One-step Calcination Method Research Articles

One step calcination of bamboo powder enhances the adsorption and photocatalytic performance of red mud

Magnetic photocatalyst (MRM) with high adsorption was prepared by one-step calcination method using industrial solid waste bamboo powder and red mud (RM). The results showed that MRM has a significant removal effect on methylene blue (MB) in wastewater compared with RM. The excellent performance of MRM may be attributed to the following factors: 1. The reducing gas of bamboo powder pyrolysis transforms hematite into maghemite in MRM, which makes the photocatalyst magnetic and easy to recover. 2. The solid product of bamboo powder pyrolysis (biochar) not only inhibits the aggregation of MRM particles, but also broadens the light absorption range of MRM. Further, biochar was used as the transport channel of photogenerated electrons to inhibit the recombination of photogenerated electrons and holes.

Fish scale-based biochar with defined pore size and ultrahigh specific surface area for highly efficient adsorption of ciprofloxacin

A fish scale-based porous activated biochar with defined pore size (DPBC) was fabricated by a one-step calcination and activation method. The DPBC possessed an ultrahigh specific surface area of 3370 m2 g−1 and its pore diameter centered at 1.49 nm which fits into the ciprofloxacin (CIP) molecular dimension, making it an ideal adsorbent for CIP adsorption due to the molecular pore-filling effect. The maximum Langmuir monolayer adsorption capacity of DPBC for CIP was higher than 1000 mg g−1 and the equilibrium time was less than 4 h, superior to most adsorbents reported in literature. Thermodynamic analysis indicated the adsorption process was spontaneous and endothermic. Notably, fixed-bed experiments showed an encouraging adsorption performance towards CIP, with a high saturated dynamic adsorption capacity of 880.3 mg g−1. Both Thomas and Yoon-Nelson models predict the fixed-bed column adsorption performance well. Hydrophobic effect, π-π interaction, π-π EDA, cation exchange, hydrogen bonding formation, pore filling effect, electrostatic and cation-π interaction involved in the CIP adsorption on the DPBC.

Controllable fabrication of nitrogen-deficient graphitic carbon nitride/magnetic ferric oxide and N2 photofixation on the active sites of surface defects

Z-scheme nitrogen-deficient graphitic carbon nitride/ferric oxide (GCNx/FO) photocatalysts were obtained by a one-step calcination method. The number of nitrogen defects was tuned by the application of KOH, while the ferric oxide phase and magnetism was controlled by the usage of ferrous oxalate. Interconversion between the hematite (α) and maghemite (γ) phases of Fe2O3 was analyzed by X-ray diffraction, and magnetism of the GCNx-0.1/FO products provided via vibrating sample magnetometer test. The introduction of nitrogen defects narrowed the bandgap and extended the spectral range of light absorption while improving the ability to capture and activate N2 effectively. Surface defects were employed as active sites, and the ammonia generation concentration reached approximately 69.7 μmol/L/h by N2 photofixation under visible light. Due to their ease of synthesis and tuning, high photocatalytic activity, convenient and rapid collection for reuse, and excellent stability, GCNx/FO composited photocatalysts possess vast potential for use in clean ammonia production.

Highly efficient and selective photoreduction of CO2 to CO with nanosheet g-C3N4 as compared with its bulk counterpart

Artificial photoreduction of CO2 to clean energy utilizing the unlimited solar energy has shown promise to suppress the greenhouse effect and alleviate the energy shortage. In this study, a simple one-step calcination method was utilized to synthesize ultrathin nanosheet g-C3N4 (NS-g-C3N4). The prepared NS-g-C3N4 with a thickness of 10 nm was demonstrated to exhibited higher efficiency and selectivity than that of bulk counterpart (B-g-C3N4) for the photocatalytic reduction of CO2 to CO under visible light irradiation. The yield of CO in the system with obtained NS-g-C3N4 was 5.8 times higher than that of B-g-C3N4. CO was measured to be the sole product detected in the system with NS-g-C3N4, while CO2 can be reduced into CO, CH4 and CH3OH in the system with B-g-C3N4 under the same photocatalytic reduction conditions. The ultrathin nanostructures and abundant surface defect sites of NS-g-C3N4 could enhance the visible light adsorption efficiency, favor the separation and transfer of photogenerated carriers, and provide strong chemisorption sites for CO2, and thus resulting in its remarkable photocatalytic activity to CO2 reduction. More importantly, the surface defects of nanosheet could shift the adsorption mode of CO2 from N–CO2- for the B-g-C3N4 to N–O–CO for NS-g-C3N4, and eventually contributing the selective photoreduction of CO2 to CO. The obtained also NS-g-C3N4 exhibited excellent stability for CO2 photoreduction. No significant change in the photoreduction efficiency of CO2 in the system with NS-g-C3N4 was observed after four cycles. This study could not only provide a novel strategy to realize the high selectivity and efficiency photocatalytic conversion CO2 to CO, but also aims to clarify the interactions between the adsorption model of CO2 on g-C3N4 surface and the selectivity and efficiency of CO2 photoreduction.

Porous cage-like hollow magnetic carbon-doped CoO nanocomposite as an advanced sorbent for magnetic solid-phase extraction of nine polycyclic aromatic hydrocarbons

In this study, porous cage-like hollow magnetic carbon-doped CoO nanocomposite (CoO@C) was successfully synthesized using a metal-organic frameworks (MOFs) as precursor by one-step calcination method in this work. The obtained nanoporous composite showed excellent magnetic response by taking advantage of the magnetism of CoO even without the Fe3O4, making it an advanced sorbent for magnetic solid-phase extraction (MSPE). The Co-MOF and CoO@C were characterized by XRD, TGA, SEM, TEM, vibrating sample magnetometry, and FT-IR spectroscopy. Based on this, a method using CoO@C for MSPE coupled with HPLC was established for the analysis of nine polycyclic aromatic hydrocarbons (PAHs) from various real water samples. The amount of sorbent, extraction times, extraction temperature, desorption times, oscillation rate, and elution volume were optimized. Under the optimal conditions, the method had good relative standard deviations (RSDs) of 1.1%–6.5% and a satisfying linearity range of 0.5–1000 μg L−1. The low LOD and LOQ for nine PAHs were found to be 0.06–1.30 μg L−1 and 0.19–4.30 μg L−1, respectively. The experimental results indicated that the prepared nanocomposite showed excellent adsorption capacity compared to other commercial sorbents and has potential applications for the removal of hazardous pollutants from environmental samples.

Study on the catalytic activities of g-C3N4@TiO2 hollow microspheres under UV–visible light

TiO2 and g-C3N4 samples were successfully prepared by simple one-step hydrothermal method and calcination method, respectively. Then, g-C3N4@TiO2 hollow microspheres were prepared by simple water bath evaporation method. This work mainly studies the photocatalytic performance of a series of g-C3N4 composite TiO2 hollow microspheres with different contents. In the experiment, the amount of g-C3N4 was adjusted to obtain the highest photocatalytic activity. Therefore, finding the most suitable amount of g-C3N4 has become the main task of this work. By degrading the catalytic effect of Rhodamine B (RhB) solution, the photocatalytic performance of a series of samples was compared. Finally, it was discovered that when the weight ratio of g-C3N4 to TiO2 was 15%, the photocatalytic effect of the sample prepared in this way was the best and the sample was recorded as 15% g-C3N4@TiO2 composite. The heterostructure of TiO2 and g-C3N4 was constructed through the synergistic effect, achieving excellent photocatalytic performance to a certain extent. Therefore, the degradation rate of 15% g-C3N4@TiO2 composite material is 90.8% within 90 min of UV–visible light irradiation. We further used SEM, TEM, XRD, FT-IR spectroscopy, DRS, XPS and other test methods to characterize the composition, morphology and chemical properties of the composite material.

Preparation of high-quality graphene oxide-carbon quantum dots composites and their application for electrochemical sensing of uric acid and ascorbic acid

Graphene oxide-quantum dots systems are emerging as a new class of materials that hold promise for biochemical sensing applications. In this paper, the eco-friendly carbon quantum dots (CQDs) are prepared with cheap and recyclable coke powders as carbon source. The graphene oxide-carbon quantum dots (GO-CQDs) composites are synthesized using graphene oxide as the conductive skeleton to load the CQDs by a one-step calcination method. The obtained GO-CQDs composites demonstrate the successful decoration of CQDs on GO nanosheets. The CQDs acting as spacers create gaps between GO sheets, resulting in a high surface area, which electively increases the electrolyte accessibility and electronic transmission. The electrocatalytic activity and reversibility of GO-CQDs composites can be effectively enhanced by tuning the mass ratio of GO to CQDs and the heating process. Furthermore, a highly sensitive and selective electrochemical sensor for determining uric acid (UA) and ascorbic acid (AA) was developed by modifying GO-CQDs composites onto a glassy carbon electrode. The results show that the linear range, minimum detection limit, and sensitivity of the GO-CQDs electrode for UA detection are 1–150 μM, 0.01 μM, and 2319.4 μA mM−1 cm−2, respectively, and those for AA detection are 800–9000 μM, 31.57 μM, and 53.1 μA mM−1 cm−2, respectively. The GO-CQDs are employed as the electrode materials for the serum and urine samples electrochemical sensing, the results indicate that the sensor can be used for the analysis of real biological samples.

Sunlight-assisted degradation of textile pollutants and phytotoxicity evaluation using mesoporous ZnO/g-C3N4 catalyst.

Accessibility of adequate safe and fresh water for human consumption is one of the most significant issues throughout the world and extensive research is being undertaken to resolve it. Nanotechnology is now an outstanding medium for water treatment and remediation from microorganisms and organic dyes, as compared to conventional treatment methods. For this task graphitic carbon nitride (g-C3N4) is a potential nanomaterial for environmental remediation, but its photogenerated charge carrier recombination rate restricts its use in practical applications. Hence, in the current study, we used a simple one-step calcination method to synthesize various ratios of ZnO/g-C3N4 binary nanocomposites. The band gap of g-C3N4 is 2.70 eV, but it is shifted to 2.60 eV by the 0.75 : 1 ZnO/g-C3N4 binary nanocomposite. Moreover, phase structure, morphology, thermal stability, oxidation state, elemental analysis, and surface area were evaluated using XRD, SEM, TEM, TGA, XPS, and BET analysis. The optimal ZnO loading content was determined and the mechanism of enhanced photocatalytic activity was studied in detail. The photocatalytic efficiency of the best catalyst was employed for the degradation of textile effluent followed by phytotoxicity evaluation using methylene blue (MB), and rhodamine B (RhB) as a model substrate was tested. Furthermore, the textile effluent treatment analysis discovered that the 75 mg concentration of 0.75 : 1 ZnO/g-C3N4 catalyst degraded up to 80% within 120 min and significantly reduced the concentrations of different physico-chemical parameters of textile effluents. These treated effluents have no phytotoxic effects on fenugreek plants, according to a pot study. It was found that the mesoporous 0.75 : 1 ZnO/g-C3N4 catalyst can be used as an effective and low-cost technique for the degradation of azo dyes in textile wastewaters.

Effect of Mn2+ dopants on the photocatalytic efficiency of MoS2

The Mn-doped MoS2 (Mn-MoS2) material is fabricated by a facile one-step calcination method. The Mn2+ content introduced into MoS2 is ranged from 1 wt% to 7 wt%. The X-ray diffraction (XRD) and scanning electron microscopy SEM results suggest that the doping of Mn2+ does not alter the crystal structure and the morphology of MoS2. However, it helps the Mn-doped MoS2 to exhibit stronger visible light absorption and higher magnetism. Especially, in the RhB degradation under visible light irradiation, better photocatalytic performance of the as-prepared Mn-doped MoS2 is observed compared to that of pure MoS2

An electrochemical sensing of phenolic derivative 4-Cyanophenol in environmental water using a facile-constructed Aurivillius-structured Bi2MoO6

Harmful chemicals are always found in the environment and it is necessary to construct a viable sensor to detect those chemicals. In order to construct an electrochemical sensing platform, designing an electrode using bismuth mixed oxides are more important and which grabbed more attention due to its high electrocatalytic ability and conductivity. In this literature, we report a facile synthesis of thorn apple like structured pure bismuth molybdate (Bi2MoO6) using a simple hydrothermal assisted one-step calcination method and we report a facile method to sense 4-cyanophenol by electrochemical technique. Bi2MoO6 modified (Glassy Carbon electrode) GCE possess two linear ranges 0.1–39.1 µM and 46.6–110.1 µM with excellent detection limit 0.008297 µM and 0.01097 µM. Also, this novel sensor is steady with good stability, repeatability, and reproducibility. Successfully, the environmental water sample is analyzed as a real sample with a feasible and quantification results which were compared with HPLC analysis.

Facile synthesis of Co9S8@NC anode with enhanced sodium storage and long cycling life

Transition metal sulfides (TMSs) are presently under extensive research and have been regarded as the prospective anode candidates for sodium ion batteries (SIBs). However, the poor intrinsic electrical conductivity and huge volume expansion of metal sulfides electrodes during the discharge-charge process eventually cause pulverization of active materials and quick capacity decay, which severely limit their further practical application. In this study, ultrafine Co9S8 nanoparticles embedded in N-doped carbon layer (Co9S8@NC) were facilely synthesized via a simple one-step solid phase calcination method with glucose as the carbon source and thiourea served as N, S-containing precursor. The Co9S8@NC hybrid with small nanoparticle size could aid in the quick penetration of the electrolyte and shorten the pathway of Na ions diffusion; Meanwhile, the N-doped disordered carbon layer could maintain structural integrity and favor the electron transport of the nanocomposite during the electrochemical reaction. The Co9S8@NC composite is firstly investigated as anode for SIBs. They exhibit a satisfied discharge/charge specific capacity of 285.3/276.3 mAh g-1 after 160 cycles at 170 mA g−1, and its discharge/charge specific capacity is capable to maintain 160.8/158.5 mAh g−1 even after 1000 cycles at 1000 mA g−1. Further kinetics analyses based on CV demonstrate that the partial pseudocapacitive behaviors partially accounts for the remarkable Na storage performances.

Stretchable Electrochemical Biosensing Platform Based on Ni-MOF Composite/Au Nanoparticle-Coated Carbon Nanotubes for Real-Time Monitoring of Dopamine Released from Living Cells

Existing electrochemical biosensing platforms, using traditional rigid and unstretchable electrodes, cannot monitor the biological signaling molecules released by cells in a mechanically deformed state in real time. Here, a stretchable and flexible electrochemical sensor was developed based on nickel metal-organic framework composite/Au nanoparticle-coated carbon nanotubes (Ni-MOF composite/AuNPs/CNTs) for sensitive detection of dopamine (DA) released by C6 living cells in real time. A Ni-MOF composite was obtained by introducing Ni, NiO, and a carbon frame onto the surface of two-dimensional (2D) Ni-MOF nanosheets using an efficient one-step calcination method. The hybrid of Ni-MOF composite/AuNPs/CNTs that deposited on the poly(dimethylsiloxane) (PDMS) film endowed the sensor with excellent electrochemical performance with a wide linear range of 50 nM to 15 μM and a high sensitivity of 1250 mA/(cm2 M) and also provided the sensor with desirable stability against mechanical deformation. Furthermore, the stretchable electrode also displayed good cellular compatibility while C6 living cells can be cultured and proliferated on it with strong adhesion. Then, the DA released by C6 living cells with chemical induction in both natural and stretched states was monitored using our stretchable and flexible electrochemical sensor in real time. This indicates that our new design of flexible Ni-MOF composite/AuNPs/CNTs/PDMS (NACP) film electrodes provides more opportunities for the detection of chemical signals released from cells and soft living organisms even under mechanically deformed states.

Templating preparation of cannular congeries of MnO2 and porous spheres of carbon and their applications to high performance asymmetric supercapacitor and lithium-sulfur battery

Cannular congeries of MnO2 (CC-MnO2) have been fabricated via the in situ chemical reaction using carbon tubes derived from polypyrrole as reductive agent and sacrificial template. Porous spheres of carbon (PSCs) are prepared by a one-step calcination and template removal method, in which silica/chitosan spheres obtained by spray-drying process are carbonized and the SiO2 templates have been etched by mixing PTFE powder as in-situ template removal agent. It has been demonstrated the porous character is beneficial to their electrochemical performance of CC-MnO2 and PSC when they are used as electrode materials for supercapacitors and lithium-sulfur batteries. The CC-MnO2//PSC asymmetric supercapacitor exhibits a high energy density of 22.5 Wh kg-1 with a power density of 237 W kg-1 in a stable potential window of 0-1.8 V and the lithium-sulfur using PSCs as sulfur host also shows excellent cycle performance with a retention of 703 mhA h-1 after 100 cycles at 0.2 C.

Co3O4-based catalysts derived from natural wood with hierarchical structure for elemental mercury oxidation

Wood vessel in natural wood (NW) as the channel for water and inorganic salt transport has a natural aligned microchannel structure and a great hydrophily. In the present work, NW was used as catalyst support which was directly impregnated in Co(NO3)2 solution and then calcined in N2 atmosphere to prepare a catalyst (denoted as Co/NWBC-OS), which was called a one-step calcination method. For comparison, NW biochar (NWBC) derived from pyrolytic NW was also impregnated in Co(NO3)2 solution and calcined in N2 atmosphere to prepare catalyst (denoted as Co/NWBC-TS), which was called a two-step calcination method. Characterization results reveal that NW possesses a greater hydrophily and wettability than NWBC, which is beneficial to impregnation process resulting in a better active components dispersion. In the meanwhile, Co/NWBC-OS has a higher Co3+/Co2+ ratio and more surface chemisorbed oxygen. The higher Co3+/Co2+ ratio can generate more oxygen vacancies which can capture and activate gaseous oxygen to form more surface chemisorbed oxygen. Surface chemisorbed oxygen as the main active site can greatly promote Hg0 removal performance. These results lead to an excellent Hg0 removal efficiency of Co/NWBC-OS which is 99% at 180 °C. Additionally, O2 and NO can promote the Hg0 removal process whereas H2O, SO2 and NH3 exert an obviously prohibited effect on Hg0 removal performance.

High catalytic performance of a Pd-loaded TaN-TaC electrocatalyst for ethylene glycol oxidation in an alkaline medium

In this work, tantalum nitride and tantalum carbide (TaN-TaC) composites are prepared using a one-step calcination method. The resulting TaN-TaC composites have excellent conductivity, and therefore, potential applications in the electrode materials of fuel cells. Then, palladium nanoparticles loading on TaN-TaC (Pd/TaN-TaC) electrocatalysts are synthesized using the reflux method. The X-ray photoelectron spectroscopy results imply that the valance states of palladium are of the form Pd0 and Pd2+ on the surface of TaN-TaC composites. The electrocatalytic activity of the Pd/TaN-TaC catalysts is measured in a 0.5 mol L−1 KOH solution and 1 mol L−1 of ethylene glycol. These results imply that the Pd/TaN-TaC electrocatalyst modified glassy carbon electrode has a high catalytic activity for ethylene glycol electrooxidation in an alkaline medium. The dosage of Pd is 7% (mass ratio of Pd and TaN-TaC) and it exhibits the higher electrocatalytic activity, and superior to the commercial Pd/C (10%).

An abundant porous biochar material derived from wakame (Undaria pinnatifida) with high adsorption performance for three organic dyes

In this study, an activated wakame biochar material (AWBM) was prepared by a one-step calcination and activation method, whose adsorption performances for methylene blue (MB), Rhodamine B (RB) and malachite green (MG) were also analyzed. The results showed AWBM was a mesoporous fluffy structure material with a higher specific surface (1156.25 m2/g), exhibiting superior adsorption capacities for MB (841.64 mg/g), RB (533.77 mg/g) and MG (4066.96 mg/g), respectively. In addition, FT-IR analysis showed that AWBM possessed abundant active groups (such as –OH, –CO and –CH), further enhancing the adsorption efficiencies. The Langmuir model could better fit the three dyes adsorption isotherms process using AWBM, and the Pseudo-second-order model could better describe the adsorption kinetic experimental data. The thermodynamic analysis showed that the three dyes adsorption using AWBM was spontaneous endothermic reaction. This study suggests AWBM has enormous potential in the application of removing organic dyes from wastewater.

Effect of Mn<sup>2+</sup> dopants on the photocatalytic efficiency of MoS<sub>2</sub>

The Mn-doped MoS2 (Mn-MoS2) material is fabricated by a facile one-step calcination method. The Mn2+ content introduced into MoS2 is ranged from 1 wt% to 7 wt%. The X-ray diffraction (XRD) and scanning electron microscopy SEM results suggest that the doping of Mn2+ does not alter the crystal structure and the morphology of MoS2. However, it helps the Mn-doped MoS2 to exhibit stronger visible light absorption and higher magnetism. Especially, in the RhB degradation under visible light irradiation, better photocatalytic performance of the as-prepared Mn-doped MoS2 is observed compared to that of pure MoS2.

Ag-Modified g-C3N4 Prepared by a One-Step Calcination Method for Enhanced Catalytic Efficiency and Stability.

Ag-decorated g-C3N4 (denoted as Ag/CN-x) was prepared by a one-step calcination method, and the influences of calcination time on structure, morphology, surface composition, photocatalytic performance, and catalytic reduction activity of the prepared Ag/CN-x samples were investigated. The tests showed that the Ag/CN-8 prepared through by calcination for 8 h exhibited the best photocatalytic degradation efficiency of methyl orange (98.7% within 2 h) and the best catalytic reduction property of 4-nitrophenol (100% within 70 s). Meanwhile, these Ag/CN-x samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), photoluminescence (PL), photocurrent response, and electrochemical impedance spectroscopy (EIS) Nyquist plots. It was found that the Ag/CN-8 prepared through calcination for 8 h had a higher specific surface area, higher dispersibility of silver nanoparticles (Ag NPs), the widest range of visible light response, and the lowest photogenerated electron–hole recombination rate. The results of the trapping experiments indicated that a superoxide radical plays a major role. Moreover, a possible mechanism of photocatalytic degradation in methyl orange and catalytic reduction 4-nitrophenol was proposed.

Construction of NiO/H2Ti3O7 nanotube composite and its photocatalytic conversion feature for ethyl mercaptan

Ethyl mercaptan is a typical stinking organic sulfide, which is harmful to the human and ecological environment. Ethyl mercaptan in chemical raw materials is also toxic to catalysts. Therefore, it must be removed before use. In the present study, NiO/H2Ti3O7 nanotube (NiO/H2Ti3O7-NT) composite was used to adsorption and decomposition of ethyl mercaptan. The NiO/H2Ti3O7-NT composite was synthesized by a facile hydrothermal synthesis and one-step calcination method. The as-prepared NiO/H2Ti3O7-NT and its precursors were characterized by powder X-ray diffraction (XRD), transmission electron-microscopy (TEM), laser Raman spectroscopy (LRS), N2 adsorption–desorption measurement and UV–Vis diffuse reflection spectroscopy (UV–Vis DRS). Adsorption and photocatalytic oxidization performance for ethyl mercaptan were evaluated under dynamic condition. The results show that the spectral response characteristics of the as-prepared composite are changed significantly, responsiveness ability of visible light is a marked improvement. There is an obvious interaction between host H2Ti3O7-NT and gust NiO particles. The photocatalytic reaction results show that the as-prepared composite has a photo-degradation activity for oxidation of ethyl mercaptan under simulated sunlight irradiation. A possible photocatalytic mechanism was discussed.

Hierarchical porous g-C3N4/Bi5O7I photocatalyst for high gaseous mercury removal

The g-C3N4/Bi5O7I photocatalyst with a hierarchical porous nanostructure (CB-HPN) was successfully synthesized via one-step calcination method. The materials were characterized by XRD, SEM, XPS and PL to investigate the properties of porous nanostructure. The mercury removal efficiency of g-C3N4/Bi5O7I reached up to 80.3%, which was much higher than that of Bi5O7I. It was found that the hierarchical porous nanostructure could modulate the interface charge transfer tracks efficiently and increase the ratio of active factors, thus accelerating photocatalytic oxidation of gaseous mercury (Hg0). Based on the characterization and experiment analysis, a reasonable charge transfer and reaction mechanism for Hg0 oxidation is proposed.