Design and Synthesis of Thin Palladium Membranes for Hydrogen Separation

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Design and Synthesis of Thin Palladium Membranes
for Hydrogen Separation

• Z. Shi, J.A. Szpunar, S. Wu

Department of Materials Engineering, McGill
University, Canada AH2T Inc. Montreal, Canada
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Outline

• Introduction
• Experiments
• Results and Discussion
• Formation of a palladium membranes
• Design of an ultra-thin membrane
• Conclusions

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Introduction

• Hydrogen is a clean fuel hydrogen economy
• Pd nanoparticles can be used for
  hydrogen-generated catalysts.
• Pd membranes can be used for high quality
  hydrogen extraction from the mixture of gases.

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Experiment Electroless deposition
2Pd(NH3)42 N2H4 4OH-1 ? 2Pd 8NH3 N2
4H2O
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Porous metal substrates

• 0.2 µm grade porous stainless steel (316)
• Pore size at the surface 0.210 µm

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Results and Discussion

• Formation of Pd membrane
• Control of Pd membrane thickness
• Test of hydrogen selectivity and permeability

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Formation of Pd membrane
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Cross section of Pd membraneThickness 3 4 ?m,
the concentration of PdCl2 4.2 g/l
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Effect of CPdCl2 on Pd nanoparticle size
(a) 3050 nm, CPdCl24.2 g/l (b) 5070 nm,
CPdCl23.0 g/l T150 s
(c)70100nm, CPdCl22.4g/l (d)100130nm,
CPdCl21.82.0g/lT150s
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Effect of deposition time on Pd deposits
(a) 30 s
(b) 60 s
(c) 75 s
(d) 150 s
CPdCl24.2 g/l
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Control of Pd membrane thickness
(a,b) Size of Pd nanoparticles 100130 nm,
T150 s CPdCl21.82.0 g/l
(c, d) Size of Pd nanoparticles 70100nm, T150
s, CPdCl2 2.4 g/l
One nano-particle monolayer Pd membrane
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Design of an ultra-thin Pd membrane

Assuming that membrane thickness is 200 nm, the
number of layers vs. the size of Pd nanoparticles

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Porous surface of the steel substrate is modified
using Ni nano-particles
(c) Surface microstructure after the modified
substrate sintered at 600oC for 2 hrs
(a, b) Surface microstructures of porous
substrate modified using Ni nanoparticles
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Fabrication of an ultra-thin membrane

• Surface microstructure (b) Cross section

(c, d) Cross-section thickness 300400 nm,
CPdCl2 1.82.0 g/l
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Experimental apparatus (a) of gas permeation
system
Permeation cell
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Hydrogen selectivity
8 Pd membrane samples Membrane thickness 24µm,
?P 50 psi (3.5x105 Pa), T 300oC 550oC

• 5 samples, with a gas mixture of H2 and N2

• 3 samples, with a gas mixture of H2, N2 and CO

Results i. Neither N2 nor (N2 and CO) are
detected in permeated side ii. Only hydrogen can
pass them
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Ultra-thin Pd membrane used for hydrogen
permeation
Hydrogen flux vs. temperature (at 50 psi)
Hydrogen flux vs. pressure (at 500 oC)
Membrane thickness 300 400 nm
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Hydrogen permeability
Hydrogen flux is inverse proportion to the
thickness of Pd membranes that are deposited on
0.2 µm grade porous steel substrate (data from
over 100 samples having different thickness)
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Conclusions

• Pd membrane is made of nanoparticles. The
  particle size can be controlled by the
  concentrations of PdCl2.
• A bridge model is presented to describe the
  membrane formation on the pore area.
• An ultra-thin Pd membrane can be designed and
  built using the electroless process after porous
  substrate surface is modified.
• Pd membranes built in this program have very good
  hydrogen selectivity and permeability.

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Thank you!