In the context of carbon neutrality, marine biomass (MB) is expected as a potential precursor to replace traditional carbon sources. In this study, we tried to develop an economic pathway to obtain porous carbon materials from MB. A simple pyrolysis of MB gave MB-based carbon (MBC) having a negligible open-pore structure, while after the water washing, it turned to be porous. The results of N2 adsorption tests revealed that the total pore volume and specific surface area of MBC were significantly influenced by both the pyrolysis temperature and the washing method. While MBC was inherently porous due to a catalytic activation function of innate elements in MB such as Na, Mg, K, Ca, and Cl, these species also induced a pore blocking effect, rendering the developed pores initially undetectable. After the washing, Na, K, and Cl in MBC were almost completely removed, and thus, a part of the hidden pores became accessible. Moreover, a unique CO2 aeration washing was able to further remove Mg and Ca elements from MBC, giving rise to further increases of specific surface area (> 1000 m2/g) without an addition of extraneous activating agents. Based on the understanding of the dual role of the innate elements of MB, a potential strategy to realize the environmental-friendly porous carbon production was successfully demonstrated.

Developing high-efficiency electrode materials is always desired for supercapacitor, in order to improve the energy density. Herein, we found that hierarchically porous carbon microtubes (HPCMTs) derived from plane tree fruit fluff via self-activation method demonstrated prominent supercapacitor performance as electrode materials, since they possessed hierarchical pore structure consisting of abundant micro- and mesopores, high specific surface area (SSA) and good wettability with electrolyte. The HPCMT-1100-6 with the largest SSA (2805 m2/g) and maximal total pore volume (1.98 cm3/g) was obtained at 1100 degrees C with dwelling time of 6 h. The HPCMT-1100-6-based cell in organic electrolyte showed an ultrahigh energy density of 46.3 Wh/kg at high power density of 1106 W/kg in 1.0 M TEABF4/AN, as well as splendid rate capability and impressive long-term cyclic stability. The energy density still can retain 35 Wh/kg even at an ultrahigh power density of 83.8 kW/kg, the capacitance retention maintains 96.4% after 10000 cycles at a current density of 10 A/g. This study provided a novel practical sustainable strategy for converting the abundant and low-cost biomass waste into high-valued porous carbons by the green self-activation method for high-energy-density supercapacitor.

Pyrolysis of marine biomass (MB) to create marine biomass-derived carbon materials (MBCs) for industry is a sustainable solution. In this study, we systematically examined pyrolysis processes and performed elemental composition analyses of MB and MBC. The results revealed that MBC contained 12.5-25.5 mass% of alkali and alkaline earth metals (AAEMs). As the pyrolysis temperature increased, some of these AAEMs underwent physical phase changes. Subsequently, we applied CO2 aeration washing for the first time or low-concentrated acetic acid washing to eliminate AAEMs from MBC, reducing potential hazards in the future industrial application.Characterization results suggested that both post-processes effectively removed AAEMs from MBC, reducing the average content of Na and K to 0 mass%, Ca to 1.4 mass%, and Mg to 1.9 mass%. The Cl content was also reduced to 0.1 mass%. After removing AAEMs, the final carbon content of MBCs was as high as 90.8 mass% (dry ash free basis) with a minimum ash content of 6.4 mass% (dry basis) according to ultimate analysis. Comparison with commercial coal products showed that carbon contents were superior and ash contents were lower than those of most coal samples, suggesting that the treated MBCs are of sufficient quality for the carbon cycle industry.

This work focuses on the controllable fabrication of polymorphic nanostructured carbons consisting of hierarchical pores via “One-for-All” strategy from a single precursor-crude oil. Five kinds of tuned carbons with tremella-, honeycomb-, waxberry-, nanorod- and nanocube-like structures were obtained from crude oil, by employing a facile room temperature curing with structural regulation methods followed by thermal treatment. All the five nanostructured carbons have high specific surface area and large pore volume with hierarchical pores. In short, this study provides an efficient and novel strategy to fabricate controllably porous carbons with desired and multifarious microstructures from a single precursor-crude oil.

Porous and Ultrafine Nitrogen-doped carbon nanofibers (NCNFs) were successfully obtained from bacterial cellulose (BC) by carbonization/activation in NH3/N-2 atmosphere at higher temperatures. Thanks to the ammonia treatment, the as-obtained NCNFs have nanoarchitectures constructed of one-dimensional (1-D) nanofiber with ultrafine fibers, hierarchically porous structures, abundant nitrogen functionalities leading to the basic and hydrophobic surface, which render them as excellent adsorbents for the adsorption removal of organic pollutants from aqueous solutions. Their adsorption performance for low-concentration 4-chlorophenol (4-CP) were investigated systematically under different conditions. In comparison with the carbon nanofibers (CNFs) without ammonia treatment and commercial activated carbon (CAC), NCNFs displayed greatly enhanced adsorption capacity, short equilibrium time and wide pH range. NCNF-1000 prepared at 1000 degrees C had adsorption capacity of 4-CP up to 604.1 mg/g for the initial low-concentration of 100 mg/L, which was superior to the previously reported adsorbents. Analyses of the equilibrium adsorption and kinetic data revealed that the adsorption process of 4-CP onto NCNFs were fitted well with the Liu isotherm and pseudo-second-order kinetic models. The thermodynamic parameters (Delta H degrees,Delta S degrees,Delta G degrees) for 4-CP adsorption onto NCNFs confirmed that the essence of 4-CP adsorption was exothermic, feasible and spontaneous. The possible adsorption mechanism of 4-CP on NCNFs was proposed. The excellent adsorption performance of NCNFs for 4-CP were mainly ascribed to their maximum effective surface area, short mass transfer path and hydrophobic surface, which resulted from their nanoarchitectures with many exposed, shallow and accessible pores and a great deal of nitrogen functionalities.

Hierarchical porous hollow carbon nanospheres (HCNSs) were fabricated directly from raw biomass via a one-step method, in which HCNSs were obtained by thermal treatment of raw biomass in the presence of polytetrafluoroethylene (PTFE). The HCNSs possess coupling merits of uniformly distributed hollow spherical architectures, and high specific surface area, abundant accessible/open micropores and reason-able mesopores, the HCNS-based electrodes deliver high electrochemical capacitance. The formation mechanisms of pores and hollow core-shell structures were explored thoroughly, it is found that the key to the formation of hollow core-shell structure is the onset-pyrolysis temperature difference between raw biomass and PTFE. Moreover, the content of silica had significant effects on the textures of HCNSs, and HCNS with the largest SSA of 1984 m(2)/g was obtained. Accordingly, a possible mechanism of HCNSs formation was proposed here, where PTFE acted as the pore creation and nucleation agents and raw biomasses were the primary carbon precursors. (C) 2020 Elsevier Inc. All rights reserved.

Metal-organic framework (MOF)-derived nanoporous carbons (NPCs) and porous metal oxide nanostructures or nanocomposites have gathered considerable interest due to their potential use in supercapacitor (SCs) applications, owing to their precise control over porous architectures, pore volumes, and surface area. Bimetallic MOFs could provide rich redox reactions deriving from improved charge transfer between different metal ions, so their supercapacitor performance could be further greatly enhanced. In this study, "One-for-All" strategy is adopted to synthesize both positive and negative electrodes for hybrid asymmetric SCs (ASCs) from a single bimetallic MOF. The bimetallic Zn/Co-MOF with cuboid-like structures were synthesized by a simple method. The MOF-derived nanoporous carbons (NPC) were then obtained by post-heat treatment of the as-synthesized Zn/Co-MOF and rinsing with HCl, and bimetallic oxides (ZnCo2O4) were achieved by sintering the Zn/Co-MOF in air. The as-prepared MOF-derived NPC and bimetallic oxides were utilized as negative and positive materials to assemble hybrid ASCs with 6 M KOH as an electrolyte. Owing to the matchable voltage window and specific capacitance between the negative (NPC) and positive (ZnCo2O4), the as-assembled ASCs delivered high specific capacitance of 94.4 F/g (cell), excellent energy density of 28.6 Wh/kg at a power density of 100 W/kg, and high cycling stability of 87.2% after 5,000 charge-discharge cycles. This strategy is promising in producing high-energy-density electrode materials in supercapacitors.

A facile and cost-effective approach to flexible high nitrogen-containing porous carbon fiber sheets (PNCFs) was disclosed. The PNCFs were fabricated through a facile strategy of activation/doping of flax fabrics in ammonia (NH3). The procedure parameters of NH3 modification, such as the timing of NH3 switching, activation temperature and duration time were systematically investigated. PNCFs with the highest specific surface area (SSA) of 1152 m(2) g(-1), largest pore volume of 0.502 cm(3) g(-1) and maximal nitrogen content of 5.56 at.% were obtained by activation via NH3 at 900 degrees C for 45 min after pre-carbonization. The optimized sample PNCF-IV-900-45 with the highest SSA, developed hierarchical micro-mesoporous structure and maximal nitrogen content exhibits a large energy density of 16.4 Wh kg(-1) at 100 W kg(-1). The NH3-activated flax-derived carbon fiber sheets assembled into a flexible supercapacitor also shows preeminent electrochemical performance and the flexibility. The symmetric flexible capacitor by PNCF-IV-900-45 electrodes displays a remarkable specific energy density of 174.7 mu Wh cm(-2) at 500 mu W cm(-2), which results from the hierarchical porous structure and N functionalities. The synergistic combination of the hierarchical micro-mesoporous textures, high specific surface area, N-doping and flexibility of flax-based PNCFs to the enhanced electrochemical performance in flexible supercapacitor.

Porous nitrogen and oxygen co-doped carbon microtubes (PCMTs) were prepared via carbonization followed by activation of plane tree fruit fluffs (PTFFs) and employed as high-performance supercapacitor electrode materials. The pore structures, surface chemistry and degree of graphitization of the final products can be facilely tailored by adjusting the activation temperature, which changed remarkably as the activation temperature increased from 650 to 900 °C. The PCMT-850 obtained by activating at 850 °C possessed despite the second largest specific surface area (1533 m2/g), but the highest mesopore ratio (9.13%), the maximal nitrogen content (2.20 at.%) and highest degree of graphitization as well as excellent electrical conductivity. The PCMT-850-based carbon electrode exhibited the highest charge storage capacity with a specific capacitance of 257.6 F/g at a current of 1 A/g and the lowest internal resistance in 6 M KOH. The high supercapacitor performance can be attributed to the combined effects of its pore structure, heteroatom doping effects and degree of crystallinity. The favorable capacitive performance render the waste biomass PTFFs serve as novel resources of nitrogen and oxygen co-doped carbon materials for high-performance supercapacitors.

The exploration of highly abundant and available biomass wastes as sustainable precursors through a scalable and cost-effective synthesis strategy is extremely important for novel materials development in energy storage and conversion technologies. Herein, we have successfully fabricated hierarchical micro-/mesoporous carbons (HMMC) from low-cost and eco-friendly agricultural residues via an easy method. The highly hierarchical porous carbons were obtained from rice husk via NaOH-assisted hydrothermal pre-treatment followed by carbonization/activation process. The NaOH-assisted hydrothermal treatment removed ash content and facilitated the development of pores, especially the mesopores, resulting in hierarchical porous carbons with high specific surface area, large pore volume and high ratio (49.3%) of mesopores. These hierarchically structural advantages guarantee the excellent performances of the resultant porous carbons as electrodes for supercapacitors. The rice husk-derived HMMC electrode exhibit a maximum capacitance of 302.2 F g(-1) at a current density of 1 A g(-1 )in a three-electrode system with 6 M KOH as electrolyte, which is significantly better than 193.7 F g(-1) at 1 A g(-1) obtained on rice husk-derived microporous carbons via direct carbonization and activation. Moreover, the NaOH-assisted HMMC electrodes also show good cycle stability. These results demonstrated that NaOH-assisted hydrothermal pre-treatment is a facile and effective way to produce hierarchical porous carbons from natural biomass wastes with improved electrochemical performances for supercapacitors. (C) 2018 The Electrochemical Society.