Solar Fuels From Light & Heat - Stanford University · Solar Fuels From Light & Heat Xiaofei Ye, Liming Zhang, ... Solar simulator 48 . RHE Thermocouple CE . ... 1 sun T . T . Thermally-enhanced

Solar Fuels From Light & Heat Xiaofei Ye, Liming Zhang, Madhur Boloor, Nick Melosh

Will Chueh

Materials Science & Engineering, Precourt Institute for Energy Stanford University

chuehlab.stanford.edu


Suni

ta W

illia

ms,

NAS

A

2


D. D

iliff

R. L

addi

sh

C.-Y

. Yu

London

Tokyo

Chicago

3


500 1000 1500 2000 25000.0

0.4

0.8

1.2

1.6

Powe

r (W

m-2 n

m-1)

Wavelength (nm)

Enhance solar utilization

5 % Ultraviolet 43 % Visible 52 % Infrared

Dionne

1.8eV

4

Photo-electrochemical cell


Unreachable Temp.

10%

Solar-to-Fuel Efficiency

Combining heat & light: what’s possible?

5 X. Ye, J. Melas-Kyriazi, A. Feng, N. A. Melosh, W. C. Chueh. PCCP 15 (2013) 15459.


Can thermal energy make existing materials

better?

6

Low mobility

Morin, F. J. Phys. Rev. 1954, 93, 1195.


Low mobility, high stability semiconductor: Fe2O3

Al2O3(0001)

Pt

Ti doped α-Fe2O3 30 nm

200 nm

7

Pulsed-Laser Deposition

SEM AFM

TEM


0.1 M NaOH pH = 13

Solar simulator

RHE

Thermocouple

CE

Nitrogen

Water bath

WE

Stirrer

5%Ti-Fe2O3

8

0

2

4

J [m

A cm

-2]

72 oC 48 oC 25 oC 7 oC

9 suns

1 sun

0.8 1.0 1.2 1.4 1.6 1.80.0

0.1

0.2

1.24

VJ [m

A cm

-2]

E vs RHE [V]1.

19 V

TOP VIEW

Enhancement with temperature & light intensity

Δη~ 70 mV

I T

T


Enhancement with temperature & light intensity

9


Thermally-enhanced fill factor

0.1% Ti-doped Fe2O3

0.1

0.2

0.3

0.4

∆E

[V]

0.45 --> 4.5 mA cm-2

10

160 mV


200 nm 5 μm

Another low-mobility semiconductor: BiVO4

0.4 0.6 0.8 1.0 1.2 1.40

1

2

3

4

Cur

rent

den

sity

(mA

/cm

2 )

E (V) vs. RHE

dark current dark current with SO3

2-

without CoPi with CoPi without CoPi with SO3

2-

Effect of catalysts

0.4 0.6 0.8 1.0 1.2 1.40.0

0.4

0.8

1.2

Cur

rent

den

sity

(mA/

cm2 )

E (V) vs. RHE

dark current pure BiVO4

0.3% Mo doped BiVO4

1% Mo doped BiVO4

3% Mo doped BiVO4

Effect of doping

0.5 M K3PO4 buffered pH = 7 Electrolyte 11


0.4 0.6 0.8 1.0 1.2 1.40

1

2

3

Cur

rent

den

sity

(mA/

cm2 )

E (V) vs. RHE

dark 9 ℃ 25 ℃ 42 ℃

°C °C

°C

1 sun

T

T

Thermally-enhanced saturation current

0 500 1000 1500 2000 2500 3000

0.4

0.6

0.8

1.0

1.2

BiVO4

Pt

E (V

) vs.

RH

E

Time (s)

light on 1 sun

light off

light on 3 suns

10 20 30 40 50600

650

700

750

800

Ope

n C

ircui

t Vol

tage

(mV

)

Temperature ( ℃)(°C)

Significant enhancement in photocurrent without significant decrease with photovoltage

1mM [IrCl6]4-/0.1 mM [IrCl6]3-

12


Stability

0 1 2 3 4 5

0.2

0.4

0.6

0.8

Curre

nt d

ensit

y (m

A/cm

2 )Time (h)

42 °C

25 °C

9 °C

BiVO4

0 1 2 3 40.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

E [V

vs

RH

E]

Time [hour]

0.1% Ti-doped9 suns, 70 oC2 mA cm-2

Fe2O3

1 sun E = 0.6V vs. RHE

9 suns, I = 2 mA cm-2

70°C

E (V

vs.

RH

E)

Time (h)

13


Thermally-enhanced PEC

14

PEC / Solar cells

cooling


< 100 °C

Light Absorber Proton-conducting Oxide

Air

300 - 700 °C

Light Absorber Liquid Electrolyte

Gas Bubbles

eSolar

15

Going > 100°C: an all-oxide approach

chuehlab.stanford.edu 16

http://pie.stanford.edu/index.html




• A new class of solid state PEC for concentrated sunlight • Compatible with elevated temperature • Single device, isothermal

19

Semiconductor/Mixed Conductor Heterojunction


• Photon absorption • Electron/hole pairs excitation • Carrier diffusion

20 Paper submitted



• Light absorber/MIEC interface: – Electrons: thermionic emission – Holes: mostly reflected

21 Paper submitted



• MIEC/gas interface – Electron transfer, HER

22 Paper submitted



• Gas diffusion (stagnation layer) – H2O: continuously supplied, diffuse to the surface – H2: diffuse away from surface, then removed

23 Paper submitted



• Oxygen ions transport to the air side and react with holes

24 Paper submitted



• Broad maximum at ~750 K, 17 % • Below 700 K: slow thermionic emission • Above 700 K: insufficient photovoltage

25

400 500 600 700 800 9000.8

1.0

1.2

1.4

1.6

Pote

ntia

l (V)

T (K)

∆µabs/q ∆µMIEC/q Erxn E0

rxn

200 300 400 500 600oC

400 500 600 700 800 9000.00

0.05

0.10

0.15

0.20oC

Effic

ienc

y

T (K)

200 300 400 500 600

400 500 600 700 800 9000.8

1.0

1.2

1.4

1.6

Pote

ntia

l (V)

T (K)

∆µabs/q ∆µMIEC/q Erxn

200 300 400 500 600oC

400 500 600 700 800 9000.8

1.0

1.2

1.4

1.6

Pote

ntia

l (V)

T (K)

∆µabs/q

200 300 400 500 600oC

400 500 600 700 800 9000.8

1.0

1.2

1.4

1.6

Pote

ntia

l (V)

T (K)

∆µabs/q ∆µMIEC/q

200 300 400 500 600oC

Paper submitted

Efficiency Simulation



c

Figure 1

200 nm

20 30 40 50 60

Inten

sity (

a.u.)

2 theta (degree)

* *

* *

*

*

* * * * * * * * * * * *

(-12

1)

(004

)

(101

)

(011

)

(002

)

(211

) (0

15)

(240

) (0

42)

(161

)

(321

) (1

23)

(200

)

5 µm

b


Figure 2

0 1 2 3 40.0

0.3

0.6

0.9

1.2

front illumination back illuminationC

urre

nt d

ensi

ty (m

A/cm

2 )

Deposition time (min)780 800 820 840 860

pure BiVO4

0.3% Mo doped BiVO4

1% Mo doped BiVO4

3% Mo doped BiVO4

Ram

an in

tens

ity (a

.u.)

Raman shift (cm-1)

0.4 0.6 0.8 1.0 1.2 1.40.0

0.4

0.8

1.2

Cur

rent

den

sity

(mA/

cm2 )

E (V) vs. RHE

dark current pure BiVO4

0.3% Mo doped BiVO4

1% Mo doped BiVO4

3% Mo doped BiVO4

c


2 µm 200 nm

a b

0.2 0.4 0.6 0.8 1.00

1

2

3

Curre

nt d

ensit

y (m

A/cm

2 )

E (V) vs. RHE

dark current macroporous BiVO4

nanoporous BiVO4

c

Figure 5


0.2 0.4 0.6 0.8 1.00

1

2

3

4

Cur

rent

den

sity

(mA/

cm2 )

E (V) vs. RHE

10 ℃ 25 ℃ 35 ℃ 45 ℃ 55 ℃

0.2 0.4 0.6 0.8 1.00

1

2

Cur

rent

den

sity

(mA/

cm2 )

E (V) vs. RHE

10 ℃ 25 ℃ 35 ℃ 45 ℃ 55 ℃

10 20 30 40 50 601

2

3

4

Cur

rent

den

sity

(mA/

cm2 )

at 0

.80

V vs

. RH

E

Temperature(℃)

a

b

c

Small BiVO4 NPs

Large BiVO4 NPs

Figure 6


1.4 1.6 1.80

10

20

30

Curre

nt d

ensit

y (m

A/cm

2 )

E (V) vs. RHE

9 ℃ 25 ℃ 42 ℃ 61 ℃ 80 ℃

1.80 1.84 1.88

0.0

0.5

1.0

1.5

log

(| j (m

A/cm

2 ) | )

E (V) vs. RHE

9 ℃

25 ℃ 42 ℃ 61 ℃ 80 ℃

Figure 8

Documents

Solar Fuels From Light & Heat - Stanford University · Solar Fuels From Light & Heat Xiaofei Ye, Liming Zhang, ... Solar simulator 48 . RHE Thermocouple CE . ... 1 sun T . T . Thermally-enhanced