Carbon‐Quantum‐Dot‐Derived Nanostructured MnO₂ and Its Symmetrical Supercapacitor Performances

Abstract

We report here synthesis of nanostructured MnO 2 by using carbon-quantum dot (CQD) as reducing agent which is obtained by environmentally benign approach from waste material. The obtained carbon quantum dot-MnO 2 nanohybrid is characterized by various analytical techniques. The spectral studies reveal the characteristic absorption/emission features of nanostructured CQD-MnO 2 . The X-ray-diffraction and microscopic analysis indicate that the synthesized CQD-MnO 2 is crystalline in nature with the grain size in the range of 250 À 300 nm. Electrochemical studies reveals that the carbon quantum dot-MnO 2 nanohybrid electrode exhibits a high specific capacitance of 189 F g -1 at 0.14 A g -1 with an excellent stability over 1200 charge-discharge cycles. The excellent electrochemical performance is attributed to the large surface area and high conductivity due to the presence of conductive nanonetwork of the CQD in the carbon quantum dot-MnO 2 matrix. The symmetric supercapacitor (CQD-MnO 2 j Na 2 SO 4 j CQD-MnO 2 ) constructed using the carbon quantum dot-MnO 2 electrodes delivers high energy and power densities with a wide operating potential window of 0 -1.6 V.

Carbon Quantum Dot-Anchored Bismuth Oxide Composites as Potential Electrode for Lithium-Ion Battery and Supercapacitor Applications

“…All of these peaks are indicative of the presence of the CQD in the Bi 2 O 3 sample. 28 The peaks located at 464 and 510 cm –1 are characteristic of Bi–O vibrations, which is in agreement with the previous reports. 35 As shown in Figure 2c, the Raman spectrum of the CQD–Bi 2 O 3 composite exhibits a broad band at 443 cm –1 , which arises due to the Bi–O Raman stretching frequency.…”

One-pot hydrothermal synthesis of molybdenum nickel sulfide with graphene quantum dots as a novel conductive additive for enhanced supercapacitive performance

“…[28][29][30][31][32][33][34][35] There are some recent studies on the effect of GQD inclusion on different types of metal oxides/ sulfides for supercapacitor applications. [36][37][38][39] The synergistic effect is one of the major factors that contribute to the enhanced electrochemical performance of electrodes, whereas transition metal sulfides doped with metals take advantage from each component because nickel and molybdenum sulfides provide richer redox chemistry compared to the corresponding individual binary sulfides, which possess a higher theoretical capacity. To the best of our knowledge, we are the first to report the effect of GQD inclusion on molybdenum doped nickel sulfide (MNS) for supercapacitor applications in a binder-free approach.…”

Disposed Dry Cells as Sustainable Source for Generation of Few Layers of Graphene and Manganese Oxide for Solid‐State Symmetric and Asymmetric Supercapacitor Applications

“…The CV curves shown for MnO 2 electrode are characterized with a redox peak indicating occurrence of Faradaic reaction. The appearance of the redox peak is attributed to the following electrosorption and desorption reaction: …”

“…It is noted that there is an anodic peak at 0.4 V and a cathodic peak at 0.3 V with a peak potential separation of 100 mV. It is obvious that with the increase of the scan rate, the peak current increase which is usually observed . For comparison, CV curves of electrodes made from unprocessed raw carbon rod and spent bobbin were recorded in 1 M H 2 SO 4 .…”

“…For example, MnO 2 ‐anchored graphene network, CNTs or carbon quantum dots (CQDs) have been explored. The carbon network could enhance the conductivity and stability of the MnO 2 resulted in high specific capacitance …”