Fuel cell electrodes: Electrochemical characterization and electrodeposition of Pt nanoparticles

(1)

Fuel Cell Electrodes: Electrochemical Characterization and Electrodeposition of Pt nanoparticles

Dr. Mmalewane Modibedi

Energy and Processes

CSIR

(2)

• Introduction

• Types of Fuel Cells

• Polymer Membrane Fuel Cell

• Electrochemical Characterization

• Future Work

Outline

(3)

What is a fuel cell?

• Device that uses a chemical fuel such as hydrogen (or hydrogen-rich fuel) and an oxidant, e.g., oxygen to generate electricity directly from electrochemical processes

• The by-products from an operating fuel cell are heat and water

(4)

• Alkaline Fuel Cell (AFC)

Electrolyte: alkaline potassium hydroxide

• Molten Carbonate Fuel Cell (MCFC)

Electrolyte: carbonate-salt-impregnated ceramic matrix

• Solid Oxide Fuel Cell (SOFC)

Electrolyte: hard, non-porous ceramic compound

• Phosphoric Acid Fuel Cell (PAFC) Electrolyte: liquid phosphoric acid

• Polymer Electrolyte Membrane Fuel Cell (PEMFC) Electrolyte: solid polymer membrane (typically Nafion)

Types of fuel cells (FC)

(5)

PEMFC

http://fuelcellsworks.com/

(6)

Electrodes

Anode Reactions: 2H

₂

=> 4H

⁺

+ 4e

^-

Cathode Reactions: O

₂

+ 4H

⁺

+ 4e

^-

=> 2 H

₂

O

(7)

Current collector plate with gas channels Catalyst layer on carbon particles (working electrode)

Nafion membrane (electrolyte)

Catalyst layer on carbon particles (ref. electrode) Current collector plate with gas channels

N₂(g)

H₂(g)

i

POTENTIOSTAT

Current collector plate with gas channels Catalyst layer on carbon particles (working electrode)

Current collector plate with gas channels Catalyst layer on carbon particles (working electrode)

Current collector plate with gas channels Catalyst layer on carbon particles (working electrode)

N₂(g) N₂(g)

H₂(g) H₂(g)

i

POTENTIOSTAT

ii

POTENTIOSTATPOTENTIOSTAT

• In situ cyclic voltammetry: Active electrochemical area, Pt utilization

Electrochemical Characterization

(8)

-0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Potential (V)

Current (A)

Pt/C

H_ad H⁺ + e^- double layer

Pt Pt oxides

Pt Pt oxides

H_ad H⁺ + e^-

PtRu/C

-0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05 0.06

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Potential (V)

Current (A)

(9)

• Catalyst preparation and MEA fabrication:

Electrodeposition methods Electrochemical Atomic Layer Epitaxy (EC-ALE)

• Characterization:

Cyclic voltammetry

Impedance spectroscopy CO stripping

Future work

(10)

Electrodeposition of Pt-based nanoparticles

Potentiostat / Galvanostat

Substrate (Working Electrode)

Pt

²⁺

X

^n-

Mn+ Y

^m-

Counter Electrode

Reference Electrode

(11)

Pump

Pump Pump Pump

Interface Card

Relay Board/

Power Supply Compute

r Precursor/

Rinse Solutions Distribution

Valve Block

Potentiostat

Reference Electrode

Substrate

(deposit Pt-M nanolayers)

Gasket Counter Electrode

Deposition cell

EC-ALE Reactor

Pt

²⁺

solution

Blank solution for Pt

²⁺

M

ⁿ⁺

solution

Blank

solution

for M

ⁿ⁺

(12)

Thank you