This work introduces a high-performance absorber based on a lightweight composite material of corn straw biochar and magnetic cobalt nickel zinc ferrite. A composite absorber of corn straw biochar with hierarchical pore structure and magnetic zinc cobalt nickel ferrite particles (Ni–Co–Zn ferrite/C) was prepared by a simple two-step approach of carbonization followed by in-situ growth method. The morphology, structure, function, and absorbing properties of the prepared samples were characterized, and RCS simulation was performed. The results show that the optimal reflection loss value of Ni–Co–Zn ferrite/C-2 reaches −38.04 dB when the layer thickness is 3.5 mm, and the effective absorption bandwidth is 4.32 GHz. The potential of Ni–Co–Zn ferrite/C-2 composite material in stealth applications is verified. It is mainly attributed to the excellent impedance matching performance caused by the multi-level pore structure and the strong polarization loss caused by the rich heterogeneous interface and active sites, which plays a key role in the attenuation of electromagnetic waves. This study provides a useful reference for the design of magnetic ferrite particles/metal oxides/biomass-derived carbon microwave absorbing materials with hierarchical porous structure characteristics.

Marine biomass (MB) offers an environmentally friendly and readily available carbon source from the ocean. However, the high concentration of alkali and alkaline earth metals (AAEMs) in MB typically reduces the carbon yield and inhibits micropore formation during heat treatment due to catalytic gasification. In this study, we successfully synthesized activated carbon (AC) with a high specific surface area (> 1,500 m2/ g) and significant mesopore content (60%, mean pore size: 3.4 nm) from MB by employing preheating, controlled acid purification, and CO₂ activation. The formation of mesopores in the MB-derived AC was driven by catalytic gasification induced by intrinsic and residual AAEMs during preheating and physical activation processes. We evaluated the potential of the MB-derived AC as an electrode material for electric doublelayer capacitors (EDLCs). The material demonstrated high specific capacitance values of 25.9 F/g and 29.4 F/g at 2.7 V and 3.3 V, respectively, during charge–discharge cycles. These high capacitance values at elevated voltages were attributed to the increased number of solvated ions (e.g., 1.93 mmol/g at 3.3 V) present in the mesopores. Fluorine-19 nuclear magnetic resonance (19F solid-state NMR) analysis revealed a substantial increase in solvated ion concentration within the mesopores of the MB-derived AC electrode at 3.3 V, demonstrating enhanced ion mobility and diffusion. These findings highlight the potential of MB-derived AC as a promising electrode material for high-voltage energy storage applications.

Incorporation of pseudocapacitive materials into porous carbon is a promising strategy to boost electrochemical performance. Herein, composite of biomass-derived porous carbon and MnO2 (a typical pseudocapacitive material) was facilely fabricated through an in-situ synthesis approach with sorghum seeds derived porous carbon (SSC) as the skeleton for MnO2 deposition. The as-prepared composite ( MnO2@SSC) exhibits hierarchical porous structure with abundant interlaced MnO2 nanowires wrapping on the surface. While the porous structure is beneficial to the active sites exposure and electrolyte ions transport, the interlaced three-dimensional (3D) network of MnO2 nanowires significantly boosts the tolerance toward volume shrinkage/expansion during the cyclic process. Consequently, the MnO2@ SSC-based electrode delivered quite promising supercapacitive performance including superior specific capacitance of 482.7 F/g at 0.5 A/g, outstanding long-term cycling stability (95.8% specific capacitance retention after 20,000 cycles) and high energy density of 13.7 Wh/kg at power density of 298.1 W/kg. Furthermore, all-solid-state flexible supercapacitor based on MnO2@ SSC can be facilely bent to various angles (0° to 150°) without significant degradation in the capacitive performance. This study provides a facile, cost-effective, and sustainable approach for the fabrication of high-performance electrode materials.

Marine biomass (MB) is gaining attention as a sustainable and eco-friendly carbon source within the carbon cycle, particularly in regions with extensive coastlines. However, the high content of alkali and alkaline earth metals (AAEMs) in MB poses challenges in producing functional carbon materials, like activated carbon (AC), with a high specific surface area (SSA). In this study, we employed a two-step CO2 activation process, coupled with acid treatment, to successfully convert MB into highly porous AC. Preheating followed by nitric acid washing reduced AAEM content from 22.4 to 2.5 wt%, and subsequent atmospheric CO2 activation produced AC with an SSA of 1700 m2/ g and mesopores of 3–5 nm. A further treatment with a mixed acid solution of nitric and acetic acids reduced impurities to below 1.0 wt%. A second pressurized CO2 activation at 1 MPa yielded AC with an SSA exceeding 2100 m2/ g, with mesopores accounting for more than 50% of the total pore volume. This method demonstrates an effective approach to producing high-performance AC from MB for advanced applications.

Industrialization and increasing consumerism have driven up energy demand and fossil fuel consumption, significantly contributing to global climate change and environmental pollution. While renewable energy sources are sustainable, their intermittent nature necessitates the development of efficient energy storage devices to ensure uninterrupted power supply and optimal energy utilization. Electrochemical energy storage devices are promising for sustainable energy. Traditionally, carbon electrode materials for these devices come from non-renewable sources. However, using biomass and biomass–coal blends can help substitute fossil fuels, reducing environmental impact. Recent advancements in carbon materials have achieved specific surface areas of over 2500 m2/ g, resulting in supercapacitor capacitances of 250–350 F/g and cycling stability exceeding 10,000 cycles with < 5% capacity loss. In lithium-ion batteries, biomass-based anodes deliver 400–600 mA h/g, outperforming graphite. Doped carbon materials enhance charge-transfer efficiency by 20–30%, while CO₂ emissions from production are reduced by 40–60%. With 50–70% lower costs than fossil-based alternatives, biomass-derived carbons present a viable pathway for scalable, eco-friendly energy storage solutions, accelerating the transition toward sustainable energy systems. Overall, this work highlights the influence of carbon materials on the electrochemical properties and hydrogen storage capacity of biomass-based carbon materials. This also underscores their potential application in energy storage.

The synthesis of functional carbon materials with controllable morphology and structure using a simple, effective, and green process starting from biomass has been an attractive and challenging topic in recent years. After decades of technological development, high value-added biomass-derived carbon nanomaterials with different morphologies and structures prepared by low-temperature hydrothermal carbonization (HTC) have been gradually developed into a huge system covering different series in different dimensions, and are widely used in the fields of adsorption, electrochemical energy storage, and catalysis. However, due to a vague understanding of the fundamental structure–performance correlation and the absence of customized material design strategies, the diverse needs in practical applications cannot be well met. Herein, we reviewed the mechanism, modifications, and applications of the low-temperature HTC method for biomass. The synthesis mechanisms, structural designs strategies, and related applications of biomass-derived hydrochar are highlighted and summarized in different dimensions, including six major categories: zero-dimensional spherical structure, one-dimensional fibrous and tubular structure, two-dimensional lamellar structure, three-dimensional hierarchical porous structure, and special-shaped asymmetric structure. Then a sustainability assessment is conducted on the hydrothermal carbonization process. Finally, the controllable preparation of biomass-derived hydrochar is summarized and prospected for the application requirements in different fields.

Super P (SP) is a conductive carbon black that significantly enhances the electrical conductivity of various types of electrodes, making it a widely preferred conductive agent in lithium-ion batteries. By contrast, activated carbon (AC), originally used in capacitors due to its porous structure, is expected to contribute to electrochemical performance through its enhanced interaction with lithium ions. First, the physical properties of both materials were analyzed through various characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) to confirm the increase in electrochemical properties through the combination of SP and AC. Furthermore, the microstructure and electrical properties of the LiFePO4 (LFP) electrode were analyzed, to determine the impact on battery performance. With a 1.15 M LiPF6 in an ethylene carbonate/diethyl carbonate (EC/DEC) electrolyte, the results indicated that SP-only electrodes exhibited the highest conductivity and lowest surface resistance, making them the most effective at maintaining stable electrochemical performance. In contrast, electrodes with only AC showed higher resistance, demonstrating that SP remains superior in improving LFP electrode conductivity, ultimately optimizing lithium-ion battery performance.

The raw material selected for this research was Brazil chestnut shells (BCs), which were utilized to gain porous carbon as a positive electrode for lithium–sulfur batteries (LSBs). The effects of N/S co-doped on the electrochemical properties of porous carbon materials were studied using thiourea as nitrogen and sulfur sources. The experimental results indicate that the N/S co-doped carbon materials have a higher mesopore ratio than the undoped porous carbon materials. The porous carbon material NSPC-2 has a lotus-like structure with uniform pore distribution. The N and S doping contents are 2.5% and 5.4%. The prepared N/S co-doped porous carbon materials were combined with S, respectively, and three kinds of sulfur carbon composites were obtained. Among them, the composite NSPC-2/S can achieve the initial specific discharge capacity of 1018.6 mAh g− 1 at 0.2 C rate. At 1 C rate, the initial discharge capacity of the material is 730.6 mAh g− 1, and the coulomb efficiency is 98.6% and the capacity retention rate is 71.5% after 400 charge–discharge cycles.

In this work, subabul wood biomass was used to prepare carbon adsorbents by physical and chemical activation methods at various carbonization temperatures. The properties of the carbon adsorbents were estimated through characterization techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, X–ray photo electron spectroscopy, laser Raman spectroscopy, scanning electron microscopy, CHNS-elemental analysis and N2 adsorption studies. Subabul-derived carbon adsorbents were used for CO2 capture in the temperature range of 25–70 °C. A detailed adsorption kinetic study was also carried out. The characterization results indicated that these carbons contain high surface area with microporosity. Surface properties were depended on treatment method and carbonization temperature. Among the carbons, the carbon prepared after treatment of H3PO4 and carbonization at 800 °C exhibited high adsorption capacity of 4.52 m.mol/g at 25 °C. The reason for high adsorption capacity of the adsorbents was explained based on their physicochemical characteristics. The adsorbents showed easy desorption and recyclability up to ten cycle with consistent activity.

In today’s world, carbon-based materials research is much wider wherein, it requires a lot of processing techniques to manufacture or synthesize. Moreover, the processing methods through which the carbon-based materials are derived from synthetic sources are of high cost. Processing of such hierarchical porous carbon materials (PCMs) was slightly complex and only very few methods render carbon nano-materials (CNMs) with high specific surface area. Once it is processed, which paves a path to versatile applications. CNMs derived from biological sources are widespread and their application spectrum is also very wide. This review focuses on biomass-derived CNMs from various plant sources for its versatile applications. The major thrust areas of energy storage include batteries, super-capacitors, and fuel cells which are described in this article. Meanwhile, the challenges faced during the processing of biomass-derived CNMs and their future prospects are also discussed comprehensively.

High-performance carbon materials were prepared via a one-step molten salt carbonization of tobacco waste used as electrode materials for supercapacitors. Carbon material prepared by carbonization for 3 h in molten CaCl2 at 850 °C exhibits hierarchically porous structure and ideal capacitive behavior. In a three-electrode configuration with 1 mol L− 1 H2SO4 aqueous solution, it delivers specific capacitance of 196.5 F g− 1 at 0.2 A g− 1, energy density of 27.2 Wh kg− 1 at 0.2 A g− 1, power density of 983.5 W kg− 1 at 2 A g− 1, and excellent cyclic stability with 94% capacitance retention after 5000 charge–discharge cycles at 1 A g− 1. Moreover, in a symmetrical two-electrode configuration with 6 mol L− 1 KOH aqueous solution, it delivers specific capacitance of 111.1 F g− 1 at 0.2 A g− 1, energy density of 3.8 Wh kg− 1 at 0.2 A g− 1, and power density of 482.0 W kg− 1 at 2 A g− 1. The relationship between hierarchically porous structure and capacitive performance is also discussed.

Cost-effective and sustainable high-performance supercapacitor material was successfully prepared from cellulosic waste (Sapindus trifoliatus nut shells) biomass-derived activated carbon (CBAC) by physical activation method. The CBAC displays nanofiber morphology, high specific surface area (786 m2/ g), large pore volume (0.212 cm3 g− 1) which are evaluated using FESEM, BET and possessed excellent electrochemical behavior analyzed through various electrochemical methods. Moreover, the assembled symmetric CBAC//CBAC device exhibits high specific capacitance of 240.8 F g− 1 with current density of 0.2 A g− 1 and it is maintained to 65.6 F g− 1 at high current density of 2.0 A g− 1. In addition, the symmetric device delivers an excellent specific energy maximum of over 30 Wh kg− 1 at 400 W kg− 1 of specific power and excellent cycling stability in long term over 5000 cycles. The operation of the device was tested by light-emitting diode. Hence, CBAC-based materials pave way for developing large-scale, low-cost materials for energy storage device applications.

To meet the increased performance and cost requirements of commercial supercapacitor, a N and O self-doped hierarchical porous carbon is fabricated via a green and simple self-activation route utilizing leaves of wild hollyhock as raw materials. Comparing to commercial activated carbon, the reported material exhibits some marked merits, such as simple and green fabrication process, low cost, and superior capacitance performance. The specific surface area of the obtained N and O codoped hierarchical porous carbon arrives 954 m2 g−1, and the content of the self-doped nitrogen and oxygen reaches 2.64 at.% and 7.38 at.%, respectively. The specific capacitance of the obtained material reaches 226 F g− 1 while the specific capacitance of the symmetric supercapacitor arrives 47.3 F g− 1. Meanwhile, more than 90.3% of initial specific capacitance is kept under a current density of 20 A g− 1, and no arresting degradation is observed for capacitance after 5000 times cycle, perfectly demonstrating the excellent cycle and rate capability of the obtained material. The obtained N and O co-doped hierarchical porous carbon are expected to be an ideal substitution for commercial activated carbon.