N, P-doped carbon nanorings for high-performance capacitive deionization

The developments of efficient carbonaceous materials are of significant importance to break through the bottlenecks of the traditional electrodes for capacitive deionization (CDI). Herein, we reported a simultaneous MOF-on-MOF growth combined with the MOF-etching strategy for the tailoring of MOF/MOF nanorings. Afterwards, N, P co-doped carbon rings (NPC-Rings) was synthesized through the thermal transformation of MOF/MOF nanorings and followed by the phosphidation activation. Taking advantage of such hierarchically porous structures, the NPC-Rings exhibited a high adsorption capacity of 43.0 mg g−1 in a 500 mg L−1 NaCl solution, fast salt adsorption rate, and superior capacity retention stability of 90.4% after 100 cycles. Finite element simulations further revealed that the unique structure of the NPC-Rings considerably promoted the current density and generates charge migration, thereby providing stronger salt adsorption capacity.