Electrocatalysis: Development of electrocatalysts for

solar fuels

Applications of interest

1. Fuel cells

2. Electro organic synthesis

3. Other industrial electrochemical application

4. CO2 Valorization

5. Green H2 production

Interesting reactions

Reaction Yield Reaction conditionsTR

LApplication

HMF + 2H2O → FDCA + 3H2 90% Ni20 - 30 0C, atm, water

pH 12-135 Plastics

PDO + H2O → Lactic acid + 2H2 80% C30 - 40 0C, atm, water

pH 9-103

Plastics, food,

pharma

Furfural + 4H2O → Maleic acid +

CO2 + 4H2

80%Pb

(V2O5)

20 - 35 0C, atm, water

pH 03

Plastics,

building block

Levunilic acid + H2O → Valeric

acid + O2

>95% Pb20 - 50 0C, atm, water

pH 03

Biofuel,

cosmetics

Levunilic acid + H2O → γ-Valerolactone

+ O2

>90% Pb20 - 50 0C, atm, water

pH 7-82 Green solvent

Pyruvic acid + H2O → DMTA + O2 60% Pb RT, atm, water pH 0 2 NA

CO2 + H2O → FA or CO + O2 >80% Sn/AuRT, 0 – 80 bar, water,

pH 6-92

Building

block/fuel

2H2O → 2H2+ O2 >90% Pt TiO2

RT, 0 – 80 bar, water,

pH 6-92 Fuel

CO

H2

Renewable energy production in The Netherlands

05/05/2016

Data source: https://transparency.entsoe.eu.

Own graphic

28/11/2016

00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 24:00

0

200

400

600

800

1000

1200

1400

1600

1800

Re

new

ab

le e

ne

rgy p

rod

uctio

n /

MW

28/11/2016

Solar

Wind Onshore

Wind Offshore

Other

10000

12000

14000

16000

18000

20000

To

tal e

nerg

y d

em

an

d /

MW

00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 24:00

0

200

400

600

800

1000

1200

1400

1600

1800

Re

new

ab

le e

ne

rgy p

rod

uctio

n /

MW

05/05/2016

Solar

Wind Onshore

Wind Offshore

Other RE

8000

10000

12000

14000

To

tal e

nerg

y d

em

an

d /

MW

Energy storage technologies

Source. Specht et al., 2010

https://www.energysage.com/

Solar fuels. The idea

CO2

capture

Valued added

chemicals and

fuels

Direct light activation

Energy

World Meteorological Organization, WMO Bulletin, Tech. Rep. 12 (2016).

Close the carbon loop

Electrocatalysis Photocatalysis

Step 1

Renewable

Electricity

Solar fuels

2 steps process 1 step process Direct solar

light capture

Step 2 Electricity to

chemical bonds

H2

Modified

Fischer-Tropsch

CO2

RW

GS

Methane

CO + H2

Methanol

Formic acid

Water splitting

- H2O

- H2O

Raw materials for chemistry

Routes CO2 into fuels. Electrocatalysis

Fuels

Fischer-Tropsch

Nanopaticles

5 nm 15 nm 50 nm100 nm

Spheres Rods

1000 nm

Control size & shape

500 nm

Synthesis scale-up

13 December 2018

Synthesis scale-up from 1 ml to 10 L

10L2L0.001 L

Electrodes preparation

13 December 2018

Ultrasonic spray Coating

Photocatalysis- Plasmon activated

13 December 2018

Why hydrogen?

13 December 201813 | Photo Water Splitting (PWS)

Key role for sustainable future

Energy carrier

Electricity

Mobility

Heating

Chemical reactant

Fertilizer production

Oil refining

Solar fuel:

harvesting the sun

(e.g. 𝐻2 + 𝐶𝑂2 → 𝐶𝐻4 +𝐻2𝑂)

Why water splitting?

‘Grey’ versus ‘Green’ Hydrogen

Steam reforming

Fossil fuel based

Additional heat required

Very low price (1$·kg-1)

Water splitting

Possibly based on renewable energy sources

Electricity required

Expensive (6 $·kg-1)

13 December 2018

H2O

O2

H2

H HH H

H H

Steam reforming

Water splitting

14 | Photo Water Splitting (PWS)

Why photo-water splitting?

Two different ways of

producing green H2

‘Direct’ is the integrated

approach with highest

efficiency, and benefits

from heat

‘Indirect’ depends on

electricity price, suffers

from large current, but is

more mature

13 December 2018

H H

HH

H H

H H

PV-electrolysis

(indirect)

H HH

H

H HH H

Photo-electrolysis

(direct)

Current ≈ 1 A·cm-2

Suffers from heatCurrent ≈ 0.01 A·cm-2

Benefits from heatHigher

efficiency

Lower

efficiency

15 | Photo Water Splitting (PWS)

How do we split water directly?

Different approaches

Photo-chemical Photo-electro-chemical

13 December 201816 | Photo Water Splitting (PWS)

How do we split water directly?

Photo-chemical water splitting: oppertinities

Particle based system (slurries)

Low efficiency system

(very) Low cost

Safety to be addressed by processing

13 December 2018

Low cost of green hydrogen

17 | Photo Water Splitting (PWS) Maeda et al., J. Photochemistry and Photobiology C: Photochemistry Reviews 12 (2011) 237– 268

How do we split water directly?

Photo-chemical: development

Typical materials: TiO2 combined with co-catalyst (e.g. Pt)

Tuning light harvesting, suitable bandgap and (photo)corrosion

Research on commercial and non-commercial catalysts

Durable catalysts

Aiming at cost efficient water splitting

13 December 201818 | Photo Water Splitting (PWS)

How do we split water directly?

Photo-electro-chemical: opportunities

Device based – resembles a PV panel

High cost

Potentially very high efficiency

No safety issues

Yielding pressurized hydrogen

13 December 201819 | Photo Water Splitting (PWS)

Low cost of

green hydrogen

0 30 60 90 120

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0,40

Curr

en

t d

en

sity (

mAc

m-2)

Time (min)

Dark

Light

1,23 V

0,0

0,5

1,0

1,5

2,0

Pote

ntial ap

plie

d (

V v

s. R

HE

)

How do we split water directly?

Photo-electro-chemical: material development

Typical materials: CIGS with Si-solar cell

Tuning suitable bandgap, required voltage bias and

(photo)corrosion

Scale up of photoelectrode manufacturing by ultrasonic

spray deposition

13 December 201820 | Photo Water Splitting (PWS) Van de Krol et al., in Photoelectrochemical Hydrogen Production (2012) 14-69

When is al this realized?

13 December 201821 | Photo Water Splitting (PWS)

Price vs. Performance: difficult to beat ‘grey hydrogen’

Photo-chemical Photo-electro-chemical

When is al this realized?

13 December 201822 | Phot Water Splitting (PWS)

Price vs. Performance: development

Focus on stability of materials, rather than high efficiency

Tailoring specific chemistry for large centralized vs. local

decentralized operation

Producing H2 with purity and pressure for industrial scale

directly

Device integration for local energy harvesting

Electrocatalysis vs. Photocatalysis ?

Location.

24/7 vs. day time.

Centralized vs. decentralized.

Return on investment.

13 December 2018

Carbon capture storage and/or utilization ?

CO2 concentration.

Location.

CO2 taxes.

13 December 2018

Green Hydrogen

Subsidies and/or CO2 taxes.

Centralized vs. decentralized

(Photo)catalyst durability.

13 December 2018