solar photocatalysis to fuel cell for energy production

1

Julien RODRIGUEZ,

Eric PUZENAT,

Pierre-Xavier THIVEL.

Solar photocatalysis to fuel cell for energy production

Photocatalysis for energy Lyon, France - 15-17 October 2014

Project funded and supported by the cluster Région Rhone-Alpes “Energie”

2

Solar photocatalysis to fuel cell for energy production


Introduction

Experimental set-up 1Optimization of photocatalytic hydrogen productionHydrogen composition

Hydrogen use in PEMFCSolar irradiation conditions

Conclusions

Experimental set-up 2

3

Introduction

Fuel cellPEMFC

H2

O2Air

HeatElectricity

Photoreactor

UVSolar energy

Wastewater

Hydrogen production Electricity and heat production

2H+ 2e-

H2

TiO2

Pt

UV


J. Rodriguez, P.-X. Thivel, E. Puzenat, “Photocatalytic hydrogen production for PEMFC supply: a new issue”,International Journal of Hydrogen Energy 38, 6344-6348 (2013)

4

Photoreactor

- UV lamp- Solar energy

Alcohol(methanol)

H2

Photocatalytic alcohol dehydrogenation mecanims

2H+

H2

TiO2

Pt

UV

Photocatalysis for energy Lyon, France - 15-17 October 2014 Introduction

Hydrogen production

5

Methanol dehydrogenation

Methanol reformingPhotoreactor

Alcohol(methanol)

H2

2H+

H2

TiO2

Pt

UV


Hydrogen production

- UV lamp- Solar energy

6


External circuit

H2 in O2in (or Air)

O2out+ H2OH2 out

I

AnodeH2 2 H+ + 2 e- Cathode

½ O2 + 2 H+ + 2 e- H2O

Electricity and heat production proton exchange membrane fuel cell

H2 + 1/2 O2 => + H2O + Q

77

Reactor characteristics:- Optical area: 20 cm² (D=5cm)- Reagent : 50 ml (methanol)- Catalyst : 50 mg (Pt/TiO2)- Photon flux: 1.9 mmol h-1

- Carrier gas flow: 30 ml min-1 (Argon)

TiO2: Aeroxide P25

Platinum deposition:-Deposition methods: Incipient wetness impregnation, ion exchange impregnation, photodeposition

Photocatalytic tests:-Photocatalytic activity: Hydrogen production rate (µGC)

Photocatalysis for energy Lyon, France - 15-17 October 2014 Experimental set-up 1

Photocatalyst synthesis and production test

8

Impact of platinum deposition method onto P25 catalyst

Best hydrogen production rate for photodeposition,Quantum yield: 47.6 %

Deposition method:A: Incipient wetness impregnationB: Ion exchange impregnationC: Photodeposition

PhotodepositionPhoton flux = 1.9 mmol h-1

Pt loading = 0.4 wt.%

Quantum yield:r(H2) = H2 production rateΦ = Photon flux in the range 300 to 400 nm

r(H2) = 0.476 ΦR2 = 0.988

η = r(H2)

Φ

Optimization of photocatalytic hydrogen production


9

Platinum loadinfluence(photodeposition)

No significant photocatalytic evolution between : 0,2 et 1,0 wt.%1,2

1P. Pichat et al. / New Journal of Chemistry, 6 (1982) 559-5642B. Ohtani et al. / Journal of Physical Chemistry B, 101 (1997) 3349-3359



Best production rate => photodeposition with 1,0 wt.%

10

Best production rate => methanol dehydrogenation (865 µmol.h-1)

P25 (0,4 pds.% Pt)

CH3OH HCHO + H2

CH3OH + H2O CO2 + 3H2

H2O O2 + H2

Dehydrogenation :

Reforming :

Water splitting :

Hydrogen production rate with methanol concentrationLow evolution for high concentration(> 5 mol.L-1)


Reaction


11

- Methanol Dehydrogenation :43,8 % H2 43,8 % HCHO 12,4% CH3OH

- Methanol Reforming (50 vol.%) 70,2% H2 23,4% CO2 6,4 % CH3OH


1Bahruji, H. et al. / Journal of Photochemistry and Photobiology A: Chemistry, 216 (2010) 115-118

+ alcohol+ aldehyde and/or ketone

Hydrogen composition

12

Experimental set-up 2Photocatalysis for energy Lyon, France - 15-17 October 2014

Hydrogen production

Direct optical area: 91cm²Reagent : 300 ml (methanol)

Photoreactor

13


PEMFC :- Self-breathing fuel cell- Active area: 25 cm²- Anode Pt/Ru loading: 0,5 mg cm-²- Cathode Pt loading: 0,5 mg cm-²

Polarisation curve under pure hydrogen condition pH2 = 1,5 bar, T ambiant

14


Characteristics:- 4 photoreactors- Optical area: 392 cm²- Reagent : 1.2 L (alcohol)- Catalyst : 1.2 g (TiO2)- Co-catalyst: Pt 1 wt.% (photodeposition)

15

When photoreactor and the PEMFC are coupled the H2 production is estimated by the determination of the limit current of the fuel cell, with the anode in continuous mode.

Flux de photon: 46,7 µmol.s-1.m-2

Flux de photon: 80,7 µmol.s-1.m-2

Tension : 220 mVH2 Production13 mmol/h23 mmol/h


FsjFH 2.0

2

Mass balances

anode side in continuous mode and steady state condition

Hydrogen use in PEMFC

Pt photodeposition Filling of the system until

reach steady steate condition

16


Methanol 100%

Ethanol 100%

Methanol 50%

Similar performances are obtained for pure H2and photocatalytic H2


17


At steady state current demand (0,3 A) in dead end mode


Accumulation of by products in the anode compartment (CO2, alcohols, aldehydes, …)

Pure hydrogen: 80 µV min-1

Photocatalytic hydrogen:200 µV min-1

FsjF

tP

RTV

HH

cell

A

2.0

22

0PrproductBy

oductBy

cell

A Ft

PRTV

Mass balances

anode side in batch mode

Cell voltage drop faster under photocatalytic hydrogen before a drastic drop.

18


But regular purges permit to recover performances (dead-end mode)

Filling phase of the system Stable operating point over 2 to 3 h


19


Regular polarization curve obtained at 1,5 barunder pure hydrogen along 9 month with photocatalytic hydrogen,


Reversible poisoning under photocatalytic H2 may be due to methanol or aldehydes, as identified by N. Nachiappan et al. for PEMFCNo irreversible poisoning of the fuel cell occurs (> 2700h of coupling)

20

Photocatalysis for energy Lyon, France - 15-17 October 2014 Solar irradiation conditions

21


Pt photodeposition

Filling of the system until reach the OCV value

Solar irradiance≈ 2.1 mW cm-2 at 365 nm wavelength

Potenstiostatic mode (0,5 V)Maximum current 0,7 A

Fluctuations due to- Wind force

convection in cathode side

- Low H2 production in our condition

22


On this experiment the electric power density was about 1 mW cm-2.

Number of photoreactorCorresponding optical surface

area (cm²)Average electric power (W)

4 364 0.302 182 0.15

The average electric power is directly proportional to the optical surface area of photoreactor exposed to the sunlight.

- An electric power of 0.35 W was maintained for few hours.- Electric power density from photoreactors surface was: 1 mW cm-2

Electric power density is lower than for photovoltaic cell (in the range 10 to 20 mW cm-2)

23

Conclusions

Perspectives :- optimization of the desing of the solar-photorecator cell (optimization of the

ratio surface/volume for irradiation, optimization of the semiconductor form (fixed or mobile)…

- Optimization of hydrogen production at the semiconductor scale by for instance mixed some semiconductors.


- A PEMFC could be directly fed with hydrogen produced by photocatalysiswithout prior purification, with performances close to pure hydrogen.- Some purges are necessary in dead-end mode due to by-products accumulation in the anodic compartment.- Methanol and aldehydes may cause a reversible poisoning of the fuel cell, however, no irreversible poisoning was detected.- Electric power density obtained under solar irradiation is ten to twenty time lower than for photovoltaic cell.

24

Merci de votre attention

Thank for your attention


solar photocatalysis to fuel cell for energy production

Documents