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Nowadays, high-performance electromagnetic wave (EMW) absorption materials derived from low-cost biomass materials have attracted widespread attention. Herein, a novel biomass‑carbon with porous array structures derived from waste soybean dregs is prepared by a hydrothermal method combined with heat treatment using formaldehyde and KOH as activators. The as-prepared biomass‑carbon with significantly enhanced specific surface area can possess more charge transmission paths, increased multiple reflections and scattering, multiple loss modes, and improved impedance matching, leading to the improvement of EMW absorption performances. The obtained single-component biomass‑carbon without any functional fillers exhibits an effective EMW absorption capability with a wide absorption bandwidth of 4.8 GHz at a thickness of 3.5 mm. This study will provide a valuable approach for the preparation of biomass‑carbon based EMW absorption materials with controllable porous structures by the activation process. [Display omitted] • High-performance single-component biomass carbon derived from soybean dregs • Unique porous array structures formed through an activation process. • Effective EMW absorption capability with a wide absorption bandwidth of 4.8 GHz. [ABSTRACT FROM AUTHOR]

Currently, electromagnetic interference (EMI) shielding and microwave absorption are two important means to alleviate the increasingly severe electromagnetic (EM) pollution. However, the application areas of EMI shielding and microwave absorption are quite different, so integrating these two capabilities in the same material is a great challenge. Herein, multiple-scale polyurethane (PU) composite foams (CFs) assisted by tadpole-like carbon nanotube (CNT)@Fe 3 O 4 nanocomposites were designed by a facile solvothermal and self-foaming method. By adjusting the CNT@Fe 3 O 4 loadings and ambient temperatures, the EM parameters and interface impedance matching of PU/CNT@Fe 3 O 4 CFs could be optimized, thus realizing the coexistence of EMI shielding and microwave absorption inside one same material. The resulting CF exhibited an effective minimum reflection loss (RL min) of −41.9 dB and EMI shielding effectiveness (SE) of ∼20 dB. Furthermore, the elevated temperatures within a range of −20-60 °C would stimulate the transformation of individual CF from microwave absorption towards EMI shielding capability and vice versa. This work will promote the development of intelligent EM compatible devices in the field of optional EM protection. [Display omitted] • Polyurethane composite foams assisted by multi-dimensional coral-like components • Reversibly switching microwave absorption towards EMI shielding capability • Outstanding and tunable temperature-stimulated EM protection ability [ABSTRACT FROM AUTHOR]

The conversion of biomass into porous carbon materials with hierarchical porosity and rich heteroatom doping is vital for supercapacitors. However, it is still challenging to efficiently synthesize high-capacitance porous carbon materials with optimized porosity. Herein, N, O co-doped hierarchical porous carbon materials with good rate performance were obtained from Zn(NO 3) 2 ·6H 2 O and soybean protein by a facile one-step chemical foaming process. Zn(NO 3) 2 ·6H 2 O not only functioned as the foaming agent, but also acted as the precursor of hard templates and activation agent. The influence of Zn(NO 3) 2 ·6H 2 O content and carbonization temperature on the microstructure and capacitance performance of the resulting carbonaceous products were investigated. The optimized sample exhibited the largest specific surface area of 1350 m2 g−1 and V t of 1.01 cm3 g−1. The specific capacitance could reach 248 F g−1 at 0.5 A g−1 and retain 109 F g−1at 100 A g−1. The symmetrical supercapacitors exhibited a maximum energy density of 15.75 Wh kg−1 which could light LED bulbs with a voltage of 3 V and power an electronic watch for more than 35 min demonstrating their potential applications. This work paves a shortcut to the synthesis of high rate performance hierarchical porous carbon materials with a low cost and multifunctional chemical foaming agent. The strategy is worth promoting to other biomass in producing hierarchical porous carbon materials for various energy storage devices. [Display omitted] • N, O co-doped hierarchical porous carbon was synthesized from soybean protein. • Zn(NO 3) 2 ·6H 2 O functioned as the foaming agent, hard templates and activation agent. • The optimized sample exhibited a high specific capacitance of 248 F g−1 at 0.5 A g−1. • The maximum energy density can reach 15.75 Wh kg−1. [ABSTRACT FROM AUTHOR]

Low conductivity of metal oxide electrode and low specific capacitance of carbon electrode restrict the further commercial application of supercapacitors. Manganese oxides/carbon composites were prepared by a simple method using homemade porous carbon and KMnO 4 as raw materials. The composites have both high capacitance of metal oxides and high conductivity of carbon due to Mn-O-C interaction. The optimized composite electrode exhibited an incredible ultra-high specific capacitance of 550, 520, 481, 402, and 318 F/g at the current densities of 1, 2, 3, 5, and 10 A/g, respectively. Moreover, the assembled asymmetric supercapacitor (ASC) device obtains an astonishing energy density of 50.2 Wh/kg at a power density of 800 W/kg, while 90.5 % capacitance after 10,000 cycles is still maintained. Meanwhile, ASC devices show great potential applications in energy storage, such as lighting 35 lights and running an electronic stopwatch. This material will promote the development of manganese/carbon composite supercapacitors for its simple preparation methods, ultra-high performance, and is expected to be a promising candidate for commercially large-scale applications. [Display omitted] • Manganese oxides/carbon composite with splendid specific capacitance was prepared by a simple method. • The assembled asymmetric supercapacitor (ASC) device obtains an astonishing energy density of 50.2 Wh/kg (800 W/kg). • The ASC device shows excellent cycling stability with a capacitance remaining of 90.5 % after 10,000 cycles. [ABSTRACT FROM AUTHOR]

Free-standing carbon nanofibrous membranes are prepared by carbonization and H 2 O 2 activation of electrospun polyimide nanofibrous membranes. The green and facile H 2 O 2 activation method not only regulates the pore structure of carbon nanofibers but also introduces rich oxygen species, rendering a hierarchically porous and heteroatom-doped carbon electrode for supercapacitors. The optimal electrode (PI800-8) shows a high specific capacitance of 339.9 F g−1 (0.5 A g−1, 6 M KOH electrolyte) and excellent cycle durability with a capacitance retention of 98.4 % after 50,000 cycles (5 A g−1). Particularly, a non-aqueous symmetric supercapacitor assembled with 1 M Et 4 NBF 4 electrolyte shows a high operating voltage of 2.8 V, and delivers the maximum energy/power density of 37.3 Wh kg−1 and 28.0 kW kg−1, respectively. The H 2 O 2 activation method provides a green, efficient, and versatile strategy to improve the pore properties and chemical compositions of porous carbon materials towards energy applications. [Display omitted] • The N/O-codoped carbon nanofibrous membranes were prepared by commercial electrospun polyimide nanofibrous membranes. • The green H 2 O 2 activation was proposed to ameliorate the pore and chemical properties of carbon nanofibrous membranes. • Excellent comprehensive performance was presented for both aqueous/non-aqueous symmetric supercapacitor. [ABSTRACT FROM AUTHOR]

Hierarchical porous carbon-based electrodes, benefiting from their facilitated ion diffusion and electron conduction, have demonstrated enormous potential in supercapacitors. The preparation of hierarchical carbons with uniformity and appropriate porosity, however, still remains a grand challenge, which hinders their widespread applications. Herein, a hierarchical porous polyimide-derived carbon electrode (CPC-Fe/Zn) has been fabricated by employing bimetallic salts (Fe/Zn) as precursor and template to activate the cellulose/polyimide (PI) carbon (CPC). Originating from suitable distribution of mesopores and micropores, the obtained CPC-Fe/Zn delivers a high specific capacitance of 420 F/g at a current density of 1 A/g. Moreover, a symmetric supercapacitor device assembled with CPC-Fe/Zn exhibits delivers an energy density of 35.5 Wh/kg at a power density of 800 W/kg. Even at a larger current density of 20 A/g, the specific capacitance retention of such device still remains 92.5 % after 10,000 cycles, showing the rate performance and stability. This work has proposed a bimetallic salts template-assisted strategy to precisely modulate of the pore structure of carbon electrodes, which provides a promising platform to design superior electrodes for various electrochemical systems. [Display omitted] • The hierarchically porous structure of the material can be modulated precisely. • The symmetric supercapacitor exhibited a remarkable energy density of 35.5 Wh/kg @ 1000 W/kg. • The specific capacitance retention of symmetric supercapacitor reached 92.5 % after 10,000 cycles. [ABSTRACT FROM AUTHOR]

Biomass resources are promising precursors for porous carbon materials attributing to their renewable, plentiful and low-cost characteristics. In this work, hierarchical porous carbon materials are synthesized by carbonizing the mixture of starch rich biomass precursor and potassium citrate. Potassium citrate is vital for the formation of hierarchical porous structure. The specific surface area of carbon material is greatly enhanced with the addition of potassium citrate and gradually increases with the rise of carbonization temperature. APCs-750 obtained from 750 °C displays the best capacitance performance attributing to a high specific surface area (1105.64 m2 g−1) and a high oxygen content (10.25 at.%). APCs-750 exhibits the highest specific capacitance of 242.5 F g−1 at 0.2 A g−1, good rate performance (119.0 F g−1 at 50 A g−1) and excellent stability (retaining 96.5 % after 20,000 cycles). In addition, the symmetric supercapacitor of APCs-750 shows a high energy density of 12.38 Wh kg−1 at the power density of 99.72 W kg−1 and keeps a capacitance retention of 91.3 % after 20,000 cycles. Hence, this work provides a facial strategy to synthesis high capacitance performance hierarchical porous carbon materials from starch rich precursor. [Display omitted] • Hierarchical porous carbon materials with 3D network structure are synthesized. • One-step carbonization and activation process is designed. • Potassium citrate is vital for the formation of hierarchical porous structure. • The effect of carbonization temperature is investigated. • The carbon materials display good rate performance and stability. [ABSTRACT FROM AUTHOR]

Renewable cellulose-based papers are considered as a good resource for energy storage devices owing to their interlaced microfibrillar structure and high electrolyte absorptivity. Herein, an all-cellulose-based solid-state high-rate supercapacitor assembled with cellulose paper-derived self-supporting porous carbon electrodes and filter paper separator is designed. Benefiting from ingenious surface chemistry and pore structure engineering, the electrodes possess interconnected network structure, hierarchical pores, and appropriate N/O doping levels. The electrode demonstrates high specific capacitance (222.2 F g−1 at 0.2 A g−1), prominent rate capability (120.1 F g−1 at 100 A g−1), and outstanding cyclic stability (98.7 % capacitance retention after 20,000 cycles at 80 A g−1), which surpass most of cellulose-based self-supporting carbon electrodes ever reported. By integrating the well-designed electrodes with a piece of filter paper separator, the assembled symmetric solid-state supercapacitor (1.2 V) achieves an encouraging specific capacitance of 115.0 F g−1 along with an impressive energy density of 22.9 Wh kg−1 and a maximum power density of 15.9 kW kg−1. Moreover, the symmetric supercapacitor with 1 M Et 4 NBF 4 organic electrolyte (3 V) delivered a maximum energy density and power density of 62.5 Wh kg−1 and 54.9 kW kg−1, respectively. This study proposes a design concept of all-cellulose-based solid-state supercapacitors, which presents a promising direction toward environmentally friendly and sustainable energy storage technology. [Display omitted] • A facile solvothermal reaction and carbonization/activation route was proposed to tailor pore and surface characteristics. • All-cellulose-based symmetric supercapacitor was designed by integrating N/O-CP-50 electrodes and filter paper separator. • Excellent comprehensive performance was achieved for N/O-CP-50-based symmetric supercapacitor. • The typical all-cellulose-based solid-state devices balance the cost and performance of portable electronic devices. [ABSTRACT FROM AUTHOR]

The reuse of the waste crumb rubber (CR) is of great significance to alleviate the increasingly serious black pollution problem. Herein, low-cost electromagnetic microwave absorption (EMA) CR composites assisted by conductive carbon nanotubes (CNTs) and magnetic Fe 3 O 4 are fabricated with the aid of microwave. The effects of the addition of CNTs and Fe 3 O 4 on the structure and morphology, and EMA properties of the CR@CNT/Fe 3 O 4 composite are evaluated in detail. The resulted composite can exhibit a superior minimum reflection loss (RL min) of −60.46 dB at 14.19 GHz with a thickness of 2.3 mm, and a wide effective absorption bandwidth of 5.5 GHz (11.2–16.7 GHz) due to the synergy effect of coordinated dielectric and magnetic losses, good interface impedance matching, and internal multiple reflections. This composite recycling from waste tire rubber is expected to become a potential candidate as a low-cost microwave absorber for reducing electromagnetic and black pollution. [Display omitted] • A CNT/Fe 3 O 4 composite recycling from waste tire rubber. • The synergistic effect of electricity and magnetism for EMA. • Highly effective EMA properties of −60.46 dB with wide bandwidth of 5.5 GHz. [ABSTRACT FROM AUTHOR]

Heteroatoms-doped biomass-derived carbon materials (HBC), a new task and hotspot of the current energy research, especially supercapacitor, have featured with low cost and rich sources with enhanced physical, chemical and electrical properties compared with those of pure counterparts. Nevertheless, converting the biomass into high-performance carbon materials by green chemical activators and dopants is still imperatively needed. Herein, a simple and cost-effective one-step method was proposed, using different nitrogen-containing compounds (NH 4 Cl, (NH 4) 2 CO 3 and urea) as both activation agent and dopant, to prepare nitrogen-doped biomass-derived hierarchical porous carbon materials (HPCs). The effect of nitrogen-containing compounds on the electrochemical performance of HPCs was also studied. Among them, NH 4 Cl is proved to be the porogen with the minimum collapse of pollen grain and urea can be identified as the most effective N dopant. Furthermore, the prepared HPC-urea (HPC-U) electrode deliver the highest specific capacitance of 300 F g−1 at 1 A g−1 and rate performance of 50% from 1 to 50 A g−1 in three electrode system, while HPC-NH 4 Cl possesses the maximum capacitance retention rate of 95.2% after 10,000 cycles. In addition, HPC-U based SCs exhibits the highest energy density (14.3 Wh kg−1). Notably this work may provide a certain guideline for choosing N dopants and porogens to prepare biomass-derived carbon materials for the target application. [Display omitted] • An integrated carbonization, activation and doping process for hierarchical porous carbon. • Heteroatoms-rich camellia pollen is used as carbon precursor. • Three nitrogenous compounds is utilized as both activation agent and dopant. • NH 4 Cl is proved to be the porogen with minimum collapse of pollen grain. • Urea can be identified as the most effective N dopant. [ABSTRACT FROM AUTHOR]