Silkworm cocoon waste-derived nitrogen-doped hierarchical porous carbon as robust electrode materials for efficient capacitive desalination

Capacitive deionization (CDI) has potential in desalination applications. However, developing a cost-effective and environmental-friendly CDI electrode is still challenging. Here, we report the synthesis of a tailored nitrogen-doped hierarchical porous carbon (NPC) derived from the waste silkworm cocoon and its promising use as a CDI electrode for desalination applications. Results show that both the graphitic N contents and defects (from ID/IG values) within NPC-x regulated the intrinsic resistance and conductivity of NPC-x electrodes, thus giving graphitic N contents and defects-dependent CDI desalination performance. The optimized NPC-1.5 electrode exhibited an electrosorption capacity of 22.19 mg g−1 with an average desalination rate of 1.1 mg g−1 min−1 (100 mg L−1 of NaCl solution, an applied voltage of 1.2 V, and a flow rate of 40 mL min−1). Such desalination performance is superior to the commonly reported activated carbon and other porous carbon electrodes under similar desalination conditions. Moreover, the optimized electrode can still maintain 97 % of its initial electrosorption capacity even after 50 cycles, indicating its outstanding reusability in the desalination application. This work shows a promising CDI electrode material of silkworm cocoon waste-derived porous carbon with highly efficient desalination performance, which will spark more efforts in the development of resource utilization-oriented desalination technologies.