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