Direct Pyrolysis Process Research Articles

Large-scale preparation of N-doped microporous-dominated carbon-based adsorbents for efficient removal of Chromium(VI): The synergistic effect of different nitrogen configurations

Carbon-based adsorbents with abundant resources, environmental friendliness, and sufficient adsorption sites have broad application prospects for efficient removal of Chromium (Cr(VI)) in aquatic environment. Pursuing a heavy metal adsorption material and advancing it from the laboratory to the actual water environment are of great importance. Herein, we developed a general synthesis strategy for large-scale preparation of N-doped microporous-dominated carbon-based adsorbents (NC-s) via a direct pyrolysis process of ethylene diamine tetraacetic acid tetrasodium. The NC-s samples had abundant microporous, different nitrogen configurations and large specific surface area (503 m2 g−1). Due to these advantages, the NC sample prepared at 800 °C (NC-800) possessed high adsorption capacity toward Cr(VI) (167.3 mg g−1) toward Cr(VI), fast adsorption process (180 min), and good reusability. Through specific experiments and density functional theory (DFT) calculations, we proposed that the adsorption mechanism of NC-s samples was primarily determined by the ion exchange/electrostatic attraction-reduction-complexation synergy, and the mechanism included adsorption-reduction of Cr(VI) and immobilization of Cr(III). Graphitic-N and pyridinic-N adsorbed Cr(VI) in solution mainly by electrostatic attraction, while pyrrolic-N mainly reduced the toxicity primarily by reducing Cr(VI) to Cr(III). These insights prove that the nitrogen-doped porous carbon-based adsorbents prepared in this study can effectively reduce Cr(VI) pollution in water environment.

Effect of pyrolysis temperature on characteristics and chloramphenicol adsorption performance of NH2-MIL-53(Al)-derived amine-functionalized porous carbons

Several activities such as aquaculture, human and feedstock therapies can directly release antibiotics into water. Due to high stability, low hydrolysis and non-biodegradation, they can accumulate in the aqueous environment and transport to aquatic species. Here, we synthesized amine-functionalized porous carbons (ANC) by a direct-pyrolysis process of NH2-MIL-53(Al) as a sacrificial template at between 600 and 900 °C and utilized them to eliminate chloramphenicol antibiotic from water. The NH2-MIL-53(Al)-derived porous carbons obtained high surface areas (304.7–1600 m2 g−1) and chloramphenicol adsorption capacities (148.3–261.5 mg g−1). Several factors such as hydrogen bonding, Yoshida hydrogen bonding, and π–π interaction, hydrophobic interaction possibly controlled adsorption mechanisms. The ANC800 could be reused four cycles along with high stability in structure. As a result, NH2-MIL-53(Al)-derived porous carbons are recommended as recyclable and efficient adsorbents to the treatment of antibiotics in water.

Production of biochar from Melia azedarach seeds for the crystal violet dye removal from water: combining of hydrothermal carbonization and pyrolysis

ABSTRACTBiochar has shown large potential in water treatment because of its low cost, good textural properties, and high reusability. In this study, two porous biochars were developed from the Melia azedarach seeds via direct pyrolysis process (B-700) and through hydrothermal carbonization followed with pyrolysis (HB-700). They were characterized by morphology, structural characteristics, and surface features and used to adsorb the crystal violet (CV) dye in water environment. Results of the isotherm approaches demonstrated that the removal capacity of these biochars reached 119.4 mg/g for B-700, and 209 mg/g for HB-700 (at 45°C). Also, the Avrami model best fitted the kinetic data. The electrostatic attraction was regarded as one of the adsorptions mechanisms of CV dye. The regeneration tests reveal that both B-700 and HB-700 are good reusable adsorbents. Finally, findings of the study showed that the hydrothermal carbonization method that precede the pyrolysis process can improve significantly the adsorption capacity of the produced biochar.

Enhancing extracellular electron transfer through selective enrichment of Geobacter with Fe@CN-modified carbon-based anode in microbial fuel cells.

Microbial fuel cells (MFCs) have been demonstrated as a renewable energy strategy to efficiently recover chemical energy stored in wastewater into clean electricity, yet the limited power density limits their practical application. Here, Fe-doped carbon and nitrogen (Fe@CN) nanoparticles were synthesized by a direct pyrolysis process, which was further decorated to fabricate Fe@CN carbon paper anode. The modified Fe@CN anode with a higher electrochemically active surface area was not only benefit for the adhesion of electrochemically active microorganisms (EAMs) and extracellular electron transfer (EET) between the anode and EAMs but also selectively enriched Geobacter, a typical EAMs species. Accordingly, the MFCs with Fe@CN anode successfully achieved a highest voltage output of 792.76mV and a prolonged stable voltage output of 300h based on the mixed culture feeding with acetate. Most importantly, the electroactive biofilms on Fe@CN anode achieved more content ratio of proteins to polysaccharides (1.40) in extracellular polymeric substances for the balance between EET and cell protection under a harsh environment. This work demonstrated the feasibility of development on anode catalysts for the elaboration of the catalytic principle about interface modification, which may contribute to the practical application of MFC in energy generation and wastewater treatment.

Cryogenic-environment resistant, highly elastic hybrid carbon foams for pressure sensing and electromagnetic interference shielding

Elastic carbon foams are promising material candidates for various applications, including strain/pressure sensing and electromagnetic interference (EMI) shielding, but typically suffer from brittleness, low sensitivity, narrow pressure detection range, and poor performance stability. Herein, a facile and scalable method was demonstrated to fabricate carbon nanotube (CNT) embedded carbonized melamine foams (CNT/CMFs) by a direct pyrolysis process. The hybrid CNT/CMFs show tunable electrical conductivity while providing ultrahigh elasticity even under deep cryogenic conditions (−196 °C). An ultrahigh sensitivity (up to 103.24 kPa−1) and a broad pressure detection range (0–175 kPa) were achieved by the hybrid foam sensors, attributing to the hierarchical structures composed of a nanofibrous CNT layer and macropores. The foam-based sensors exhibit ultrahigh cryogenic-temperature resistance, which retains stable performance after immersing in liquid nitrogen for 36 h and experiencing 5000 cycles of repeated compression-release. Moreover, the CNT/CMFs show an exceptional EMI shielding effectiveness and a high specific shielding effectiveness of 6147.3 dB cm2 g−1 with an absorption-dominant shielding mechanism due to the highly porous structure. The cryogenic-temperature resistant CNT/CMFs with these superior strain/pressure sensing and EMI shielding performance are promising for their practical applications as wearable electronics operating in both mild and harsh environments.

Pyrolyzing soft template-containing poly(ionic liquid) into hierarchical N-doped porous carbon for electroreduction of carbon dioxide

• Soft template-containing poly(ionic liquid) was pyrolyzed to N-doped carbon. • Porosity and N species were modulated by controlling pyrolysis temperatures. • The resultant carbon featured hierarchically small-/ultra-microporous structure. • High-proportioned surface Grap-N species served as the major active sites. • Hierarchical small-/ultra-micropores accounted for the electrocatalysis activity. Heteroatom-doped carbon materials have demonstrated great potential in the electrochemical reduction reaction of CO 2 (CO 2 RR) due to their versatile structure and function. However, rational structure control remains one challenge. In this work, we reported a unique carbon precursor of soft template-containing porous poly(ionic liquid) (PIL) that was directly synthesized via free-radical self-polymerization of ionic liquid monomer in a soft template route. Variation of the carbonization temperature in a direct pyrolysis process without any additive yielded a series of carbon materials with facile adjustable textural properties and N species. Significantly, the integration of soft-template in the PIL precursor led to the formation of hierarchical porous carbon material with a higher surface area and larger pore size than that from the template-free precursor. In CO 2 RR to CO, the champion catalyst gave a Faraday efficiency of 83.0% and a current density of 1.79 mA∙cm −2 at −0.9 V vs. reversible hydrogen electrode ( vs. RHE). The abundant graphite N species and hierarchical pore structure, especially the unique hierarchical small-/ultra-micropores were revealed to enable better CO 2 RR performance.

Study on the Staged and Direct Fast Pyrolysis Behavior of Waste Pine Sawdust Using High Heating Rate TG-FTIR and Py-GC/MS.

To understand the fast pyrolysis kinetics and product evolution of waste pine sawdust, high heating rate thermogravimetry-Fourier transform infrared (TG-FTIR) was used to obtain the kinetic parameters and the chemical groups formed during the pyrolysis process, while pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was used to investigate the detailed compositions of products under the staged (seven stages from 300 to 600 °C) and direct fast pyrolysis process. Spectral bands were identified for acids, alcohols, aldehydes, aromatics, esters, ethers, hydrocarbons, ketones, phenols, and sugars. Research found that the apparent activation energy for fast pyrolysis is much higher than that of slow pyrolysis. The evolution of CO2 is the major deoxygenation route. Cracking mainly occurred at the 450 °C stage with phenols, ketones, aldehydes, and sugars as the main products. The product distributions for different stages are significantly different; the selectivity of aldehydes decreased, while phenols showed an upward trend with an increase in pyrolysis temperature. Ketones and sugars reached their peak values at 450 °C. The changes in the molecular composition of each stage helped to understand the pyrolysis process. Compared with the staged pyrolysis, the direct pyrolysis process had higher selectivity of acids, aldehydes, esters, and sugars and lower selectivity of phenols, ketones, and alcohols.

Hierarchical porous structure formation mechanism in food waste component derived N-doped biochar: Application in VOCs removal

Nitrogen-doped (N-doped) hierarchical porous carbon was widely utilized as an efficient volatile organic compounds (VOCs) adsorbent. In this work, a series of N-doped hierarchical porous carbons were successfully prepared from the direct pyrolysis process of three food waste components. The porous biochar that derived from bone showed a high specific surface area (1405.06 m2/g) and sizable total pore volume (0.97 cm3/g). The developed hierarchical porous structure was fabricated by the combined effect of self-activation (Carbon dioxide (CO2) and water vapor (H2O)) and self-template. The emission characteristics of activation gas analyzed by Thermogravimetric-Fourier transform infrared spectrometer (TG-FTIR) and the transformation of ash composition in the biochar help to illustrate the pore-forming mechanism. Calcium oxide (CaO) and hydroxylapatite were confirmed as the major templates for mesopores, while the decomposition processes of calcium carbonate (CaCO3) and hydroxylapatite provided a large amount of activation gas (CO2 and H2O) to form micropores. The materials also obtained abundant N-containing surface functional groups (up to 7.84 atomic%) from pyrolysis of protein and chitin. Finally, the porous biochar showed excellent performance for VOCs adsorption with a promising uptake of 288 mg/g for toluene and a high adsorption rate of 0.189 min−1. Aplenty of mesopores distributed in the materials effectively improved the mass transfer behaviors, the adsorption rate got a noticeable improvement (from 0.118 min−1 to 0.189 min−1) benefited from mesopores. Reusable potentials of the hierarchical porous carbons were also satisfying. After four thermal regeneration cycles, the materials still occupied 84.8%–87.4% of the original adsorption capacities.

Pyrolysis Carbonization of Sago Starch

Battery requirements are increasing over time, the anode for sodium ion batteries (SIB) can use amorphous carbon. Carbon synthesis is carried out via pyrolysis. Research on the synthesis of carbon derived from sago starch is still rare. This study aims to determine the carbon characteristics of sago starch treated with nitrogen doping according to the SIB anode by taking into account the morphology, size distribution, material structure, material composition, and the distance between layers. The carbonization method used in this research is the pyrolysis process at 900 o C for 1 hour. Variations in the experiment were carried out through direct pyrolysis process with variations of urea against starch 3:1, 2:1, and pure starch. The experimental results were analysis using SEM (EDS) and XRD. The results showed that the pyrolysis process doped with nitrogen with a ratio of 3:1 urea had an interlayer distance of 0.353304 nm, 2:1 had an interlayer of 0.368059 nm, and 0.390178 nm of pure sago starch. This value indicates that carbon is a non-graphite material (> 0.3354 nm). The carbon produced from pyrolysis produces carbon that is amorphous and has a similar shape, which is like wood.

N-doped MWCNTs from catalyst-free, direct pyrolysis of commercial glue

We report a unique, catalyst-free, direct pyrolysis process to obtain nitrogen-doped multiwall carbon nanotubes (N-MWCNTs). The process includes the polymerization of ethyl cyanoacrylate (ECA) based commercial super glue with aqueous NaCl solution. The resultant poly-ethyl cyanoacrylate (PECA)-NaCl composite was washed to remove NaCl and subsequently calcined at 1000 °C in an inert atmosphere to obtain carbon nanotubes. The field emission scanning electron microscopy and high-resolution transmission electron microscopy studies confirm that these are nitrogen-doped multiwall carbon nanotubes (N-MWCNTs) with diameters in the range of 80–110 nm. Compared to conventional MWCNTs, these nanotubes exhibit distinct multilayer stacking of carbon with short-range ordering with interlayer spacing slightly larger than graphitic carbon. XPS studies reveal the presence of doped nitrogen substituting for carbon atoms, whereas Raman spectroscopy data shows that these nitrogen-doped nanotubes exhibit nanocrystalline, graphitic carbon. Washing of PECA-NaCl composite results in the removal of NaCl leading to the unique porous PECA intermediate structure. These unique morphological changes and structural transformations of PECA in DI water along with the peculiar degradation behavior of PECA during the heat treatment process may be responsible for the formation of N-MWCNTs.

Unraveling the Properties of Biomass-Derived Hard Carbons upon Thermal Treatment for a Practical Application in Na-Ion Batteries

Biomass is gaining increased attention as a sustainable and low-cost hard carbon (HC) precursor. However, biomass properties are often unexplored and unrelated to HC performance. Herein, we used pine, beechwood, miscanthus, and wheat straw precursors to synthesize HCs at 1000 °C, 1200 °C and 1400 °C by a two-steps pyrolysis treatment. The final physicochemical and electrochemical properties of the HC evidenced dissimilar trends, mainly influenced by the precursor’s inorganic content, and less by the thermal treatment. Pine and beechwood HCs delivered the highest reversible capacity and coulombic efficiency (CE) at 1400 °C of about 300 mAh·g−1 and 80%, respectively. This performance can be attributed to the structure derived from the high carbon purity precursors. Miscanthus and wheat straw HC performance was strongly affected by the silicon, potassium, and calcium content in the biomasses, which promoted simultaneous detrimental phenomena of intrinsic activation, formation of a silicon carbide phase, and growth of graphitic domains with temperature. The latter HCs delivered 240–200 mAh·g−1 of reversible capacity and 70–60% of CE, respectively, at 1400 °C. The biomass precursor composition, especially its inorganic fraction, seems to be a key parameter to control, for obtaining high performance hard carbon electrodes by direct pyrolysis process.

Hemoglobin-derived Fe-Nx-S species supported by bamboo-shaped carbon nanotubes as efficient electrocatalysts for the oxygen evolution reaction

Herein, we report a facile route to synthesize isolated single iron atoms on nitrogen-sulfur-codoped carbon matrix via a direct pyrolysis process in which hemoglobin, a by-product of the meat industry, was utilized as a precursor for iron, nitrogen and sulfur while bamboo-shaped carbon nanotubes served as a support owing to their excellent conductivity and numerous defects. The resulting metal-nitrogen complexed carbon showed outstanding catalytic performance for the oxygen evolution reaction (OER) in alkaline solutions. At an overpotential of 380 mV, the optimal sample yielded a current density of 83.6 mA cm−2, which is 2.5 times that of benchmark IrO2 (32.8 mA cm−2), rendering it as one of the best OER catalysts reported so far. It also showed negligible activity decay in alkaline solutions during long-term durability tests. Control experiments and X-ray absorption fine structure analyses revealed that Fe-Nx species in the samples are the active sites for OER. Further density functional theory calculations indicated that the presence of sulfur in the carbon matrix modified the electronic structures of active species, thereby leading to the superior activity of the sample.

Facile control of corncobs-based carbons with eutectic salt ZnCl2/NaCl templated for the adsorption of organic aldehyde

Corncob, a renewable biomass waste, has been successfully explored as a low-cost crude carbon source to prepare controlled morphology, and result in higher value-added carbons through a ZnCl2/NaCl treatment and direct pyrolysis process. The synthesis route is simple, green, and results in carbons with different morphology and porous structures by varying the ratio of the eutectic salt ZnCl2/NaCl. Moreover, the adsorption capacities of different carbon materials for formaldehyde and butyraldehyde were tested further. It was demonstrated that NaCl and ZnCl2 could be utilized as a mesopore template, and as a micropore activation agent for carbon materials, respectively. Although the mesopores can provide a fast diffusion channel, and the micropores can enhance adsorption ability, the specific surface area originating from the mesopores was proportional to the amount of butyraldehyde adsorption, and the specific surface area of the micropores was beneficial to the amount of formaldehyde adsorption taking place. The adsorption isotherms follow Langmuir and pseudo first-order kinetic modeling. Additionally, the whole process belongs to physical adsorption.

N-Doped Mo2C Nanobelts/Graphene Nanosheets Bonded with Hydroxy Nanocellulose as Flexible and Editable Electrode for Hydrogen Evolution Reaction.

SummaryThe large-scale application of economically efficient electrocatalysts for hydrogen evolution reaction (HER) is limited in view of the high cost of polymer binders (Nafion) for immobilizing of powder catalysts. In this work, nitrogen-doped molybdenum carbide nanobelts (N-Mo2C NBs) with porous structure are synthesized through a direct pyrolysis process using the pre-prepared molybdenum oxide nanobelts (MoO3 NBs). Nanocellulose instead of Nafion-bonded N-Mo2C NBs (N-Mo2C@NCs) exhibits superior performance toward HER, because of excellent dispersibility and multiple exposed catalytically active sites. Furthermore, the conductive film composed of N-Mo2C NBs, graphene nanosheets, and nanocellulose (N-Mo2C/G@NCs) is fabricated by simple vacuum filtration, as flexible and editable electrode, which possesses excellent performance for scale HER applications. This work not only proposes the potential of nanocellulose to replace Nafion for binding powder catalysts, but also offers a facile strategy to prepare flexible and conductive films for a wide variety of nanomaterials.

Structural model of Longkou oil shale kerogen and the evolution process under steam pyrolysis based on ReaxFF molecular dynamics simulation

ABSTRACT The product distribution and reaction mechanism of steam pyrolysis of Longkou oil shale kerogen was researched by molecular dynamics simulation. Molecule structural model used in the simulation was constructed according to the analysis results of a series of detection about kerogen extracted from Longkou oil shale. Reactive force field molecular dynamics (ReaxFF MD) was used to simulate both steam pyrolysis and direct pyrolysis process of the kerogen at the temperature of 1600, 2000, 2400 and 2800 K. The results show that temperature is a critical factor affecting product distribution in steam pyrolysis, and 2000 K is a proper set temperature for studying steam pyrolysis via molecular simulation method. Besides that, adding the H2O molecules during steam pyrolysis can form complexes with heterogeneous atoms, thus destroying the intermolecular interactions in kerogen. Moreover, as the hydrogen radicals come from H2O molecules can inhibit cross-linking reactions between small fractions, it can reduce the average molecular weight of organic molecules product. These conclusions could be helpful for rational use of oil shale.

Influence of CaO and HZSM-5 on oxygen migration in Chlorella vulgaris polysaccharide pyrolysis

With polysaccharides of Chlorella pyrenoidosa as the raw material, the effects of CaO and HZSM-5 on the yield of bio-oil and the oxygen content in each phase in the pyrolysis of Chlorella vulgaris polysaccharides (CVP), which occurred in a tube furnace at 600 °C, were comprehensively investigated. The reaction path of deoxidation was also analyzed by TG, GC and GC–MS. The GC–MS analysis of liquids showed that liquids from the pyrolysis of chlorella polysaccharides included a range of light oxygenated compounds (e.g., furans, ketones and phenols), and the oxygen content of furan compounds decreased significantly with CaO and HZSM-5. Compared with the direct pyrolysis of polysaccharides (CVP), the catalytic pyrolysis contributed to the decrease in the oxygen content of organic components by 7.32% and 5.76%. The GC analysis showed that there was a remarkable downtrend in the release of oxygen-containing gas (CO and CO2), and the emission of CO2 decreased from 53.11% to 32.92%. The results of the thermogravimetric analysis indicated that the reaction paths of deoxidation in the pyrolysis process of polysaccharides (CVP) with CaO and HZSM-5 varied from those of the direct pyrolysis process: the catalytic pyrolysis with HZSM-5 promoted the conversion of carbohydrate from furans to aromatics over strong acid sites, which was consistent with previous studies; CaO not only acted as a catalyst but also participated in the reaction to change the reaction paths. All results and findings can help to further understand the thermochemical utilization of CPP for bio-oil.

Preparation of N,F,B-Doped Carbon Materials for High-Performance Electric Double Layer Capacitors

The incorporating heteroatom species into carbon materials give opportunities for improving electrochemical properties. Single N-doping strategies are widely studied because of easy preparations and relative abundance in nature. However, facile synthetic methods of multiple-heteroatom-doped carbons are urgent for high-performance supercapacitors. In this study, we propose N,F,B-doped carbons for electric double layer capacitors derived from polyamic acid mixed with boric acid using pyrolysis process. Fluorinated polyamic acid is applied for a N,F-doping source and boric acid acts as a B-doping source. The synthesized carbon materials exhibit excellent electrochemical performances because of the synergetic effects of each N, F, and B atoms. The N and F atoms improve electronegativity property and also low doped B atoms improve redox reactivity in the carbon. The electrode is fabricated by direct pyrolysis process with carbon fabrics, which is an advantage for binder-free type electrodes and flexibility. The morphology and surface properties of the fabricated electrodes are studied by SEM, XPS, Raman, sheet resistance, and contact angle measurement. Furthermore, the flexible symmetric device with PVA-1M H2SO4 gel electrolyte fabricated from the N,F,B-doped carbon indicates a high volumetric capacitance and an energy density as well as mechanical stabilities under various deformations. These results are expected that the synthesized N,F,B-heteroatom-doped carbons offer great potentials as electrode materials for supercapacitor applications.

Ultrafine CuO nanoparticles decorated activated tube-like carbon as advanced anode for lithium-ion batteries

Recently, copper oxide (CuO) as promising anode material for lithium-ion batteries (LIBs) has received much interest. Hybridizing CuO with carbon is considered as a valid way to improve the conductivity and alleviate the volume effect of CuO, but how to achieve more optimized utilization rate of CuO-based anodes still remains a big challenge for us. In this work, activated tube-like carbon (ATC) is firstly prepared by pre-carbonization followed by alkali etching process using palm tree bark hair as initial carbon source, then the ATC is used as carbon matrix to load CuO by a modified phase-transfer approach. As a result, ultrafine CuO nanoparticles decorated ATC (ATC/CuO) can be obtained. For comparison, we also synthesize tube-like carbon (TC) by a direct pyrolysis process, and obtain TC/CuO hybrid by similar loading method. The morphology, structure, composition and surface property of the two carbon matrixes and the corresponding C/CuO hybrids are all systematically investigated. The results show that ATC/CuO hybrid possesses rich COCu bond and unique ultrafine CuO structure, which is attributed to the co-effect of abundant oxygen-containing groups, large specific surface area and special microporous property of ATC matrix. Consequently, the ATC/CuO electrode exhibited much enhanced cycling stability and rate capability when compared to sole CuO and TC/CuO electrodes. Obviously, our work provides a good guidance on the design and development of advanced carbon/metal oxide-based anodes for LIBs.

Analysis and utilization of temple waste flowers in Coimbatore District.

The present work deals with collection, handling, utilization, and management of the waste flowers that are coming out of the temples in Coimbatore District, Tamilnadu, India. An attempt has been made to provide a current situation and complete analysis of temple waste flowers (TWFs) with suggestions and recommendations. As a part of Clean India, Clean and Green Kovai (Green Coimbatore) mission, this paper gives an idea to reduce the volume of temple waste flowers by converting into activated carbon by direct pyrolysis process and chemical activation with sulfuric acid and phosphoric acid process, respectively. The products were analyzed and compared based on the results of physicochemical parameters including pH, conductivity, moisture content, ash content, volatile content, fixed carbon, bulk density, porosity, specific gravity, water soluble matter, acid soluble matter, iodine number, methylene blue number, yield, and Brunauer-Emmett-Teller (SBET) surface area. The structure, surface morphology, and chemical compositions of carbon were determined by field emission scanning electron microscopy (FeSEM), and energy-dispersive X-ray spectroscopy (EDS), respectively. From the comparison of results, the activated carbon produced from temple waste flowers by direct pyrolysis process is fairly better due to low moisture content, low ash content, better yield, and higher surface area.

Facile Synthesis of Three-Dimensional Heteroatom-Doped and Hierarchical Egg-Box-Like Carbons Derived from Moringa oleifera Branches for High-Performance Supercapacitors.

In this paper, we demonstrate that Moringa oleifera branches, a renewable biomass waste with abundant protein content, can be employed as novel precursor to synthesize three-dimensional heteroatom-doped and hierarchical egg-box-like carbons (HEBLCs) by a facile room-temperature pretreatment and direct pyrolysis process. The as-prepared HEBLCs possess unique egg-box-like frameworks, high surface area, and interconnected porosity as well as the doping of heteroatoms (oxygen and nitrogen), endowing its excellent electrochemical performances (superior capacity, high rate capability, and outstanding cycling stability). Therefore, the resultant HEBLC manifests a maximum specific capacitance of 355 F g-1 at current density of 0.5 A g-1 and remarkable rate performance. Moreover, 95% of capacitance retention of HEBLCs can be also achieved after 20 000 charge-discharge cycles at an extremely high current density (20 A g-1), indicating a prominent cycling stability. Furthermore, the as-assembled HEBLC//HEBLC symmetric supercapacitor displays a superior energy density of 20 Wh kg-1 in aqueous electrolyte and remarkable capacitance retention (95.6%) after 10 000 charge-discharge cycles. This work provides an environmentally friendly and reliable method to produce higher-valued carbon nanomaterials from renewable biomass wastes for energy storage applications.