In Situ Nitrogen Functionalization of 2D-Ti3C2Tx-MXenes for High-Performance Zn-Ion Supercapacitor

Abstract

Zinc (Zn) ion supercapacitors (ZISCs) have attracted considerable attention as a viable energy storage technology because they are cost-effective, safe, and environmentally friendly. However, cathode materials with suitable properties are rare and need to be explored. In this regard, metal carbides (MXenes) are a good choice for capacitive energy storage, but they exhibit low capacitance. The energy storage performance of MXenes can be bossed using functionalization with heteroatom doping, e.g., nitrogen (N), to simultaneously modify ZISCs’ fundamental characteristics and electrochemical properties. Herein, we present an in-situ N-functionalization of Ti3C2Tx-MXene via a hydrothermal reaction with urea (denoted as N-Ti3C2Tx-MXene). N-functionalization into Ti3C2Tx-MXene raised Ti3C2Tx-MXene’s interlayer spacing and boosted the Zn-ion storage in 1 M ZnSO4 electrolyte. The N-Ti3C2Tx-MXene electrode delivered an excellent specific capacitance of 582.96 F/g at 1 A/g and retained an outstanding cycle stability of 94.62% after 5000 cycles at 10 A/g, which is 1.8 times higher than pristine Ti3C2Tx-MXene at identical conditions. Moreover, the N-Ti3C2Tx-MXene//Zn device demonstrated a maximum capacitance of 153.55 F/g at 1 A/g, retained 92% of its initial value after 5000 cycles, and its Coulombic efficiency was ~100%. This strategy considerably reduced Ti3C2Tx-MXene nanosheet restacking and aggregation and enhanced electrochemical performance. Further, this research elucidated N-Ti3C2Tx-MXene’s charge–storage process and offered a fresh approach to the rational design of novel electrode materials for ZISCs.

Surface Modification Effect on V-Doped Ti3C2Tx as Bifunctional Catalyst Electrodes for Symmetric Supercapacitor and the Hydrogen Evolution Reaction

“…Furthermore, Figure d demonstrates the mechanisms controlled by diffusion and capacitance for pristine V (0.05)-doped K + –Ti 3 C 2 T x at different scan rates ranging from 10 to 100 mV s –1 . The capacitance-controlled mechanism increased as the scan rate increased, indicating that the capacitive mechanism dominated the overall capacitance, particularly at varying scan rates. , …”

“…The capacitance-controlled mechanism increased as the scan rate increased, indicating that the capacitive mechanism dominated the overall capacitance, particularly at varying scan rates. 50,51 5.4. Electrochemical Performance of the Symmetric Device.…”

Atomic Layer Deposition—A Versatile Toolbox for Designing/Engineering Electrodes for Advanced Supercapacitors

“…The development of nanoscale or nanostructured materials is a vital research area in this perspective because of the unique enhancements of material properties at these dimensions vis-avis their bulk counterparts. [8,48,49] Therefore, efficient preparation methods are imminently required for constructing SC electrodes exhibiting the desired geometry, thickness, and surface kinetics for effective charge-transport characteristics. Compared to conventional thin-film deposition processes such as PLD and CVD, ALD is emerging as a state-of-the-art technique for depositing high-quality, stoichiometric thin-films of diverse materials.…”

“…Transition metal oxides (TMOs) are one of the most optimal candidate materials owing to their high theoretical capacity aided by the redox activity and natural abundance. [49,50,[206][207][208][209][210][211][212] To this end, coating the nanosized particles and/or films of active materials on high conductivity hosts, e.g., various types of carbon materials, is the most widely adopted strategy. In this architecture, the ultrasmall active materials permit electron exchange with the conducting host.…”

“…In a capacitor, the charge is electrostatically stored in the metal plates and an electric field emerges across the dielectric medium. [34,[47][48][49][50][51][52] The SCs store charges via multiple mechanisms-reversible adsorption/desorption of ions between the surface of the active materials/electrodes and electrolytes, and swift and changeable Faradaic process at the surface of electrodes during the charge and discharge processes. [3,[53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] Depending upon the mechanism involved in charge storage, the SCs can be classified into three classes: electrical double layer capacitor (EDLC), pseudocapacitors (PCs), and hybrid SCs (Figure 2).…”