2.2. Preparation of CoB/Ni flow-through electrode
Before everything started, the Ni foam was pretreated first based on the subsequent steps. First of all, it was put into a 3 mol L-1 HCl solution for 10 min to remove surface native oxides. Then it was placed in acetone for 10 min to degrease under ultrasonic conditions. Afterward, it was immersed in DI water for 10 min to clean further under ultrasonic conditions. Lastly, it was rinsed thoroughly with DI water and stored in DI water at room temperature for later use.
As shown in figure 1A, the active Co-based flow-through electrodes were prepared within two facile stages. First, CoB nanocatalysts were assembled on Ni foam after the flowing synthesis process.29, 30 In brief, cobalt salt aqueous (0.5 M) and NaBH4 aqueous (1.0 M) were alternately flowing through the Ni foam pores. During the process, Co2+and NaBH4 can contact in Ni foam pores. As a result, CoB can be formed in Ni foam pores. The steps were repeated in 4 cycles. Next, the prepared CoB immobilized on the flow-through electrode wasin-situ restructured after HER/OER activation.