Carbon Quantum Dots-Modulated Interfacial Charge Transfer between Highly Nitrogen-Doped Tubular-Like Carbon and Cobalt Molybdate for Surface-Capacitive Sodium-Ion Seizing

Compositing carbon with Faradaic materials is a facile, efficacious method to boost electrochemically seizing sodium ions, yet it suffers from sluggish interfacial charge transfer due to high contact resistance. Herein, we proposed a carbon quantum dots (CQDs)-modulated strategy to enhance electrical charge transfer between nitrogen-doped tubular-like carbon (NTLC) and cobalt molybdate (CMO). The CQDs also serve as nucleation growth sites, allowing CMO to be anchored on the surface of NTLC, which contributes to the formation of the CQDs-bridged heterogeneous interface. Intriguingly, the capacitive deionization system equipped with CMO/CQDs/NTLC as the cathode and activated carbon as the anode displays a specific adsorption capacity of 61.5 mg_NaCl g_electrodes^–1 (corresponding to ∼52.8 mg-Na⁺ g_cathode^–1) in a 1000 mg L^–1 synthetic NaCl solution, which is about 2.3 times higher than that of CMO/NTLC. Further advanced electrochemical investigations unveil that the introduction of CQDs can lower the activation energies of ion transport and charge transfer processes, which kinetically facilitates the generation of abundant charges that are bound for sodium-ion capture. This work provides a powerful strategy to design carbon-Faradaic composites for highly efficient electrochemical ion storage.