Flow-electrode capacitive deionization (FCDI) is a prospective
alternative for large-scale desalination applications due to the efficient
flowability of the electrode slurry. However, flow channel blockages
and slurry leakage in conventional FCDI cells have severely limited
the salt removal and stable operation. Based on the synergistic effects
of diverting and guiding flow, a hexagonal honeycomb-shaped flow channel
(HH-channel) was innovatively applied to the FCDI system to optimize
the hydrodynamic behavior of the slurry, which greatly reduced the
hydraulic pressure and enhanced the desalination performance. What
is more, we first introduced a Two-Phase Transport Mixture model and
combined it with computational fluid dynamics (CFD) simulations to
further confirm that more uniform distribution of carbon particles
in the HH-channel facilitates the construction of a charge percolation
network and charge transfer compared to a serpentine single-track
flow channel (SS-channel) and rectangular-cavity flow channel (RC-channel).
After a long-term operation test (1800 min, U = 1.6
V), the FCDI system with the HH-channel exhibited superior desalination
stability, with a faster average salt removal rate (ASRR) of 2.05
μmol cm–2 min–1 and salt
removal efficiency (SR) of 64.89% and charge efficiency (CE) of 96.06%.
In summary, our work developed a facile strategy for optimizing the
flow channel geometry to improve slurry flowability and obtain an
efficient and steady desalination application.