Because of their availability, adjustable microstructure, varieties of forms, and large specific surface area, porous carbon materials are of increasing interest for use in hydrogen storage adsorbents and electrode materials in supercapacitors and lithium–sulfur cells from the viewpoint of social sustainability and environmental friendliness. Therefore, much effort has been made to synthesize and tailor the microstructures of porous carbon materials via various activation procedures (physical and chemical activation). In particular, the chemical activation of various carbon sources using KOH as the activating reagent is very promising because of its lower activation temperature and higher yields, and well-defined micropore size distribution and ultrahigh specific surface area up to 3000 m2 g−1 of the resulting porous carbons. In this feature article, we will cover recent research progress since 2007 on the synthesis of KOH-activated carbons for hydrogen and electrical energy storage (supercapacitors and lithium–sulfur batteries). The textural properties and surface chemistry of KOH-activated carbons depend on not only the synthesis parameters, but also different carbon sources employed including fossil/biomass-derived materials, synthetic organic polymers, and various nanostructured carbons (e.g. carbon nanotubes, carbon nanofibers, carbon aerogels, carbide-derived carbons, graphene, etc.). Following the introduction to KOH activation mechanisms and processing technologies, the characteristics and performance of KOH-activated carbons as well as their relationships are summarized and discussed through the extensive analysis of the literature based on different energy storage systems.

KOH activation of carbon-based materials for energy storage

Rapid growth in the market for electric vehicles is imperative, to meet global targets for reducing greenhouse gas emissions, to improve air quality in urban centres and to meet the needs of consumers, with whom electric vehicles are increasingly popular. However, growing numbers of electric vehicles present a serious waste-management challenge for recyclers at end-of-life. Nevertheless, spent batteries may also present an opportunity as manufacturers require access to strategic elements and critical materials for key components in electric-vehicle manufacture: recycled lithium-ion batteries from electric vehicles could provide a valuable secondary source of materials. Here we outline and evaluate the current range of approaches to electric-vehicle lithium-ion battery recycling and re-use, and highlight areas for future progress. Processes for dismantling and recycling lithium-ion battery packs from scrap electric vehicles are outlined.

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Recycling lithium-ion batteries from electric vehicles

Porous carbons have several advantageous properties with respect to their use in energy applications that require constrained space such as in electrode materials for supercapacitors and as solid state hydrogen stores. The attractive properties of porous carbons include, ready abundance, chemical and thermal stability, ease of processability and low framework density. Activated carbons, which are perhaps the most explored class of porous carbons, have been traditionally employed as catalyst supports or adsorbents, but lately they are increasingly being used or find potential applications in the fabrication of supercapacitors and as hydrogen storage materials. This manuscript presents the state-of-the-art with respect to the preparation of activated carbons, with emphasis on the more interesting recent developments that allow better control or maximization of porosity, the use of cheap and readily available precursors and tailoring of morphology. This review will show that the renewed interest in the synthesis of activated carbons is matched by intensive investigations into their use in supercapacitors, where they remain the electrode materials of choice. We will also show that activated carbons have been extensively studied as hydrogen storage materials and remain a strong candidate in the search for porous materials that may enable the so-called Hydrogen Economy, wherein hydrogen is used as an energy carrier. The use of activated carbons as energy materials has in the recent past and is currently experiencing rapid growth, and this review aims to present the more significant advances.

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Energy storage applications of activated carbons: supercapacitors and hydrogen storage

Replacement of part of the fossil fuel consumption by renewable energy, in particular in the chemical industry, is a central strategy for resource and energy efficiency. This perspective will show that CO2 is the key molecule to proceed effectively in this direction. The routes, opportunities and barriers in increasing the share of renewable energy by using CO2 reaction and their impact on the chemical and energy value chains are discussed after introducing the general aspects of this topic evidencing the tight integration between the CO2 use and renewable energy insertion in the value chain of the process industry. The focus of this perspective article is on the catalytic aspects of the chemistries involved, with an analysis of the state-of-the-art, perspectives and targets to be developed. The reactions discussed are the production of short-chain olefins (ethylene, propylene) from CO2, and the conversion of carbon dioxide to syngas, formic acid, methanol and dimethyl ether, hydrocarbons via Fischer–Tropsch synthesis and methane. The relevance of availability, cost and environmental footprints of H2 production routes using renewable energies is addressed. The final part discusses the possible scenario for CO2 as an intermediary for the incorporation of renewable energy in the process industry, with a concise roadmap for catalysis needs and barriers to reach this goal.

Catalysis for CO2 conversion: a key technology for rapid introduction of renewable energy in the value chain of chemical industries

A review on the preparation of the activated carbon from agricultural waste material is presented. The physical properties such as proximate and ultimate analysis of agricultural waste material were reviewed. The chemical compositions such as cellulose, hemicelluloses and lignin contents were also discussed. The effects of various parameters on the preparation such as carbonization and activation temperature, time, types of activating agents and impregnation ratio were reviewed. Various physical and chemical processes for the activation of the agricultural residues and their effects on the textural properties such as surface area and pore volume were discussed. The low cost, renewable and relatively less expensive of the agricultural waste were found to be efficiently being converted into wealth. The uses of activated carbon derived from agricultural residues in many fields were evidently proven in the review. The reaction kinetic modeling on the pyrolysis and activation of agricultural wastes were also reviewed.

Agricultural bio-waste materials as potential sustainable precursors used for activated carbon production: A review

Comprehensive kinetic model for acetylene pretreated mesoporous silica supported bimetallic Co-Ni catalyst during fischer-trospch synthesis

A 200 MWe circulating fluidized bed (CFB) boiler with three cyclone separators was built in Inner Mongolia in China, and tests were carried out with the coal combustion process. The objective of this research is to investigate the effect of primary (secondary) air flow rate on the combustion process and the effect of multicyclone separator arrangement on solids circulation characteristics. Temperature and pressure drops at different positions in the boiler chamber and cyclone separator diplegs were measured. On the basis of the measured temperature and pressure, heat flux and solids void fraction distribution in the chamber are derived and analyzed. The profiles of temperature, pressure, heat flux, and solids void fraction along the height of the CFB boiler chamber and in the dipleg of cyclone separators at different operation conditions are given and discussed. The secondary air penetration depth in the dense area was tested at different operation conditions, and the effect of secondary air on the combustion process has been investigated. The preliminary test results indicate that the solid distribution in the three parallel cyclone separators is nonuniform and future research is necessary to optimize the arrangement of multicyclone separators for large scale CFB boilers. Key issues on superhigh pressure CFB boiler design, scaling up of CFB boilers, and further work on computational fluid dynamics (CFD) simulation for hydrodynamic behavior in the CFB boiler and cyclone separators are given at the end of this paper.

Commercial Operation Test and Performance Analysis of a 200 MWe Super-High-Pressure Circulating Fluidized Bed Boiler

Preparation of catalyst from phosphorous rock using an improved wet process for transesterification reaction

Potato peel waste (PPW) from food processing was used for removing As3+, Pb2+, and Hg2+ heavy metals from water. The response surface methodology (RSM) and the central composite design (CCD) were employed for determining optimal conditions for heavy metal removal. The statistical analysis indicates that the effect of pH is the most significant parameter. The optimal condition for achieving the maximum removal was obtained for removing different metals using RSM. Desorption study indicates its good reusability within three recycling steps.

Biosorption of heavy metals: A case study using potato peel waste

Activated carbon was produced by K2CO3 chemical activation of furfural production waste. The results showed that the product is essentially microporous carbon whose BET surface area and pore volume when the carbon was activated at 800 degrees C were 2218 m2/g and 1.04 cm3/g, respectively. The potential usefulness of resultant carbons for gas storage is closely investigated. The hydrogen adsorption study showed that all the carbons exhibited a fast adsorption rate and the carbon activated at 800 degrees C had the largest amount of adsorbed hydrogen due to its greater specific surface area and micropore volume. The hydrogen adsorption capacity of the carbon activated at 800 degrees C can reach 1.7 wt % at 77K 1 atm and 0.48 wt % at 298K 6 MPa, respectively. The isosteric heat of adsorption with zero loading of hydrogen on carbon with the largest specific surface area can be 5 kJ/mol. The adsorption model based on Toth equation together with Benedict-Webb-Rubin (BWR) equation of state is proposed for this carbon in adsorbing hydrogen under high pressure. (C) 2010 American Institute of Chemical Engineers Environ Prog, 2010.

Yong Sun

Papers

Comprehensive kinetic model for acetylene pretreated mesoporous silica supported bimetallic Co-Ni catalyst during fischer-trospch synthesis

Commercial Operation Test and Performance Analysis of a 200 MWe Super-High-Pressure Circulating Fluidized Bed Boiler

Preparation of catalyst from phosphorous rock using an improved wet process for transesterification reaction

Biosorption of heavy metals: A case study using potato peel waste

Production of activated carbon by K2CO3 activation treatment of furfural production waste and its application in gas storage