Sustainable Carbon Materials Research Articles

Nanoarchitectonics of hierarchical porous biochars from heavy bio-oil by coupling calcium salts assisted template carbonization and K2CO3 activation for high-performance supercapacitors

Biochar derived from biomass has shown potential as electrode materials for supercapacitors, but controlling its pore structure is a challenge. Additionally, coking issues have limited the industrial application of heavy bio-oil, which could be used to prepare carbonous biochar as a substitute for biomass. Herein, to widen the utilization of bio-oil and to control the pore structure, this study introduces a novel approach to utilize heavy bio-oil and regulate pore structure by combining the hard template method and activation method, in which calcium citrate tetrahydrate (CCT), calcium acetate and calcium carbonate act as templates and K2CO3 acts as activator. Through CCT-assisted template carbonization at 700 °C and K2CO3 activation with a mass ratio of 1:2, a hierarchical porous biochar (CCT-700–1:2) with a specific surface area of 2213.09 m2 g−1 was successfully synthesized. The CCT-700–1:2 electrode shows outstanding capacitive performance with a specific capacitance of 213.86 F g−1 at 0.5 A. The assembled solid-state symmetric supercapacitor displays impressive rate capability, maintaining the capacity retention ratio being 69.7 % at 20 A g−1. Furthermore, it demonstrates exceptional cycle stability and the capacitance retention is around 98 % even after 60,000 cycles. The symmetric supercapacitors also show the high energy density being 16.36 W h kg−1 at 250 W kg−1. This study presents a hopeful method for producing sustainable carbon materials by bio-oil used as energy storage devices, enhancing the potential utilizations of biomass derived products in the area of supercapacitors.

Green fabrication of cost-effective and sustainable nanoporous carbons for efficient hydrogen storage and CO2/H2 separation

In this study, sustainable nanoporous carbon materials that are efficient, renewable, cost-effective and adaptable were developed. These microporous feature carbon adsorbents were synthesized utilizing a straightforward and efficient method. Plum stones are residual fruit materials that offer a financially feasible and sustainable carbon source with exceptional porosity and desirable elemental composition. The plum stones underwent carbonization and were subsequently chemically modified with polyaniline nanofibers and then subjected to chemical activation using different activating agents. This yielded sustainable nanoporous carbon with a high degree of porosity, in conjunction with doping with precious high electron density elements such as O, N and S. The sustainable nanoporous carbons that have been developed exhibits exceptional microporosity, with BET-SSA of 1705 m2 g−1 and a pore volume of 0.726 cm3 g−1, besides, the dominance of ultramicropores of 0.6 nm size. This in addition to convenient doping of oxygen, nitrogen and sulfur elements which are crucial for H2 uptake. The developed nanoporous carbon demonstrated highly promising capabilities for storing H2 molecules at cryogenic and ambient temperatures. The sustainable adsorbent achieved hydrogen storage capacities of 4.63 and 0.45 wt% at 77, 296 K, and a pressure of 40 and 80 bar, respectively. This H2 storage capacity at RT is often regarded as one of the highest reported in the literature for nanoporous adsorbents. Moreover, study investigated the separation selectivity of developed adsorbents for CO2/H2 based on uptake ratio at 30 bar and RT. The results demonstrated a significant separation selectivity reaching a value of 382.5 for the CO2/H2, which is regarded as one of the most elevated values documented in the existing literature for nanoporous carbon materials. Thus, the presented sustainable nanoporous materials have shown great promise for hydrogen storage, pre-combustion CO2 capture and H2 purification applications at ambient temperature.

Development of graphitic and non-graphitic carbons using different grade biopitch sources

The growing demand for bio-renewable alternatives to fossil fuels in the production of sustainable carbon materials, aimed at reducing environmental impact, is crucial for advancing a greener future. This research explores an innovative approach for producing biopitches from bio-oils, which are subsequently utilized as a sustainable precursor for developing advanced graphitic carbons (GC) and non-graphitic carbons (NGC) through carbonization and graphitization processes. The study emphasizes the impact of the chemical composition of bio-oils and biopitches, including heteroatom structures, aromatic/aliphatic ratio, and oxygen content with oxygen-bearing functional groups, on the production of GC and NGC. The research also examines their structural parameters at various heating temperatures using characterization techniques such as X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. XRD analysis revealed that GC samples have lower interplanar spacing (d002) and larger crystallite size than NGC, while Raman shows more short-range order and defects in NGC. Furthermore, HRTEM images and fringe analysis demonstrated differences in lamellae structures, tortuosity, and fringe length. These observations, unveiling differences in crystallite size and degree of graphitization between GC and NGC, underscore the influence of temperature on structural order and defect annealing, which is crucial for optimizing material properties.

From waste to resource: Transforming Kraft black liquor into sustainable porous carbon fillers for radome applications

The study addresses environmental and commercial challenges posed by weak black liquor (WBL) generated through the Kraft process in the paper industry. WBL, a toxic waste, annually reaches a staggering 1.3 billion tonnes globally. Currently, it is either incinerated for energy production or subjected to costly and complex chemical treatments to extract valuable compounds. Despite efforts to develop a scalable value-added material, the existing methods are inefficient in fully reusing WBL. Here, we report a simple chemical synthesis process that reuses 100 % of WBL without generating any waste materials; even salts recovered during the process might be reintegrated into the industry as chemical byproducts. Furthermore, given the simplicity and efficiency of the proposed synthesis methodology to transform WBL into a novel and sustainable porous carbon material, the carbon Kraft (CK). The process can also be scaled by using the right synthesis proportions and within a circular economy. CK exhibited desirable characteristics with a renewable content of 65 wt%, including a turbostratic graphitic-like structure (48.8 % graphitized), carbon content of 85 wt%, large specific surface area of 234.0 m2∙g−1, nanoporosity of 0.13 cm3∙g−1, and density of 1.92 g∙(cm3)-1. Moreover, CK showed electrical and thermal insulating characteristics, essential for use as fillers for elastomeric composite in electromagnetic transparent radome structures used to protect antennas and radars of unmanned aerial vehicles (UAV) from harsh environmental effects. Radomes were designed through the electromagnetic impedance match theory of half-wavelength calculations over specific frequencies of 1.3, 10, 15, 20, and 30 GHz. Results showed excellent transmission loss between −0.41 and −1.48 dB, representing 90.8 % and 70.5 % of transmittance, respectively.

Advances in sustainable nano-biochar: precursors, synthesis methods and applications.

Nano-biochar, characterized by its environmentally friendly nature and unique nanostructure, offers a promising avenue for sustainable carbon materials. With its small particle size, large specific surface area, abundant functional groups and tunable pore structure, nano-biochar stands out due to its distinct physical and chemical properties compared to conventional biochar. This paper aims to provide an in-depth exploration of nano-biochar, covering its sources, transformation mechanisms, properties, applications, and areas requiring further research. The discussion begins with an overview of biomass sources for nano-biochar production and the conversion processes involved. Subsequently, primary synthesis methods and strategies for functionalization enhancement are examined. Furthermore, the applications of nano-biochar in catalysis, energy storage, and pollutant adsorption and degradation are explored and enhanced in various fields.

Simultaneous synthesis of sulfonated reduced graphene oxide@graphene oxide hybrid material for efficient electrochemical sensing of silver ions in drinking water

One of the most important concerns around the world nowadays is the drinking water quality. Silver ions (Ag+) are one of the heavy metal ions that can seriously degrade the water quality and therefore, the human health. Hence, the World Health Organization (WHO) fixed the maximum acceptable concentration of these ions in drinking water at approximately 0.93 µM. Thus, the development of cost-effective and efficient techniques and tools that can help to quantify Ag+ ions in drinking water is of great importance. Herein, we used a new, simple, eco-friendly and low-cost synthesis route to synthesize a sustainable hybrid carbon material, namely sulfonated reduced graphene oxide@graphene oxide (S-rGO@GO) that was utilized as electrode material for Ag+ ions electroanalysis in drinking water. The successful synthesis of S-rGO@GO was evidenced by XRD, Raman spectroscopy, XPS, FE-SEM and EDX. The electrochemical characterization of S-rGO@GO revealed its good affinities towards Ag+ and its good electron transport abilities. The sensor prepared from S-rGO@GO (S-rGO@GO/GCE) showed good repeatability and reproducibility. S-rGO@GO/GCE optimization revealed that its best performance is achieved when 5 µL of 1 mg/mL of S-rGO@GO suspension in ultrapure water is used for its fabrication and when the electrodeposition (Ag+ to Ag0) is carried out at -0.1 V vs. SCE for 200 s. The calibration of S-rGO@GO/GCE exhibited a linear relationship in the concentration range of 0.2 to 1.4 µM, with a sensitivity of (0.605 ± 0.015) µA/µM; the statistic LOD was found to be 0.0007 µM. Furthermore, S-rGO@GO/GCE has shown a great potential for real samples analysis.

Sustainable Hard Carbon as Anode Materials for Na‐Ion Batteries: From Laboratory to Upscaling

Sodium‐ion batteries (NIBs) are an alternative to lithium‐ion batteries (LIBs), particularly in applications where cost, availability, and sustainability are more critical. Hard carbon is emerging as a promising anode material for NIBs, however, the scale up remains in developmental stages. In this study, we focus on the development and potential upscaling of sustainable hard carbon materials as anodes for NIBs. The synthesis of hard carbon starts from D‐glucose, a scalable and environmentally benign precursor. A facile process combining hydrothermal carbonisation and subsequent pyrolysis at 1500°C allows the hard carbon to become an industrially viable material. The resulting hard carbon demonstrates competitive performance metrics including a high initial Coulombic efficiency, high reversible capacity, long‐term cycling stability, and rate capability. This study concludes with a discussion of the techno‐economic analysis of adopting such sustainable materials in the battery industry, highlighting the potential for significant advancements in energy storage technologies.

Municipal Solid and Plastic Waste Co-pyrolysis Towards Sustainable Renewable Fuel and Carbon Materials: A Comprehensive Review.

The substantial rise in global energy demand, propelled by industrial expansion, population growth, and transportation needs, poses a formidable challenge. The concurrent urbanization places pressure on the disposal of solid municipal solid waste and the management of plastic waste. Addressing the global waste crisis requires innovative and sustainable garbage disposal solutions with an environmentally friendly approach. This review tackles the challenges of worldwide waste management, focusing on renewable and sustainable fuels and waste recycling through the exploration of co-pyrolysis as an innovative method. It explores the characteristics and environmental impact of municipal solid waste (MSW) and plastic waste (PW), delving into pyrolysis fundamentals, processes, and challenges. The primary emphasis is on co-pyrolysis, elucidating its integration of municipal and plastic waste, synergistic effects, and advantages. The manuscript thoroughly analyzes reaction kinetics, thermodynamics, and the feasibility of co-pyrolysis for energy recovery. It also delves into the synthesis of renewable fuels and valuable chemical intermediates, considering optimization of product distribution. Environmental and economic sustainability aspects, including impact assessment, greenhouse gas emissions, life cycle analysis, and cost analysis of co-pyrolysis processes, are comprehensively investigated. The review underscores the economic benefits of renewable fuel and chemical materials synthesis. The conclusion addresses challenges, proposes future directions, outlines limitations, technical challenges, environmental considerations, and recommends further exploration and integration with other waste management techniques. The manuscript emphasizes the ongoing importance of research in this critical field, aiming to contribute to the development of effective solutions for the escalating global waste management crisis.

Carbonyl Chemistry for Advanced Electrochemical Energy Storage Systems.

On the basis of the sustainable concept, organic compounds and carbon materials both mainly composed of light C element have been regarded as powerful candidates for advanced electrochemical energy storage (EES) systems, due to theie merits of low cost, eco-friendliness, renewability, and structural versatility. It is investigated that the carbonyl functionality as the most common constituent part serves a crucial role, which manifests respective different mechanisms in the various aspects of EES systems. Notably, a systematical review about the concept and progress for carbonyl chemistry is beneficial for ensuring in-depth comprehending of carbonyl functionality. Hence, a comprehensive review about carbonyl chemistry has been summarized based on state-of-the-art developments. Moreover, the working principles and fundamental properties of the carbonyl unit have been discussed, which has been generalized in three aspects, including redox activity, the interaction effect, and compensation characteristic. Meanwhile, the pivotal characterization technologies have also been illustrated for purposefully studying the related structure, redox mechanism, and electrochemical performance to profitably understand the carbonyl chemistry. Finally, the current challenges and promising directions are concluded, aiming to afford significant guidance for the optimal utilization of carbonyl moiety and propel practicality in EES systems.

Bio-based protic salts as precursors for sustainable free-standing film electrodes

Transforming amines with low boiling points and high volatilities into protic salts is a versatile strategy to utilize low molecular weight compounds as precursors for N-doped carbon structures in a straightforward carbonization procedure. Herein, conventional mineral acids commonly used for the synthesis of protic salts were replaced by bio-derived phytic acid, which, combined with various amines and amino acids, yielded partially or fully bio-derived protic salts. The biomass-based salts showed higher char-forming ability than their mineral acid-based analogs (up to 55.9% at 800°), simultaneously providing carbon materials with significant porosity (up to 1177 m2g−1) and a considerable level of N,P,O-doping. Here, we present the first comprehensive study on the correlation between the structure of the bio-derived protic precursors and the properties of derived carbon materials to guide future designs of biomass-derived precursors for the one-step synthesis of sustainable carbon materials. Additionally, we demonstrate how to improve the textural properties of the protic-salt-derived carbons (which suffer from high brittleness) by simply upgrading them into highly flexible nanocomposites using high-quality single-walled carbon nanotubes. Consequently, self-standing electrodes for the oxygen reduction reaction were created.

Simultaneously improving surface area and hydrophilicity of biomass activated carbon for achieving superior desalination performance in CDI

Super activated carbon is a promising electrode material for capacitive deionization (CDI), an emerging sustainable desalination technology. Increasing its CDI performance requires improving hydrophilicity while maintaining high specific surface area. Traditionally this is challenging, but modifying super activated carbon with earth-abundant metal ions at room temperature can achieve both aims through a low-energy process aligned with sustainability. The modified super activated carbon showed higher specific surface area, improved hydrophilicity, and enhanced desalination performance. Particularly, the salt adsorption capacity of Cu2+-modified super activated carbon in 500 mg/L NaCl solution at 1.2 V increased from 35.4 mg/g to 49.3 mg/g, among the highest for sustainable carbon materials. The capacity increase was enabled by simultaneously increasing specific surface area and hydrophilicity through themetal modification process. Along with high charge efficiency (93.4%), fast adsorption rate, and good cycling stability (80% capacity retention over 50 cycles), the modified super activated carbon displayed superior overall desalination performance. This study exemplifies how sustainable design principles can be applied to synthesize high-performance CDI electrode materials, through green chemistry and engineering for optimized efficiency.

Advancements in Olive-derived Carbon: Preparation Methods and Sustainable Applications.

In the realm of material science, carbon materials, especially olive-derived carbon (ODC), have become vital due to their sustainability and diverse properties. This review examines the sustainable extraction and use of ODC, a carbohydrate-rich by-product of olive biomass. We focus on innovative preparation techniques like pyrolysis, which are crucial forenhancing ODC's microstructure and surface properties. Variables such as activating agents, impregnation ratios, and pyrolysis conditions significantly influence these properties. ODC's high specific surface area renders it invaluable for applications in energy storage (batteries and supercapacitors) and environmental sectors (water purification, hydrogen storage). Its versatility and accessibility underscore its potential for broad industrial use, makingit as a key element in sustainable development. This review provides a detailed analysis of ODC preparation methodologies, its various applications, and its role in advancing sustainable energy solutions. We highlight the novelty of ODC research and its impact on future studies, establishing this review as a crucial resource for researchers and practitioners in sustainable carbon materials. As global focus shifts towards eco-friendly solutions, ODC emerges as a critical component in shaping a sustainable, innovation-driven future.

Towards Negative Emissions: Hydrothermal Carbonization of Biomass for Sustainable Carbon Materials.

The contemporary production of carbon materials heavily relies on fossil fuels, contributing significantly to the greenhouse effect. Biomass is a carbon-neutral resource whose organic carbon is formed from atmospheric CO2. Employing biomass as a precursor for synthetic carbon materials can fix atmospheric CO2 into solid materials, achieving negative carbon emissions. Hydrothermal carbonization (HTC) presents an attractive method for converting biomass into carbon materials, by which biomass can be transformed into materials with favorable properties in a distinct hydrothermal environment, and these carbon materials have made extensive progress in many fields. However, the HTC of biomass is a complex and interdisciplinary problem, involving simultaneously the physical properties of the underlying biomass and sub/supercritical water, the chemical mechanisms of hydrothermal synthesis, diverse applications of resulting carbon materials, and the sustainability of the entire technological routes. This review starts with the analysis of biomass composition and distinctive characteristics of the hydrothermal environment. Then, the factors influencing the HTC of biomass, the reaction mechanism, and the properties of resulting carbon materials are discussed in depth, especially the different formation mechanisms of primary and secondary hydrochars. Furthermore, the application and sustainability of biomass-derived carbon materials are summarized, and some insights into future directions are provided.

Investigation of Several Bio Wastes as Sustainable Carbon Materials for Supercapacitor Manufacturing

This work presents various inquests on the utilization of bio wastes, agricultural wastes and sea shells to develop activated carbon as a veritable and sustainable electrode (terminals) substance for supercapacitors-(SC) also known as electrochemical double layer capacitors (EDLC) gadgets for preserving energy. We also looked at how electrode materials are processed with a view to improve or maximise the supercapacitor performance. This review entails how several bio wastes has been singed, synthesized and utilized to produce activated carbon material for long lasting, low-cost and environmentally-friendly EDLCs via the processes of pyrolysis, carbonization, physical activation and/or chemical activation with reagents and then characterized to show attributes making them suitable for application in supercapacitor manufacturing. Some of the features making the samples suitable for use as EDLC electrode materials include pore structure, very large surface area, power density, energy density, pore volume, cyclic stability specific capacitance, iodine adsorption with other attributes. This work also showcases how the various properties were determined by different tests including Brunauer-Emmett-Teller-(BET), Fourier Transform Infrared-(FTIR) Spectrometry, Field Emission Scanning Electron Microscopy-(FESEM), Raman-Spectroscopy, Scanning Electron Microscopy-(SEM), Energy Dispersive X-Ray-(EDX), X-Ray Diffraction-(XRD), TGA-Thermo-Gravimetric Analysis, Cyclic Voltammetry-(CV), Transmission Electron Microscopy-(TEM), and other procedures.

Cobalt-molybdenum bimetallic catalyst effect on biomass-derived graphitic carbon

The development of highly graphitized and porous carbon materials is important for the evaluation of wastes and their use in energy applications. In this study, we focused on the production of simple, safe, and sustainable porous graphitic carbon (GC) materials using an important waste source in the Black Sea region. Catalytic graphitization method was used for the conversion of hazelnut shell powder with low ash (0.11 %) and high carbon (50.85 %) content to GC. The effects of metallic Co and bimetallic Co-Mo catalysts at different ratios on the graphitization mechanism as well as the chemical, structural and surface properties of the produced GCs were investigated. It was determined that Co:Mo= 1:4 is the most suitable ratio due to the emergent synergistic effect. In the HS-Co-Mo-1-4, the ID/IG ratio was found to be 0.876, while the Braun-Emmet-Teller surface area (SBET) was measured as 266.5 m2/g.

One-step synthesis of a sustainable carbon material for high performance supercapacitor and dye adsorption applications

The sustainable transformation of bio-waste into usable, material has gained great scientific interest. In this paper, we have presented preparation of an activated carbon material from a natural mushroom (Suillus boletus) and explor its properties for supercapacitor and dye adsorption applications. The produced cell exhibited a single electrode capacitance of ∼247 F g−1 with the energy and power density of ∼35 Wh kg−1 and 1.3 kW kg−1, respectively. The cell worked well for ∼20,000 cycles with ∼30% initial declination in capacitance. Three cells connected in series glowed a 2.0 V LED for ∼1.5 min. Moreover, ultrafast adsorption of methylene blue dye onto the prepared carbon as an adsorbent was recorded with ∼100% removal efficiency in an equilibrium time of three minutes. The performed tests indicate that the mushroom-derived activated carbon has the potential to become a high-performance electrode material for supercapacitors and an adsorbent for real-time wastewater treatment applications.

Porous Carbon Materials Based on Blue Shark Waste for Application in High-Performance Energy Storage Devices

The scientific community’s interest in developing sustainable carbon materials from biomass waste is increasing steadily, responding to the need to reduce dependence on fossil fuels. Every day, different biomass sources are suggested for obtaining porous carbon materials with characteristics for application in different areas. Porous carbon materials with a high specific surface area are a subject of interest for application in energy storage devices. This work reports the use of blue shark chondroitin sulfate and gelatine as precursors for developing porous carbon materials for energy storage devices. Commercial chondroitin sulfate was used for comparison. The porous carbons obtained in this study underwent various characterization techniques to assess their properties. A BET surface area analyzer measured the specific surface area and pore size. Additionally, scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX), a high resolution-scanning transmission electron microscope (HR-STEM), Raman spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were employed to examine the morphology, composition, and structure of the carbons. A modified glassy carbon (GC) electrode was used as the working electrode for the electrochemical characterization. Cyclic voltammetry and galvanostatic charge/discharge techniques were employed with ethaline, an environmentally friendly and sustainable electrolyte based on choline chloride, to assess the electrochemical performance. Furthermore, the most promising samples were subjected to ball-milling to investigate the impact of this process on surface area and capacitance. Blue shark chondroitin sulfate-based carbon presented a specific surface area of 135.2 m2 g−1, compared to 76.11 m2 g−1 of commercial chondroitin sulfate, both carbonized for 1 h at 1000 °C. Blue shark gelatine presented a specific surface area of 30.32 m2 g−1. The associated specific capacitance of these three samples is 40 F g−1, 25 F g−1, and 7 F g−1. Ball-milling on these samples increased the specific surface area and capacitance of the three studied samples with different optimal milling times. This study presents the novel utilization of carbon materials derived from blue shark (with and without ball-milling) through a one-step carbonization process. These carbon materials were combined with an environmentally friendly DES electrolyte. The aim was to explore their potential application in energy storage devices, representing the first instance of employing blue shark-based carbon materials in this manner.

Electrochemical Performance of Corn Waste Derived Carbon Electrodes Based on the Intrinsic Biomass Properties.

The exploration of cost-effective and sustainable biomass-derived carbon materials as electrodes for energy conversion and storage has gained extensive attention in recent research studies. However, the selection of the biomass and the electrochemical performance regulation of the derived biochar, as well as their interrelationship still remain challenging for practical application. Herein, corn wastes with high carbon content (>40%), corn cob and corn silk, were selected as precursors for the preparation of high value-added and high yield carbon materials via a modified synthetic process. Uniquely, this work put emphasis on the theoretical and experimental investigations of how the biomass properties influence the composition and nanostructure regulation, the electrolyte ion adsorption free energy, and the electrical conductivity of the derived carbon materials as well as their electrochemical performance optimization. Owing to the favorable specific surface area, the hierarchical porous structure, and the diverse elemental distribution, corn cob and corn silk derived carbon materials (CBC and SBC) present great potential as promising electrodes for alkaline aqueous zinc batteries and supercapacitors. The assembled CBC//Zn and SBC//Zn zinc batteries deliver high energy densities of 63.0 Wh kg-1 and 39.1 Wh kg-1 at a power density of 575 W kg-1, with excellent cycling performance of 91.1% and 84.3% capacitance retention after 10,000 cycles. As for the assembled symmetric supercapacitors, high energy densities of 14.9 Wh kg-1 and 13.6 Wh kg-1, and superior long-term cycling stability of 99.3% and 96.6% capacitance retention after 20,000 cycles could be achieved. This study highlights the advantages of utilizing corn cob and corn silk as carbon sources on the designed synthesis of carbon electrodes, and presents a meaningful perspective in the investigation of biomass-derived carbon materials and their potential applications in rechargeable devices.

The effects of lignin structure on the multiscale properties and electrochemical performance of activated carbons

Lignin is a nature’s wonder most abundant aromatic biopolymer and a promising precursor for a wide range of sustainable carbon materials (CMs). However, the effects of lignin structural heterogeneity on the properties and performance of lignin-based CMs are still poorly understood. In this paper, we address the influence of the lignin structural heterogeneity on the properties of lignin-based activated carbons (ACs). Taking two structurally different kraft (KL) and hydrolysis (HL) lignins, we show that they result into ACs with different properties and electrochemical performance in supercapacitor application. In similar carbonization and activation conditions, ACs from HL showed higher specific capacitances than ACs from KL. The difference between the two groups of ACs could not be solely attributed to the difference in their specific surface areas. They were rather found to result from different particle morphologies, pore size distributions, pore wall nanostructures, and surface chemistries, as revealed by multivariate data analyses. Moreover, we observed that KL and HL had different thermophysical behaviors and reactivities during the thermal treatment, which would have influenced the porosity development and surface oxygenation levels and consequently the electrochemical performance of the derived ACs. This work also shows that it is possible to engineer ACs from HL with electrochemical performance close to the commercial YP-50F Kuraray AC, which implies that less pure, carbohydrate-containing lignins are no less advantaged compared to purer KL to produce high-performance ACs for supercapacitor application.

N-doped sponge-like biochar: A promising CO2 sorbent for CO₂/CH₄ and CO2/N₂ gas separation

Sponge-like biochar sorbents were prepared from the dissolution of chitosan followed by freeze-drying methodology and pyrolysis at three different temperatures (400, 600, and 800 °C) to produce sustainable N-enriched carbon materials with enhanced CO2 uptake from CO2/CH4 and CO2/N2 gas mixtures. The pyrolysis process was reproduced by operando TGA-IR to study the gas evolved from the pyrolysis process. It was found that the pyrolysis temperature highly influences the textural properties of the chitosan sponge-like biochar materials, impacting mainly the amount and type of the N-species on the sample but also at the microporosity. XPS revealed the transformation of the amino groups from chitosan into pyridinic-N, pyrrolic-N, graphitic center-N, and graphitic valley-N or pyridine-N oxide species during the pyrolysis process. Increasing the pyrolysis temperature enhanced the quantity of the latter two N-type species. All sponge-like biochars adsorbed higher amounts of CO2 compared with CH4 and N2 gases, with maximum CO2 uptake (∼1.6 mmol⋅g−1) at 100 kPa and 25 °C for the sample pyrolyzed at 600 °C (named CTO_P600). Biochar produced at 800 °C showed no longer adsorption capacity for CH4 and N2, having the highest selectivity value for CO2/N2 separation under continuous flux conditions among all prepared biochar sorbents. Isobaric CO2 adsorption measurements on the CTO_P600 sorbent revealed that physisorption phenomena predominantly governed the CO2 adsorption process, which was confirmed by its consistent adsorption capacity after 10 consecutive adsorption–desorption cycles. Moreover, the biochar exhibited tolerance to water vapor adsorption, indicating its suitability to work under moisture-rich conditions.