Enhancing effect of cobalt phthalocyanine dispersion on electrocatalytic reduction of CO2 towards methanol.

This paper focuses on enhancing the performance of electrocatalytic CO2 reduction reaction (CO2RR) by improving the dispersion of cobalt phthalocyanine (CoPc), especially for the methanol formation with multi-walled carbon nanotubes (CNTs) as a support. The promising CNTs-supported CoPc hybrid was prepared based on ball milling technique, and the surface morphology was characterized by means of those methods such as scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectra (XPS). Then, the synergistic effect of CNTs and ball milling on CO2RR performance was analyzed by those methods of cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), gas chromatography (GC), and proton nuclear magnetic resonance spectroscopy (1HNMR). Subsequently, the reduction mechanism of CO2 on ball-milled CoPc/CNTs was revealed based on the DFT calculations. The results showed that the electrocatalyst CoPc/CNTs hybrid prepared with sonication exhibited a conversion efficiency of CO2 above 60% at -1.0 V vs. RHE, accompanied by the Faradaic efficiencies of nearly 50% for CO and 10% for methanol, respectively. The addition of CNTs as the support improved the utilization efficiency of CoPc and reduced the transfer resistance of species and electrons. Then the ball-milling method further improved the dispersion of CoPc on CNTs, which resulted in the fact that the methanol efficiency was raised by 6% and partial current density was increased by nearly 433%. The better dispersion of CoPc on CNTs adjusted the reduction pathway of CO2 and resulted in the enhancement of methanol selectivity and catalytic activity of CO2. The probable pathway for methanol production was proposed as CO2 → *CO2- → *COOH → *CO → *CHO → *CH2O → *OCH3 → CH3OH. This suggests the significance of the ball-milling method during the preparation of better supported catalysts for CO2RR towards those high-valued products.

Porous Structure of ß-Cyclodextrin for CO2 Capture: Structural Remodeling by Thermal Activation.

With a purpose of extending the application of ß-cyclodextrin (ß-CD) for gas adsorption, this paper aims to reveal the pore formation mechanism of a promising adsorbent for CO2 capture which was derived from the structural remodeling of ß-CD by thermal activation. The pore structure and performance of the adsorbent were characterized by means of SEM, BET and CO2 adsorption. Then, the thermochemical characteristics during pore formation were systematically investigated by means of TG-DSC, in situ TG-FTIR/FTIR, in situ TG-MS/MS, EDS, XPS and DFT. The results show that the derived adsorbent exhibits an excellent porous structure for CO2 capture accompanied by an adsorption capacity of 4.2 mmol/g at 0 °C and 100 kPa. The porous structure is obtained by the structural remodeling such as dehydration polymerization with the prior locations such as hydroxyl bonded to C6 and ring-opening polymerization with the main locations (C4, C1, C5), accompanied by the release of those small molecules such as H2O, CO2 and C3H4. A large amount of new fine pores is formed at the third and fourth stage of the four-stage activation process. Particularly, more micropores are created at the fourth stage. This revealed that pore formation mechanism is beneficial to structural design of further thermal-treated graft/functionalization polymer derived from ß-CD, potentially applicable for gas adsorption such as CO2 capture.

Intermolecular interactions between ß-cyclodextrin and water.

This study focused on demonstrating the intermolecular interactions between ß-cyclodextrin and water, with the aim to better understand the transfer of small molecules to ß-cyclodextrin. The intermolecular interaction strength between ß-cyclodextrin and water was analyzed using different methods such as the dynamic adsorption of water, the TG-DSC of ß-cyclodextrin and molecular modeling employing MM2 force field calculations. The experiments for the adsorption of water on ß-cyclodextrin was aimed to systematically investigate the adsorption characteristics, such as adsorption capacity, adsorption rate, adsorption heat and activation energy, influenced by the adsorption temperature and vapor pressure of water. The results indicated that the water adsorption on ß-cyclodextrin is an exothermic process. The hysteresis loop type in the adsorption isotherms at multiple temperatures indicated that water adsorption is not purely a traditional physical adsorption due to the existence of structure effects such as the cavity effect and hydrogen bonding. The activation energy during water adsorption was 7.4 kJ mol-1. However, the activation energy during water desorption was in the range of 35-45 kJ mol-1, which decreased with an increase in the amount of water adsorbed. This indicated that water adsorption is much easier than water desorption from ß-cyclodextrin and that water desorption is more difficult with a small amount of adsorbed water compared with a large amount of adsorbed water. Subsequently, the obtained average intermolecular interaction strength between ß-cyclodextrin and water under the experimental conditions was 67.5 kJ mol-1 (water), which was verified by DSC.

Single and binary adsorption of heavy metal ions from aqueous solutions using sugarcane cellulose-based adsorbent.

A high efficient and eco-friendly sugarcane cellulose-based adsorbent was prepared in an attempt to remove Pb2+, Cu2+ and Zn2+ from aqueous solutions. The effects of initial concentration of heavy metal ions and temperature on the adsorption capacity of the bioadsorbent were investigated. The adsorption isotherms showed that the adsorption of Pb2+, Cu2+ and Zn2+ followed the Langmuir model and the maximum adsorptions were as high as 558.9, 446.2 and 363.3mg·g-1, respectively, in single component system. The binary component system was better described with the competitive Langmuir isotherm model. The three dimensional sorption surface of binary component system demonstrated that the presence of Pb2+ decreased the sorption of Cu2+, but the adsorption amount of other metal ions was not affected. The result from SEM-EDAX revealed that the adsorption of metal ions on bioadsorbent was mainly driven by coordination, ion exchange and electrostatic association.

Experimental study on elemental mercury removal by diperiodatonickelate (IV) solution.

A novel method has been developed to remove elemental mercury from simulated flue gas by a diperiodatonickelate (IV) solution. The influencing factors, such as diperiodatonickelate (IV) concentration, reaction temperature, solution pH, the initial Hg(0) concentration, SO2 concentration and NO concentration were investigated at a bubbling reactor. In the presence of SO2 and NO, removal efficiency of 86.2% for elemental mercury was obtained. Meanwhile, 56.2% of NO and 98% of SO2 were simultaneously removed, under the optimal experimental conditions, in which diperiodatonickelate (IV) concentration was 6 × 10(-3)mol/L, reaction temperature was 50°C, the initial Hg(0) concentration was 20 µg/m(3) and pH was 8.5. Moreover, based on the research results of the hydrolyzing products of IO(4-), and the analysis of the removal products of Hg(0), the reaction mechanism of Hg(0) removal was proposed.

Simultaneous desulfurization and denitrification from flue gas by Ferrate(VI).

An innovative semidry process has been developed to simultaneously remove NO and SO2 from flue gas. According to the conditions of the flue gas circulating fluidized bed (CFB) system, ferrate(VI) absorbent was prepared and added to humidified water, and the effects of the various influencing factors, such as ferrate(VI) concentration, humidified water pH, inlet flue gas temperature, residence time, molar ratio of Ca/(S+N), and concentrations of SO2 and NO on removal efficiencies of SO2 and NO were studied experimentally. Removal efficiencies of 96.1% for SO2 and 67.2% for NO were obtained, respectively, under the optimal experimental conditions, in which the concentration of ferrate(VI) was 0.03 M, the humidified water pH was 9.32, the inlet flue gas temperature was 130 °C, the residence time was 2.2 s, and the molar ratio of Ca/(S+N) was 1.2. In addition, the reaction mechanism of simultaneous desulfurization and denitrification using ferrate(VI) was proposed.