VTT TECHNICAL RESEARCH CENTRE OF FINLAND LTD

Inkjet printable anode ink for fuel cell applications

Printing for Fabrication 2016, the 32nd International Conference on Digital Printing Technologies (NIP)12.-16.9.2016Liisa Hakola, Tiina Maaninen*, Saara Tuurala, Anu Vaari; VTT Technical Research Centre of Finland; Espoo / Oulu*, Finland

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Symbiotic projecthttp://symbiotic-project.eu/

Funding from the EU’s Horizon 2020 programme, 2015-2018 (Grant Agreement No 665046) Aims to develop an autonomous electrochemical biosensor that

is lightweight, disposable and low cost by using innovative approach: hosting its bioreceptor element inside a passive direct methanol fuel cell (DMFC). The electrical signal directly related to the concentration of

the cancer biomarker in the sample analyzed.

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Passive Direct Methanol Fuel Cells (DMFC)

Stand-alone power source for portable applications Proton-exchange fuel cell, methanol as the fuel Printing methods enable flexible structure, tailored performance

and cost-effective manufacturing process Inkjet printing potential for making the electrodes

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Objective

Formulation and printability of an inkjet printable anode inkfor application as part of MEA (Membrane ElectrodeAssembly) in a flexible passive DMFC device

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Materials

Functional components Catalyst: mixture of carbon black (C), Platinum (Pt,

27-31 wt-%) and Ruthenium (Ru, 14-16.5 wt-%) Selection of Nafion solution

Nafion 1: 10 wt-% Nafion in water (eq. wt. 1000) Nafion 2: 10 wt-% Nafion in water (eq. wt. 1100) Nafion 3: 5 wt-% Nafion in alcohols and water

Selection of solvent vehicle1. Water based: 1,2-propandiol + non-ionic surfactant2. Solvent based: diacetone alcohol

Substrates Nafion film, 183 µm thickness Carbon paper, 190 µm thickness Photographic paper, reference

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Selection of Nafion solution

FormulationWater : 1,2 propandiol = 2:1Surfactant 0.05 wt-%Nafion solution 10 wt-%

CharacterisationNafion 1: 5 cP / 47.3 mN/m, unstableNafion 2: 4.2 cP / 49.3 mN/mNafion 3: 6.2 cP / 37.6 mN/m

SelectionNafion 3 in alcohol & water vehicleSurface tension and viscosity close to optimal, stable

Optimal values:8-20 cP24-36 mN/m

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Ink formulation and characterisation

Water based inkWater : 1,2 propandiol = 2:1Surfactant 0.05 wt-%C-Pt/Ru 0.5 wt-%Nafion solution 10 wt-%

Solvent based inkDiacetone alcoholC-Pt/Ru 0.5 wt-%Nafion solution 10 wt-%

Sonication + magnetic stirring + filtering stable, homogenous ink

Ink Surface tension ViscosityWater based 37.5 mN/m 4.5 cP

Solvent based 30 mN/m 5 cP

Target values:8-20 cP24-36 mN/m

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Inkjet printing

Nafion film Carbon paper

Nafion film Carbon paper

Water based ink

Solvent based inkFujifilm Dimatix DMP-2831• 10 pl drop size• 1270 dpi• 1, 2, 3 and 5 ink layers

PiXDRO LP50With Fujifilm Dimatix SE-128 printhead30 pl drop size500 dpi1, 2, 3 ink layers

Water based ink, 3 layers

Upscaling:

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Electronic performance

Water based ink Layer resistance

Photographic paper, 3 layers, 35.5 Ω Nafion film, no conductivity (wrinkling)

Sheet resistance Carbon paper, 5 layers, 3.59 Ω/sq

Solvent based ink Layer resistance

Photographic paper, 5 layers, 2.9 MΩ Nafion film, 5 layers, 0.8 MΩ

5324.42ln I

VIV

s

whereρs = sheet resistance (Ω/sq)V = voltage between the inner probes (V)I = current through the outer probes (A)Sample size = 4S

Sheet resistance measurement

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Discussion

Water based ink and Nafion film compatibility Surfactant might interfere with the electrochemical performance

Solvent based ink preferred

Poor electrical performance with solvent based ink

Improvement in ink formulation

Recent results show improvement of 800 kΩ 78 kΩ with Nafionfilm resulting in sufficient electrochemical performance

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SEM images of solvent based inkNafion film Carbon paper

5 la

yers

10 la

yers

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Conclusions

Water based and solvent based inks formulated to be used for fabrication of MEAs for passive DMFC

Stability and inkjet printability achieved

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Acknowledgements

EU for funding the research work

Symbiotic project partners for collaboration

Pirjo Hakkarainen, Senior Research Technician at VTT, for dedicated laboratory work

TECHNOLOGY FOR BUSINESS

Liisa HakolaSenior Scientist, M.Sc. (Tech.)VTT TECHNICAL RESEARCH CENTRE OF FINLANDSensing and integration (research area)Printed sensors and electronic devices (research team)www.vtt.fi, liisa.hakola@vtt.fi