Figure 1. Illustration of the preparation of Co-based flow-through electrodes (A). The morphology of the pore surface of Ni foam (B), raw CoB/Ni flow-through electrode (C), and CoB/Ni flow-through electrode after HER activation (D) and OER activation (E).
2.3. Electrochemical measurements
Electrochemical measurements were performed in a custom two-compartment H-cell with cathode and anode compartments separated using an anion exchange membrane (AEM, Fumasep FAA-3-50) using a CHI 660E electrochemical workstation. A three-electrode configuration was employed with CoB/Ni flow-through electrode as the working electrode, Ti mesh coating with Pt as the counter electrode, and a Hg/HgO reference electrode, as shown in figure S1. Among those, the CoB/Ti membrane electrode was put in a self-made module with a module made of PTFE, a Ti ring as a current collector, and a silicone seal. The electrolyte flow rate was controlled by a peristaltic pump and recirculated in the corresponding compartment of the cell. We calculated the current density by electrode area (0.785 cm2, based on the seal’s inner diameter). All measurements were performed at room temperature. The electrolyte (1 M KOH) was purged with dry N2 15 minutes before. All reported potentials were calibrated by an RHE based on the following equation:
The volume of H2 and O2 generated from cathode and anode cells was collected by the Drainage method. Before the hydrogen/oxygen evolution starts, the electrode was subjected to continuous CV scans until stabilized CV curves were observed. After electrochemical activation, the electrodes are named according to the active substance obtained by in-situ reconstitution.