Kilogram-Scale Synthesis and Functionalization of Carbon Dots for Superior Electrochemical Potassium Storage

Abstract

Carbon dot is a type of carbon material with an ultrasmall size of less than 10 nm for all three dimensions, which has attracted more and more attention due to its useful merits. Unfortunately, the complicated synthesis method and low yield largely limit its wide large-scale application. Herein, an inexpensive and high-efficiency aldol condensation method under ambient temperature and pressure was proposed for the large-scale synthesis of CDs, which can obtain products with 1.083 kg in 2 h and realize the functionalization of carbon dots doped with nitrogen (NCDs) and sulfur/nitrogen doubly (NSCDs), and then the mechanism and structure of CDs formation were explained. Moreover, utilizing the feature of controllable assembly of carbon dots, and combined with theoretical calculations, we have designed functionalized 1D carbon fibers (CF) to construct high-performance potassium storage anode materials through the assembly of carbon dots induced by a Zn compound. Benefitting from the microstructure and surface functional groups derived from CDs, the N-doped CF (NCF700) exhibits superior electrochemical energy storage performance for potassium ion batteries (PIBs). This study provides a low-cost and high-yield method to produce CDs and promotes the practical application of CDs in electrochemical energy storage.

A review of carbon dots and their composite materials for electrochemical energy technologies

“…Overall, this study demonstrated the novel template role of CQDs and provided useful guidance for the design of porous structures to store large potassium ions. Li et al 139 proposed a cheap and efficient aldol condensation method at ambient temperature and pressure for the large‐scale synthesis of CDs. This method can obtain 1.083 kg of product within 2 h and achieve nitrogen‐doped carbon dots (NCDs).…”

Oxygen-Containing Functional Groups Regulating the Carbon/Electrolyte Interfacial Properties Toward Enhanced K+ Storage

“…However, since K + has a larger ionic radius, 1.38 vs 0.76 Å (Li + ), the development of K-based host materials with large interlayer distance is needed. Enormous investigations have been dedicated to, for example, carbonaceous materials because they are cheap, electrically conductive and highly controllable in terms of structure/ composition [1,2]. Early in 2015, highly reversible K + de-/ intercalation in graphite was reported [3][4][5].…”

“…This strategy has been proven to be effective in energy storage applications (e.g., lithium/ sodium-ion batteries, supercapacitors and oxygen reduction/evolution reaction (ORR/OER)) [9][10][11][12]. In the aspect of K + energy storage systems, heteroatoms-doped carbon fibers [1], graphene [13] or hard carbon [14] exhibit excellent cyclability and rate performance. N-doped porous carbon nanosheets [15] show ultra-stable K + storage capability because its abundant edge-N facilitates the surface-driven pseudocapacitive behavior alleviating structural degradation.…”

Synthesis of Colloidal Carbon Quantum Dots

“…[38] For example, Wang et al used the hydrothermal approach to produce C-dots with different colors, and the quantum yield of red C-dots reaches ~50%; [15] Ye et al used p-phenylenediamine as carbon source and ethanol as solvent to synthesize C-dots. The as-prepared C-dots have strong antibacterial activity; [39] Li et al proposed a cheap and efficient aldol condensation method to synthesize C-dots at room temperature; [40] Yan et al used miscanthus plants as carbon precursors to prepare C-dots with good quality and size uniformity via an ultrasound-assisted mechano-chemical cracking method; [41] Yao et al used a microwave-assisted approach to close-loop condensation of glucose molecules for C-dots production. [42] Although these approaches can produce C-dots, it is still a quite challenge to produce the C-dots with mono-size distribution because of the uncontrolled reaction conditions.…”