Hierarchical Micro/Mesoporous Carbons Synthesized with a ZnO Template and Petroleum Pitch via a Solvent-Free Process for a High-Performance Supercapacitor

Optimizing the Micro/Mesoporous Structure of Hierarchical Porous Carbon Synthesized from Petroleum Pitch Using the Solvent-Free Method for Ultra-Fast Capacitive Deionization

In this work, a solvent-free ZnO-template method is used to synthesize hierarchical porous carbons (denoted as HPC-X; X = 1, 1.5, 2, and 4 g of ZnO) via the pyrolysis of petroleum industrial-residual pitch with ZnO. The proposed method allows precise control of the micro/meso/macroporous structure of the HPC by adjusting the amount of ZnO. The results show that the average pore size of HPCs prominently increases from 2.4 to 3.7 nm with the increase in the ZnO/pitch ratio. In addition, it is shown that HPCs have a high surface area between 1141 and 1469 m² g^-1, a wide-range pore size distribution (micro-, meso-, and macropores), and a tap density ranging from 0.2 to 0.57 g cm^-3. The capacitive deionization performances of HPCs for sodium and chloride ions are investigated. The results show that HPC-2 exhibits the highest electrosorption capacity of 9.94 mg g^-1 within 10.0 min and a maximum electrosorption capacity of 10.62 mg g^-1 at 1.2 V in a 5.0 mM NaCl solution. Hence, HPC-2 is a highly promising candidate as an electrode material for rapid deionization.

Green and Highly-Efficient Microwave Synthesis Route for Sulfur/Carbon Composite for Li-S Battery

Multiporous carbons (MPCs) are prepared using ZnO as a hard template and biomass pyrolysis oil as the carbon source. It is shown that the surface area, pore volume, and mesopore/micropore ratio of the as-prepared MPCs can be easily controlled by adjusting the ZnO/oil ratio. Sulfur/MPC (S/MPC) composite is prepared by blending sulfur powder with the as-prepared MPCs followed by microwave heating at three different powers (100 W/200 W/300 W) for 60 s. The unique micro/mesostructure characteristics of the resulting porous carbons not only endow the S/MPC composite with sufficient available space for sulfur storage, but also provide favorable and efficient channels for Li-ions/electrons transportation. When applied as the electrode material in a lithium-ion battery (LIB), the S/MPC composite shows a reversible capacity (about 500 mAh g⁻¹) and a high columbic efficiency (>95%) after 70 cycles. Overall, the method proposed in this study provides a simple and green approach for the rapid production of MPCs and S/MPC composite for high-performance LIBs.

Zinc-salt assisted synthesis of three-dimensional oxygen and nitrogen co-doped hierarchical micro-meso porous carbon foam for supercapacitors

Nitrogen and oxygen co-doped hierarchical micro-mesoporous carbon foams has been synthesized by pyrolyzation treatment of a preliminary foam containing melamine and formaldehyde as nitrogen, carbon and oxygen precursors and Zn(NO3)2. 6H2O and pluronic F127 as micro-meso pores generators. Several characterizations including thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and Raman spectroscopy, FTIR and X-ray photoelectron spectroscopy, N2 adsorption-desorption, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were performed on the prepared foams. X-ray diffraction patterns, Raman spectra and N2 adsorption-desorption results confirmed that ZnO has pronounced effect on the graphitization of the prepared carbon foam. From X-ray diffraction, thermal gravimetric and N2 adsorption-desorption analysis results it was confirmed that the carbothermal reaction and the elimination of ZnO and also the elimination of pluronic F127 are the main factors for the induction of porosities in the foam structure. The presence of Zn(NO3)2. 6H2O and pluronic F127 in the initial composition of the preliminary foam results in the specific surface area as high as 1176 m2.g-1 and pore volume of 0.68 cm3.g-1. X-ray photoelectron and FTIR spectroscopy analyses results approved the presence of nitrogen (about 1.9 at %) in the form of pyridinic, graphitic and nitrogen oxide and oxygen (about 7.5 at. %) functional groups on the surface of the synthesized carbon foam. Electrochemistry analysis results including cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) and also electrochemical impedance spectroscopy (EIS) analysis illustrated the formation of an electric double layer supercapacitor with the capacitance as high as 137 Fg-1.

Synthesis of Multiporous Carbons from the Water Caltrop Shell for High-Performance Supercapacitors

In this study, an economic, sustainable, and green synthesis method of multiporous carbons from agricultural waste, water caltrop shell (denoted as WCS), was presented. To prepare the WCS biochar, the dried WCS was first carbonized to a microporous carbon with a surface area of around 230 m² g^-1 by using a top-lit-updraft method. Then, the microporous WCS biochar was directly mixed with an appropriate amount of ZnO nanoparticles and KOH as activating agents via a solvent-free physical blending route. After further activation at 900 °C, the resulted carbons possess both micropores and mesopores that were named as WCS multiporous carbons. The carbon yield of the prepared WCS multiporous carbons with high surface area in the range of 1175-1537 m² g^-1 is up to 50%. Furthermore, the micropore/mesopore surface area ratio can be simply tuned by controlling the ZnO content. For supercapacitor applications, the as-prepared WCS multiporous carbon electrodes showed high specific capacitance (128 F g^-1 at 5 mV s^-1) with a good retention rate at 500 mV s^-1 scan rate (>60% compared to the capacitance at 5 mV s^-1) and low Ohmic resistance in a 1.0 M LiClO₄/PC electrolyte. In addition to the ZnO nanoparticles, CaCO₃ nanoparticles with low environmental impact were also used to prepare the WCS multiporous carbons. The assembled supercapacitors also demonstrate high specific capacitance (102 F g^-1 at 5 mV s^-1) and good retention rate (∼70%).

Synthesis of mesoporous carbon with tunable pore size for supercapacitors

Mesoporous carbon (MC) has wide applications, including in drug delivery, catalysis, absorption, energy storage/conversion, etc.

Synthesis and characterization of a supported ionic-liquid phase catalyst with a dual-mesoporous structure derived from poly(ionic liquids) and P123

A novel heterogeneous catalyst with high efficiency and recovery shows excellent performance in the alkylation of o-xylene and styrene.

Coupled ultrasonication-milling synthesis of hierarchically porous carbon for high-performance supercapacitor

Activated carbon (AC) based supercapacitors exhibit intrinsic advantages in energy storage. Traditional two-step synthesis (carbonization and activation) of AC faces difficulties in precisely regulating its pore-size distribution and thoroughly removing residual impurities like silicon oxide. This paper reports a novel coupled ultrasonication-milling (CUM) process for the preparation of hierarchically porous carbon (HPC) using corn cobs as the carbon resource. The as-obtained HPC is of a large surface area (2288 m² g^-1) with a high mesopore ratio of ∼44.6%. When tested in a three-electrode system, the HPC exhibits a high specific capacitance of 465 F g^-1 at 0.5 Ag^-1, 2.7 times higher than that (170 F g^-1) of the commercial AC (YP-50F). In the two-electrode test system, the HPC device exhibits a specific capacitance of 135 F g^-1 at 1 A g^-1, twice higher than that (68 F g^-1) of YP-50F. The above excellent energy-storage properties are resulted from the CUM process which efficiently removes the impurities and modulates the mesopore/micropore structures of the AC samples derived from the agricultural resides of corn cobs. The CUM process is an efficient method to prepare high-performance biomass-derived AC materials.

Three-dimensional hierarchical porous sludge-derived carbon supported on silicon carbide foams as effective and stable Fenton-like catalyst for odorous methyl mercaptan elimination

The poor reusability of catalysts and secondary pollution are critical issues for sulfur-containing volatile organic compounds (S-VOCs) removal. In this paper, a three-dimensional (3D) hierarchical porous sludge-derived carbon supported on silicon carbide foams (SiC) has been fabricated for deep decomposition of S-VOCs under ambient conditions. The sludge-derived Fenton-like catalyst has been confirmed to be hierarchical 3D porous structure based on detailed characterization by scanning electron microscopy (SEM), X-ray diffraction (XRD), Nitrogen adsorption-desorption measurements and Raman spectroscopy. Significantly, the catalyst after KOH activation (SC_FeK-SiC) shows excellent catalytic decomposition of methyl mercaptan (CH₃SH) with almost complete CH₃SH oxidation into sulfate using hydrogen peroxide as an oxidant under ambient conditions. This catalyst also possesses relative low iron dissolution and excellent cycling performance. The efficient catalytic ability of SC_FeK-SiC can be attributed to SiC foam functioned as a stable 3D macroporous skeleton, in which the porous sludge-derived carbon immobilizes the active iron species and promotes the efficient capture of gaseous CH₃SH, thus facilitating the decomposition of CH₃SH by generating reactive species, specifically ·OH. The reaction mechanism was systematically investigated. Herein, the design of the porous sludge-derived carbonaceous Fenton-like catalyst paves an avenue for efficient VOCs treatment and rational sludge disposal.

Activated Biomass-derived Graphene-based Carbons for Supercapacitors with High Energy and Power Density

Here, we present a facile and low-cost method to produce hierarchically porous graphene-based carbons from a biomass source. Three-dimensional (3D) graphene-based carbons were produced through continuous sequential steps such as the formation and transformation of glucose-based polymers into 3D foam-like structures and their subsequent carbonization to form the corresponding macroporous carbons with thin graphene-based carbon walls of macropores and intersectional carbon skeletons. Physical and chemical activation was then performed on this carbon to create micro- and meso-pores, thereby producing hierarchically porous biomass-derived graphene-based carbons with a high Brunauer-Emmett-Teller specific surface area of 3,657 m2 g-1. Owing to its exceptionally high surface area, interconnected hierarchical pore networks, and a high degree of graphitization, this carbon exhibited a high specific capacitance of 175 F g-1 in ionic liquid electrolyte. A supercapacitor constructed with this carbon yielded a maximum energy density of 74 Wh kg-1 and a maximum power density of 408 kW kg-1, based on the total mass of electrodes, which is comparable to those of the state-of-the-art graphene-based carbons. This approach holds promise for the low-cost and readily scalable production of high performance electrode materials for supercapacitors.