Biomass-derived Activated Carbon Research Articles

Structural changes and electrochemical properties of lacquer wood activated carbon prepared by phosphoric acid-chemical activation for supercapacitor applications

Lacquer wood (LW) goes through one-step and two-step H3PO4 activation process to prepare activated carbons (ACs) at different temperature, and its performance was evaluated by testing CV, EIS, GCD and cycling respect to an electrode material in supercapacitors. The performance of lacquer wood activated carbon prepared by different activation methods and temperature (300, 400, 500, 600, 700, and 800 °C) was studied, and the influence on its electrochemical properties provides valuable guidance for the high-efficient energy utilization of lacquer wood. The results showed that the AC generated via one-step activation process at 400 °C demonstrate excellent specific surface area (SBET 1609.09 m2/g) than those from two-step activation method. Besides, the biomass-derived ACs presented overall better electrochemistry characteristic than those from charcoal-derived ACs. The largest specific capacitance (354 F/g) was obtained in the ACs-based electrodes which was generated from one-step activation process (activated at 600 °C). After 10000 cycles, its capacity retention reached 95.3%, which provides a meaningful guidance into the application of energy storage supercapacitors. This study proves that the LW derived ACs are promising electrodes of the high-performance supercapacitors, which is beneficial for value-added and industrial supercapacitors application of lacquer wood ACs.

Comparison of activated carbons prepared by one-step and two-step chemical activation process based on cotton stalk for supercapacitors application

Cotton stalk (CS) was successively treated via one-step and two-step activation process to synthesize activated carbons (ACs), which were utilized for electrode substances in the supercapacitors. The results showed that the activated carbon generated via one-step activation process at 600 °C demonstrate excellent specific surface area (1342.93 m2/g), which accompanied with high proportion of mesopores pore volume (97%) than those from two-step activation process. Moreover, a large specific capacitance of 338 F/g was observed in the AC that generated at the activated temperature of 600 °C via one-step activation process. The biomass-derived ACs presented an overall better electrochemistry characteristic than those from biochar-derived ACs, suggesting that the electrochemical performances of activated carbon generated from biomass-derived were better than those from biochar-derived. The data proved that the as-prepared ACs are promising materials for advanced energy storage, which is beneficial for value-added and industrial supercapacitors application of cotton stalk activated carbons.

Biomass-derived porous activated carbon from Syzygium cumini fruit shells and Chrysopogon zizanioides roots for high-energy density symmetric supercapacitors

Synthesis of biomass derived microporous activated carbon materials has fascinated attention in the emerging field of energy storage due to its high specific surface area, excellent electrical conductivity, low cost and environmental benevolence. Herein, we report facile and cost-effective method to produce porous activated carbons for the first time by physical activation method using two different biomass sources Syzygium cumini fruit shells (SCFS) and Chrysopogon zizanioides roots (CZR) for fabrication of symmetric supercapacitors. Biomass-derived activated carbon (BAC) materials were obtained via a two-step synthesis: (i) carbonization at 700 °C in N2 atmosphere (ii) CO2 activation at 700 °C in N2 atmosphere. The formation of high surface area and disordered micropores on the carbon by CO2 activation was identified by N2 adsorption-desorption and FE-SEM techniques. SCFS-AC and CZR-AC exhibit enhanced electrochemical performances in three-electrode configuration showing their high specific capacitances with good capacitance retention. These biomass derived activated carbon (BAC) based symmetric supercapacitors deliver energy density maximum of 27.22 W h kg−1 (SCFS-AC) and 16.72 W h kg−1 (CZR-AC) at 200 W kg−1 power density with an outstanding cycling stability over 5000 cycles. This work offers an environmentally safe and innovative approach to control the porosity in BAC for energy storage applications.

Jet fuel and hydrogen produced from waste plastics catalytic pyrolysis with activated carbon and MgO

Catalytic pyrolysis of waste plastics to produce jet fuel and hydrogen using activated carbon and MgO as catalysts was studied. The effects of catalyst to waste plastics ratio experimental temperature, catalyst placement and activated carbon to MgO ratio on the yields and distributions of pyrolysis products were studied. The placement of catalysts played an important role on the catalytic pyrolysis of LDPE, and the pyrolytic volatiles first flowing through MgO and then biomass-derived activated carbon (BAC) could obtain an excellent result to produce H2 and jet fuel-rich products. The higher pyrolysis temperature converted diesel range alkanes into jet fuel range alkanes and promoted the aromatization of alkanes to generate aromatic hydrocarbons. BAC and MgO as catalysts had excellent performance in catalytic conversion of LDPE to produce hydrogen and jet fuel. 100 area.% jet fuel range products can be obtained in LDPE catalytic pyrolysis under desired experimental conditions. The combination of BAC and MgO as catalysts had a synergy effect on the gaseous product distribution and promoted the production of hydrogen, and up to 94.8 vol% of the obtained gaseous components belonged to hydrogen. This work provided an effective, convenient and economical pathway to produce jet fuel and hydrogen from waste plastics.

A benchmark for CO2 uptake onto newly synthesized biomass-derived activated carbons

To properly address the threat of global warming, there is an urgent need to reduce CO2 from the atmosphere through the development of environment-friendly technologies. Therefore, capturing/storage and utilization of CO2 as a refrigerant for adsorption cooling/heating technologies have been gaining momentum in the last decades. This study focuses on the development of novel activated carbons (ACs) with extremely large pore volume and high surface area from environment-friendly and abundantly available biomass precursor seeking higher CO2 adsorption capacity. Four AC samples are synthesized from the two biomass precursor’s namely waste palm trunk (WPT) and mangrove (M) employing potassium hydroxide as an activating agent. The porous properties of the synthesized ACs are investigated from the N2 adsorption/desorption data. It is praiseworthy to elucidate that the highest surface area and pore volume for biomass-derived ACs (BACs) are obtained 2927 m2 g−1 and 2.87 cm3 g−1, respectively. CO2 adsorption characteristics are investigated using a high precision magnetic suspension balance unit at five different temperatures ranging from 25 to 70 °C with various pressures. The WPT-AC (C500)/CO2 pair shows the highest adsorption uptake as high as 1.791 g g−1 (excess adsorption) and 2.172 g g−1 (absolute adsorption) at 25 °C and 5.04 MPa, which is superior to any other ACs reported to date. To the best of our knowledge, porous properties and adsorption uptake of CO2 reported in this study are the up-to-date benchmarks. The results show that novel BACs/CO2 pairs possess remarkably high adsorption performance, which will contribute towards the advancement of various adsorption-based technologies.

Soybean-waste-derived activated porous carbons for electrochemical-double-layer supercapacitors: Effects of processing parameters

Abstract The electrochemical performance of electrical-double-layer capacitors is dependent on the microstructures and porous structures of electrode materials, which are controlled by the processing parameters. In this work, we synthesize porous activated carbons (ACs) of submicron sizes from low-cost, ground soybean waste via hydrothermal carbonization (HTC) and facile, environment-friendly physical activation, and systematically investigate the effects of the processing parameters on the electrochemical properties of the synthesized ACs. The experimental results reveal that the activation agent of H2O steam and high activation temperature can effectively improve the capacitance of the ACs with an optimum, specific capacitance up to 220 F/g and outstanding long-term stability over 98% after 10,000 cycles. The ACs activated with the flow of an inert gas exhibit excellent rate capabilities and relatively low electrochemical impedance. The results likely provide some guidance for the preparation of biomass-derived ACs, and help better understand the fundamental mechanisms for the energy storage in electrochemical double layer.

Solvent-free catalytic deoxygenation of palm fatty acid distillate over cobalt and manganese supported on activated carbon originating from waste coconut shell

The deoxygenation of palm fatty acid distillate (PFAD) containing very large amounts of free fatty acids was performed over Co and Mn supported on activated carbon (AC) derived from waste coconut shells to produce green diesel. The biomass-derived AC synthesised from waste coconut shell offers a competitive edge from the aspect of production costs. The effects of mixed metal oxide acid–base Co/AC and Mn/AC catalysts were investigated in the deoxygenation of PFAD in a zero-hydrogen environment. It was found that Co/AC catalysts exhibited higher deoxygenation activity, with 46% selectivity towards n-(C15+C17) compared to Mn/AC (34%). When varying Co dopant concentration (Cox/AC; x = 5, 10, 15, 20 and 25 wt %), 25 wt % Co achieved the highest hydrocarbon yield (90%) and n-(C15+C17) selectivity (72%) in the deoxygenation screening study. The excellent deoxygenation efficacy was attributed to the employment of a catalyst rich in acid–base-sites, which consecutively catalysed the reaction, favouring C–O bond cleavage through a decarboxylation/decarbonylation route.

Exploring Biomass-Derived Electrode Precursors for Vanadium Redox Flow Batteries

Redox flow batteries (RFBs) are promising technologies for grid-scale energy storage capable of meeting increasing energy demands, seamlessly integrating intermittent renewable energy sources into the electric grid, and improving overall grid reliability and resilience. However, further cost reductions are needed for widespread adoption of RFBs, thus necessitating the advancement of critical system components to improve RFB performance. In particular, the porous carbon electrode plays a crucial role in RFBs by providing active sites for redox reactions, distributing liquid electrolyte, and governing pressure drop. RFB electrodes are typically repurposed gas diffusion layers (GDLs) developed for fuel cells. Though functional, these materials are suboptimal for flow battery applications in terms of surface chemistry and microstructural properties. Post-process modification of commercial GDLs is a common, but limited, approach to improving performance. For example, all-vanadium redox flow batteries (VRFBs), the current state-of-the-art technology, are plagued by sluggish redox reaction kinetics on carbon electrodes, resulting in large activation overpotential. To combat this issue, electrodes are typically oxidized through a variety of methods to alter the surface chemistry, thus improving reaction kinetics and wettability [1]. However, these methods are ultimately incremental as they target existent commercial materials with limited maxima, even when optimized [2]. Re-envisioning electrode materials derived from low-cost, sustainable precursors with inherently favorable properties (i.e., surface functionalities, high surface area, and hierarchical pore structure) is a promising pathway towards RFB performance enhancement and cost reduction. In this work, we demonstrate that biomass from refuse streams such as food waste and wood byproducts can be used to obtain electrode materials that enhance redox reaction kinetics through the introduction of surface functionalities presented in the selected precursor. Unlike fossil-derived carbon precursors (i.e., polyacrylonitrile), the biochemical constituents of biomass (e.g., proteins, carbohydrates, lipids) enable the manufacturing of electrodes with chemical functionalities uncommon in current-generation carbon electrodes. Activated carbon (AC) with hierarchical porosity and high surface area is produced by first stabilizing the biomass via hydrothermal processing at 200-300 °C for 6 h to obtain hydrochar, which is subsequently converted into AC by thermal activation at 850 °C in an inert environment. Evaluation of the electrochemical properties via ex-situ cyclic voltammetry and impedance spectroscopy of the biomass-derived ACs compared to carbon black (Vulcan XC-72) reveals that the ACs are not only conductive and electrochemically active, but also, in some cases, show higher activity for vanadium redox reactions. X-ray photoelectron spectroscopy suggests that increasing the amount of nitrogen heteroatoms reduces charge-transfer resistance and improves electrochemical activity, a hypothesis that is further supported by density functional theory calculations. Finally, we demonstrate that the combination of heat-treated electrodes and biomass electrocatalyst leads to synergistic benefits and increased power density in a full-cell VRFB. These results suggest a pathway to designing next-generation electrode materials with tailored properties for RFBs through the use of low-cost and sustainable feedstocks. [1] K.J. Kim, M.-S. Park, Y.-J. Kim, J.H. Kim, S.X. Dou, M. Skyllas-Kazacos, A technology review of electrodes and reaction mechanisms in vanadium redox flow batteries, J. Mater. Chem. A. 3 (2015) 16913–16933. doi:10.1039/C5TA02613J. [2] K.V. Greco, A. Forner-Cuenca, A. Mularczyk, J.J. Eller, F.R. Brushett, Elucidating the Nuanced Effects of Thermal Pretreatment on Carbon Paper Electrodes for Vanadium Redox Flow Batteries, ACS Appl. Mater. Interfaces. (2018). doi:10.1021/acsami.8b15793.

Capping with activated carbon reduces nutrient fluxes, denitrification and meiofauna in contaminated sediments

Sediment capping with activated carbon (AC) is an effective technique used in remediation of contaminated sediments, but the ecological effects on benthic microbial activity and meiofauna communities have been largely neglected. This study presents results from a 4-week experiment investigating the influence of two powdered AC materials (bituminous coal-based and coconut shell-derived) and one control material (clay) on biogeochemical processes and meiofauna in contaminated sediments. Capping with AC induced a 62–63% decrease in denitrification and a 66–87% decrease in dissimilatory nitrate reduction to ammonium (DNRA). Sediment porewater pH increased from 7.1 to 9.0 and 9.7 after addition of bituminous AC and biomass-derived AC, respectively. High pH (>8) persisted for at least two weeks in the bituminous AC and for at least 24 days in the coconut based AC, while capping with clay had no effect on pH. We observed a strong impact (nitrate fluxes being halved in presence of AC) on nitrification activity as nitrifiers are sensitive to high pH. This partly explains the significant decrease in nitrate reduction rates since denitrification was almost entirely coupled to nitrification. Total benthic metabolism estimated by sediment oxygen uptake was reduced by 30 and 43% in presence of bituminous coal-based AC and coconut shell-derived AC, respectively. Meiofauna abundances decreased by 60–62% in the AC treatments. Taken together, these observations suggest that AC amendments deplete natural organic carbon, intended as food, to heterotrophic benthic communities. Phosphate efflux was 91% lower in presence of bituminous AC compared to untreated sediment probably due to its content of aluminum (Al) oxides, which have high affinity for phosphate. This study demonstrates that capping with powdered AC produces significant effects on benthic biogeochemical fluxes, microbial processes and meiofauna abundances, which are likely due to an increase in porewater pH and to the sequestration of natural, sedimentary organic matter by AC particles.

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.

Study on biomass derived activated carbons for adsorptive heat pump application

Biomasses are renewable resources and suitable precursors for synthesis of activated carbons (ACs). Two biomass sources: (i) Waste Palm Trunk (WPT) and (ii) Mangrove (M) are employed to synthesis activated carbons with huge surface area by chemical activation with potassium hydroxide (KOH). Thermophysical characteristics of the derived activated carbons namely thermal conductivity, particle size distribution, pore size distribution, surface area and pore volume are assessed. The total surface area of WPT-derived AC and mangrove-derived AC are found to be as high as 2927m2g−1 and 2924m2g−1, respectively. The adsorption capacities of the synthesized biomass-derived ACs for ethanol are evaluated for assorted temperature and pressure conditions. It is observed that WPT-AC shows an ethanol uptake of 1.90kgkg−1 whilst the M-AC can adsorb up to 1.65kgkg−1. The isosteric heat of adsorption associated with the present adsorbents/adsorbate (ACs/ethanol) calculated at different coverages showed only marginal difference. For a typical operating condition of adsorption heat pump, both biomass derived ACs showed similar net ethanol uptake which is significantly higher than the net uptake of commercially prevalent Maxsorb III AC.

Biomass-derived functional porous carbons as novel electrode material for the practical detection of biomolecules in human serum and snail hemolymph.

The biomass-derived activated carbons (ACs) have been prepared with high surface areas up to 793 m2 g−1 is by ZnCl2 activation at three different temperatures, viz. AC700, AC800, and AC900. The AC samples were characterized by a variety of analytical and spectroscopy techniques. The as-synthesized ACs were adopted for the simultaneous electrochemical detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). For comparison, reduced graphene oxide (RGO) was employed for the proposed sensor. The high surface area, modulated pore size and the presence of oxygen surface functional groups like heteroatoms (83.427% C, 1.085% N, 0.383% S, and 0.861% H) in the biomass-derived AC is found to be responsible for the excellent catalytic activities of biomolecules. Fascinatingly, the facile sensor further used to detect biomolecules levels in the snail hemolymph and human blood serum. Notably, the obtained analytical parameters for the biomolecules detection over the AC modified GCE, outperforming several carbon-based modified electrodes in literatures.

Electrochemical detection of 4-nitrophenol based on biomass derived activated carbons

A novel method for detecting an environmental pollutant, 4-nitrophenol (4-NP), by exploiting biomass-derived activated carbon (AC) is reported. The electrochemical performances of the 4-NP sensor were assessed by cyclic and linear sweep voltammetries. The presence of oxygen surface functional groups and heteroatoms (72.6% C, 6.1% H, 6.5% N, and 7.5% S) in the biomass-derived AC with high surface area (1555 m2 g−1) are found to be responsible for the excellent catalytic activities and reversible redox behaviors observed during the detection of 4-NP. The effects of pH of the electrolyte buffer solution, accumulated potential and duration as well as the analyte concentration on the electrocatalytic performance of the sensor were investigated. Consequently, a linear correlation between the cathodic reduction peak current with 4-NP concentration up to 500 μM with a detection limit and sensitivity of 0.16 μM and 5.810 μA μM−1 cm−2, respectively, were observed over the AC-modified GCE in 0.05 M acetate buffer solution (pH 5.0), surpassing the existing modified electrodes in the literature. The facile 4-NP sensor thus implemented is also advantageous for its simplicity, stability, reliability, durability, and low cost, rendering practical applications for real sample systems.

Sorption of PAHs and PCBs to activated carbon: Coal versus biomass-based quality

The addition of activated carbon (AC) is an increasingly popular method for pollutant immobilization, and the AC material can be made of biomass or coal/fossil feedstock. The aim of the present study was to investigate whether there are differences between pollutant sorption to biomass and coal-based AC in the presence and absence of sediment. Through N2 and CO2 adsorption to probe surface area and pore size it was shown that the biomass-based AC had a stronger dominance of narrow pores in the size range 3.5–15Å than the anthracite-based material. In the absence of sediment, sorption isotherms for the probe compounds pyrene and PCB-101 showed stronger sorption for the biomass-based AC (logarithmic Freundlich coefficients 8.15 for pyrene; 9.91 for PCB-101) than for the anthracite-based one (logarithmic Freundlich coefficients 7.20 and 9.70, respectively). In the presence of sediment, the opposite trend was observed, with the stronger sorption for anthracite-based AC. Thus, the presence of competing and/or pore-blocking sediment constituents reduces sorption to a larger extent for biomass-derived AC (factor of 5 for pyrene to almost 100 for PCB-101) than for anthracite-based AC (no reduction for pyrene to factor of 5 for PCB-101). This difference is tentatively attributed to the difference in pore size distribution, narrow pores being more prone to clogging, and could have implications for remediation feasibility with AC from different sources.