Densely Functionalized Cyanographene Bypasses Aqueous Electrolytes and Synthetic Limitations Toward Seamless Graphene/β‐FeOOH Hybrids for Supercapacitors

Abstract

Supercapacitors are a promising energy storage technology owing to their unparalleled power and lifetime. However, to meet the continuously rising demands of energy storage, they must be equipped with higher energy densities. For this purpose, the seamless integration of metal oxides on carbon matrices, such as iron oxides/oxyhydroxides, has been pursued through hydrothermal, atomic layer and electro-deposition methods directly on current collectors. Nevertheless, such methods present limited compatibility with commercial paste-coating processes on the current collectors. Furthermore, iron oxides/oxyhydroxides lack conductivity and are hydrophilic, operating with low-voltage aqueous electrolytes, limiting their power and energy and requiring corrosion-resistant H 2 O current collectors. To mitigate these challenges, a seamless and paste-ready material is successfully developed through a 15 min wet-chemical method, via the coordination of ultrasmall β-FeOOH (akaganéite) nanoparticles to the nitrile groups of a covalent graphene derivative. Endowed with graphene-like impedance response and very high wettability in organic electrolytes, combined high power and energy densities are obtained, with respect to the total mass of both electrode materials and current collectors, overcoming the identified challenges. This offers future prospects for the exploration of alternative molecular handles for improved interfaces and their application in different energy-storage chemistries.

Kinetically Controlled, Scalable Synthesis of γ‐FeOOH Nanosheet Arrays on Nickel Foam toward Efficient Oxygen Evolution: The Key Role of In‐Situ‐Generated γ‐NiOOH

“…The high‐resolution O 1s XPS spectrum exhibits three sub‐peaks located at 529.9, 531.3, and 532.6 eV, which are successively ascribed to the FeOFe, FeOH, and absorbed H 2 O (Figure 1h). [ 1b,14 ] All the above results demonstrate the successful preparation of γ‐FeOOH NAs on NF (abbreviated as γ‐FeOOH/NF). Nevertheless, in the absence of NF, γ‐FeOOH powder with seriously stacked morphology is obtained (Figure S6, Supporting Information).…”

Advanced asymmetric supercapacitors with a squirrel cage structure Fe3O4@carbon nanocomposite as a negative electrode

“…7f shows the Ragone plot, where the specic power is plotted versus specic energy. For comparison, many previously reported ASCs 22,32,[43][44][45][46][47] are also displayed in Fig. 7f.…”

Oxygen Vacancies Enhanced NiCo2O4 Nanoarrays on Carbon Cloth as Cathode for Flexible Supercapacitors with Excellent Cycling Stability

“…Many works have been carried out to realize the high energy density of SCs, among which pseudo‐capacitive materials, especially transition metal oxides (TMOs) are widely investigated since they involve Faradaic process, rather than purely electrostatic process, which thus dramatically increase the capacitance as well as the energy density of supercapacitors [7,10,11] . In addition, the natural abundance, low cost and environmental benignity of most TMOs also make them ideal candidates for energy storage applications [12–15] . In particular, many efforts have been devoted to binary transition metal oxides, such as NiCo 2 O 4 , due to their high reversible redox capability, the good electrochemical conductivity as well as the multivalences of transition metal elements [16–19] .…”

“…[7,10,11] In addition, the natural abundance, low cost and environmental benignity of most TMOs also make them ideal candidates for energy storage applications. [12][13][14][15] In particular, many efforts have been devoted to binary transition metal oxides, such as NiCo 2 O 4 , due to their high reversible redox capability, the good electrochemical conductivity as well as the multivalences of transition metal elements. [16][17][18][19] However, the limited surface area of NiCo 2 O 4 frequently hinders its fully utilization as an active pseudo-capacitive material and leads to dissatisfied electrochemical performance.…”