orbit.dtu.dk

orbit.dtu.dk

Development of novel High Temperature and
Pressure Alkaline Electrolysis Cells (HTP-AEC)
Jens Q Adolphsen ([email protected]); Vanesa Gil, Bhaskar R. Sudireddy and Christodoulos
Chatzichristodoulou ([email protected])
Introduction
The cell concept
Background

A HTP-AEC with gas diffusion electrodes (metal foams) and an aqueous KOH
electrolyte immobilized in a mesoporous ceramic matrix structure has been
developed at DTU Energy.

Very high current density and performance has been demonstrated with shirt
Record sized
data from
earlier
button
cells:

Mesoporous
electrolyte matrix

work [1]:

3.75 A/cm2 at 1.75 V with
el = 85 % (200C, 20 bar)
[1]
[1]
[1
]

Motivation

High temperatures (200C) increase the activity of the electrodes and the
conductivity of the electrolyte significantly.

A cell that allows for high efficiency and current density simultaneously using
non-noble metals.

The mesoporous electrolyte matrix contains the KOH electrolyte. The porous
electrodes will allow some infiltration of the electrolyte into the electrode to
increase the surface area where the electrochemical reactions take place.

Results - Electrochemical activity towards the OER

Challenges
Corrosion issues at the oxygen electrode. Identification of more stable materials,
which
also show sufficiently high catalytic activity towards the oxygen evolution
The
experiments
reaction.

Electrode
materials
for the
oxygen
electrode
Processing
of cell layers
with
optimized
microstructure using a low cost &
scalable processing
method. methods.based on La, Ni and Fe for the oxygen
Electrode
materials (electrocatalysts)

evolution reaction (OER) have been identified and evaluated.

The electrochemical activity of the materials has been tested at room
temperature and pressure conditions in N 2 atmosphere using densely sintered
pellets polished down to 1 m roughness.
The chemical stability of the powder , immersed in 45 wt% KOH, and heated in
an autoclave to 220C has been examined comparing XRD patterns before and
after.

Three-electrode setup for
Working
Counter
electrochemical characterization

electrode
(pressed bars,
Au current
collector)Separa
tor

electrode (Pt
mesh)

The iR-corrected chronopotentiostatic measurements of LaNi 0.6Fe0.4 O3 and the
Nyquist plot of the EIS measurements performed after each chronopotentiostatic
measurement. Current densities are based on geometric surface areas.

Chemical stability assessment

Reference
electrode (RHE
from Gaskatel)

Results chemical stability
7

LaNi0.6Fe0.4O3 pellet surface
before and after ~20 h
electrochemical
Initial polished surface testing.

Comparisson of the 2nd set of
chronopotentiostatic tests performed at
10 mA/cm2. LaNiO3 could not be
sintered dense without decomposition
so
it is
a multiphase
of mainly Material
LaNiO3,
The
calculated
Tafel
NiO
and La2NiO4(E = a
fit parameters
LaNiO3

Polished surface after electrochemical
testing

XRD patterns of the as-received LaNiO3
powder and the same powder after exposure
to 45 wt% KOH at 220 C for 1 week. The
symbols represent the following phases:
LaNiO3, LaO(OH), NiO(OH), + La2O3, *
NiO. The LaNi0.6Fe0.4O3 and La2Ni0.9Fe0.1O4
powder showed similar decomposition
ICP
analysis
of supernatants
behaviour
though
at a slowerfrom
rate.the KOH
solution used for the chemical stability
testing. If any dissolution is happening the
ions seem to be consumed by the
decomposed products.
DTU Energy, Technical University of Denmark
Department of Energy Conversion and Storage
Ris Campus
Frederiksborgvej 399, 4000 Roskilde

The tafel plot of the measurements.
The fit is from 0.5 10 mA/cm2. There
is a slight increase in the tafel slope
above 2 mA/cm2 which is then not
accounted for.
(V) @
2
b (V/dec)

a

R

0.083

0.30

0.97

0.38

0.34

0.97

0.44

0.31

0.95

0.44

0.33

0.97

0.45

0.32

0.98

0.40

-

-

0.32

-

-

0.34

-

-

~0.38

+b log[i]) from the
La0.97NiO3
0.092
tafel plot together
LaNi0.6Fe0.4O3
0.13
with the
LaNi0.6Fe0.4O3
0.11
overpotential, , at 10
mA/cm2. The state-ofLa2Ni0.9Fe0.1O4
0.079
the-art, IrOx, and two
IrOx [2]
of the best
Ni0.9Fe0.1Ox [3]
0.030
performing nonPrBaCo2O5+x [4]
~0.07
noble oxygen
evolution catalysts
Outlook
are also included as
benchmarking.
Processing
of porous oxygen electrodes

10 mA/cm2

Based on the electrochemical screening LaNi0.6Fe0.4O3 is going to be used as
oxygen evolution electrocatalyst. The microstructure of the oxygen electrode is
going to be optimized using the processing method screen printing. An
electrode with a bimodal porosity distribution is envisioned to allow for
electrolyte infiltration (~10-100 m pore sizes) and gas diffusion (2-10 m pore
sizes) of evolved oxygen.
Successful fabrication and electrochemical characterization of upscaled cells (5 x 5 cm2) with the microstructurally optimized oxygen
References
electrode
is the expected outcome of the project.
[1] C. Chatzichristodoulou, F. Allebrod, M. B. Mogensen, J. Electrochem. Soc., 163 (1) (F3036-F3040), 2016
[2] C. C. L. McCrory, S. Jung, J. C. Peters, T. F. Jaramilllo, J. Am. Chem. Soc. 135 (16977-16987), 2013
[3] L. Trotochaud, J. K. Ranney, K. N. Williams, S. W. Boettcher, J. Am. Chem Soc. 134 (17253-17261), 2012
[4] A. Grimaud, K. J. May, C. E. Carlton, Y-L. Lee, M. Risch, W. T. Hong, J. Zhou, Y. Shao-Horn, Nat. Commun. 4 (2439-2445), 2013

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