Study on the Effect of Graphene/Carbon Nanotubes on the Enhanced Capacitance of IrO₂-ZnO-G(CNT)/Ti Electrodes

Abstract

Compounding different materials with different properties to be one electrode is a good and common way in supercapacitors. IrO 2 was used as an active and conductive oxide, and ZnO was used as a semiconductive oxide to change the band gap of IrO 2 . Carbon nanotubes (CNT) and graphene (G) were used to improve the microstructure of the oxides. The electrodes of IrO 2 -ZnO-carbon nanotube (CNT)/Ti and IrO 2 -ZnO-graphene oxide (G)/Ti were prepared by a thermal decomposition method, and the different effects of CNT or G on the properties were studied in detail. The surface of IrO 2 -ZnO-CNT/Ti had a "hill-bag" structure, and the IrO 2 -ZnO-G/Ti had a graphene sheet-layered fold structure. Their specific surface area and pore volume were significantly greater than those of an electrode without a carbon material. The specific capacitances of IrO 2 -ZnO-G/Ti and IrO 2 -ZnO-CNT/Ti were 681 and 501 F g −1 , respectively, which were higher than that of IrO 2 -ZnO/Ti (399 F g −1 ). The capacitance retention rate of the IrO 2 -ZnO-G/Ti electrode coating was better than that of IrO 2 -ZnO/Ti within 15,000 cycles but less than that of IrO 2 -ZnO/Ti after 15,000 cycles. Moreover, only a retention rate of 80.24% after 20,000 cycles was kept, which was worse than that of IrO 2 -ZnO/Ti (90.65%). The reasons were worth further investigation. The addition of carbon materials reduced the cycle stability, but the binding effect of graphene and the coating was better than that of carbon nanotubes. Graphene improved the overall performance better than carbon nanotubes. A binder-free asymmetric supercapacitor working in H 2 SO 4 solution was assembled with RuO 2 -MoO 3 /Ti and IrO 2 -ZnO-G/Ti as cathodic and anodic electrodes, respectively. It exhibited energy densities of 29.6 and 25.3 W h kg −1 when the power densities were 700 and 3505 W kg −1 , respectively. The primary charge/discharge mechanism of the asymmetric supercapacitor in the H 2 SO 4 solution was presented.

Design, Synthesis, Crystal Structure, and Thermal Studies of Ni0.779SbF3(SO4): A New Electrode Material for Electrochemical Supercapacitors

“…Figure 6c presents the TEM image of the sample in the 50 nm range, which exhibited a typical flake-like morphology consistent with the findings from FESEM analysis. In Figure 6d, the selected area of diffraction pattern (SAED) revealed the presence of several bright concentric rings that are well indexed with (2)(3)(4)(5)(6)(7)(8)(9)(10)(11), (2-20), ( 500 This SAED pattern result also shows good agreements with the PXRD analysis.…”

“…The efficiency of these supercapacitors in energy storage is directly related to the electrochemical performance of the electrode. The most commonly known electrode materials are transition metal oxides, − carbon materials, − conducting polymers, , and transition metal sulfides. , The enhanced capacitive performance of the supercapacitors depends on the choice of electrode materials and their fabrication. They must provide high thermal stability, corrosion resistance, high electrical conductivity, appropriate chemical stability, and suitable wettability.…”

“…45−47 These studies gave rise to different new compounds with exciting physical properties such as magnetic frustration and nonlinear optical second harmonic generation, 48−54 dye degradation, 46,55 water splitting reactions, 56−58 organic catalysis, 59 etc. Since the tetrahedral SO 4 2− has been proven to be an ideal anion group to explore new promising inorganic materials, a series of compounds associating sulfate tetrahedra and transition metals or rare earth metals or p-block elements have been extensively studied. 31,60,61 A 3 Sn 2 (SO 4 ) 3−x Cl 1+2x (A = K, Rb, Cs; x = 0, 1), (NH 4 ) 2 SbCl(SO 4 ) 2 , (NH 4 )SbCl 2 (SO 4 ), Cs 2 Zn 2 (SO 4 ) 3 , CeF 2 (SO 4 ), Sb 4 O 5 SO 4 , and KTb(SO 4 ) 2 are some examples of such type of compounds.…”

CNTs-Supercapacitors: A Review of Electrode Nanocomposites Based on CNTs, Graphene, Metals, and Polymers

“…Supercapacitors in several industries are used for energy harvesting and high-power systems in electric vehicles. Recently, supercapacitors based on CNTs composite electrodes have received more attention due to the electrical and chemical properties of CNTs [1][2][3][4][5][6][7]. Growth in the publication of CNT-based supercapacitors is shown in Figure 1.…”