Frontiers Science Program Long-Term Fellowship (A.C.); a
Washington Research Foundation Senior Fellowship (A.C.); Howard
Hughes Medical Institute research (A.C.); Howard Hughes Medical
Institute Hanna Gray fellowship grant GT11817 (N.B.). An S10
award (S10OD032290 to D.B., D.V., J.K., and J.Q.) funded the
purchase of a Glacios microscope. SAXS data were collected
at the Advanced Light Source (ALS) SIBYLS beamline on behalf
of US DOE-BER, through the Integrated Diffraction Analysis
Technologies (IDAT) program. Additional support comes from
the NIGMS project ALS-ENABLE (P30 GM124169) and a High-End
Instrumentation Grant (S10OD018483). The Berkeley Center for
Structural Biology is supported in part by the National Institutes
of Health (NIH), National Institute of General Medical Sciences,
and the Howard Hughes Medical Institute. This research used
resources of the ALS, a US DOE Office of Science User Facility under
contract DE-AC02-05CH11231. Some of this work was performed
at the Pacific Northwest Center for Cryo-EM (PNCC), which
was supported by NIH grant U24GM129547 and performed at
the PNCC at Oregon Health & Science University and accessed
through EMSL (grid.436923.9), a DOE Office of Science User
Facility sponsored by the Office of Biological and Environmental
Research. Molecular graphics and analyses were performed with
UCSF Chimera, developed by the Resource for Biocomputing,
Visualization, and Informatics at the University of California,
San Francisco, with support from NIH P41-GM103311.Author
contributions:Conceptualization: A.C. and D.B. Methodology:
A.C., D.B., J.H., and J.K. Software: A.C., Y.H., C.X., S.E.B.,
G.U., U.N., P.B., D.B., D.S., A.M., N.K., W.S., and N.B. Validation:
A.C., D.B., J.H., J.K., and Y.H. Formal analysis: A.C., J.H., and
N.B. Investigation: A.C., J.H., N.B., Y.-J.P., A.N., D.N., and J.Q.
Resources: A.C., D.B., J.H., J.K., and J.Q. Data curation: A.C.,
J.H., and Y.H. Writing–original draft: A.C. Writing–review &
editing: A.C., D.B., J.H., Y.H., and J.K. Visualization: A.C., J.H.,
and N.B. Supervision: D.B. and J.K. Project administration:
A.C. and D.B. Funding acquisition: D.B., J.K., D.V., A.C., and
Y.H.Competing interests:A.C., D.B., J.H., J.K., N.B., and
Y.H. are inventors on a provisional patent application submitted
by the University of Washington for the design, composition,
and function of the proteins created in this study.Data and
materials availability:All data are available in the main text orthe supplementary materials. All the EM maps have been
deposited in the Electron Microscopy Data Bank (accession
codes EMD-25575, EMD-25576, EMD-25577, EMD-25578, EMD-25579,
and EMD-25580). All code is available from GitHub (https://github.
com/alexiscourbet/) and is archived on Zenodo ( 34 ).SUPPLEMENTARY MATERIALS
science.org/doi/10.1126/science.abm1183
Materials and Methods
Figs. S1 to S22
Tables S1 to S3
References ( 35 – 59 )
Movies S1 to S5
Data S1 to S5
MDAR Reproducibility Checklist26 August 2021; accepted 21 March 2022
10.1126/science.abm1183REPORTS
◥CATALYSIS
Single-step hydrogen production from NH 3 , CH 4 ,
and biogas in stacked proton ceramic reactors
Daniel Clark^1 , Harald Malerød-Fjeld^1 , Michael Budd^1 , Irene Yuste-Tirados1,2, Dustin Beeaff^1 ,
Simen Aamodt^1 , Kevin Nguyen^1 , Luca Ansaloni^3 , Thijs Peters^3 , Per K. Vestre^1 , Dimitrios K. Pappas^1 ,
María I. Valls^4 , Sonia Remiro-Buenamañana^4 , Truls Norby^2 , Tor S. Bjørheim^1 ,
Jose M. Serra^4 , Christian Kjølseth^1
Proton ceramic reactors offer efficient extraction of hydrogen from ammonia, methane, and biogas
by coupling endothermic reforming reactions with heat from electrochemical gas separation and
compression. Preserving this efficiency in scale-up from cell to stack level poses challenges to
the distribution of heat and gas flows and electric current throughout a robust functional
design. Here, we demonstrate a 36-cell well-balanced reactor stack enabled by a new interconnect
that achieves complete conversion of methane with more than 99% recovery to pressurized
hydrogen, leaving a concentrated stream of carbon dioxide. Comparable cell performance was also
achieved with ammonia, and the operation was confirmed at pressures exceeding 140 bars. The
stacking of proton ceramic reactors into practical thermo-electrochemical devices demonstrates
their potential in efficient hydrogen production.
H
ydrogen can be produced from CH 4 -rich
streams through steam reforming and
water-gas shift (SMR+WGS, CH 4 + 2H 2 O=
CO 2 + 4H 2 ,DrxnH° = 164.7 kJ/mol) or
from the emerging C-free H-carrier NH 3
through ammonia dehydrogenation (ADH,
NH 3 =1/2N 2 + 3/2H 2 ,DrxnH° = 45.9 kJ/mol)
( 1 – 3 ). In a conventional multistage H 2 produc-
tion process, fuel combustion generates the
heat for these endothermic reactions, and sub-
sequent separation and compression occur
downstream by pressure-swing adsorption
and mechanical compressors. Efficiencies typ-
ically improve with scale, which favors large,
centralized processes over distributed H 2 pro-
duction for energy-carrier applications ( 4 ).
H 2 can also be separated and compressed
electrochemically with proton (H+)–conducting
ceramic membranes such as Y-doped BaZrO 3 -
BaCeO 3 solid solutions (BZCY), which are
functional and stable over a wide range of
temperatures (300° to 800°C) and chemical
environments ( 5 – 10 ). Proton ceramic electro-
chemical reactors (PCERs) extract pure H 2
from gas mixtures by electrolytically pumping
protons across the membrane (Fig. 1A). These
offer process intensification ( 9 ) by integrating
reactions such as SMR+WGS or ADH with H 2
separation and compression, high energy ef-
ficiencies by supplying heat electrically ( 3 ),
and reduced CO 2 emissions when that elec-
tricity is renewable ( 11 ).As for any compression process, the work
associated with electrochemical H 2 compres-
sion is minimized by operating isothermally
( 12 ). In a continuous-flow type of PCER, the
compression ratio and associated entropy dif-
ference of H 2 across the membrane increase
with the extent of separation along the reactor
(Fig. 1B and fig. S1). This entropy difference is
expelled as heat (Q=TDS) during the com-
pression process, which, if left unbalanced,
leads to gradually increasing temperature along
the reactor and in turn larger electric energy
consumption per kilogram of compressed H 2
(Fig. 1B).
More efficient isothermal operation can be
achieved by locally balancing this heat evolu-
tion with a reversible heat sink such as an
endothermic chemical reaction (Fig. 1C) ( 9 ).
However, matching the spatial distribution of
heat from compression with the extent of
chemical reactions throughout a stacked re-
actor poses one of the main hurdles in scaling
PCERs from laboratory to commercial scale.
Furthermore, scaled reactors with efficient
current distribution have been hindered by
the lack of interconnect materials with high
electrical conductivity and chemical stability
up to 800°C that match the low thermal ex-
pansion coefficient (8 × 10−^6 K−^1 )ofthepre-
ferred proton conductor BZCY. Mismatches in
thermal expansion of reactor components can
lead to mechanical stresses and electrical con-
tact failures during thermal cycling.
We present an optimized reactor architec-
ture aided by multiphysics simulations and a
new expansion-matched metal/glass-ceramic
composite interconnect (IC) enabling deploy-
able modular PCER stacks that retain the en-
ergy efficiencies and H 2 recoveries of single
cells ( 9 ) while achieving a 36-fold increased
H 2 production capacity. The reactor is designed
with gas flows that allow internal heat ex-
change from exothermic to endothermic pro-
cesses to minimize auxiliary heat input.
Our PCER can separate H 2 by decompres-
sion while recovering electric energy or by390 22 APRIL 2022¥VOL 376 ISSUE 6591 science.orgSCIENCE
(^1) CoorsTek Membrane Sciences AS, 0349 Oslo, Norway.
(^2) Department of Chemistry, Centre for Materials Science and
Nanotechnology, University of Oslo, 0316 Oslo, Norway.
(^3) Department of Sustainable Energy Technology, SINTEF
Industry, 0314 Oslo, Norway.^4 Instituto de Tecnologia
Química, Consejo Superior de Investigaciones Científicas-
Universitat Politècnica de València, 46022 Valencia, Spain.
*Corresponding author. Email: [email protected] (J.M.S.);
[email protected] (C.K.)
RESEARCH