02/09/2021

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Developments in electrolytic hydrogen generation

Joint Supergens Net Zero Conference

2/9/2020

Professor Anthony Kucernak

Theme lead Polymer Electrolyte Fuel Cells and Electrolysers

Imperial College London

anthony@imperial.ac.uk

UK Hydrogen Strategy, August 2021

UK Hydrogen Strategy, August 2021

• 250-460 TWh (7.5-14 Mtonnes) p.a. Hydrogen by 2050• Produced through a range of technologies

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4UK Hydrogen Strategy, August 2021 OSW-H2: SOLVING THE INTEGRATION CHALLENGE. July 2020

Water Electrolysis

5

Increasing

TRL

~100MW (5 MW,

2.1 tonneH2 day-1)

~minutes time scale

Moderate turndown

Low cost

~50 MW (2 MW, 0.9 tonnes day-1)

~s time response

Good turn down ratio (ITM Power, Bramble

Energy). Compact – high intensity

(0.225 MW, 0.14 tonnes day-1)

Moderate-poor turndown and time response

Ceres. Higher efficiency

NEL

ITM Power

Isothermal compression at low energy cost

Sunfire

An

od

e –

oxyge

n e

volu

tion

Ca

tho

de

–

Hyd

rog

en

evo

lutio

n

50-70oC

50-80oC

~800oC

30,000 Nm3/h (65 tonnes/day)

135 MW (hydroelectricity)

Source: nel

KOH solution

H+ conducting polymer

Metal oxide

ceramic

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PEM Water Electrolysis – reducing cost

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• Hydrogen from SMR or coal (even with CCS) much less expensive at the moment because of electricity costs

PEM Electrolyser

Stack ~50% of Capex costs

(majority is bipolar plate, not catalyst)

OSW-H2: SOLVING THE INTEGRATION CHALLENGE. July 2020

Issues for water electrolysis –increasing efficiency, reducing cost

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PEM Water Electrolysers Alkaline Electrolysers

Solid Oxide Electrolysers

Cross-cutting issues

Data from: OSW-H2: SOLVING THE INTEGRATION CHALLENGE. July 2020

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Breakdown of water electrolyser loses• Need for better understanding of different loses

• Major inefficiencies in low temperature electrolysers are• Electrocatalysis

• Resistive loses (electrolyte loses)

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Increasing current density/hydrogen production →

PEM Electrolyser

Increasing current density /hydrogen production →

Alkaline Electrolyser

Resistance loses (mostly ionic)

Oxygen evolution loses

Hydrogen evolution loseson

cathode are small

1 gPt cm-2 needed (1000-

fold less then used today)

Zalitis, C. M.; Kucernak, A. R.; Sharman, J.; Wright, E., Design principles for platinum nanoparticles catalysing electrochemical hydrogen

evolution and oxidation reactions: edges are much more active than facets. Journal of Materials Chemistry A 2017, 5 (44), 23328-23338.

Re

sis

tan

ce

lose

s

Oxyg

en

an

d

hyd

rog

en

lose

s

Testing standards for catalysts• In PEM electrolyser, performance is limited by oxygen evolution electrode • Studied to assess intrinsic performance and deactivation

• “Thrifting” and assessment of new catalysts

• In Alkaline system, look for improved catalysts for anode and cathode

30

µm

Pt or Ir

10gPt cm-2

<1m

9

50 100 150 200 250 300

0%

10%

20%

30%

40%

50%

60%

70%

80%

IrO2

Pro

po

rtio

n o

f su

rfa

ce a

tom

s o

n e

dg

e s

ite

s

Surface area/ m2 g-1

tetrahedron

cube

octahedron

truncatedoctahedron

cubooctahedron

5020 10 5 4 3 2

particle diameter / nm

100%

90%

80%

70%

60%

50%

40%

30%

20% Pro

po

rtion o

f su

rface a

tom

s o

n fa

cet s

ites

b

e

a

50 100 150 200 250 300 3500.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

1.6 V

1.65 V

ECSAaverage/ m2 g-1

avera

ge j

sp

ecific/ m

A c

m-2 IrOx_400 °C

IrOx_500 °C

IrOx_600 °C

Premetek

Alfa

R2=0.966

R2=0.987

50 20 10 5 4 3 2

particle diameter / nm

c

+H2O

O

Ir (IV) Ir(IV)OO O

Ir (IV) Ir(IV)OO

OHOHO

Ir (VI) Ir(VI)OO OO O=OO

Ir (IV) Ir(IV)OO

O

Ir (VI) Ir(VI)OO OO

+H2O

O

Ir (VI) Ir(VI)OO OO

OH

Ir (IV)O O O

Ir(VI)O

O

O

+H2OIr Iredge

OHO O

Ir

OO O OH

Ir (III) Ir

O OO=O

Ir(III)

IrIr

O

H(1)

(2)

(3)

Highpotential

1 10 100101

102

103

104

105

106

107

108

109

m

ass a

ctivity /

A g

-1

specific surface area / m2 g-1

e=1

e=2

e=0.66

0

1

2

3

4

5

j osp

ecific / m

A m

-21000 100 10

particle diameter / nm

d

particle size jspecific

particle size jspecific

No size effect on jspecific

Xiao, M.; Jackson, C; Kucernak, A. R.;, Size-dependent performance of IrO2 OER

elecrocatalysts, ACS Catalysis, submitted

0.1 M KOH 0.1 M HClO4

Hyd

roge

n E

volu

tio

n (

HER

)

Oxy

gen

Re

du

ctio

n (

OR

R)

Oxy

gen

Evo

luti

on

(O

ER)

-0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0

-40

-30

-20

-10

0

EweIRc vs. RHE / V

j geo /

mA

cm

-2

PGC

Ni2P-40

Co2P-40

WP-40

CrP-40

MoP-40

Pt

(a)

-0.4 -0.3 -0.2 -0.1 0.0-20

-15

-10

-5

0

(b)

j ge

o /

mA

cm

-2

EweIRc vs. RHE / V

PGC

Ni2P-40

Co2P-40

WP-40

CrP-40

MoP-40

Pt

0.0 0.2 0.4 0.6 0.8 1.0-6

-5

-4

-3

-2

-1

0

(c)j geo

/ m

A c

m-2

EweIRc vs. RHE / V

PGC

Ni2P-40

Co2P-40

WP-40

CrP-40

MoP-40

Pt

0.0 0.2 0.4 0.6 0.8 1.0-6

-5

-4

-3

-2

-1

0

(d)

j geo /

mA

cm

-2

EweIRc vs. RHE / V

PGC

Ni2P-40

Co2P-40

WP-40

CrP-40

MoP-40

Pt

1.3 1.4 1.5 1.6 1.7-8

-6

-4

-2

0

2

4

6

8

10

12(e)

j geo

/ m

A c

m-2

EweIRc vs. RHE / V

PGC

Ni2P-40

Co2P-40

WP-40

CrP-40

MoP-40

IrO2

1.2 1.3 1.4 1.5 1.6 1.7

0.0

0.5

1.0

1.5

2.0

2.5(f)

j geo

/ m

A c

m-2

EweIRc vs. RHE / V

PGC

Ni2P-40

Co2P-40

WP-40

CrP-40

MoP-40

IrO2

Parra-Puerto, A.; …Kucernak, A., Supported Transition Metal

Phosphides: Activity Survey for HER, ORR, OER, and Corrosion

Resistance in Acid and Alkaline Electrolytes. Acs Catalysis 2019, 9

(12), 11515-11529. doi:10.1021/acscatal.9b03359 (2019).

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Combine best of both low temperature electrolysers

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J. Am. Chem. Soc. 2012, 134, 22, 9054-9057

J.R. Varcoe, P. Atanassov, D.R. Dekel, A.M. Herring, M.A. Hickner, P.A. Kohl, A.R.

Kucernak, W.E. Mustain, K. Nijmeijer, K. Scott, T. Xu, L. Zhuang, Anion-exchange

membranes in electrochemical energy systems, Energy & Environmental Science,

7 (2014) 3135-3191.

Equivalent performance to liquid

alkaline electrolysers

~5x lower than PEM electrolyers

• Hydroxide conducting ion exchange polymers• Developed for fuel cells but suffer from two problems:

• Temperature stability (T>60oC tend to decompose c.f. “Green Cremation”)

• Reaction with atmospheric CO2

Solid oxide electrolyser

J.H. Myung, D. Neagu, D.N. Miller & J.T.S. Irvine, Nature, 2016. 537, 528-531

Using ex-solvation to grow catalyst

particles on the surface

ElectrolyserFuel Cell

Increasing hydrogen production rate

Inc

rea

sin

g

eff

icie

nc

y

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Economics of electrolytic chemicals production

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o Oxygen evolution is a poor counter reaction

o Choosing other counter reactions could drastically reduce hydrogen costs

o For some co-produced products hydrogen is a minor cost component

Process Electrochemical reaction Product(s) Mass (Product)

Mass (Hydrogen)

Product price /$ tonne-1

Value (Product)

Value (Hydrogen)

Hydrogen evolution 2H+ + 2e-

H2

2H2O + 2e- H2 +2OH-

H2 1 2450

Combined with one of the reactions below Combined with one of the reactions below

Water electrolysis H2O ½O2 + 2H++ 2e- 2OH- ½O2 + H2O + 2e-

O2 7.9 60 0.2

Chlor Alkali 2Cl- Cl2 + 2e-

Cl2 35.2 350 13.8

NaOH 39.7 540

Hydrogen peroxide 2H2O H2O2 + 2H+ + 2e- H2O2 16.9 450 3.1

Ozone H2O 1/3O3 + 2H+ + 2e- O3 7.9 2500 8.0

Persulphate 2HSO4- S2O8

2- + 2H+ + 2e- X2S2O9 118.1 3300 160.4

Organic oxidation CxHyOz+H2OCxHy+1Oz+1+H++e- CxHy+wOz+w ? ? ?

Work

performed

H2 Mole

fraction

[%]

Limiting

current

[A/cm2]

Recovery

rate

[%]

Energy

demand

[kWh/kg]

Resistance

[mΩ*cm2]

Model, FZJ 50 0.43 74 5.3 625

Model, HyET 50 0.44 100 5.3 300

Mutlicell test, HyET 85 0.86 <42 5.3 417

Cross reference test, DHBW 50 0.45 39 5.3 455

Cross reference test, HyET 50 0.45 27 5.3 540

Simplest case: Electrochemical Hydrogen pump

Single Cell

EHP Stack

• Separation of hydrogen from

• Diluent

• Poisons (improve purity)

• Hydrogen compression

• >1 kbar possible

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Max recovery (90%) requires ~

11-13 kWh/kgFor low energy of 5 kWh/kg,

recovery is ~30%

Conditions

50 % H2 diluted in N2,

35 °C, anode pressure at 6.5

bar and the cathode pressure

50 bar, 0.3136 Nl/min of H2

Jackson, C.; Raymakers, L.; Mulder, M.; Kucernak, A., Poison mitigation strategies

for the use of impure hydrogen in electrochemical hydrogen pumps and fuel cells.

Journal of Power Sources 2020, 472, 1-13.

Purify hydrogen from

dilute/contaminated source

0 2000 4000 6000 8000 10000 12000 140000

20

40

60

80

100

Cu

rre

nt

/ %

Time / s

H2 + 20 ppm CO

H2 + 20 ppm CO + 1.15% O

2 + 0.05% O

3

78.6% H2 + 2.9% CH

4 + 18.5% CO

2 + 20 ppm CO

78.6% H2 + 2.9% CH

4 + 18.5% CO

2 + 20 ppm CO + 1.15% O

2 + 0.05% O

3

H2+20 ppm CO

Reformate

No mitigation

Recovery of hydrogen from dilute stream

Economics of electrolytic chemicals production

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o Oxygen evolution is a poor counter reaction

o Choosing other counter reactions could drastically reduce hydrogen costs

o For some co-produced products hydrogen is a minor cost component

Process Electrochemical reaction Product(s) Mass (Product)

Mass (Hydrogen)

Product price /$ tonne-1

Value (Product)

Value (Hydrogen)

Hydrogen evolution 2H+ + 2e-

H2

2H2O + 2e- H2 +2OH-

H2 1 2450

Combined with one of the reactions below Combined with one of the reactions below

Water electrolysis H2O ½O2 + 2H++ 2e- 2OH- ½O2 + H2O + 2e-

O2 7.9 60 0.2

Chlor Alkali 2Cl- Cl2 + 2e-

Cl2 35.2 350 13.8

NaOH 39.7 540

Hydrogen peroxide 2H2O H2O2 + 2H+ + 2e- H2O2 16.9 450 3.1

Ozone H2O 1/3O3 + 2H+ + 2e- O3 7.9 2500 8.0

Persulphate 2HSO4- S2O8

2- + 2H+ + 2e- X2S2O9 118.1 3300 160.4

Organic oxidation CxHyOz+H2OCxHy+1Oz+1+H++e- CxHy+wOz+w ? ? ?

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Co-production of valuable chemicals

• Hydrogen is a by-product in the membrane chlor-alkali process (7% value)

• Electrolytic production of hydrogen in chlor-alkali industry far exceeds water electrolysis (by at least 10-fold)

• 10-15% of hydrogen is not used

• Market for chlorine/sodium hydroxide saturated, so no benefit for more production

• Other markets for oxidants may be very large

• e.g. oxidants for water treatment/scission of lignin

• CO2 reduction to CO/syngas also possible

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Eurochlor –

chlor-alkali industry review 2019-2020

Hyd

rogen

Oxy

gen

Chlo

rine

Sodiu

mhyd

roxi

de

Hyd

rogen

pero

xide

Ozo

ne

Pers

ulfa

te

Lig

nin

0.1

1

10

100

Electrolytic production

Other production process

Chemical sector value

Wo

rldw

ide

pro

duction

/ M

tonn

e p

.a.

Ch

em

ica

l se

cto

r va

lue

/ G

$ p

.a.

Commodity chemical

~0.5% electricity used in chlor-alkali

Thank you

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