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.