Removal Of Functional Groups Research Articles

Reduction of Electrochemically Exfoliated Graphene Films for High-Performance Electromagnetic Interference Shielding.

Two-dimensional graphene is of great interest for electromagnetic interference (EMI) shielding owing to its inherent electrical conductivity, lightweight, and excellent mechanical flexibility even at minor thicknesses. However, the complex synthesis and quality-control difficulties limit its application. In this study, we demonstrate that electrochemically exfoliated graphene (EEG) with post-reduction treatment is a promising candidate for lightweight EMI shielding materials. A facile electrochemical exfoliation approach produces a high-quality multilayer graphene with a high electrical conductivity of ∼600 S cm-1, owing to its low degree of oxidation. The reduction of EEG by three different methods, including chemical, thermal, and microwave treatments, causes the removal of surface functional groups as well as significant changes in the microstructure of the final films. The reduced graphene films by microwaves, which are driven by the improved electrical conductivity and large volume expansion, exhibit an EMI shielding effectiveness of 108 dB at a thickness of 125 μm, one of the largest EMI shielding values ever reported for graphene at comparable thicknesses.

Effects of gaseous environments on physicochemical properties of thermally exfoliated graphene oxides for hydrogen storage: a comparative study

The present study compared the effect of different gaseous environments on physicochemical properties and subsequent hydrogen storage ability of thermally exfoliated graphene oxide (EGO). The reducing, inert or oxidizing environments were generated using hydrogen, argon or air as the carrier gas, respectively. The structure of thermally exfoliated graphene oxide depended on the type of gaseous environment. The EGO prepared in presence of Air showed the fluffiest layered structure having highest surface area. The surface area order was EGO(Air) (268 m2/g) > EGO(H2) (248 m2/g) > EGO(Ar) (155 m2/g). The average pore sizes of EGO(Air) and EGO(H2) were 2.9 and 2.8 nm, with pore volumes of 1.2 and 1.6 cm3/g, respectively. The average pore size for EGO(Ar) was highest at 4.1 nm, associated with presence of larger void space and lowest total pore volume of 1.0 cm3/g. Thus, presence of oxidative or reducing atmosphere seemed to be more conducive to exfoliation of layers by gradual removal of functional groups. The inert atmosphere of argon caused severe thermal separation of layers and functional groups, adversely affecting the layered structure as observed. The EGO(Air) also showed highest O/C ratio suggesting presence of significant amount of oxygen–containing functional groups on the surface. The hydrogen uptake order at 77 K and 30 bar was: EGO (Air) 3.34 wt.% > EGO (H2) 3.12 wt.% > EGO (Ar) 2.2 wt.%. The highest uptake of EGO(Air) might have resulted from highest surface area, highest O/C ratio and presence of considerable pore volume.

Characterization of oxygen-bearing geolipids in the Upper Permian Lucaogou shale, Santanghu Basin, NE China, using stepwise pyrolysis and hydrous pyrolysis

Oxygen-bearing geolipids, including fatty acids, lactones, and ketones, have been identified in abundance in the Upper Permian shale of the Lucaogou Formation in the Sangtanghu Basin in China. However, the potential for petroleum generation, possible origin, and occurrence state of these compounds remain undetermined. Pyrolysis experiments were conducted by combining flash pyrolysis with hydrous pyrolysis. Flash pyrolysis revealed that the oxygen-bearing geolipids, including fatty acids, lactones, and isoprenoid ketones, exist in both free and adsorbed states, and methyl ketones can be produced by pyrolysis at temperature above 400 °C. The evolution behaviors of pyrolyzates and gases produced at different temperatures are related to the thermal desorption and cleavage of chemical bonds in kerogen. Comparison of the oxygen-bearing compounds detected in flash pyrolysis and gases produced in hydrous pyrolysis suggested that the oxygen-bearing geolipids were possible sources of CO2 formation at low temperatures in the Lucaogou shale. The decomposition of fatty acids, lactones, and ketones causes the removal of oxygen-containing functional groups and the formation of CO2 and petroleum. Our study firstly demonstrates that the oxygen-bearing geolipids in the Lucaogou shale occur primarily in the free and/or adsorbed state, which indicates that these geolipids derived from microbial degradation. The short chain C19–C26 steranes and C26–C29 norhopanes detected in Lucaogou shale are also proved this source. Furthermore, petroleum and gases can be produced via deoxygenation of oxygen-bearing compounds, may revealing that the oxygen-bearing geolipids play a significant role in the process of petroleum generation.

Microwave-assisted reduction of graphene oxide for an electrochemical supercapacitor: Structural and capacitance behavior

Here, we demonstrate a fast and facile method for rapid production of reduced graphene oxide (rGO) through a microwave-assisted reaction using the green reducing agent sodium cholate at temperatures between 120 and 180 °C for 1 h. Characterization with ultraviolet–visible, Fourier-transform infrared, and Raman spectroscopy confirmed that reduction occurred at each tested temperature. Higher temperatures resulted in greater removal of oxygen-containing functional groups from the graphene oxide (GO). The morphology of GO and rGO samples was observed by field emission scanning electron microscope. The electrochemical properties and cycle performance of rGO samples were evaluated by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The rGO sample reacted at 140 °C achieved specific capacitance values of up to 293% those of samples reacted at other temperatures. Furthermore, rGO-140 °C demonstrated remarkable capacitance retention, maintaining at 104.1% after 5000 cycles, suggesting that it can be used as a promising electrode material for supercapacitor applications.

Activated carbons effectively purified by post-heat treatment under vacuum conditions

The effect of heat treatment and vacuum conditions on the textural properties and electrochemical performance of commercially available activated carbons (ACs) was investigated. The AC after post-heat treatment was characterized by nitrogen adsorption–desorption, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy measurements. The ACs treated under vacuum conditions exhibit a higher specific surface area and micropore surface area than those treated under nitrogen atmospheric pressure without significantly affecting the graphite structure of the AC. Under 800 °C temperature and vacuum conditions (AC-V800), the AC with the highest Brunauer–Emmett–Teller surface area of 1951.9 m2 g−1 (16.4% improvement relative to that of the original AC (1677.2 m2 g−1)) was obtained. This is attributed to the removal of oxygen-containing functional groups and volatile matters in the carbon by thermal treatment under vacuum conditions. Consequently, the electric double-layer capacitor using ACs treated under vacuum conditions (1 kPa) at 800 °C (AC-V800) shows considerably improved electrochemical performance in terms of higher specific capacitance and better cycling stability at a high working voltage (3.1 V), compared to the nitrogen-treated and commercial ACs.

Near-UV light assisted green reduction of graphene oxide films through l-ascorbic acid

ABSTRACT Recent studies have highlighted the effects of various stimuli on the chemical reduction of graphene oxide (GO) through green reductant L-ascorbic acid (L-AA); however, the combination of near ultraviolet (NUV) light to increase the reduction rate has yet to be thoroughly explored. In this study, drop-casted GO films were subjected to chemical reduction through L-AA with various levels of exposure under 405 nm NUV radiation. The structure and uniformity of GO stackings that form the film were characterized through scanning electron microscopy (SEM) and wide-angle x-ray scattering (WAXS). Additionally, WAXS was used to track the removal of oxygen-containing functional groups along with Fourier-transform infrared (FT-IR) spectroscopy and x-ray photoelectron spectroscopy (XPS) as a function of L-AA and NUV light exposure times. XPS results demonstrated that the interaction between L-AA and NUV exposure has a significant effect on the reduction of films. Furthermore, the results that yielded the highest reduction (C-C bond concentration of 60.7%) were the longest L-AA and NUV light exposure times (48 hours and 3 hours, respectively). This report provides a study on the effects of NUV on the green reduction of GO films through L-AA with potential application in solar energy and chemical sensing applications.

The electrochemical performance of reduced graphene oxide prepared from different types of natural graphites.

Graphene, as a new type of carbon material in the forefront of research, has been applied widely in the area of supercapacitors with the advantages of a large positive specific surface, high conductivity, stable chemical properties and good supercapacitor performance. In this study, an investigation on the electrochemical performance of reduced graphene oxides (rGOs) prepared from various natural graphites was conducted. X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, atomic force microscopy and electrochemical performance analysis were performed to characterize the as-prepared GOs and rGOs. The results demonstrated that a reduction modification of GO was necessary to optimize its electrochemical performance. The rGO has a great electrochemical performance with a good repair ability, better oxygen-containing functional group removal effect, lower structural defects, larger average size of the in-plane sp2 region and great specific capacitance.

Porous reduced graphene oxides derived by selective removal and formation of oxygen functional groups and their electrochemical capacitances

In this study, reduced graphene oxides (rGOs) with a porous structure were synthesized through a facile sequential low-temperature treatment at 150 and 250 °C in air and nitrogen atmosphere, respectively, without toxic chemicals. For the first treatment under oxygen-rich conditions, competitive oxidation and reduction reactions between various kinds of oxygen functional groups were observed, leading to the formation of preferential pore-forming groups such as carboxyl. Weakly bound groups on the GO surface (such as hydroxyl and carboxyl groups) were removed in the second step, leading to the formation of pores and improving electrical conductivity. The rGO suitable for use as an electrode material had a surface area of 636.6 m2/g and a capacitance of 191.3 F/g. Therefore, we believe that this mild treatment could be a potentially cost-effective, efficient, and environmentally friendly strategy to synthesize electrode materials.

Ultrasonic doping and photo-reduction of graphene oxide films for flexible and high-performance electrothermal heaters

Thermotherapy has emerged as one of the most promising treatments for arthritis, a prevalent, crippling, painful bone disease. This demands more flexibility, energy-efficiency, safety, and light-weight in thermotherapy packs and hot clothing. Heteroatom doping is a metal-free, cost-effective way to improve carrier concentration and hence electrical and thermal conductivity in reduced Graphene Oxide (rGO) thus rendering it suitable for wearable joule heaters. However, the current doping techniques result in complex chemical structures that hinder phonon propagation and suffer other problems such as low yield, low scalability, and rigidity of the final product. Here, we disclose a novel and facile, low-temperature technique for nitrogen doping and photoreduction of graphene oxide (GO) films for high-performance, flexible graphene-based electrothermal heaters. The nitrogen atoms are introduced into the GO lattice with the aid of ultrasonic power in a wet chemical doping phase and maskless, automated, rapid CO2 laser scanning is used for the concurrent removal of oxygen-containing functional groups and the rearrangement of nitrogen atoms in the graphene lattice. X-ray Photoelectron Spectroscopy (XPS) studies reveal up to 5.43% nitrogen dopant concentration with a high carbon to oxygen ratio of 16, while Raman studies uniquely show improved atomic ordering with ID/IG ratio of 0.51 in the nitrogen-doped Laser reduced graphene oxide (N-LrGO) films. The fabricated N-LrGO heater has a sheet resistance of 26 O/sq. and attains a higher steady-state temperature of up to 245.7 °C at a low driving voltage of 9 V with a low power demand of 0.7 Wcm−2 and a heating rate of 103 °C/s. Its excellent temperature distribution and high flexibility join with the scalability of the preparation technique to demonstrate great potential for its incorporation with next-generation wearable electronics powered by low voltage portable energy storage devices.

Effects of plant functional group removal on CO2 fluxes and belowground C stocks across contrasting ecosystems.

Changes in plant communities can have large effects on ecosystem carbon (C) dynamics and long‐term C stocks. However, how these effects are mediated by environmental context or vary among ecosystems is not well understood. To study this, we used a long‐term plant removal experiment set up across 30 forested lake islands in northern Sweden that collectively represent a strong gradient of soil fertility and ecosystem productivity. We measured forest floor CO2 exchange and aboveground and belowground C stocks for a 22‐yr experiment involving factorial removal of the two dominant functional groups of the boreal forest understory, namely ericaceous dwarf shrubs and feather mosses, on each of the 30 islands. We found that long‐term shrub and moss removal increased forest floor net CO2 loss and decreased belowground C stocks consistently across the islands irrespective of their productivity or soil fertility. However, we did see context‐dependent responses of respiration to shrub removals because removals only increased respiration on islands of intermediate productivity. Both CO2 exchange and C stocks responded more strongly to shrub removal than to moss removal. Shrub removal reduced gross primary productivity of the forest floor consistently across the island gradient, but it had no effect on respiration, which suggests that loss of belowground C caused by the removals was driven by reduced litter inputs. Across the island gradient, shrub removal consistently depleted C stocks in the soil organic horizon by 0.8 kg C/m2. Our results show that the effect of plant functional group diversity on C dynamics can be relatively consistent across contrasting ecosystems that vary greatly in productivity and soil fertility. These findings underline the key role of understory vegetation in forest C cycling, and suggest that global change leading to changes in the relative abundance of both shrubs and mosses could impact on the capacity of boreal forests to store C.

Superior antibacterial activity of reduced graphene oxide upon decoration with iron oxide nanorods

Iron oxide (Fe2O3) nanorods (NRs) decorated reduced graphene oxide (rGO) nanocomposite, endowed with high antibacterial activity, was prepared through the one-pot calcination of pre-synthesized Fe2O3 NRs in rGO aqueous dispersion. The Fe2O3 NRs were well infused between the rGO layers as revealed by the AFM, SEM, and TGA analysis, whereas the removal and distribution of oxygen-containing functional groups were distinguished with UV–vis and FT-IR spectroscopy. The antibacterial activity of Fe2O3/rGO nanocomposite towards methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Staphylococcus aureus (VRSA), and ciprofloxacin-resistant Staphylococcus aureus (CRSA) was investigated by disk diffusion method and growth curve analysis. The nanocomposite demonstrated excellent antibacterial activity as compared to bare rGO and inhibited nearly 87 % of the bacterial growth. The CRSA was more sensitive to nanocomposite compare MRSA and VRSA. More importantly, the nanocomposite obtained was found to achieve minimum inhibitory concentration (MIC) of ∼ 5 μg/mL. Besides, measurements of the charge transfer resistance, which is used to interpret bacterial response towards rGO or Fe2O3/rGO modified glassy carbon electrode, were performed using electrochemical impedance spectroscopy (EIS). The noteworthy antibacterial performance of the Fe2O3/rGO nanocomposite was probably attributed to the synergistic effect Fe2O3 NRs decorated rGO. The mechanism study suggested that nanocomposite can induce death to the bacteria by direct contact with the sharp edges of rGO and through the release of Fe3+ ions. The data, altogether, indicated that the Fe2O3 NRS decoration of rGO resulted in nanocomposite with enhanced antibacterial performance, hence, it may be used for developing new, safe, and effective antibiotics.

Facile two-step synthesis of innovative anode design from tin-aminoclay (SnAC) and rGO for Li-ion batteries

A tin-aminoclay/reduced graphene oxide (SnO2-SnAC/rGO) electrode with significantly enhanced electrochemical performance was successfully fabricated by a facile two-step method entailing microwave treatment (1st step) and heat treatment (2nd step) synthesis processes. In step 1, the complete reduction of GO to rGO by microwave ensures the removal of most oxygen-containing functional groups on the material surface leading to improvement of its electrical conductivity along with the formation of SnO2 dots of 3–4 nm diameter. In step 2, the tin crystals are formed more stably in the SnAC/rGO framework by the heat-treatment process under Argon (Ar) gas via the direct conversion process of Sn2+ active sites within the SnAC structure. With this two-step process, the synthesized material possesses many unique synergistic effects, all leading to beneficial features (i.e., improved specific capacity, high rate capability, and long cycle life stability compared with SnO2-SnAC and pure rGO electrodes) for application to battery electrodes. Especially, SnO2-SnAC/rGO-500 °C (1:1) exhibits outstanding performance in terms of cyclic performance (650 mAh g−1 after 100 cycles at 100 mA g−1) and rate capability.

Influence of torrefaction, hydrothermal carbonization and degradative solvent extraction pretreatments on moisture absorption and self-ignition characteristics of biomass

Three main pretreatment methods (torrefaction, hydrothermal carbonization and degradative solvent extraction) have been developed to deoxygenate and upgrade biomass into biochar, hydrochar and extract, respectively, which have a variety of high-value applications. However, the influence of the three pretreatment methods on the moisture absorption and self-ignition characteristics of biomass still remains unclear, which greatly affects the subsequent storage, transportation and utilization process of the biochar, hydrochar and extract. Therefore, the effects of torrefaction, hydrothermal carbonization and degradative solvent extraction on the moisture absorption and self-ignition characteristics of biomass were investigated and compared in this study. The resultsshowedthat the moisture absorption ratios of the pretreated products (biochar, hydrochar and extract) were as low as 3.8%, 1% and 0.8%, respectively, which was obviously lower than that of RS (8%), indicating that the moisture absorption propensities of biochar, hydrochar and extract were all obviously inhibited compared to RS. These results were caused by the dramatic removal of oxygen functional groups during the three pretreatment processes. The heat release of biochar (6950 kJ/kg) and hydrochar (7134 kJ/kg) below 300 °C were obviously higher than that of RS (5950 kJ/kg), while the heat release of extract (5063 kJ/kg) below 300 °C was much lower than that of RS. Compared with RS, biochar and hydrochar had higher specific surface areas and higher contents of inorganic metallic elements, which contributed to their higher self-ignition susceptibilities than those of RS. In contrast, the extract had a dense structure and extremely low oxygen functional groups contents as well as low inorganic metallic elements contents, which jointly led to its lower self-ignition susceptibility than that of RS. This research is expected to provide a comprehensive understanding of the influence mechanism of pretreatment on the moisture absorption and self-ignition characteristics of biomass.

Reactivity of Ca and P precursors to form hydroxyapatite and its influence on the properties of the obtained powders

Synthesis of hydroxyapatite has been profusely studied in the literature due to the similarities between this calcium phosphate and the inorganic component of natural bone. Despite the numerous synthesis methods explored, most of the previous studies are focused on the effect of experimental conditions reducing the importance of the chemical reagents selected as precursors. In this work, four combinations of chemical reagents were used for synthesizing hydroxyapatite powders by a sol-gel method. Conditions for removal of residual functional groups from precursors and its influence on the evolution from amorphous to crystalline powders were studied. Nanocrystalline hydroxyapatite with high thermal stability was obtained by using calcium nitrate or calcium acetate with phosphoric acid or ethyl phosphite as precursors of Ca and P respectively. The use of calcium acetate combined with ethyl phosphite delays the formation of the inorganic network due to retention of acetate groups requiring higher calcining temperatures.

Green preparation of reduced graphene oxide by Bougainvillea glabra flower extract and sensing application

In this paper, we report the application of Bougainvillea glabra flower extract as a green-reducing agent for the reduction of chemically prepared graphene oxide (GO). The removal of oxygen-containing functional groups after reduction of GO was due to the presence of phenolic compounds in the flower extract of Bougainvillea glabra. Towards the sensing of Pb2+, a simple drop-casting technique was adopted to fabricate the sensing element by modifying the surface of screen-printed carbon electrode (SPCE) with rGO-nafion nanocomposite. Differential pulse voltammetry was employed as an electroanalytical technique to study the sensing capability of the proposed electrode for different concentrations of Pb2+. The fabricated SPCE exhibited a low limit of detection of 0.05 nM toward Pb2+ with an improved sensitivity of 25.273 µA nM−1 over a linear range of 0.05–8.67 nM.

Fabrication of Few-Layer Graphene-Supported Copper Catalysts Using a Lithium-Promoted Thermal Exfoliation Method for Methanol Oxidative Carbonylation.

Exfoliation of graphene oxide (GO) via thermal expansion is regarded as the most promising approach to obtain few-layer graphene (FLG) in bulk. Herein, we introduce an efficient strategy for improving the exfoliation process by adding a tiny amount of lithium nitrate in the precursors, which significantly enhances the removal of oxygen-containing functional groups and produces 1-2 layer graphene. FLG-supported highly dispersed Cu nanoparticles (NPs, ≈4.2 nm) can be further synthesized through exfoliating the mixture of GO, lithium nitrate, and copper(II) nitrate, which displayed superior catalytic activity and stability in the synthesis of dimethyl carbonate (DMC) using liquid methanol oxidative carbonylation. The characterization results demonstrate that during the thermal expansion process, lithium nitrate was decomposed to Li2O and immediately reacted with CO2 released by the decomposition of GO to form stable Li2CO3, which promotes efficient charge transfer and produces Cuδ+ (0 < δ < 1) species in the Cu/Li-PGO catalyst. Density functional theory calculations prove that the presence of Cuδ+ markedly facilitates CO adsorption over the resulting catalyst and causes a decrease of the energy barrier of the rate-limiting step for DMC formation (CO insertion). These findings give a theoretical explanation of the enhanced catalytic performance of the Cu/Li-PGO catalyst. The present work provides a simple and practical avenue to the exfoliation of graphene and the dispersions of metal NPs on graphene sheets.

Asynchrony among species and functional groups and temporal stability under perturbations: Patterns and consequences

Abstract A number of theoretical and empirical studies have demonstrated the effects of perturbations on ecosystem stability. Compensatory dynamics among taxonomic units have been proposed as a major mechanism regulating the temporal stability of biomass production (hereafter ‘temporal stability’). However, most studies have focused on the effects of species asynchrony on temporal stability in response to perturbations, and few studies examined how compensatory changes among functional groups affected temporal stability. Here, we conducted a 4‐year functional group removal experiment and a 4‐year experimental warming and nitrogen addition experiment in an alpine meadow of Qinghai‐Tibetan Plateau to investigate the effects of perturbations (functional group removal, experimental warming and nitrogen addition) on temporal stability and the potential mechanisms. In both experiments, temporal stability was positively related to both species and functional group asynchrony. However, species asynchrony and functional group asynchrony responded differently to different types of perturbations. In the removal experiment, although asynchrony among both species and functional groups decreased as more functional groups were removed, structural equation modelling showed that removal of different functional groups could affect temporal stability through altering either species or functional group asynchrony. Warming suppressed temporal stability through decreasing asynchrony among species, while nitrogen addition reduced temporal stability mainly through decreasing functional group asynchrony. Synthesis. Our findings demonstrate the importance of considering compensatory dynamics at different taxonomic levels for predicting temporal stability under anthropogenic perturbations in alpine meadows, and throw light on the importance of protecting both species and functional group richness to maintain temporal stability in the context of global change.

Capacitance Enhancement of Hydrothermally Reduced Graphene Oxide Nanofibers.

Nanocarbon materials present sp2-carbon domains skilled for electrochemical energy conversion or storage applications. In this work, we investigate graphene oxide nanofibers (GONFs) as a recent interesting carbon material class. This material combines the filamentous morphology of the starting carbon nanofibers (CNFs) and the interlayer spacing of graphene oxide, and exhibits a domain arrangement accessible for fast transport of electrons and ions. Reduced GONFs (RGONFs) present the partial removal of basal functional groups, resulting in higher mesoporosity, turbostratic stacking, and surface chemistry less restrictive for transport phenomena. Besides, the filament morphology minimizes the severe layer restacking shown in the reduction of conventional graphene oxide sheets. The influence of the reduction temperature (140–220 °C) on the electrochemical behaviour in aqueous 0.5 M H2SO4 of RGONFs is reported. RGONFs present an improved capacitance up to 16 times higher than GONFs, ascribed to the unique structure of RGONFs containing accessible turbostratic domains and restored electronic conductivity. Hydrothermal reduction at 140 °C results in the highest capacitance as evidenced by cyclic voltammetry and electrochemical impedance spectroscopy measurements (up to 137 F·g−1). Higher temperatures lead to the removal of sulphur groups and slightly thicker graphite domains, and consequently a decrease of the capacitance.

Graminoid Removal Reduces the Increase in N2O Fluxes Due to Nitrogen Fertilization in a Boreal Peatland

The increase in nitrogen (N) deposition may affect nitrous oxide (N2O) emission in boreal peatlands by increasing N availability and/or altering vegetation composition. However, the effects of changes in vegetation composition (due to the increase in N deposition) on N2O emission are still unknown. Therefore, we used a factorial design, comprising the removal of plant functional groups and N fertilization to investigate their independent effects and combined effects on N2O fluxes at an ombrotrophic blanket bog in Western Newfoundland, Canada. The results reveal that N2O emission significantly increased with N fertilization. Notably, the effect of N addition on N2O fluxes was modulated by the removal of graminoids. In particular, the removal of graminoids reduced 69% of the N2O emission increases due to N fertilization in the third year of the experiment. This result suggests that the enhancement of graminoid abundance due to increases in N deposition/fertilization may dramatically increase N2O emissions in boreal peatlands leading to stronger impacts on the global climate and stratospheric ozone depletion in the future if no countermeasures to reduce reactive N emission are undertaken.

Study on the pyrolysis properties of corn straw by TG–FTIR and TG–GC/MS

Corn straw, an agricultural waste with huge yields, can be thermochemically treated to promote its comprehensive utilization. Compared with traditional methods, thermogravimetry coupled with Fourier transform infrared spectroscopy (TG–FTIR) and thermogravimetry coupled with gas chromatography–mass spectrometry (TG–GC/MS) can be used to analyze more clearly the pyrolysis of corn straw. In this study, the distributed activation energy model was used to analyze the pyrolysis kinetics in order to elucidate the pyrolysis process. The distributed activation energy of corn straw changed from 93.39 to 186.57 kJ mol−1 at the conversion rates from 0.1 to 0.9 with a high correlation coefficient. The evolution of volatile products from corn straw pyrolysis was discussed by TG–FTIR and TG–GC/MS. Results showed that CO2, CH4, CO, H2O, and carbonyls were produced below 337 °C and reached their peak values at the maximum mass loss rate of corn straw corresponding to the pyrolysis temperature of 337 °C. Carbonyl compounds were mainly composed of C4–C5, which come from the pyrolysis of cellulose and hemicellulose. At high pyrolysis temperatures, the organic species of furans, phenols, ketones, and aldehydes increased because of the fracture and isomerization of cellulose and hemicellulose. Meanwhile, Benzene and long-chain alkanes have been found due to the removal of oxygen-containing functional groups and the rupture of benzene ring in lignin structure.