Figure 5. LSV curves (A) for CoOOH/Ni flow-through electrode
with a pore size of 75 PPI under different flux. Decreases in potential
under different current densities (B) and different flux (C)
compared with that of HER.
Increases in current density (D) at different current densities compared
with that of HER. Durability of HER and OER process.
A novel electrolyzer assembled with flow-through electrode for AWE under
high current density was also conducted with the results illustrated in
Figure 6A and Figure S24. The AWE process was assessed at 6 M KOH, 338
K, and 1 atm, and the cell voltage is limited to 3 V to prevent
excessive oxidation of the Ti current collector. The electrolyte was
flowed through the electrode pores and recirculated in the corresponding
compartment of the cell by peristaltic pumps. As can be seen in Figure
6B, the cell voltage can be decreased as the electrolyte flux rises from
22.5 m3 m-2 h-1 to
195 m3 m-2 h-1,
which can be attributed to the rapid detachment of generated
H2/O2 bubbles reducing the bubble
induced overpotential. The degree of cell voltage reduction becomes
larger with the increasing current density under the condition of
electrolytes flowing through electrode pores. For Ni foam immobilized
nanosheet-shaped Co-based catalysts, the cell voltage can be reduced
from 2.92 V to 2.78 V at 1000 mA cm-2 (Table S3), and
the corresponding consumption can be reduced by approximately 0.55 kWh
Nm-3. Compared with the electrolyzer by introducing
other external fields, the cell voltage of flow-through electrolyzer is
lower (Figure 6C). In addition, it is worth to notice that
the energy consumption of 5 kWh
Nm-3 can be achieved at 400 mA cm-2at 6 M KOH, 338 K, and 1 atm
(Figure S25), without any noble metals (Pt, Ir, Ru) added as well as any
complicated catalyst (high entropy alloys, single-atom catalysts)
preparation processes. The energy required for AWE could be reduced more
in this novel electrolyzer assembled with flow-through electrode, if AWE
is conducted under the real industrial conditions with higher pressure
and higher temperature, or immobilized state-of-the-art catalysts with
better catalytic activityon flow-through electrodes.