Novel Gram‐Scale Synthesis of Carbon Nano‐Onions from Heavy Oil for Supercapacitors

Abstract

Moreover, the abundant nanovoids on the sp 2 -hybridized carbon shell and interior space of CNOs facilitate the loading of pseudocapacitive species (metal oxides, [11] the conductive polymer, [12] functional groups, [13,14] etc.) and corresponding charge transport during the charge-storage process. Although fascinating performance has been achieved by CNOs, the efficient synthesis of CNOs remains a great challenge, seriously impeding its application in supercapacitors.Great efforts have been made on the synthesis of CNOs in the past decades. Series of synthetic techniques such as chemical vapor deposition (CVD), [15] underwater electric arc discharge, [16] carbon ion implantation, [17] and annealing of nanodiamonds [18] have been developed to achieve CNOs with tunable sizes (5-200 nm), shapes (spherical and polyhedral), and types of cores (hollow and dense). Among various techniques, chemical methods including CVD, the thermal transformation of nanodiamonds, and thermal pyrolysis of carbon precursor were considered as more viable methods for the production of CNOs, especially in large-scale (gram quantities). For instance, Chen et al. [19] reported a gramscale CVD synthesis of hollow CNOs with MgO supported Co as the catalyst. The hollow CNOs consist of defective carbon shells with diameters ranging from 10 to 50 nm. Recently, the functionalized onion-like graphitic carbon nanospheres (5-30 nm in diameter) were fabricated by a high-temperature transformation of nanodiamonds at 2700 °C, providing the high surface area with multiple oxygen functional groups for enhanced Li-ion storage. [20] Nevertheless, these techniques still suffer from the use of large contents of catalyst (>50 wt%) and high temperature (>1700 °C) [21] in the gram-scale synthesis of CNOs.Herein, we demonstrate a novel bubble template for efficient assembly of CNOs at gram-scale, by using sticky pitch to coat on petroleum coke. The corresponding formation mechanism was proposed and the key feature of this approach is the confinement of petroleum coke generated gas bubbles (H 2 ) to serve as the pristine fragments of graphitic shells for the assembly of CNOs. The as-synthesized CNOs present a uniform particle size of ≈5-30 nm, a superior surface area up to 2665.5 m 2 g −1 , and a large pore volume of 1.2 cm 3 g −1 , which favor the ionic diffusion as well as electronic transport in supercapacitors. Significantly, the CNOs electrode delivered a high specific capacitance of 312 F g −1 at 1 A g −1 and retained as high Carbon nano-onions (CNOs), recognized as multilayered fullerenes, display superior electrical conductivity (comparable with carbon black) and large surface area due to the highly defective sp 2 carbon shells, making it a promising member of carbon nanomaterials for energy applications. However, the lack of efficient synthesis of CNOs in large-scale production (gram quantities) has impeded their range of commercial applications. Herein, for the first time, it is demonstrated that the gram-scale synthesis of CNOs is developed by simply an...

Spinel CoFe2O4 Nanoflakes: A Path to Enhance Energy Generation and Environmental Remediation Potential of Waste-Derived rGO

“…The survey spectrum of rGO/Co 3 O 4 exhibited the peak at 282.7 eV corresponds to the C1s, 529.2 eV corresponds to the O 1s, and the peaks at 777.8 and 794eV corresponding to Co 2p 3/2 and Co 2p 1/2 , respectively. The core level spectrum for Co exhibited two peaks corresponding to Co 2p 3/2 and Co 2p 1/2 at 780.6 and 795.7 eV, respectively, with two satellite peaks at 786.7 and 802.9 eV, respectively, which proved the Co 2+ valance states [ 23 ]. The core level spectrum of Fe 2p shows the peaks at 711.2 and 724.5 corresponding to the Fe 2p 3/2 and 2p 1/2 , respectively.…”

“…With an attractive combination of properties such as good conductivity, high surface area and chemical reactivity, these multipurpose materials can underpin sustainable circular economy by enabling new efficient nanomaterial-based devices [ 13 , 14 ] and functional coatings [ 15 , 16 , 17 ]. In particular, the visible light driven catalytic platforms for environmental remediation [ 18 , 19 ], and the efficient energy storage and conversion devices [ 20 , 21 ] such as supercapacitors and fuel cells (e.g., direct methanol fuel cells, DMFCs) which attract tremendous interest because of the higher efficiency, low pollution emission and flexible fuel choice [ 22 , 23 ]. Both of these types of energy devices require electroactive materials with excellent electro-chemical activity (i.e., multiple oxidation states, low onset potential, more surface-active sites for redox reaction, etc., that affect the exchange current density) [ 24 ].…”

Nanoengineered Carbon‐Based Interfaces for Advanced Energy and Photonics Applications: A Recent Progress and Innovations

“…Recently, Lei et al. have demonstrated the synthesis of activated carbon (P@PC‐AC) material for supercapacitors derived from pitch‐coated petroleum coke, [ 161 ] both petroleum pitch and coke being carbon‐rich products of petroleum refining. Carbon nano‐onions of sizes between ≈5 and 30 nm in diameter, possessing abundant micropores, have been produced.…”

“…Reproduced with permission. [ 161 ] Copyright 2021, Wiley‐VCH. Graphene nanocomposite‐based electrodes for high‐energy‐density supercapacitors.…”

“…This increases also the supercapacitor-like behavior at high current densities. Reproduced with permission [161]. Copyright 2021, Wiley-VCH.…”