urr
en
t D
en
sit
y (
mA
/cm
2)
Time (hour)
CrNN + Ni powder
Ni-NiO-Cr2O3 HER Catalyst: Active and Stable
Ming Gong, et al., Angew Chemie,
2015.
With Dr. Wu Zhou &
S. Pennycook, Oakridge National Labs;
B. J. Hwang
Ni+NiO+Cr2O3
Ni+NiO
Why is Ni-NiO-Cr2O3 Stable for HER
No CrOx
with CrOx
HER
HER
Figure 4
0.0 0.5 1.0 1.5 2.0
2
4
6
8
10
12
14mA/cm
2
Cu
rre
nt
De
ns
ity
(m
A/c
m2
so
lar
ce
ll)
Voltage (V)
RT Electrolyzer
two GaAs solar cell
(AM1.5, 100 mW/cm2)
two GaAs solar cell
(desk light, 20 mW/cm2)
12.10
mA/cm2
2.45
0 4 8 12 16 20 24
2
4
6
8
10
12
14
desk light 20 mW/cm2
Cu
rre
nt
De
ns
ity
(m
A/c
m2
so
lar
cell)
Time (hour)
AM 1.5 100 mW/cm2
0 100 200 300 400 5001.4
1.5
1.6
1.7
1.8200 mA/cm
2 (23
oC)
200 mA/cm2
(60oC)
Vo
lta
ge
(V
)
Time (hour)
20 mA/cm2
(23oC)
0 10 20 30 40 50
Stable, Active Water Splitting Driven by
GaAs Solar Cells
With R. Capusta, S.
Cowley
Alta Devices, Sunnyvale
(Hanergy, 汉能)
1.4 1.6 1.8 2.0 2.2 2.4 2.60
50
100
150
200
Ni + S
S
Cu
rren
t D
en
sit
y (
mA
/cm
2)
Voltage (V)
RT (23oC)
60oC
CrN
N +
NiF
e L
DH~15% efficiency
Desk Lamp Driven Electrolysis
Split water using night light
Ultrathin Ni Metal Film Protection
for Si Photoanode
(M. Kenney, M. Gong, et
al., Science, Nov. 15, 2013)
An Ultra-Stable
Si Photoanode
5 nm 200 nm
Cobalt Oxide−Graphene Hybrid Materials
for Oxygen Reduction Reaction (ORR)
Y. Liang et al., Nature Mater. 2011, 10, 780.
1. low temp hydrolysis
2. solvothermal treatment
Co3O4 nanocrystals
graphene
XPS
CoO/Oxidized-Nanotube Electrocatalyst for ORR
20 30 40 50 60 70
2(degree)
Inte
nsi
ty (
a.u
.)
220
311
400
511 440
0.2 0.4 0.6 0.8 1.0
50 A
Potential (V vs RHE)
Co3O4/rmGO
Co3O4/N-rmGO
Pt/C
(Y. Liang, Y. Li, H. Wang, et al., J. Am. Chem. Soc. 2012)
0.7 0.8 0.9 1.0-60
-40
-20
0
Co3O
4
Co3O
4 + N-rmGO mixture
Co3O
4/N-rmGOC
urr
ent
Den
sity
(m
A/c
m2)
Potential (V vs RHE)
Activity due to
Co3O4 covalent
coupling to GO
10 nm
100 nm
• Metal-oxide/Nanotube hybrid
outperform metal-oxide/graphene
• Higher electrical conductivity of
oxidized multi-walled nanotubes
Battery Research
Ultrafast NiFe Alkaline Battery
• Making the Ni-Fe Edison battery much faster
26
Ultrafast Ni-Fe Battery
Anode Cathode
FeOx
Fe
Ni(OH)2
NiOOH
0 50 100 150 200
0.4
0.8
1.2
1.6
2.0
Vo
lta
ge
(V
)
Time (s)
37A/g
(e)
0 40 80 120
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Vo
lta
ge
(V
)
Discharge Capacity (mAh/g)
1.5A/g
3.7A/g
7.4A/g
15A/g
37A/g
0 200 400 600 800 0.0
0.2
0.4
0.6
0.8
1.0
Ca
pa
cit
y R
ete
nti
on
Cycle Number
(f) 0.5 1.0 1.5 2.0 -0.15
-0.10
-0.05
0.00
0.05
0.10
0.15 C
urr
en
t (A
)
Voltage (V)
100mV/s
40mV/s
20mV/s
10mV/s charging
discharging
Ultra-Fast Ni-Fe Battery
(H, Wang, et al., Nature Comm., 2012)
To demonstrate the reliability of the Edison nickel-iron battery, a battery-powered Bailey was entered in a 1,000-mile endurance run in 1910. (National Park Service / June 26, 2012)
SCIENCE
Stanford researchers update safer, cheaper Edison battery
Towards
recharging a
car in minutes
Lithium Ion Battery Materials Grown
on Graphene
- Cathode Material
- Anode Material
• High rate, high capacity
LiMn0.75Fe0.25PO4
graphene
20 nm
Mn3O4
LiMn0.75Fe0.25PO4 /GO as a Fast, High-Voltage,
Stable Cathode Material for Li Ion Battery
0 50 100 150
2.0
2.5
3.0
3.5
4.0
4.5
Vo
ltag
e v
s L
i/L
i+ (
V)
Specific Capacity (mAh/g)
charge
discharge
0 20 40 60 80 1000
40
80
120
160
S
pecif
ic C
ap
acit
y (
mA
h/g
)
Cycle Number
0 20 40 60 80 1000
40
80
120
160
Sp
ec
ific
Ca
pac
ity (
mA
h/g
)
Discharge Rate (C)
0 30 60 90 120 150
2.0
2.5
3.0
3.5
4.0
100C
50C
20C
10C
2C
Vo
ltag
e v
s L
i/L
i+ (
V)
Discharge Capacity (mAh/g)
0.5C
3 min discharge time
(H. Wang et al.,
with Yi Cui
group, Angew
Chemie, 2011)
0 10 20 30 40
0
200
400
600
800
1000
1200
1400
discharge
charge
400mA/g
1600mA/g
800mA/g
400mA/g
40mA/g
Ca
pa
cit
y (
mA
h/g
)
Cycle Number
0 2 4 6 8 10
0
200
400
600
800
1000
1200
1400
discharge
charge40mA/g
Ca
pacit
y (
mA
h/g
)
Cycle Number
Mn3O4/Graphene Anode
Wang*, Cui* et al., J. Am. Chem. Soc. 2010, 132, 13978.
31
100 nm Graphene
hybrid
electrode:
100nm
Conventional
mixture
electrode:
Mn3O4/GO
Free Mn3O4
Need more active and stable electrocatalysts for ORR &
OER to increase energy efficiency
Electrocatalysts for Rechargeable Zn Air Batteries
Anode:
Cathode: 2 22 4 4O H O e OH
2
44 ( ) 2Zn OH Zn OH e
(ORR/OER)
ORR: oxygen reduction reaction
OER: oxygen evolution reaction
Figure 1 CoO/N-CNT
NiFe LDH/CNT
OH-
O2
b c
e f
CoO nanocrystals
CNT
CNT
NiFe LDH plates
NiFe LDH plates
CNT
Electrocatalysts for Zn-Air Oxygen Electrodes
ORR:
OER:
(Y. Liang, Nature Mater. 2011, JACS, 2012)
(M. Gong, JACS, 2013)
0 100 200 300 400 500 6000.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Vo
lta
ge
(V
)
Specific Capacity (mAh/g)
10 mA/cm2
100 mA/cm2
0.0 0.1 0.2 0.3 0.4 0.5 0.60.4
0.6
0.8
1.0
1.2
1.4
CoO/N-CNT
Pt/C Pow
er
De
nsity (
W/c
m2)
Volta
ge
(V
)
Current Density (A/cm2)
0.00
0.05
0.10
0.15
0.20
0.25
Primary Zn-Air Battery
• High discharge peak power density
~265 mW/cm2
• Current density ~200 mA/cm2 at 1 V
• Energy density > 700 Wh/kg.
Y Li et al., Nature Comm., 2013
Summary 1. Systematic study of inorganic nanocrystal
growth on graphene
2. Using graphene hybrid materials to boost
the performance of supercapacitors, Ni-Fe
batteries, and Li ion batteries
35
0 20 40 60 80 100 120 140 160 180 200
1.2
1.4
1.6
1.8
2.0j = 20 mA/cm
2 CoO/N-CNT + NiFe LDH
Pt/C + Ir/C
Vo
lta
ge
(V
)
Time (h)
• Low charge-discharge voltage polarization of
~ 0.70 V at 20 mA/cm2
• High reversibility and stability over long charge
and discharge cycles (10 h discharge time)
High Performance Rechargeable
Zn-Air Battery
Y Li et al., Nature Comm., 2013
+ AlCl3 =
Aluminum + Graphite + Salts = Al Ion Battery
1 : 1.3
Abundant anions in ionic liquid solution:
AlCl4¯ & Al2Cl7
¯
Mengchang Lin, Ming Gong, Yingpeng Wu, Bingan Lu, et. al., Nature, 2015
Collaboration with ITRI Taiwan & Prof. B. J. Hwang.
4Al2Cl7¯ + 3e¯ ⇄ Al + 7AlCl4
¯ Cn+ AlCl4– ⇄ Cn[AlCl4] + e–
V ~ 2.0 volt
Al Redox + Graphite/Anion Redox Reactions
4Al2Cl7¯ + 3e¯ ⇄ Al + 7AlCl4
¯
3Cn+ 3AlCl4– ⇄ 3Cn[AlCl4] + 3e–
4Al2Cl7¯ + 3Cn+ 3AlCl4
– ⇄ Al + 7AlCl4¯ + 3Cn[AlCl4]-
Al Ion Battery with Graphite Paper Cathode
• Cathode capacity is
now increased to ~ 100
mAh/g
a b
c
Fast Charging of Al Ion Battery with Graphite
Foam Cathode
b
Al Anion/Graphite Paper Intercalation
f
AlClx- Intercalation During Charging/Oxidation
of Graphite
• High activity and fast speed.
• Durable.
• Low cost; non-precious metal based
• Low cost:
- Uses earth abundant
Al and C.
- Ionic liquid: 20$/kg at large
scale quoted by a chemical
company.
• Safe, non flammable
• Fast charging
• Long cycle life, > 10,000
• Energy density up to ~ 62.5
wh/kg with active materials,
higher than supercapacitors;
• Pb acid replacement
Potential of Al Battery
Applications:
• Grid storage
• Home use
• Mechanical tools
Fuel cells
Convert wind- and solar-energy into:
- H2 and methane fuels
- Energy stored in low cost, safe, high performance batteries
Hydrogen fuels
Clean Energy for a Sustainable Future
Acknowledgement
Professor B. J. Hwang, C. J. Chen
Professor Stephen Pennycook, Wu Zhou
Professor Wei Fei
Ming Gong, Michael Angell
Mengchang Lin, Bingan Lu
Yingpeng Wu, Di-yan Wang
Mike Kenney, Sebastian Schneider
Hailiang Wang
Yongye Liang, Yanguang Li
Tyler Medford, Wesley Chang
Guosong Hong, Kevin Welsher, Sarah Sherlock,
Joshua Robinson, Shuo Diao, Alexander Antaris,
Omar K. Yaghi
Nadine Wong Shi Kam, Zhuang Liu,
Giuseppe Prencipe, Andrew Goodwin
Yuichiro Kato, Sasa Zaric, Zhuo Chen.
Professor Zhen Cheng
Professor John Cooke
Dr. Jeffrey Blackburn
Professor Calvin Kuo
Nano-Bio: Energy:
Stanford
GCEP
and PIE
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