SnO₂ Nanosphere/Carbon Dot-Embedded Ti₃C₂T_x MXene Nanocomposites for High-Performance Binder-Free Asymmetric Supercapacitor Electrodes

Abstract

Herein, a 3D-0D-2D-ternary heterostructure nanocomposite comprising pseudocapacitive SnO 2 nanospheres (3D) and carbon dot (0D)embedded Ti 3 C 2 T x (MXene) nanosheets (2D) on Ni-foam was synthesized via a simple hydrothermal strategy for the use of positive electrodes in asymmetric supercapacitor devices. Yellow-emissive carbon dots were synthesized using the nontoxic polyphenolic precursor 2,4,6-tridihydroxybenzoic acid through a simple thermal heating method by dehydrating sulfuric acid medium through dehydration-induced carbonization. SnO 2 played a crucial role by providing reactive centers on the surface of the carbon-dot-embedded MXene, thereby significantly enhancing the capacitive performances. Encapsulation of MXene by the 3D SnO 2 nanospheres restricted the restacking tendency of the MXene nanosheets, enhancing their ability to store surface charge. Owing to its excellent morphological features, SnO 2 /carbon dots@MXene afforded superior electrochemical activities, having a specific capacitance of 1074 F/g in a three-electrode study. Moreover, the asymmetric supercapacitor device composed of the synthesized SnO 2 /carbon dots@MXene nanocomposite exhibited the maximum specific capacitance of 92 F/g at 2 A/g, with an enhanced energy density of 51.11 W h/kg. The supercapacitor device exhibited approximately 103% retention of the specific capacitance after 10,000 cycles and was able to illuminate light-emitting diode bulbs of different colors, demonstrating its practical applicability. Because of its superior electrochemical performance, the SnO 2 /carbon dots@MXene ternary nanocomposite may be a promising candidate for nextgeneration binder-free supercapacitor electrodes. KEYWORDS: Ti 3 C 2 T x , carbon dots, yellow emission, SnO 2 nanospheres, asymmetric supercapacitor