Abstract
Introducing new inexpensive materials for supercapacitors application with high energy density and stability, is the current research challenge. In this work, Silver doped carbon xerogels have been synthesized via a simple sol-gel method. The silver doped carbon xerogels are further surface functionalized with different loadings of nickel cobaltite (1 wt.%, 5 wt.%, and 10 wt.%) using a facile impregnation process. The morphology and textural properties of the obtained composites are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen physisorption analysis. The silver doped carbon xerogels display a higher surface area and larger mesopore volume compared to the un-doped carbon xerogels and hierarchically porous structure is obtained for all materials. The hybrid composites have been utilized as electrode materials for symmetric supercapacitors in 6 M KOH electrolyte. Among all the hybrid composites, silver doped carbon xerogel functionalized with 1 wt.% nickel cobaltite (NiCo1/Ag-CX) shows the best supercapacitor performance: high specific capacitance (368 F g−1 at 0.1 A g−1), low equivalent series resistance (1.9 Ω), high rate capability (99% capacitance retention after 2000 cycles at 1 A g−1), and high energy and power densities (50 Wh/Kg, 200 W/Kg at 0.1 A g−1). It is found that the specific capacitance does not only depend on surface area, but also on others factors such as particle size, uniform particle distribution, micro-mesoporous structure, which contribute to abundant active sites and fast charge, and ion transfer rates between the electrolyte and the active sites.
Highlights
The energy crisis is one of the main problems facing our world today, especially energy production and storage [1,2]
It seems that incorporation of Ag in the carbon matrix as a polymerization catalyst increases the carbon yield which appeared in higher micropore volume (Wo )
Polymerization catalyst increases the carbon yield which appeared in higher micropore volume (Wo) compared to pristine carbon xerogel (CX), Table 1
Summary
The energy crisis is one of the main problems facing our world today, especially energy production and storage [1,2]. Lithium ion battery (LIB) and supercapacitors (SCs) are the two main devices for energy storage [6]. A supercapacitor can be used in many applications like consumer electronics, memory back-up systems, and low-emission hybrid electric vehicles [10]. Based on their mode of energy storage, supercapacitors can be classified into two types: (i) Electrochemical double layer capacitors (EDLCs), where energy storage occurs through electrostatic storage which takes place by separating of charges in a Helmholtz double layer at the interface between the electrode and electrolyte interface, so the capacitance depends on the surface area of the used electrode. Based on their mode of energy storage, supercapacitors can be classified into two types: (i) Electrochemical double layer capacitors (EDLCs), where energy storage occurs through electrostatic storage which takes place by separating of charges in a Helmholtz double layer at the interface between the electrode and electrolyte interface, so the capacitance depends on the surface area of the used electrode. (ii) Pseudocapacitors, where energy storage occurs through Faradaic electrochemical storage with electron charge transfer by redox reactions [11]
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