Solid Acid Electrolytes - ARPA-E

42 Pages·2013·1.63 MB·English

by  Dane A. Boysen

@2013 SAFCell, Inc.
@2013 SAFCell, Inc. 1
Solid Acid Fuel Cells:
Overview and Opportunities
ARPA-E Workshop June 7th 2013
Chicago, IL
Contents
Solid Acid Electrolytes

Cesium Dihydrogen Phosphate

Solid Acid Fuel Cells

SAFC Fuel Flexibility

Cost Reduction Opportunities

Summary


@2013 SAFCell, Inc. 3
Solid Acid Electrolytes
Solid Acid Electrolytes
Intermediate salts and acids

Solid Acid Conductivity
1Cs PO + 2H PO  3CsH PO

3 4 3 4 2 4

General Formula: M H (XO )

x y 4 z 1 Polymer (Nafion)

M = Cs, Rb, K, NH , Tl
4
X = S, Se, P, As m) superprotonic
c
 0.01
 Properties (Low Temperature) 1/
(

y
Slow proton conductor t
 vi
ti 1E-4 Solid Acid
c
 Brittle/Gas permeable u
d (CsH PO )

n 2 4
Water soluble o
 C
1E-6
Properties (High Temperature)

normal phase
transition
Fast proton conductor

1E-8
solid state 50 100 150 200 250 300


Plastic-like/Gas impermeable Temperature (C)


Water (steam) insoluble


Haile, Nature, 2001; Boysen, Science, 2004
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“Superprotonic” Solid Acids
Structural solid-solid phase transition (order-disorder)

Heat  100 -1000 fold increase in proton conductivity

Superprotonic (σ ~ 10-2 Ω-1cm-1)

 Ox y-anions “freely” ro tate

Ordered Disordered
Normal Structure Superprotonic
heat
Cs+
H+
SO –2
4
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Proton Transport Mechanism
Grotthus Mechanism
1. Oxy-anion Reorientation
H
1012 Hz
S
O
2. Proton Transfer
109 Hz
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Cesium Dihydrogen Phosphate
Cesium Dihydrogen Phosphate
What about other solid acids?
Proton Conductivity Thermal Gravimetric Analysis
in Hydrogen
Temper ature (C)

250 200 150 100 50
-1
100
CsHSO Cs SO
4 2 4
-2 superprotonic Cs (HSO )(HPO )
2 4 2 4
98
-1m) -3 t%) Rb H(SeO(N)H4)3H(SeO4)2
w
c 96 3 4 2 CsHSO
-1 -4 (NH) H(SO) s ( 4
 4 3 4 2 s
/ a
 M 94
-5 CsHSeO
g CsHPO 4
o 2 4
l Cs (HSO)(HPO) 92
-6 2 4 2 4
Rb H(SeO )
3 4 2
90 (NH) H(SO)
-7 4 3 4 2
2.0 2.5 3.0 3.5 0 2 4 6 8 10 12
1000/T (K-1 ) Time (hours)
SSuullffaatteess aanndd sseelleennaatteess aarree nnoott ssttaabbllee iinn hhyyddrrooggeenn
oonnllyy pphhoosspphhaatteess aanndd aarrsseennaatteess uussaabbllee iinn ffuueell cceellllss
Merle, Energy & Fuels, 2003
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Cesium Dihydrogen Phosphate
Thermodynamic stability
H Atmosp here O Atmo sphere
2 2
w DSC 285C DSC 285C
No evolution of Heat flo endo 5C min-1 238C endo 5C min-1 238C
phosphate %)100 100
species from (wt 98 TG/DTG 223C -6.3 wt% 98 TG/DTG 223C -6.3 wt%
CsH PO (Pt) in ass 9946 9946
M
2 4 92 285C 92 285C
either hydrogen Mass Spec Mass Spec
10-8 10-8
and oxygen Ar
10-9 H 10-9
atmospheres A) 2 Ar
m
nt (10-10 285C 10-10 O2
e H O
urr10-11 2 10-11 285C
c
n O P
o 2
I10-12 10-12 H O
P/P /PO /P H PH2 /P /P H /PO
10-13 PO/2PH32 2 4 10-13 H2/3PO2 2 4 2
100 150 200 250 300 350 400 100 150 200 250 300 350 400
T (C) T (C)

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