Fuel cell catalysts and membrane development at the CSIR: Presentation

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MSM ENERGY MATERIALS

Fuel Cell Catalysts and Membrane Development at the CSIR

Mmalewane Modibedi

[email protected]

Korea- South Africa H

2

Fuel cell workshop, 15-17 July 2013

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Outline of the presentation

 Overview of the CSIR

 Overview of Material Science and Manufacturing (MSM)

 Overview of Energy Materials (EM)

 Fuel cell (FC) research activities

 Membrane development

 Electrocatalysis

 MEA Fabrication: new developments

 Future Work

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Technology development - development of

technology (process, product,

service) Strategic basic

& applied research - generation of new knowledge

and application of existing

knowledge

Technology transfer &

implementation - impact on economy and

society Fundamental

research -understanding

fundamental principles

Industry/

public sector CSIR

The CSIR spans the research and innovation value chain but its role is differentiated from TEIs and industry/public sector

Tertiary education institutes

Strategic position in the National System of Innovation

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CSIR sites, people and financials

Pretoria

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Durban Pietermaritzburg Nelspruit

Johannesburg Kloppersbos

Modderfontein

Cape Town

• 2370 members of staff

• 1537 in SET * base

• 299 with Doctorates

• 475 with Master’s

• 54% of SET base black

• 34% of SET base female

• Contract Income: R1 273 m

• Parliamentary Grant: R557 m

• Royalties: R10 m

• Total operating income: R1.88 billion People and demographics

Financials

*SET: Science, engineering and technology

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R& D O utco mes M anagemen t C o n tr act R & D Su p p o rt M an ag eme n t

Smart Structures

& Materials Biomaterials

Advanced Casting Technologies

Primary Processes

Powder Metallurgy Technologies

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Micro manufacturing

Clean Coal Technologies

Renewable Energy Technologies

Electro-optic Sensing &

Imaging

Light Metals

Mechatronics

& Micro Manufacturing Polymers

&

Composites

Energy Materials

Engineering Design &

Analysis

Ultrasonics

SET Leadership & Competence Management

National Centre For Nano- Structured

Materials (NCNSM)

Nano-composites

Nano-structured materials

Quantum dots Nonwovens &

Composites Encapsulation

& Delivery

Sensor Science &

Technology

Sector focused Growth and Impact Strategies

Aerospace Automotive Health Energy Built Environment Micro Manufacturing

High Impact Projects

New materials for

aerospace New materials for BE Micro fluidics Rapid bacterial

detection Battery electrode

materials Visual inspection

technologies

Ultra sound technologies for health

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Luo et al., International Journal of Hydrogen Energy 34, 2009

Zheng et al., International Journal of Hydrogen Energy, 35(8), 2010, Zheng et al.,Journal of Power Sources, 196 (3), 2011

1.1 Fuel cell types: Low temperature PEMFC, DMFC

1. Fuel Cells

• Membrane development:

• Covalently cross-linked polyetheretherketone PEM for DMFC

• Incorporation of nanoparticles such ZrO

₂

in Nafion membrane

• Characterisation: methanol crossover studies, conductivity tests, thermal stability

• MEA fabrication and testing (performance 10% less than Nafion

membrane)

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• Electrocatalysts:

• Oxygen reduction reaction (ORR):

(a) ORR in H

₂

SO

₄

Best catalyst: Pt

(b) ORR in H

₂

SO

₄

+ MeOH Potential drop-

~220mV: Pt catalyst Max 58mV: Pd catalysts

No current drop: Pd-catalysts

Best catalyst: Pd

₃

Pt/C

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1.2 Anion exchange membrane: (DAFC)

Why AAEM?

• Catalysts: use non-noble metals, faster kinetics of oxygen reduction and alcohol oxidation

• Membrane: reduced or no alcohol crossover

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Why Lithium ion batteries?

Preparation of nano-composite membrane

• The OH- form of QPSU was dissolved in DMAc and different proportion of TiO₂ nano filler was added to this solution and then stirred for 24 h, followed by casting.

• Dried at 80 ^oC overnight.

1. ¹H-NMR SPECTRA 1. ¹H-NMR SPECTRA

2. FT-IR SPECTRA

500 1000

1500 2000

2500 3000

3500 4000

Wavenumber, cm^-1

Transmission, %

PSU CMPSU QPSU QPSU-TiO2

2. FT-IR SPECTRA

500 1000

1500 2000

2500 3000

3500 4000

Wavenumber, cm^-1

Transmission, %

PSU CMPSU QPSU QPSU-TiO2

Abuin et al. IJHE, 35 (2010) p 5489.

Nonjola et al. IJHE, 38 (2013) p 5115 Multi-step synthesis of quaternary polysulfone (QPSU)

Avram et al. J macromol Sci Pure Appl Chem, A34 (1997) p1701

PNAS, vol 105 (2008) p20611 IJHE, vol 36 (2011) p7291

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Membrane morphology

 All membranes defect free surface

 QPSU shows a smooth and uniform (1a&b)

 TiO

₂

particles are well dispersed in the membrane with 2.5% loading (2a&b).

 TiO

₂

dispersion in 10% loading (3a&b) shows negligible agglomeration.

 This implies that prepared composite membranes can be expected to perform consistently in alkaline fuel cell

SEM images of surface and cross section (1) QPSU, (2) QPSU/2.5%TiO₂ and (3) QPSU/10%TiO₂.

1a 1b

2a 2b

3a 3b

Nonjola et al. IJHE, 38 (2013) p 5115

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reducing agent: mixture NaBH

₄

and ethylene glycol

Low ethanol oxidation

performance vs Pd+Ru-Ni/C

• Electrocatalysts: Synthesis methods

Modibedi et al., International Journal of Hydrogen Energy, 36 (8) (2011) 4664, Mathe et al., Energy Procedia 29 (2012) 401

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XRD micrographs of nanocatalysts

20 40 60 80 100

2 Theta (degree)

Int en si ty (a. u. )

C (002)

Ru (101) Pd (200)

Pd (220)

PdRuNi/C (a)

RuNi/C

Pd (111)

20 40 60 80 100

2 Theta (degree)

Intensity (a.u.)

RuNi/C C (002)

Ru (101)

Ru/C

20 40 60 80 100

In te nsity (a.u .)

2 Theta (degree)

C (002)

Pd (200)

Pd (220)

Pd/C

(b) ^{Pd (111)}

PdNi/C

no significant shift in peak:

Ni did not alloy well with Pd using this preparation method at rt.

Ramulifho et al., Electrochim. Acta, 59 (2012) 310, Ramulifho et al., J. Electroanal. Chem., 692 (2013) 26

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Effect of ethanol concentration on current

PdNi/C PdRuNi/C

-40 -20 0 20 40 60 80 100 120

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2

Potential (V vs Ag/AgCl) Current density (mA/cm2 )

0.25M 0.5M 1.0M 2.0M 3.0M 4.0M CEtOH =

-1.0 -0.8 -0.6

0.25M 0.5M 1.0M 2.0M 3.0M 4.0M C_{EtOH =}

-40 -20 0 20 40 60 80 100 120

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2

0.25M 0.5M 1.0M 2.0M 3.0M 4.0M CEtOH =

-1.0 -0.8 -0.6

0.25M 0.5M 1.0M 2.0M 3.0M 4.0M C_EtOH =

[EtOH] up to 3 M coverage of the CH

₃

COads species on the nanocatalyst surface

Resulting in increase in current density

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Electrocatalysts: Microwave-assisted polyol method

• Oxygen reduction catalysts

N-doped CNTs:

thermal chemical vapour deposition Ru/N-CNTs:

microwave assisted reduction

Mabena, Modibedi et al., Fuel Cells 12(5) (2012) 862

Koutecky-Levich plots

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ORR catalysts characterization

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• Graphene oxide-MWCNT hybrid for Alcohol oxidation reaction in alkaline electrolyte

Supported Pd and PdNi

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Electrocatalysts: Electrochemical Atomic Layer Deposition technique (ECALD)

Definition:

alternated electrodeposition of atomic layers of elements on a substrate, employing under-potential deposition (UPD) in which one element deposits onto another element at a voltage prior to that necessary to deposit the element onto itself

Advantages:

• ambient temperature,

• use small concentrations of precursor solutions,

• optimized solutions and potential separately

Offers atomic layer control- fundamental for controlled growth

processes

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Sequential electrodeposition coupled to Surface-limited Redox- replacement reactions: Synthesis of multilayered Pt electrocatalyst

Cu ²⁺

(1) Clean substrate with blank electrolyte (BE);

Inject Cu ²⁺solution at E >> E _Cu_-_Cu2+

S S S S S S S

(2) Potentiostatic electrodeposition at – E _dep> E _Cu_-_Cu2+(Underpotential

Deposition (UPD)) or E _dep< E _Cu_-_Cu2+

(small Overpotential Deposition (OPD) - to produce sacrificial Cu

adlayer on active sites of the substrate; Rinse with BE Cu ²⁺ Cu ²⁺

S S S S S S S Cu Cu Cu Cu Cu

- 2e

S S S S S S S Pt Cu Pt Cu Cu

(3) Inject H ₂PtCl ₆solution and allow surface - limited redox - replacement

(SLRR) of Cu by Pt at open circuit (OC)

Pt ⁴⁺

S S S S S S S Pt Pt Pt Pt Pt

(4) Pt nanodeposit on substrate;

Rinse with BE and inject Cu ²⁺

solution at E >> E _Cu_-_Cu2+

Pt ⁴⁺

Cu ²⁺

S S S S S S S Pt Pt Pt Pt Pt Cu Cu Cu Cu Cu

S S S S S S S Pt Pt Pt Pt Pt Ru Cu Ru Ru Cu

Cu ²⁺ - 2e Cu ²⁺ Cu ²⁺

(5) Potentiostatic electrodeposition at – E _dep to produce sacrificial Cu

adlayer on active sites on Pt adlayers; Rinse with BE

Ru ³⁺

Cu ²⁺

S S S S S S S Pt Pt Pt Pt Pt Ru Ru Ru Ru Ru

(6) Inject RuCl ₃solution and allow surface - limited redox - replacement

(SLRR) of Cu by Ru at OC S S S S S S S

Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt Cu ²⁺

S S S S S S S S S S S S S S

(2) Potentiostatic electrodeposition at – E _dep> E _{Cu -}_Cu2+ (Underpotential

(small OverPotential Deposition (OPD) - to produce sacrificial Cu

S S S S S S S Cu Cu Cu Cu Cu S S S S S S S S S S S S S S

Cu Cu Cu Cu Cu - 2e

Pt Cu Pt Cu Cu

Pt ⁴⁺

S S S S S S S Pt Pt Pt Pt Pt S S S S S S S S S S S S S S

Pt Pt Pt Pt Pt

Pt ⁴⁺

Cu ²⁺

Pt Pt Pt Pt Pt Cu Cu Cu Cu Cu

Pt Pt Pt Pt Pt Pt Cu Pt Pt Cu

Cu ²⁺ - 2e Cu ²⁺ Cu ²⁺

Pt ⁴⁺

Cu ²⁺

Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt

(6) Inject H₂PtCl₆ solution and allow surface - limited redox - replacement

(SLRR) of Cu by Pt at OC S S S S S S S S S S S S S S Pt Pt Pt Pt Pt

Pt Pt Pt Pt Pt

Sequential electrodeposition coupled to Surface-limited Redox- replacement reactions: Synthesis of multilayered Pt electrocatalyst

Cu ²⁺

S S S S S S S

(2) Potentiostatic electrodeposition at – E _dep> E _Cu_-_Cu2+(Underpotential

(small Overpotential Deposition (OPD) - to produce sacrificial Cu

S S S S S S S Cu Cu Cu Cu Cu

- 2e

S S S S S S S Pt Cu Pt Cu Cu

Pt ⁴⁺

S S S S S S S Pt Pt Pt Pt Pt

Pt ⁴⁺

Cu ²⁺

S S S S S S S Pt Pt Pt Pt Pt Cu Cu Cu Cu Cu

S S S S S S S Pt Pt Pt Pt Pt Ru Cu Ru Ru Cu

Cu ²⁺ - 2e Cu ²⁺ Cu ²⁺

Ru ³⁺

Cu ²⁺

S S S S S S S Pt Pt Pt Pt Pt Ru Ru Ru Ru Ru

(6) Inject RuCl ₃solution and allow surface - limited redox - replacement

(SLRR) of Cu by Ru at OC S S S S S S S

Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt Cu ²⁺

(2) Potentiostatic electrodeposition at – E _dep> E _Cu_-_Cu2+ (Underpotential

(small OverPotential Deposition (OPD) - to produce sacrificial Cu

S S S S S S S Cu Cu Cu Cu Cu S S S S S S S S S S S S S S

Cu Cu Cu Cu Cu - 2e

Pt Cu Pt Cu Cu

Pt ⁴⁺

S S S S S S S Pt Pt Pt Pt Pt S S S S S S S S S S S S S S

Pt Pt Pt Pt Pt

Pt ⁴⁺

Cu ²⁺

Pt Pt Pt Pt Pt Cu Cu Cu Cu Cu

Pt Pt Pt Pt Pt Pt Cu Pt Pt Cu

Cu ²⁺ - 2e Cu ²⁺ Cu ²⁺

Pt ⁴⁺

Cu ²⁺

Pt Pt Pt Pt Pt Pt Pt Pt Pt Pt

(6) Inject H₂PtCl₆ solution and allow surface - limited redox - replacement

(SLRR) of Cu by Pt at OC S S S S S S S S S S S S S S Pt Pt Pt Pt Pt

Pt Pt Pt Pt Pt

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Tuning Electrocatalysis using sequential electrodeposition…

T.S.Mkwizu, M.K. Mathe, and I. Cukrowski, ECS Transactions, Vol.19, 97-113 (2009) T.S.Mkwizu, M.K. Mathe, and I. Cukrowski, Langmuir, Vol. 26, 570 - 580 (2010)

Electro-activity increases with increasing deposition cycles

(i) Sequentially-deposited with Cu SLRR bimetallic PtRu / GC (ii) Sequentially- codeposited with Cu SLRR bimetallic Pt-Ru/GC (iii) Sequentially-deposited with Cu SLRR monometallic Pt/GC Pt < PtAu < PtRu

Order of activity: Methanol electro-oxidation

Impedance of methanol

electro-oxidation

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AFM images of Pt|Ru nanoparticles obtained after 8 deposition cycles with Cu SLRR

Tuning Electrocatalysis using sequential electrodeposition…

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Noble-Metal: Pt, Pd

Substrates: Carbon paper, Ni foam

Repeat cycles 1X, 4X, 8X: 8X, Small OPD

• Cu(s) deposition occurs through

kinetically controlled 3D nucleation

Modibedi et al., ECS Trans. 50, 2013

2.3 Membrane Electrode Assembly (MEA)

1. Rinse cell with BE at 0.2V, rinse with Cu²⁺ solution 2. Cu deposition at -0.05V,

rinse with BE at -0.05V 3. Rinse with Pd²⁺ solution at

OCP, SLRR at OCP Carbon paper

1

2 3

Ni foam

1

3 2

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Pt supported on FC gas diffusion layer: SEM micrographs and EDX profile

Carbon paper TGPH090 Pt/carbon paper TGPH090

0 1 2 3 4 5 6

Energy (keV)

Pt

Cu Pt O

Pt/carbon paper TGPH090 C

Carbon paper TGPH090 Pt/carbon paper TGPH090

0 1 2 3 4 5 6

Energy (keV)

Pt

Cu Pt O

Pt/carbon paper TGPH090 C

Carbon paper TGPH060 Pt/Carbon paper TGPH060

0.0 1.0 2.0 3.0 4.0 5.0

Energy (keV) C

Cu Pt

Pt Pt/Carbon paper

O Carbon paper

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Cyclic voltammograms at 50 mV/s

Pt supported on Carbon paper: Electrochemical Evaluation

(ii) 0.1 M HClO4 + 0.1 M Methanol

Catalyst showed activity towards methanol electro-oxidation in acid media

(i) 0.1 M HClO4 + CO saturated

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Pd/carbon paper and Ni foam: SEM micrographs and EDX profile

Carbon paper

Nickel foam

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Pd supported on Carbon paper: Electrochemical Evaluation

(ii) 0.1 M KOH + 0.1 M Methanol

(iii) 0.1 M HClO4 + 0.1 M Ethanol

Potential (V) vs Ag/AgCl

Current Density (mA/cm2)

Ads CO

Catalyst showed activity towards methanol and ethanol electrooxidation in alkaline media Catalyst is tolerant to CO poisoning

(i) 0.1 M KOH + CO and N2

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Pd supported on Ni foam: Electrochemical Evaluation

(ii) 0.1 M KOH + 0.1 M Ethanol

Ads CO

(i) 0.1 M KOH + CO and N2 Catalyst Methanol

Onset potential (V) vs Ag/AgCl

Ethanol Onset potential (V) vs Ag/AgCl

Pd/C paper -0.456 -0.555

Pd/Ni foam -0.429 -0.590

MeOH: 27 mV more negative on Pd/Carbon paper EtOH: 35 mV more negative on Pd/Ni foam

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Pd on Carbon paper or Ni foam: Electrochemical Evaluation- ORR

(i) CV in 0.1 M HClO4 + N₂at 50 mV/s

(ii) LSV in 0.1 M HClO4 + O₂ at 10 mV/s (iv) LSV in 0.1 M KOH + O₂ at 10 mV/s

(iii) CV in 0.1 M KOH + N₂at 50 mV/s

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Electro-Catalyst Onset potential (V) vs Ag/AgCl

Limiting current density (mA/cm

²

)

Pd/C paper in acid 0.407 0.4492

Pd/Ni foam in acid 0.606 1.8862

Ni foam in alkaline -0.508 0.400

Pd/C paper in alkaline -0.073 0.880 Pd/Ni foam in alkaline -0.052 2.2985

Electrochemical evaluation: summary

at 3 ml/min, 10 mV/s

Acid: 200 mV more positive on Pd/Ni foam than on Pd/Carbon paper Alkaline: 21 mV more positive on Pd/Ni foam Pd/Carbon paper

: 456 mV more positive on Pd/Ni foam than on Ni foam Ni foam is a better substrate than carbon paper

Pd enhanced the activity on Ni foam

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Future Work

• Membrane work: FC testing including AE ionomer optimisation

• Electrocatalysis: MEA fabrication and FC testing under active conditions

• FC tests using MEAs fabricated with ECALD technique

• Intense FC tests in collaboration with, for example, HySA, Korea, Argentina

• Ultimately, proudly South African materials for local and

export markets

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Acknowledgements

• Dr Mkhulu MATHE (EM Manager)

• Dr Kenneth OZOEMENA (EET research group leader)

• EET research group

** Students/interns/in-service-trainees

Finances: CSIR DST NRF

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Shaping a better future through science

Thank you