Influence of boron doping on characteristics of glucose based hydrothermal carbons

In this study, the influence of boron doping on structural and surface properties of carbon material synthesized by hydrothermal method was investigated, and the obtained results were compared with the previously published influence that boron has on characteristics of carbonized boron-doped hydrothermal carbons (CHTCB). Hydrothermal carbons doped with boron (HTCB), were obtained by hydrothermal synthesis of glucose solution with the different nominal concentrations of boric acid. It was found that glucose based hydrothermal carbon does not have developed porosity, and the presence of boron in their structure has insignificant influence on it. On the contrary, additional carbonization increases the specific surface area of the undoped sample, while the increase in boron content drastically decreases specific surface area. Boron doping leads to a decrease in the amount of surface oxygen groups, for both, hydrothermally synthesized and additionally carbonized material. Raman analysis showed that boron content does not affect the structural arrangement of HTCB samples, and Raman structural parameters show higher degree of disorder, compared to the CHTCB samples. Comparison of structural and surface characteristics of hydrothermal carbons and carbonized materials contributes to the study of the so far, insufficiently clarified influence that boron incorporation has on the material characteristics.

Beech sawdust based adsorbents for solid-phase extraction of pesticides and pharmaceuticals

Carbonaceous solid-phase extraction (SPE) sorbent, efficient in isolation and enrichment of multiclass pesticides and pharmaceuticals from water, was synthesized starting from cheap waste beech sawdust and using KOH as the activated agent. The first step in carbon material preparation was hydrothermal carbonization of the waste beech sawdust. Following hydrothermal treatment, the obtained material was activated, using different amounts of KOH. It was found that applied activation leads to changes in material structure, an increase in specific surface area, and a decrease in the number of surface oxygen groups compared to carbonized sample. SPE procedure of multiclass pesticides and pharmaceuticals from water using activated carbonized beech sawdust (AcSD) was optimized by selecting the appropriate elution solvents, the sample pH, and the sample volume to obtain the highest enrichment efficiency. The optimized SPE procedure was applied for water analysis using different AcSD samples as a sorbent for analyte preconcentration. Activated carbon sorbent, obtained with the highest amount of KOH, showed the highest recoveries regarding the most analytes, which were comparable with the recoveries obtained by commercial cartridges.

Characterization of Chemically Activated Carbons Prepared from Miscanthus and Switchgrass Biomass

Lignocellulosic biomass, including that of energy crops, can be an alternative source to produce activated carbons (ACs). Miscanthus and switchgrass straw were used to produce ACs in a two-step process. Crushed plant material was carbonized at 600 °C and then obtained carbon was activated using NaOH or KOH at 750 °C. The content of surface oxygen groups was determined using Boehm’s method. The porosity of ACs was assayed using the nitrogen adsorption/desorption technique, while their thermal resistance using the thermogravimetric method. The ACs derived from miscanthus and switchgrass were characterized by surfaces rich in chemical groups and a highly developed porous structure. The highest specific surface areas, over 1600 m2/g, were obtained after carbon treatment with NaOH. High values of iodine number, 1200–1240 mg/g, indicate an extensive system of micropores and their good adsorption properties. The type of activator affected the contents of oxygen functional groups and some porosity parameters as well as thermal stability ranges of the ACs. Among obtained carbons, the highest quality was found for these derived from M. sacchariflorus followed by switchgrass, after activation with NaOH. Hence, while these crop species are not as effective biomass sources as other energy grasses, they can become valuable feedstocks for ACs.

Ageing remarkably alters the toxicity of carbon black particles towards susceptible cells: determined by differential changes of surface oxygen groups

Ageing process remarkably alters the toxicity of carbon black particles towards susceptible cells via changing the species of their surface oxygen groups.

Highly Active Electrode With Efficiently Added Surface Oxygen Groups for a Vanadium Redox Flow Battery

Higher power output by a lower kinetic resistance of the vanadium redox flow battery is needed for its commercialization. In this study, we focused on the air oxidation conditions of carbon paper, which is the electrode material, to reduce the kinetic resistance. The air oxidation is considered to affect the number of surface oxygen groups such as the phenol-type hydroxyl group due to oxidation of the carbon fiber. The surface oxygen groups may correspond to the active sites for the charge/discharge reaction. We quantitatively evaluated the number of surface oxygen groups by temperature-programmed desorption. In addition, we measured the double-layer capacitances of the carbon papers, which may reflect the surface area of the carbon fiber. The single-cell performances, i.e., current–voltage curves and charge–discharge profile, of the electrodes were studied. The air oxidized carbon paper, heat-treated at 500 °C for 3 h (8.4% mass decrease from the pristine sample), showed the highest power density (960 mW cm−2) in this study with thin electrode material (ca., 0.2 mm for one sheet). The negative half-reaction was enhanced by air oxidation. This result could be explained by the reduction of the kinetic resistance by increasing the number of phenol groups, and this power output was relatively high as the vanadium redox flow battery by using a commercial carbon paper and the standard flow field.