The electrochemical properties of reduced graphene oxide film with capsular pores prepared by using oxalic acid as template

Abstract

Summary By using oxalic acid (OA) as template and reducer, a novel approach is developed to prepare reduced graphene oxide films with capsular pores (C‐rGOFs) under a hydrothermal condition. The effect of preparation conditions including concentrations of OA and reaction temperatures on the films' structure and capacitive performances has been systematically investigated. The optimal C‐rGOF shows uniform capsule‐like morphology and exhibits a density of 1.18 g cm−3. Tested by using a two‐electrode system, the optimal film shows gravimetric specific capacitance of about 234.9 F g−1 and volumetric specific capacitance of 277.2 F cm−3. Additionally, the optimal film which shows good rate capability can retain 63.9% of initial capacitance at high scan rate of 1.0 V s−1, which is much higher than that of the controlling reduced graphene oxide film (rGOF, 180.5 F g−1, 373.6 F cm−3 and retain only 45.0% of its initial capacitance at 1.0 V s−1). The cells assembled by the optimal C‐rGOF exhibit maximum energy density of 7.5 Wh kg−1, power density of 16.9 kW kg−1, and excellent cycling stability with 91.2% capacitance retention after 21 000 cycles. It is believed that this method can be developed as a useful strategy to prepare rGO‐based materials for energy storage applications.

Boosting the energy storage performance of cobalt molybdate microspheres constructed from urotropin‐induced ultrathin nanosheets

“…The electrochemical behaviors of the assembled hybrid devices were recorded in a two‐electrode architecture. The specific capacity ( C M or C′ M , mAh/g), energy ( E , Wh/kg), and power ( P , W/kg) were determined in the light of Equations where i (A) and Δ t (s) refer to the discharge current and time; Δ v (V) and m (g) are the potential range and quality of the active materials in a single electrode; Δ V (V), S (V/s), and M (g) correspond to the potential range, scan rate, and total quality of the active materials for the device, respectively.…”

“…The specific capacity (C M or C 0 M , mAh/g), energy (E, Wh/kg), and power (P, W/kg) were determined in the light of Equations (3) to (5). [24][25][26]…”

Organic solar cells: Current perspectives on graphene‐based materials for electrodes, electron acceptors and interfacial layers

“…178 Nevertheless, in practice, the graphene films often contain grain boundaries, which introduce lattice defects and/or oxidative traps that increase the sheet resistance to a few hundred Ω sq −1 at 80% transmittance, 82 which is very high, compared to 10-30 Ω sq −1 at 90% visible transmittance for the commonly used ITO anode. 94 Therefore, there is a strong need to enhance the electronic properties of graphene without compromising its optical transmittance and other physical properties, such as its crystal structure and surface morphology. Interestingly, graphene sheets are more appealing than ITO since they can be flexed without cracking, and their chemical inertness permits dual application as an anode and a water-or air-resistant layer.…”

“…Interestingly, graphene sheets are more appealing than ITO since they can be flexed without cracking, and their chemical inertness permits dual application as an anode and a water-or air-resistant layer. 94 Graphene-based anode layers have been commonly prepared by employing either CVD-grown graphene or solution-processed GO and/or rGO, owing to their high film homogeneity over large areas. 179 CVD results in the preparation of graphene sheets with perfect sp 2 carbon networks and excellent electrical conductivity.…”

“…16,93 This promotes the transport of charge carriers and converts the electrically insulating GO into conducting rGO sheets. 94 The chemical reduction of GO, for example, by hydrazine vapour treatment, removes the epoxy groups, whereas the thermal reduction of GO in inert nitrogen or argon environment removes the hydroxyl and carboxyl groups. 16 Nevertheless, hydrazine, the commonly used chemical reducing agent, is highly toxic and explosive; hence, it is not suitable for commercial bulk production since it requires complex long-term procedures and serious precautions when dealing with it in large quantities.…”