reflecting the catalytic versatility of the porous
Ni-BZCY support. With CH 4 , the single cells
even achieved >90% faradaic efficiency up to
7.4 A/cm^2 (corresponding to a H 2 flux of 47
normal milliliters-per-minute square centi-
meter) (fig. S12) thus doubling the H 2 produc-
tion capacity to-date with these materials ( 9 ).
The 36-cell PCER stack achieves nearly full
CH 4 conversion and high H 2 recoveries (>99%;
Fig.4andfigs.S13andS14)forCH 4 and biogas,
enabling complete equilibrium shift and a CO 2
rich effluent stream for facile carbon capture.
The series and parallel design of the stack fa-
cilitates an effective aggregated current of up
to 400 A (i> 0.73 A/cm^2 )withaH 2 production
rate up to 0.34 kg/day from CH 4 ,0.31kg/day
from biogas, and 0.34 kg/day from simulated
fully decomposed NH 3 streams (Fig. 4D). We
furthermore demonstrate H 2 compression to
31 bar with a purity of 99.995% (Fig. 4E) facili-
tated for additional compression and use. The
PCER stack shows promising stability, retaining
aH 2 production rate of 2 normal liters per
minute after 1400 hours of operation (fig. S14B).
Both the H 2 production rate [0.34 versus
0.025 kg/day ( 9 )] and active area [584 versus
81 cm^2 ( 14 )] greatly surpass those of any re-
ported for proton ceramic applications. More-
over, the PCER stacks have demonstrated that
it is possible to deliver high-pressure H 2 at high
purity and a CO 2 rich effluent at a hydrogen
recovery and methane conversion >99%, which392 22 APRIL 2022¥VOL 376 ISSUE 6591 science.orgSCIENCE
Fig. 2. PCER stack for electrochemical H 2 production.(A) PCER stack (dimensions: height 43 cm,
diameter 4 cm). (B) Schematic of microthermal heat integration with outward heat flux from the cells.
(C) Schematic of U-bend type of gas flow of the generic molecule AHxreacting to form H 2 , which is
electrochemically extracted as H+through the membrane and recovered as compressed H 2 in the outer
chamber. (D) Thermal expansion upon cooling of the BZCY/Ni support and the IC, and IC electrical
conductivity as a function of temperature. (E) Scanning electron micrograph cross section of the interface
between the BZCY/Ni support and IC, connected by a conductive glass-ceramic washer. (F) Schematics
of IC and washer assembly.
Fig. 3. Multiphysics simulations of PCER stack
thermally balanced operation.Multiphysics
simulations for a stack operating at 750°C external
temperature with 20 bars of total pressure on
both sides of the membrane and a mean
current density of 0.60 A/cm^2. Feed: 28.6%
CH 4 (0.597 NL/min), 71.4% H 2 O. Sweep: H 2 O
(0.18 g/min). (A) Simulated temperature fields in
a U-bend PCER stack architecture, also showing
the gas inlet and outlet flow distribution. (B) Simulated
temperature fields in an axial PCER stack architecture.
(C) Temperature profiles on the reforming side in
the axial and U-bend architecture along the reactor
length. The thermal balancing by heat transfer
between first cell (net endothermic) and last cell
(net exothermic) for U-bend PCER is illustrated by
vertical arrows. (D) Mean compression work and
Nernst voltage for each segment along the reactor
length for the U-bend and axial PCERs. The values
were obtained by integrating the compression work
over each segment divided by the corresponding total
flux or current. (E) Effect of H 2 recovery on the
temperature distribution in U-bend and axial PCERs.
(F) Effect of H 2 recovery on the mean stack
compression work and Nernst voltage for U-bend
and axial PCERs.
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