Determination of the Surface Oxidation Degree of the Carbonaceous Materials by Quantitative TG-MS Analysis

Hotová, Gabriela; Slovák, Václav

doi:10.1021/acs.analchem.6b03914

Cited by 27 publications

(6 citation statements)

References 16 publications

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“…1b-d) shows specific DTG profiles. These may be interpreted as baselines for each activated carbon and represent functional groups and oxygen containing surface complexes released from the adsorbent 42 .…”

Section: Characterisation Of the Thermal Decomposition Processesmentioning

confidence: 99%

Specific adsorption sites and conditions derived by thermal decomposition of activated carbons and adsorbed carbamazepine

Dittmann

Eisentraut

Goedecke

et al. 2020

Sci Rep

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The adsorption of organic micropollutants onto activated carbon is a favourable solution for the treatment of drinking water and wastewater. However, these adsorption processes are not sufficiently understood to allow for the appropriate prediction of removal processes. In this study, thermogravimetric analysis, alongside evolved gas analysis, is proposed for the characterisation of micropollutants adsorbed on activated carbon. Varying amounts of carbamazepine were adsorbed onto three different activated carbons, which were subsequently dried, and their thermal decomposition mechanisms examined. The discovery of 55 different pyrolysis products allowed differentiations to be made between specific adsorption sites and conditions. However, the same adsorption mechanisms were found for all samples, which were enhanced by inorganic constituents and oxygen containing surface groups. Furthermore, increasing the loadings led to the evolution of more hydrated decomposition products, whilst parts of the carbamazepine molecules were also integrated into the carbon structure. It was also found that the chemical composition, especially the degree of dehydration of the activated carbon, plays an important role in the adsorption of carbamazepine. Hence, it is thought that the adsorption sites may have a higher adsorption energy for specific adsorbates, when the activated carbon can then potentially increase its degree of graphitisation. Increasing amounts of pharmaceuticals enter the water bodies and are detected all over the world 1-3. Many of them are persistent and may accumulate within water cycles 4-6. These organic micropollutants already show adverse effects in aquatic ecosystems despite their comparably low concentrations 7-9. Therefore, technical measures are introduced as advanced wastewater treatment 10. One of the favoured techniques is the removal by adsorption onto activated carbon 11,12. Activated carbon has been used in water purification for more than hundred years. In modern times, we face more ecological and economical challenges that require the accurate prediction of removal efficiencies prior to the upgrade of wastewater treatment plants. Hence, several approaches have been applied to gain fast and efficient predictions through laboratory experiments and the optimization of operating parameters through data driven modeling 13-16. The removal of the target substances has been shown to be strongly influenced by the composition of the waters and that of the activated carbons used in the removal 17,18. The underlying adsorption processes have been extensively described in theory and investigated experimentally 19,20. However, adsorption in the liquid phase has been proven to be much more complicated than adsorption in gas phases, especially in complex water matrices that are governed by the presence of dissolved organic matter, the ionic strength and the pH value 21-23. Hence, both the adsorbate solution and the adsorbent, are mutually influenced. Moreover, activated carbon has a highly heterogeneous pore stru...

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Section: Characterisation Of the Thermal Decomposition Processesmentioning

confidence: 99%

Specific adsorption sites and conditions derived by thermal decomposition of activated carbons and adsorbed carbamazepine

Dittmann

Eisentraut

Goedecke

et al. 2020

Sci Rep

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“…This might be ascribed to the strong hygroscopic properties of carbon spheres after HNO 3 oxidation (more adsorption sites). 39,40 When the temperature increases to 800 °C, the weight losses of N-CS are 19.5, 33.3, 38.7, 45.9, and 54.7%, which can be ascribed to the decomposition of oxygen-containing functional groups and the different oxygen contents after a gradient HNO 3 hydrothermal treatment. In the DTG curves (Figure S1b), three obvious peaks can be observed, extending from 30 to 150 °C (P-I), 150 to 350 °C (P-II), and 350 to 800 °C (P-III).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Rational Surface Tailoring Oxygen Functional Groups on Carbon Spheres for Capacitive Mechanistic Study

Zhang

Wang

et al. 2019

ACS Appl. Mater. Interfaces

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Porous carbons represent a typical class of electrode materials for electric double-layer capacitors. However, less attention has been focused on the study of the capacitive mechanism of electrochemically active surface oxygen groups rooted in porous carbons. Herein, the degree and variety of oxygen surface groups of HNO3-modified samples (N-CS) are finely tailored by a mild hydrothermal oxidation (0.0–3.0 mol L–1), while the micro–meso–macroporous structures are efficiently preserved from the original sample. Thus, N-CS is a suitable carrier for separately discussing the contribution of oxygen functional groups to the electrochemical property. The optimized N-CS shows a high capacitance of 279.4 F g–1 at 1 A g–1, exceeding 52.8% of pristine carbon sphere (CS) (182.8 F g–1 at 1 A g–1) in KOH electrolyte. On further deconvoluting the redox peaks of cyclic voltammetry curves, we find that the pseudocapacitance not only associates with the surface-controlled faradic reaction at high scan rate but also dramatically stems from the diffusion-controlled capacitance through potassium and hydroxyl ion insertion/deinsertion into the underutilized micropores at low scan rate. The assembled supercapacitor based on N-CS presents a stable energy density of 5 Wh kg–1 over a wide range of power density of 250–5000 W kg–1, which is higher than 0.0N-CS in KOH electrolyte. In TEABF4 electrolyte, the N-CS supercapacitor has an energy density of 26.9 Wh kg–1 at the power density of 1350 W kg–1 and exhibits excellent cycling stability with a capacitance retention of 93.2% at 2 A g–1 after 10 000 cycles. These results demonstrate that surface oxygen groups alter the capacitive mechanism and contribution of porous carbons.

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“…The amount of surface oxygen and the proportions of functionality arising in CX were analysed through TG-MS experiments ( Figure 3 ). For this purpose, the MS signals from the evolution of H 2 ( m / z = 2) , H 2 O ( m / z = 18) , CO ( m / z = 28), CH 4 ( m / z = 16), and CO 2 ( m / z = 44) were analysed for the determination of the amount of surface elements (C, H, O) [ 35 ]. The TG profiles ( Figure 3 a) show a decrease in the mass of the CX samples with temperature and follow a trend with an increase in the carbonisation temperature.…”

Section: Resultsmentioning

confidence: 99%

Revisiting the Effect of Pyrolysis Temperature and Type of Activation on the Performance of Carbon Electrodes in an Electrochemical Capacitor

et al. 2022

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Hierarchical porous carbons are known to enhance the electrochemical features of electrodes in electrochemical capacitors. However, the contribution of surface oxygen and the resulting functionalities and wettability, along with the role of electrical conductivity and degree of amorphous or crystalline nature in the micro-mesoporous carbons, are not yet clear. This article considers the effect of carbonisation temperature (500–900 °C) and the type of activation (CO2, KOH) on the properties mentioned above in case of carbon xerogels (CXs) to understand the resulting electrochemical performances. Depending on the carbonisation temperature, CX materials differ in micropore surface area (722–1078 m2 g−1) while retaining a mesopore surface area ~300 m2 g−1, oxygen content (3–15%, surface oxygen 0–7%), surface functionalities, electrical conductivity (7 × 10−6–8 S m−1), and degree of amorphous or crystalline nature. Based on the results, electrochemical performances depend primarily on electrical conductivity, followed by surface oxygen content and meso-micropore connectivity. The way of activation using a varied extent of CO2 exposure and KOH concentrations played differently in CX in terms of pore connectivity from meso- to micropores and their contributions and degree of oxidation, and resulted in different electrochemical behaviours. Such performances of activated CXs depend solely on micro-mesopore features.

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Determination of the Surface Oxidation Degree of the Carbonaceous Materials by Quantitative TG-MS Analysis

Cited by 27 publications

References 16 publications

Specific adsorption sites and conditions derived by thermal decomposition of activated carbons and adsorbed carbamazepine

Specific adsorption sites and conditions derived by thermal decomposition of activated carbons and adsorbed carbamazepine

Rational Surface Tailoring Oxygen Functional Groups on Carbon Spheres for Capacitive Mechanistic Study

Revisiting the Effect of Pyrolysis Temperature and Type of Activation on the Performance of Carbon Electrodes in an Electrochemical Capacitor

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