Free‐standing Reduced Graphene Oxide/MoO_3‐x Composite Film with High Performance for Flexible Supercapacitors

Abstract

For the fabrication of flexible supercapacitors, the biggest challenge is still the preparation of flexible electrodes with both high gravimetric and areal specific capacitances. Herein, we have successfully designed a novel rGO (reduced graphene oxide)/MoO 3-x composite film electrodes for high-performance flexible supercapacitor. The as-prepared electrodes exhibit a galvanostatic capacitance of 1374 F⋅g À 1 and an area specific capacitance as high as 21300 mF⋅cm À 2 at 0.1 A⋅g À 1 , which have been significantly larger compared with most recent reports. Meanwhile, the rGO/MoO 3-x composite electrodes have remarkable flexibility and solid mechanical strength. This composite film could be easily folded into various shapes, and then could recover its original appearance without any crease. Excellent cycle stability has also been validated with nearly 100% capacitance retention even after 30,000 cycles. The electrochemical performance of rGO/MoO 3-x composite films remain surprisingly stable even after continuous U-shape bending up to 10,000 times. Moreover, flexible all-solid-state symmetric supercapacitors were successfully fabricated with PVA (polyvinyl alcohol)-H 2 SO 4 gel electrolyte. Our strategy provides a convenient and versatile method for designing new flexible electrode for energy storage devices and is promising for portable and wearable electronics.

Boosting the volumetric capacitance of MoO3-x free-standing films with Ti3C2 MXene

“…Figure 2e plots the XPS peaks at 232.8 eV and 235.8 eV -that correspond to Mo 6+ 3d5/2 and 3d3/2, respectively -for the MoO3-x (bottom) and MT (top) films [10]. As expected, besides the Mo 6+ peaks, are two small peaks at 231.6 eV and 234.6 eV that we assign to Mo 5+ 3d5/2 and 3d3/2, respectively [15]. These peaks are absent from the XPS spectra of the MoO3 films (bottom spectrum in Figure S8b).…”

“…Designing free-standing films without additives is needless to say advantageous. Yu et al designed rGO/MoO3-x films with impressive gravimetric and areal specific capacitances in 1M H2SO4 (8371 mF cm -2 and 540 C g -1 at 1 A g -1 respectively) [15]. Xiao et al fabricated freestanding MoO3-x/CNTs films with Cv of 291 F cm -3 and excellent rate capability [16].…”

Advanced Oxygen‐Vacancy Ce‐Doped MoO3 Ultrathin Nanoflakes Anode Materials Used as Asymmetric Supercapacitors with Ultrahigh Energy Density

“…This phenomenon may originate from the transmission of H + that cannot completely follow the transmission of electrons, which causes surface processes to dominate gradually, and the corresponding electrochemical reaction slightly delayed. [ 9,22,44 ] At 2 mV s –1 , OV‐MoO 3 /Ce = 30/1 has the largest specific capacitance of 1439.0 F g –1 , greater than 1109.4 F g –1 of OV‐MoO 3 , 1334.4 F g –1 of OV‐MoO 3 /Ce = 40/1, and 846.8 F g –1 of OV‐MoO 3 /Ce = 20/1. Even when the scan rate increases to 100 mV s –1 (Figure 6c), the specific capacitance of OV‐MoO 3 /Ce = 30/1 (913.6 F g –1 ) is still greater than that of OV‐MoO 3 (487.6 F g –1 ), OV‐MoO 3 /Ce = 40/1 (753.4 F g –1 ), and OV‐MoO 3 /Ce = 20/1 (423.5 F g –1 ).…”

Flexible Free‐Standing MoO3/Ti3C2Tz MXene Composite Films with High Gravimetric and Volumetric Capacities

“…These peaks are assigned to Mo 5+ 3d 5/2 and 3d 3/2 , respectively. [ 6 ] When the pure and composite films Ti 2p regions are compared (Figure 3c), it is obvious that the fraction of Ti 4+ increased in the latter. Based on these results, it is reasonable to conclude that when the two suspensions are mixed, a fraction of the Mo 6+ ions are reduced by Ti ions in the Ti 3 C 2 T z .…”

“…To overcome these problems, various conducting materials such as graphene, [ 6 ] carbon nanotubes, [ 7 ] polypyrrole, [ 8 ] polyaniline, [ 9 ] and others have been mixed with MoO 3 to fabricate electrodes. Although this composite approach can effectively enhance C g and the rate capabilities of MoO 3 , for the most part the low density of the introduced materials reduces C v to some extent.…”