Degradation of biomass components to prepare porous carbon for exceptional hydrogen storage capacity

Porous carbon has been constructed in various strategies for hydrogen storage. In this work, a simple-effective strategy was proposed to transform sustainable biomass into porous carbon by degrade partial lignin and hemicellulose with Na₂SO₃ and NaOH aqueous mixture. This method collapses the biomass structure to provide more active sites, and also avoid the generation and accumulation of non-porous carbon nanosheets. As a result, the as-prepared sample possesses high specific surface area (2849 m² g^?1) and large pore volume (1.08 cm³ g^?1) concentrating almost completely on micropore. Benefit to these characteristics, the as-prepared sample exhibits appealing hydrogen storage capacity of 3.01 wt% at 77 K, 1 bar and 0.85 wt% at 298 K, 50 bar. The isosteric heat of hydrogen adsorption is as high as 8.0 kJ mol^?1, which is superior to the most biochars. This strategy is of great significance to the conversion of biomass and the preparation of high-performance hydrogen storage materials.     

N,P, S co-doped biomass-derived hierarchical porous carbon through simple phosphoric acid-assisted activation for high-performance electrochemical energy storage

Porous carbon materials are the most widely used electrode materials in Electric Double Layer Supercapacitor (EDLS). Optimize specific surface area, improving hierarchical pores structure, and doping heteroatoms are all important methods to improve the capacitance performance of electrodes. Herein, we synthesize walnut shell-derived hierarchical porous carbon (WSPC) with cost-effective and well-developed pore for electrochemical energy storage via simple phosphoric acid-assisted activation method. The final porous carbon products have perfect microporous structure, abundant heteroatom functional groups (the atomic content ratio of nitrogen, phosphorus and sulfur reaches 10.3%), and high specific surface area and pore volume (up to 2583 m² g^?1 and 1.236 cm³ g^?1, respectively). In the three-system, the electrode shows an optimal specific capacitance of up to 332 F g^?1 and excellent rate performance. In the symmetric system, the symmetric device WSPC//WSPC shows a maximum gravimetric specific energy of ~14.08 Wh kg^?1. And the device still has a specific energy of 9.75 Wh kg^?1 even under the high gravimetric specific power of 7 kW kg^?1. In addition, the device has excellent cycle stability and retains an initial specific capacitance of 90.2% after 8000 galvanostatic charge-discharge (GCD) cycle. In summary, these outstanding results suggest the biomass derived porous carbon possessing the potential and will show great commercial value for the fabrication of high performance supercapacitors.     

Green and facile synthesis of porous carbon spheres from waste solution for high performance all-solid-state symmetric supercapacitors

Porous carbon spheres materials display huge potential for energy storage, but their general synthesis need chemical activation agent with highly corrosive to create pores. In this work, a simple, environment-friendly and less time-demanding method is used to prepared porous carbon spheres using K₂FeO₄ as activation agent and waste solution as the precursor. The K₂FeO₄ employ in this work acts both as an activating agent and a catalyst. In addition, replacing KOH with K₂FeO₄ does not only reduce the corrosion of equipment but also increases the content of oxygen. The optimized porous carbon spheres with high specific surface area, hierarchical pore structure and surface heteroatom can deliver a high specific capacitance of 260 F g⁻¹ at 0.1 A g⁻¹ and good cycling stability (90% retention after 15000 cycles at 5 A g⁻¹). Furthermore, the all-solid-state symmetric supercapacitors fabricated based on as-prepared samples exhibit good electrochemical performance in the PVA/KOH electrolyte. This work offers a green route to convert waste solution into porous carbon spheres, which are promising candidate material for supercapacitors to energy storage.     

Nitrogen doped porous carbon derived from EDTA: Effect of pores on hydrogen storage properties

N doped carbon samples have been prepared from commonly available precursor EDTA and thoroughly characterised using a variety of techniques. It has been found that with increase in annealing temperature graphitic character increases along with decrease in nitrogen content. During chemical activation by treatment with H₃PO₄, C atoms from the network structure get oxidised preferentially giving rise to larger pores, as confirmed by TEM and SAXS analysis. Possible mechanism of activation has been proposed based on NMR and XPS results. From NMR it is established that the activated samples consist of both orthophosphate (Q^o) and pyrophosphate (Q¹) structural units and are weakly linked to carbon network. Pore size has been correlated with hydrogen storage capacity and it has been found that the presence of large number of pores with lower diameter is preferable for getting better hydrogen storage capacity in porous carbon based materials.     

One-step synthesis of 3D sulfur-doped porous carbon with multilevel pore structure for high-rate supercapacitors

In this work, three-dimensional (3D) interconnected S-doped porous carbon materials are fabricated using bio-waste sodium lignosulfonate as carbon and sulfur precursor by in situ carbonization and subsequent KOH activation process. The as-obtained S-PC-50 has high specific surface area of 1592 m² g^?1, high S weight percentage up to 5.2 wt% and interconnected porous framework consisting of micro-, meso- and macropores. As a result, the S-PC-50 exhibits a high specific capacitance of 320 F g^?1 at 0.2 A g^?1, excellent rate performance with 76.5% capacitance retention after a current density increasing from 2 A g^?1 (200 F g^?1) to 100 A g^?1 (153 F g^?1) and 99% capacitance retention after 10,000 cycles at 5 A g^?1. Besides, the symmetric supercapacitor can deliver a high energy density up to 8.2 Wh kg^?1 at 50 W kg^?1.     

Facile synthesis of hybrid porous composites and its porous carbon for enhanced H2 and CH4 storage

The anticipated energy crisis due to the extensive use of limited stock fossil fuels forces the scientific society for find prompt solution for commercialization of hydrogen as a clean source of energy. Hence, convenient and efficient solid-state hydrogen storage adsorbents are required. Additionally, the safe commercialization of huge reservoir natural gas (CH₄) as an on-board vehicle fuel and alternative to gasoline due to its environmentally friendly combustion is also a vital issue. To this end, in this study we report facile synthesis of polymer-based composites for H₂ and CH₄ uptake. The cross-linked polymer and its porous composites with activated carbon were developed through in-situ synthesis method. The mass loadings of activated carbon were varied from 7 to 20 wt%. The developed hybrid porous composites achieved high specific surface area (SSA) of 1420 m²/g and total pore volume (TPV) of 0.932 cm³/g as compared to 695 m²/g and 0.857 cm³/g for pristine porous polymer. Additionally, the porous composite was activated converted to a highly porous carbon material achieving SSA and TPV of 2679 m²/g and 1.335 cm³/g, respectively. The H₂ adsorption for all developed porous materials was studied at 77 and 298 K and 20 bar achieving excess uptake of 4.4 wt% and 0.17 wt% respectively, which is comparable to the highest reported value for porous carbon. Furthermore, the developed porous materials achieved CH₄ uptake of 8.15 mmol/g at 298 K and 20 bar which is also among the top reported values for porous carbon.     

A study on the hydrogen storage capacity of Ni-plated porous carbon nanofibers

In this study, we prepared highly porous carbon-nanofiber-supported nickel nanoparticles as a promising material for hydrogen storage. The porous carbons were activated at 1050 °C, and the nickel nanoparticles were loaded by an electroless metal-plating method. The textural properties of the porous carbon nanofibers were analyzed using N₂/77 K adsorption isotherms. The hydrogen storage capacity of the carbons was evaluated at 298 K and 100 bar. It was found that the amount of hydrogen stored was enhanced by increasing nickel content, showing 2.2 wt.% in the PCNF-Ni-40 sample (5.1 wt.% and 6.4% of nickel content and dispersion rate, respectively) owing to the effects of the spill-over of hydrogen molecules onto the metal–carbon interfaces. This result clearly indicates that the presence of highly dispersed nickel particles can enhance high-capacity hydrogen storage.     

Transformation of biomass into carbon nanofiber for supercapacitor application – A review

This paper starts with a review on challenges and need of improved supercapacitor application, which is then followed by advantages of biomass compared with other materials for use in supercapacitor application. The conversion of biomass into carbon nanofiber using different techniques was extensively reviewed for its advantages and limitations. It was revealed that the materials currently used are yet to be fully sustainable or feasible for energy storage application. In contrast, biomass represents a widely available and sustainable material to be converted into carbon nanofiber for energy storage application. Different techniques were employed for carbon nanofiber production to achieve different objectives, comprising high product yield, feasible diameter adjustment, low electric consumption, and shorter production time. Nevertheless, it was revealed that many key properties of the biomass-derived carbon nanofiber have yet to be fully investigated, as there are still knowledge gaps to be filled for each technique. Thus, more studies are needed to broaden the existing understanding in the key parameters of different techniques in order to develop a highly desirable carbon nanofiber from biomass for sustainable energy storage application.     

Construction and preparation of nitrogen-doped porous carbon material based on waste biomass for lithium-ion batteries

Biomass derived carbon materials have been widely studied as electrodes in energy storage devices due to their renewable nature, low-cost and tunable physical/chemical properties. However, the influences of different treatments for biomass derived carbon materials are still lack of in-depth discussion. In this work, we investigate the effects of the treatment for biomass on the structure and composition of the resulted carbon materials. Especially, the optimal N-doped porous carbon (NPCCS), which was fabricated by H₂SO₄-assisted hydrothermal treatment and subsequent pyrolysis process using corn silk as raw material, shows a unique interconnected layered nanostructure with ultra-high nitrogen content (18.79 at%). As a result, the NPCCS electrode displays excellent cycling stability and outstanding rate performance in lithium-ion half-cell test and shows high first reversible specific capacity of 523.6 mAh g^?1 in full-cell test. This work provides some guidance for preparing biomass derived carbon materials with superior electrochemical performance for the applications in advanced energy storage devices.     

Hydrogen storage ability of porous carbon material fabricated from coffee bean wastes

The hydrogen storage ability at 298 and 77 K of porous carbon materials with microporous structures fabricated from coffee bean wastes through KOH activation was investigated regarding pore structure. The dependence of hydrogen storage ability on the pore structure of porous carbon materials was investigated at 298 and 77 K to clarify the storage mechanism of carbon materials. Hydrogen storage ability at 298 K was increased linearly with increasing of specific surface area increasing. The maximum amount of stored hydrogen was 0.6 wt.% on porous carbon material with 2070 m²/g specific surface area. The hydrogen storage ability at 77 K was 4.0 wt.% on the same sample. The hydrogen storage ability showed a linear relationship with the micro-pore volume size. These changes in the dependence of the hydrogen storage ability on pore size suggested that the storage configuration changed from two- to three-dimensional. The stored hydrogen densities in porous carbon materials calculated from these values were 5.7 and 69.6 mg/cm³ at 298 and 77 K, respectively. The change in density indicated that the state of stored hydrogen in porous carbon materials was filled up aggregational state, which is extremely close to the liquid state, and suggested the realizing of high hydrogen storage ability on carbon materials fabricated from agricultural waste.     

Activated carbon synthesis from tangerine peel and its use in hydrogen storage

Activated carbon samples were synthesized by chemical and physical activations of tangerine peel. The activated carbons were characterized via using Fourier Transform Infrared-Attenuated Total Reflectance spectroscopy (FTIR-ATR), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET), Differential Thermal Analysis-Thermogravimetry (DTA/TG) techniques. It was found that the activated carbon samples were porous, and their surface areas were increased by treating with the various concentrations of ZnCl₂ and KOH. After the formation of activated carbons, they turned into a structure that was formed from carbon atoms, and their residual amounts decreased. In addition, the hydrogen storage capacities of the activated carbon samples were measured in different pressures at 77 and 298 K using the Hiden IMI PSI instrument. The results, confirmed that the hydrogen storage capacities of the activated carbons were higher at the cryogenic temperatures, and higher hydrogen storage capacity were observed by the increasing concentrations of activation agents in the synthesized activated carbons. The activated carbons synthesized by ZnCl₂ had higher hydrogen storage capacity than those by KOH.     

Novel 2D porous carbon nanosheet derived from biomass: Ultrahigh porosity and excellent performances toward V2+/V3+ redox reaction for vanadium redox flow battery

In this paper, biomass-derived carbon-based nanosheet from a kind of domestic waste (fish scales) has been successfully prepared as catalysts with high electrocatalytic activity for V²⁺/V³⁺ couple of vanadium redox flow battery (VRFB) using hydrothermal, lyophilization, and carbonization treatments. KOH is employed as template and activator, which results in nanosheet structure, ultrahigh porosity, and introduction of oxygen-containing groups. The obtained catalyst (FSC-K) exhibits the advantages of large surface area, many active sites and excellent wettability. FSC-K can effectively reduce electrochemical polarization of electrode reaction and accelerate mass transfer of active species. The cell using FSC-K demonstrates a high energy storage efficiency. Compared with pristine cell, the discharge capacity of FSC-K modified cell is 67.2 mA h at 150 mA cm⁻², increased by 18 mA h, and the corresponding energy efficiency reaches 63.8%, enhanced by 7.9%. The capacity retention of FSC-K modified cell keeps 83.1% after 50 cycles at 75 mA cm⁻², 16.7% larger than that for pristine cell. This work reveals that the electrocatalyst for V²⁺/V³⁺ couple obtained from biomass is significant for improving the comprehensive energy storage performance of VRFB.     

Perspective and potential of CO2: A focus on potentials for renewable energy conversion in the Mediterranean basin

Figures commonly quoted on the soon shortage of generating energy from fossil sources which may give the impression that it will be possible to switch to renewable energies conversion as foundations for the future of industrial instances in the Mediterranean basin. In this study, CO₂ energy potential and perspectives in the Mediterranean basin have been investigated in terms of efficiency, feasibility, geographical patterns and savings. Two conjoint mathematical protocols have been carried out in order to yield a simplified extracted scheme for prototype CO₂ trapping/storage plants.     

Green synthesis of molybdenum-based nanoparticles and their applications in energy conversion and storage: A review

In the scope of the rapid technological advancements, nanoparticles (NPs) have gained prominence due to their excellent and tunable biological, and physicochemical properties. Nowadays, different methods are used for their synthesis. In particular, the green synthesis of metal precursors for the synthesis of NPs, represents a cost-effective, environmentally friendly, and hazardous chemical-free method for developing a large variety of NPs. By exploiting plant extracts, the production rate of NPs is relatively faster. Due to fossil reserves and high fuel consumption, renewable and clean energy materials are urgently needed to improve environmental sustainability. With outstanding electrochemical and physicochemical characteristics, molybdenum-based NPs (Mo-NPs) are gaining increasing attention in the fields of energy conversion and storage. Considering the significance of Mo-NPs synthesized from greener routes and their energy applications, it is necessary to review recent trends and developments in this field. This review summarizes important research studies and future research guidelines for the preparation of Mo-NPs through green routes and their applications to meet global energy and environmental demands. Moreover, future research directions are also highlighted to achieve sustainable greener precursors and Mo-NPs based energy storage devices.     

Electrocatalysis by design: Enhanced electro-oxidation of glycerol at NiOx nanoparticle modified 3D porous carbon felts

This paper addresses the preparation of three-dimensional functionalized carbon felts (CFs), which were coated with nickel (Ni) nanostructures and used as an electrocatalyst for glycerol electrooxidation in alkaline medium. The commercial CFs (3D-carbon fibers) were first functionalized with O- and S- like functionalities via electrochemical pretreatment in NaOH and H₂SO₄, then the impacts of this pretreatment on the electrodeposited Ni nanoparticles (NiNPs) morphology, distribution, structure and performance for glycerol electrooxidation was investigated. X-ray diffraction (XRD) together with cyclic voltammetry (CV) techniques were used to detect the changes of the electrodeposited Ni oxide phases. Contact angle was used to determine impact of pretreatment on the wettability of CF. X-ray photoelectron spectroscopy (XPS) was used to get information about the added functional groups while scanning electron microscope (SEM) was used to observe the changes of NiNPs morphology, distribution, and particle size. As-synthesized NiNPs modified functionalized CFs exhibited an excellent activity concurrent with good stability for glycerol electrooxidation. The pretreatment of CF in either NaOH or H₂SO₄ resulted in a significant increase in the Ni surface active sites and improved their electrocatalytic activity for glycerol electrooxidation.     

Recent progress on self-supported two-dimensional transition metal hydroxides nanosheets for electrochemical energy storage and conversion

Transition metal hydroxides (TMHs) nanosheets have attracted wide attention in electrochemical energy storage and conversion because of their superior surface area, highly tunable composition, and low cost. Moreover, the self-supported electrode has been extensively studied for electrochemical devices due to its fast electron transfer and mass transport, resulting in enhanced stability and electrode performance. Hence, reviewing the recent advances in self-supported TMHs nanosheets is crucial for developing high-performance electrodes for electrochemical devices. In this review, we first introduce the fundamental properties of TMHs in terms of layered single metal hydroxides (LSHs) and layered double hydroxides (LDHs). Then, we review various synthetic approaches utilized to construct self-supported TMHs nanosheets with tunable compositions and structures. Afterwards, the electrode performance and durability of self-supported TMHs nanosheets in various electrochemical applications (water electrolysis, zinc-air battery and supercapacitor) are comprehensively summarized. Finally, the further perspectives on current challenges and research directions of self-supported TMHs nanosheets towards electrochemical energy storages and conversion applications are proposed.     

Sodium alginate assisted preparation of oxygen-doped microporous carbons with enhanced electrochemical energy storage and hydrogen uptake

Microporous carbons with large oxygen content have been successful synthesized from biomass by the sodium alginate assisted strategy. During the activation process, the Na₂O formed by the decomposition of sodium alginate combines with the activator KOH to undergo a redox reaction in situ with precursor, thereby forming a rich porosity in the samples. The obtained samples possess not only high SSA (2310~3001 m² g^?1) and large pore volume (0.89~1.19 cm³ g^?1) arising almost completely (>90%) from micropores, but also retains a high content of oxygen (21.86~32.47 wt %). As supercapacitor electrodes, the oxygen-doped microporous carbons display a high specific capacitance of 385 F g^?1 at 0.5 A g^?1 with capacity stability of 91.5% after 20 000 cycles at 5 A g^?1. As hydrogen storage materials, the oxygen-doped microporous carbons exhibit enhanced hydrogen storage capacity of 2.84 wt% (77 K, 1 bar) and 0.91 wt% (303 K, 50 bar). Experimental data indicate that this work provides a simple-efficient and universal strategy for preparing oxygen-doped microporous carbon for high-performance energy and hydrogen storage.     

The green metric evaluation and synthesis of diesel-blend compounds from biomass derived levulinic acid in supercritical carbon dioxide

Levulinate compounds are the biomass derived important energy products which are primarily used as diesel-blending components. These levulinates are the oxygenated fuel additive which promote complete combustion of fuel and reduces emission of pollutants like particulate matters and nitrogen oxides. In the present study, we have investigated sustainable synthesis of biomass derived levulinate compounds catalyzed by Cal B lipase in supercritical carbon dioxide (SC-CO₂) as a green biocatalyst in green reaction media which provided an excellent mass yield. Various reaction parameters were optimized in details such as butanol, levulinic acid, biocatalyst, co-solvent, temperature and pressure to obtain 99% mass yield of the desired product. Moreover various green metric parameters (e.g. E-factor, carbon efficiency and mass productivity) of present methodology were evaluated. The green metrics evaluation suggested that developed procedure is a promising and a greener alternative as compared to various reported conventional synthetic protocols. The biocatalyst was efficiently recycled up to the five cycles. Moreover, the developed protocol can be used for synthesis of various industrially important levulinate compounds which also provided excellent mass yield. Thus, the present protocol demonstrated (i) robust biocatalytic application for transformation of renewable biomass derived levulinic acid (LVA) into value added chemicals and (ii) various green metric evaluation study for the sustainability.     

Energy generation from biomass and waste in the Netherlands: A brief overview and perspective

For a number of years, the interest in energy generation on the basis of biomass and waste has been increasing. A brief overview is given of biomass waste availability in the Netherlands. In recent years several new projects related to energy generation from biomass and waste are initiated in the Netherlands. The results and status of some major projects are outlined in this paper. In the short term only biomass waste (available at low and even negative prices) can play an important role. Establishment of a carbon tax will increase the feasibility of energy crops for energy generation.     

Preparation and hydrogen storage capacity of highly porous activated carbon materials derived from polythiophene

Highly porous carbons have been successfully synthesized by chemical activation of polythiophene with KOH. The activation process was performed under relatively mild activation conditions, i. e., a KOH/polymer weight ratio of 2 and reaction temperatures in the 600-850 °C range. The porous carbons thus obtained possess very large surface areas, up to 3000 m²/g, and pore volumes of up to 1.75 cm³/g. The pore size distribution of these carbons can be tuned via modification of the activation temperature. Thus, by increasing the activation temperature from 600 to 850 °C, the nature of the carbons changes gradually from microporous to micro-mesoporous (with small mesopores of up to 2.5 nm). The polythiophene-derived activated carbons are sulfur-doped with sulfur contents in the 3-12 wt% range. The sulfur content decreases at higher activation temperature. The hydrogen storage capacity of these activated carbons, at cryogenic temperature and 20 bar, is up to 5.71 wt% with an estimated maximum hydrogen uptake of 6.64 wt%. Their ease of preparation and high uptake makes the polythiophene-derived carbons attractive hydrogen storage materials.