is highly competitive with Pd-based membrane
reformers (table S2). These key performance
indicators build the foundation for highly
energy-efficient hydrogen production at sys-
tem level.
System modeling ( 13 ) of a 1 ton/day dis-
tributed H 2 production plant adopting our
PCER stack (figs. S15 to S21) reveals that ef-
ficiencies of 91% for CH 4 and as high as 95%
for anhydrous NH 3 canbeachievedbyvirtue
of microthermal integration and downstream
heat recovery. Furthermore, the PCER delivers
a concentrated and pressurized stream of CO 2
when operated on methane or biogas (Fig. 4F)
that can be purified and liquefied by cryogenic
distillation, eliminating the need for complex
downstream absorption-based CO 2 capture.
The high degree of process intensification
achieved by our PCER stacks enables a fuel-
flexible energy-efficient alternative to established
technologies for distributed H 2 production.
Using a California 2020 electric grid carbon
intensity scenario (82.92 gCO2/MJelec; see table
S3 for references), H 2 production with PCERs
using CH 4 as fuel would operate at lower em-
issions (75.7 vs. 124.1 gCO2/MJH2) than water
electrolysis powered by grid electricity, even
without CO 2 sequestration. With decarboni-
zation of the electric grid, CO 2 sequestra-
tion is required for methane reforming to
remain competitive with water electrolysis. In
a California 2050 grid scenario, PCERs can pro-
duce H 2 from CH 4 with lower CO 2 -emissions
than water electrolysis (18.7 vs. 26.2 gCO2/MJH2)
when CO 2 is sequestrated. PCERs operated
on biogas even offer H 2 production with net-
negative carbon emission, as CH 4 from a bio-
genic process is considered carbon-neutral.
Calculated scenarios have used the CA GREET
model ( 15 ) which includes fugitive methane
emissions from natural gas production that
can be important ( 16 ).
To illustrate the practical implications of the
PCER technology, comparable well-to-wheel
emissions for battery electric vehicles (BEVs),
internal combustion engines (ICEs) with diesel
fuel, and H 2 fuel-cell electric vehicles (FCEVs)
are provided in figs. S22 and S23 with sensi-
tivity to electric grid carbon intensity. In the
California 2050 scenario, the emissions of
FCEVs (14.6 gCO2/km) using H 2 produced
from CH 4 with PCERs including CO 2 seques-
tration are 90% lower than those of ICE with
diesel fuel (145.4 gCO2/km) and 26% lower
than FCEVs using H 2 from grid-powered water
electrolysis (19.8 gCO2/km). NH 3 -based H 2 can
offer reduced emissions compared with on-
site electrolysis for a wide range of electric gridcarbon intensities, making FCEVs fueled with
NH 3 -based H 2 directly comparable to BEVs in
terms of CO 2 emissions (6.3 gCO2/km, a reduc-
tion of 21% compared with BEV in the California
2050 scenario). Here, NH 3 is assumed pro-
duced at off-site locations with favorable re-
newable energy resources and transported as
a liquid to the fueling station where efficient
ADH and separation to H 2 takes place using
the PCER technology.
The growth of a new energy technology can
be limited by access to raw materials. A de-
tailed examination of raw materials’usage of
the PCER stack (fig. S24) shows it is composed
of nonprecious, earth-abundant materials, sug-
gesting no material availability setbacks for
scaling.REFERENCES AND NOTES- R. F. Service,Science 345 , 610–610 (2014).
- I. Staffellet al.,Energy Environ. Sci. 12 , 463–491 (2019).
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157 – 169 (1983). - J. M. Serra,Nat. Energy 4 , 178–179 (2019).
- S. Choi, T. C. Davenport, S. M. Haile,Energy Environ. Sci. 12 ,
206 – 215 (2019). - C. Duanet al.,Nature 557 , 217–222 (2018).
- C. Duanet al.,Science 349 , 1321–1326 (2015).
- H. Malerød-Fjeldet al.,Nat. Energy 2 , 923–931 (2017).
- H. Anet al.,Nat. Energy 3 , 870–875 (2018).
- J. L. Barton,Science 368 , 1181–1182 (2020).
- B. L. Keeet al.,Membranes (Basel) 9 , 77 (2019).
- Materials and methods are available as supplementary
materials. - R. J. Braunet al.,ECS Trans. 91 , 997–1008 (2019).
- California Air Resources Board,“CA-GREET3.0 lookup table
pathways: Technical support documentation”(California Air
Resources Board, 2018); https://ww2.arb.ca.gov/sites/
default/files/classic//fuels/lcfs/ca-greet/lut-doc.pdf. - R. W. Howarth, M. Z. Jacobson,Energy Sci. Eng. 9 , 1676– 1687
(2021).
ACKNOWLEDGMENTS
Funding:This work was supported by Norway’s Ministry of
Petroleum and Energy through the Gassnova project CLIMIT grant
618191 in partnership with Engie SA, Equinor, ExxonMobil, Saudi
Aramco, Shell, and TotalEnergies and the Research Council of
Norway NANO2021 project DynaPro grant 296548.Author
contributions:Conceptualization: D.C., H.M.-F., T.P., P.K.V., T.S.B.,
J.M.S., C.K.; Investigation: D.C., H.M.-F., M.B., I.Y.-T., D.B., K.N.,
L.A., T.P., D.K.P., M.I.V., S.R.-B., T.S.B., C.K.; Methodology:
D.C., H.M.-F., M.B., I.Y.-T., S.A., L.A., T.P., P.K.V., D.K.P., S.R-.B.,
C.K.; Resources: M.B., D.B., K.N., M.I.V.; Software: I.Y.-T., S.A.;
Supervision: T.N., T.P., J.M.S., C.K.; Writing–original draft: D.C.,
H.M.-F., M.B., I.Y.-T., S.A., P.K.V., D.K.P., T.N., T.S.B., J.M.S.,
C.K.; Writing–review and editing: D.C., H.M.-F., M.B., I.Y.-T., T.S.B.,
D.B., S.A., L.A., T.P., P.K.V., D.K.P., S.R.-B., T.N., T.S.B., J.M.S.,
C.K.Competing interests:D.C., H.M.-F., M.B., I.Y.-T., D.B., S.A.,
K.N., D.K.P., T.S.B., and C.K. are employed by CoorsTek Membrane
Sciences (CTMS). CTMS has filed relevant patent application
PCT/EP2017/076340. T.N. is a member of the CTMS board.
I.Y.-T.’s doctoral studies at the University of Oslo (UiO) are partially
funded by CTMS. The remaining authors declare no competing
interests.Data and materials availability:All data are available in
the main text or the supplementary materials. Experimental data
are available online at http://hdl.handle.net/10251/181917.SUPPLEMENTARY MATERIALS
science.org/doi/10.1126/science.abj3951
Materials and Methods
Figs. S1 to S30
Tables S1 to S7
References ( 17 Ð 50 )
16 June 2021; resubmitted 28 October 2021
Accepted 10 February 2022
10.1126/science.abj3951SCIENCEscience.org 22 APRIL 2022•VOL 376 ISSUE 6591 393
Fig. 4. PCER single-cell and stack performance.(A) NH 3 conversion as a function of H 2 recovery,
measured on a representative single cell (fig. S3) at 650°C and 10 bars (pNH 3 = 7.25 bars;pH 2 O = 2.75 bars),
and aqueous NH 3 at 750°C and 10 bars (pNH 3 = 3.1 bars;pH 2 O = 5.8 bars; andpinert= 1.1 bars). Purple
and green lines show the equilibrium conversion for NH 3 and aqueous NH 3 , respectively. (B) and (C) CH 4
conversion and yield of CO 2 versus H 2 recovery, respectively, of PCER stack at 750°C. (D)H 2 production
rate as a function of applied current density for the stack with N 2 /H 2 mixture simulating complete NH 3
decomposition (750°C, 10 bars), methane (800°C, 15 bars, S/C = 2.5), and biogas (750°C, 20 bars,
S/C = 2.5). Effective current is calculated as current density × PCER stack area (36 × 15 cm^2 ) and applied
current as effective current/6 due to the series and parallel electric architecture. (EandF)H 2 purity
(dry basis) versus H 2 delivery pressure and differential pressure across the membranes (E) and CO 2 purity
versus H 2 recovery (F) for SMR+WGS in the stack at 750°C. Reforming side pressure = 25 bars, H 2 side
pressure = 25 to 31 bars. Current density = 0.69 A/cm^2.
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