Binder-free 3D graphene nanostructures on Ni foam substrate for application in capacitive deionization

Hereby a simple, low-cost and scalable route is being presented for preparation of binder-free electrodes of reduced graphene oxide (RGO) on Ni foam (Ni/Gr). In this regard, the Ni foams are dipped in graphene oxide (GO) slurry. Next, the GO loaded Ni foams are kept in a freeze dryer for 24 h and heated up to 800 degrees C in an inert atmosphere. In this approach, the amount of active materials can be easily optimized for capacitive deionization (CDI). The characterization of Ni/Gr electrodes revealed a 3D porous assembly of RGO on Ni substrate which is helpful for the fast ion diffusion and rapid electron transport. The electrochemical performance of the prepared electrodes is investigated in both 3-electrode system and symmetric 2-electrode assembly. Then, the prepared electrodes are applied for capacitive deionization (CDI) studies in saline water samples. Results revealed a specific capacitance of about 77 F/g (in 1 M of NaCl at 2.5 A/g) and an ion removal capacitance of 22.3 mg/g (in 50 mL of 500 ppm of NaCl) for the fabricated system. The stability of the CDI system was surveyed in 500 ppm of NaCl solution which showed 65% of the initial capacity after 200 consecutive cycles (9 days). These results indicate that this method is efficient for both supercapacitive energy storage applications and CDI technology.

Automated summary

A simple, low-cost and scalable method has been proposed for the preparation of binder-free electrodes of reduced graphene oxide (RGO) on Ni foam. The 3D porous assembly of RGO on Ni substrate created using this method facilitates fast ion diffusion and rapid electron transport. These electrodes show promising electrochemical performance for both supercapacitive energy storage applications and capacitive deionization (CDI) technology.