The synthesis of cyclic carbonates from epoxides and carbon dioxide using metal-free catalyst systems is critically reviewed.

superior performance and have been used for practical applications. [13] Recently, hard carbons including highly graphitized hard carbons and porous hard carbons have been widely investigated, and a specific capacity of 200-500 mA h g −1 , initial Coulombic efficiency (ICE) in the 30-80% range, and an acceptable rate capability were achieved. [14][15][16][17][18] However, these three key indicators of electrochemical performance are often contradictory. For example, the high rate capability of porous hard carbons is always accompanied by a low ICE, whereas the opposite is obtained for highly graphitized hard carbons. This phenomenon originates from the complex sodium-storage behaviors arising from the diversity of the active sites in hard carbons. The control of homogeneous active sites of hard carbons remains a great challenge and requires ongoing research effort.Sodium storage behaviors are mainly divided into three categories: adsorption on the edges, defects, and functional groups, insertion in the graphitic interlayers, and pore filling. In the charge curve of anode materials, highly graphitized hard carbons normally exhibit two regions: a low-potential plateau (0.01-0.10 V) and a high-potential slope (0.10-1.00 V). The reversible capacity of the materials is mainly due to the plateau region. However, this plateau capacity is easily affected by polarization at a high current density, resulting in a decreased sodium storage capacity. Although the correspondence of sodium storage behaviors to different potential regions has been controversial, it is known that the diffusion kinetics of Na + can be improved by the introduction of porosity as an effective strategy for reducing the influence of polarization. [13,[19][20][21] Previous studies have shown that porous hard carbons normally have high reversible capacity and high rate capability, yet low ICE due to a large irreversible capacity loss arising from numerous defects and a large specific surface area. [13,[22][23][24] Their sodium storage behaviors generally exhibit a slope potential region (0.01-3.00 V), but the charge specific capacity below 1.00 V is usually lower than 50%. [18,25,26] In practical use, the charge capacity below 1.00 V of a halfcell is considered to determine its realistic capacity, and a Hard carbon attracts considerable attention as an anode material for sodiumion batteries; however, their poor rate capability and low realistic capacity have motivated intense research effort toward exploiting nanostructured carbons in order to boost their comprehensive performance. Ultramicropores are considered essential for attaining high-rate capacity as well as initial Coulombic efficiency by allowing the rapid diffusion of Na + and inhibiting the contact of the electrolyte with the inner carbon surfaces. Herein, hard carbon nanosheets with centralized ultramicropores (≈0.5 nm) and easily accessible carbonyl groups (CO)/hydroxy groups (OH) are synthesized via interfacial assembly and carbonization strategies, delivering a large capacity (318 mA h ...

The objective of this research is to develop a cost-effective carbonaceous CO2 sorbent. Highly nanoporous N-doped carbons were synthesized with coconut shell by combining ammoxidation with KOH activation. The resultant carbons have characteristics of highly developed porosities and large nitrogen loadings. The prepared carbons exhibit high CO2 adsorption capacities of 3.44-4.26 and 4.77-6.52 mmol/g at 25 and 0 °C under atmospheric pressure, respectively. Specifically, the sample NC-650-1 prepared under very mild conditions (650 °C and KOH/precursor ratio of 1) shows the CO2 uptake 4.26 mmol/g at 25 °C, which is among the best of the known nitrogen-doped porous carbons. The high CO2 capture capacity of the sorbent can be attributed to its high microporosity and nitrogen content. In addition, the CO2/N2 selectivity of the sorbent is as high as 29, higher than that of many reported CO2 sorbents. Finally, this N-doped carbon exhibits CO2 heats of adsorption as high as 42 kJ/mol. The multiple advantages of these cost-effective coconut shell-based carbons demonstrate that they are excellent candidates for CO2 capture.

The goal of our research is developing an efficient and cost-effective carbonaceous CO2 sorbent. Using petroleum coke as the precursor, porous nitrogen-doped carbons were prepared by combining ammoxidation with KOH activation. The as-synthesized samples possess highly developed microporosities and large nitrogen loadings. High CO2 adsorption capacities of 3.76–4.57 mmol/g at 25 °C and 5.80–6.62 mmol/g at 0 °C under atmospheric pressure were achieved. Specifically, the sample prepared under mild temperature (650 °C) and low KOH/precursor ratio (KOH/precursor = 2) shows a CO2 uptake of 4.57 mmol/g at 25 °C, among the highest achieved for nitrogen-doped porous carbons. This high CO2 capture capacity can be attributed to the synergistic effect of nitrogen doping and high narrow microporosity of the sorbent. However, experimental evidence suggests that nitrogen doping contributes less than narrow microporosity. Additionally, the CO2/N2 selectivity and CO2 heats of adsorption of the sorbent are as high as 22 and 37 kJ/mol, respectively. The sorbent also shows high cyclic stability, fast kinetics, and superior dynamic CO2 capture capacity under simulated flue gas conditions, thereby demonstrating that it is an excellent candidate for CO2 capture.

A series of porous carbons for CO2 capture were developed by simple carbonization and KOH activation of coconut shells under very mild conditions. Different techniques such as nitrogen sorption, X-ray diffraction, scanning emission microscopy, and transmission electron microscopy were used to characterize these sorbents. Owing to the high amount of narrow micropores within the carbon framework, the porous carbon prepared at a KOH/precursor ratio of 3 and 600 °C exhibits an enhanced CO2 adsorption capacity of 4.23 and 6.04 mmol/g at 25 and 0 °C under 1 bar, respectively. In addition to the high CO2 uptake, these samples also show fast adsorption kinetics, moderate heat of adsorption, high CO2 over N2 selectivity, excellent recyclability and stability, and superior dynamic CO2 capture capacity. The application of coconut shell as precursors for porous carbons provides a cost-effective way for the development of better adsorbents for CO2 capture.

Owing to the unique advantages of ionic liquids, the preparation and industrial application of ionic liquids have attracted considerable interest. Herein, we report that a series of simple ammonium ionic liquids has been synthesized and characterised. These ionic liquids are air and water stable, easy to prepare from amine and acid, and relatively cheap. They have been used as catalysts and environmentally benign solvents for the cracking reactions of dialkoxypropanes, eliminating the need for volatile organic solvents and additional catalysts. The results clearly demonstrate that these ionic liquids can be easily separated and reused without losing their activity and quality. Furthermore, the conversion and selectivity obtained with this method are significantly increased in comparison with those reported in traditional organic solvents to date. These ionic liquids provide a good alternative way for the synthesis of alkoxypropenes.

Antimony sulfide as a cost-effective, low-toxic, and earth-abundant solar cell absorber with the desired bandgap was successfully deposited using a scalable close space sublimation technique. The deposition process can separately control the substrate and source temperature with better engineering of the absorber quality. The device performance can reach 3.8% with the configuration of glass/FTO/CdS/Sb2S3/graphite back contact. The defect formation energy and the corresponding transition levels were investigated in detail using theoretical calculations. Our results suggest that Sb2S3 exhibits intrinsic p-type owing to S-on-Sb antisites (SSb) and the device performance is limited by the S vacancies. The localized conduction characterization at nanoscale shows that the non-cubic Sb2S3 has conductive grains and benign grain boundaries. The study of the defects, microstructure, and nanoscale conduction behavior suggests that Sb2S3 could be a promising photovoltaic candidate for scalable manufacturing.

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