The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

In pursuit of more sustainable and competitive biorefineries, the effective valorisation of lignin is key. An alluring opportunity is the exploitation of lignin as a resource for chemicals. Three technological biorefinery aspects will determine the realisation of a successful lignin-to-chemicals valorisation chain, namely (i) lignocellulose fractionation, (ii) lignin depolymerisation, and (iii) upgrading towards targeted chemicals. This review provides a summary and perspective of the extensive research that has been devoted to each of these three interconnected biorefinery aspects, ranging from industrially well-established techniques to the latest cutting edge innovations. To navigate the reader through the overwhelming collection of literature on each topic, distinct strategies/topics were delineated and summarised in comprehensive overview figures. Upon closer inspection, conceptual principles arise that rationalise the success of certain methodologies, and more importantly, can guide future research to further expand the portfolio of promising technologies. When targeting chemicals, a key objective during the fractionation and depolymerisation stage is to minimise lignin condensation (i.e. formation of resistive carbon–carbon linkages). During fractionation, this can be achieved by either (i) preserving the (native) lignin structure or (ii) by tolerating depolymerisation of the lignin polymer but preventing condensation through chemical quenching or physical removal of reactive intermediates. The latter strategy is also commonly applied in the lignin depolymerisation stage, while an alternative approach is to augment the relative rate of depolymerisation vs. condensation by enhancing the reactivity of the lignin structure towards depolymerisation. Finally, because depolymerised lignins often consist of a complex mixture of various compounds, upgrading of the raw product mixture through convergent transformations embodies a promising approach to decrease the complexity. This particular upgrading approach is termed funneling, and includes both chemocatalytic and biological strategies.

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Chemicals from lignin: an interplay of lignocellulose fractionation, depolymerisation, and upgrading

Polymer nanoparticles: Preparation techniques and size-control parameters

With the arising of global climate change and resource shortage, in recent years, increased attention has been paid to environmentally friendly materials. Trees are sustainable and renewable materials, which give us shelter and oxygen and remove carbon dioxide from the atmosphere. Trees are a primary resource that human society depends upon every day, for example, homes, heating, furniture, and aircraft. Wood from trees gives us paper, cardboard, and medical supplies, thus impacting our homes, school, work, and play. All of the above-mentioned applications have been well developed over the past thousands of years. However, trees and wood have much more to offer us as advanced materials, impacting emerging high-tech fields, such as bioengineering, flexible electronics, and clean energy. Wood naturally has a hierarchical structure, composed of well-oriented microfibers and tracheids for water, ion, and oxygen transportation during metabolism. At higher magnification, the walls of fiber cells have an interes...

https://www.fpl.fs.fed.us/documnts/pdf2016/fpl_2016_zhu001.pdf

Wood-Derived Materials for Green Electronics, Biological Devices, and Energy Applications.

Polychlorinated biphenyls (PCBs) in the environment pose long-term risk to public health because of their persistent and toxic nature. This study investigates the degradation of PCBs using sulfate radical-based advanced oxidation processes (SR-AOPs). These processes are based on the generation of sulfate radicals through iron (Fe(II), Fe(III)) mediated activation of peroxymonosulfate (KHSO 5 , PMS) or persulfate (Na 2 S 2 O 8 , PS). This study is the first instance for coupling of Fe(II)/Fe(III) with PMS for PCB degradation in aqueous and sediment systems. The high oxidation efficiencies of the free radicals (SO 4 − ), in combination with the slow rate of consumption of the oxidants, make these processes very effective for the degradation of recalcitrant organic compounds. The effectiveness of the process was evaluated based on the degradation of a model polychlorinated biphenyl, 2-chlorobiphenyl and total organic carbon (TOC) removal. The kinetics of 2-chlorobiphenyl degradation along with the effect of oxidant and catalyst concentrations on the degradation efficiency was studied. Near complete removal of 2-chlorobiphenyl was observed when Fe(II) was used with PMS or PS. Fe(II) acts as a sulfate radical scavenger at higher concentrations indicating that there is an optimum concentration of Fe(II) that leads to most effective degradation of the target contaminant. A chelating agent, sodium citrate, was used to control the quantity of iron in the solution for activation of the oxidant. For the first time, we studied the feasibility of the activation of PMS using iron citrate complexes for PCB degradation. In the presence of sodium citrate, increase in degradation efficiency was observed up to a metal:ligand ratio of 1:2, after which the increase in citrate concentration led to a decrease in removal efficiency. Fe(II)/PMS systems were found to be very effective in degrading PCB in a sediment-slurry system with more than 90% PCB removal being observed within 24 h.

Sulfate radical-based ferrous-peroxymonosulfate oxidative system for PCBs degradation in aqueous and sediment systems

Ternary phase equilibria for acetic acid-water mixtures with supercritical carbon dioxide

Inhibitory effects of lignin on enzymatic hydrolysis: The role of lignin chemistry and molecular weight

Supercritical-fluid processing technique for nanoscale polymer particles.

Biorefinery and paper pulping lignins, referred hereto as technical lignins, contain condensed C–C interunit linkages. These robust C–C linkages with higher bond dissociation energies are difficult to disrupt under hydrogenolysis conditions, which are generally used for cleaving C–O bonds of native lignin in biomass or model C–O linked compounds. Thus, selective interunit C–C cleavage to release aromatic monomers for high-value applications is a challenge. We report an effective catalytic system to cleave such C–C bonds selectively under mild conditions. A representative methylene-linked C–C model dimer achieves 88% yield of mainly two aromatic monomers within 1.5 h at a reasonably low temperature (250 °C) using a commercial CoS2 catalyst. Aromatic monomers convert to nonaromatic products upon the reaction for a prolonged time. The interunit C–C bond of the dimer become unreactive to cleavage upon dehydroxylation of aromatic rings, while the methoxyl group has little effect on the cleavage. β-1 and 5-5 C–...

Selective C–C Bond Cleavage of Methylene-Linked Lignin Models and Kraft Lignin

RESS experiments were performed on the semicrystalline fluoropolymer poly(heptadecafluorodecyl acrylate) [poly(HDFDA); Mw = 254 000, Mw/Mn = 2.95] from solutions in carbon dioxide, with both concentration and degree of saturation being varied in a systematic manner. Phase-behavior measurements were carried out beforehand to locate the liquid−liquid equilibrium phase boundaries and thus establish the degree of saturation for a given concentration and preexpansion temperature and pressure. Concentrations of 0.5−5 wt % polymer were rapidly expanded through a short orifice (L/D = 5.08) at preexpansion temperatures and pressures corresponding to unsaturated, saturated, and supersaturated solutions. The results indicate that the size of the polymer product is controlled by the degree of saturation (S); however, the morphology of the product is controlled primarily by the concentration, not by S. Only at some intermediate concentration, a threshold concentration where fiber formation first starts to occur, does ...

Mark C. Thies

Papers

Ternary phase equilibria for acetic acid-water mixtures with supercritical carbon dioxide

Inhibitory effects of lignin on enzymatic hydrolysis: The role of lignin chemistry and molecular weight

Supercritical-fluid processing technique for nanoscale polymer particles.

Selective C–C Bond Cleavage of Methylene-Linked Lignin Models and Kraft Lignin

Effect of Concentration and Degree of Saturation on RESS of a CO2-Soluble Fluoropolymer