Bio-composite nanoarchitectonics for graphene tofu as useful source material for capacitive deionization

The development of low cost, naturally sustainable, and high-performance electrode materials is the primary issue that determines the large-scale application of capacitive deionization (CDI). In this work, the nitrogen-doped activated porous carbon decorated by 3D interconnected graphene (NAPC/G) was synthesized by pre-carbonization and KOH activation of soy milk and graphene oxide composite gel (graphene tofu). The NAPC has an ultra-high specific surface area (SSA) of 2993.5 m2 g−1, rich micro-mesoporous structure, and good hydrophilicity. In addition, the 3D graphene network enhances the conductivity of the composite. Therefore, benefited from the synergetic effect of abundant ions adsorption sites and improved conductivity, the specific capacitance of NAPC/G electrodes is up to 370 F g−1 and maintains capacitance retention of 97% after 3000 cycles. For CDI electrode materials, the salt adsorption capacity (SAC), desalination rate, and cycle stability are the three important parameters. In this work, the NAPC/G electrode achieves an high SAC of 38.5 mg g−1, large desalination rate of 6.6 mg g−1 min−1 and good cycle stability that desalination performance remains 93.5% after 50 cycles. This research provides an effective way to promote the sustainable large-scale application of CDI.