Large BET Surface Area Research Articles

Phosphine-based covalent organic framework for highly efficient iodine capture

The efficient capture of nuclear waste such as radionuclide iodine has received more worldwide attention because of the effects of radiation on biological health. Adsorption is considered to be an efficient, low-cost, and environmentally friendly method for iodine removal. Recently, a new kind of phosphine-based covalent organic frameworks (P-COFs) with flexible and nonplanar structure have attracted great attention because of their high specific surface area and good thermal stability. The existence of electron-rich heteroatoms (P, N) as well as the large π-conjugated network structure may be beneficial to the absorption of iodine. In this study, a biphenyl linked P-COF was synthesized for the capture of iodine. It shows a uniform microsphere structure with a diameter of about 1.2 μm, a large BET surface area up to 1056 m 2 g −1 , and a high thermal stability (up to 500 °C). This P-COF exhibits rapid and exceptional iodine uptake in both volatile iodine and iodine/cyclohexane solution with adsorption capacities of 6.19 g g −1 and 1.30 g g −1 , respectively, suggesting that P-COF may be a potential candidate for radioiodine capture from nuclear waste. • A phosphine-based covalent organic framework (P-COF) is developed for the capture of iodine. • P-COF exhibits rapid volatile iodine uptake with an adsorption capacity of 5.00 g g −1 within 2 h. • The equilibrium adsorption capacity of vapor iodine reaches as high as 6.19 g g −1 . • P-COF shows tremendous iodine adsorption with capacity of 1.30 g g −1 in cyclohexane solution.

Facile synthesis of MIL-100 metal-organic framework via heatless technique for the adsorptive treatment of cationic and anionic pollutants

The facile synthesis of an iron-based metal-organic framework, MIL-100(Fe) has been successfully conducted via a heatless water-based technique. The unique features have been evaluated with respect to the X-ray diffraction, field emission scanning electron microscopy, nitrogen adsorption-desorption analysis, Fourier transform infrared spectroscopy, and zero point of charge measurement. The adsorptive potential was examined using the cationic (methylene blue, MB) and anionic (naproxen, NPX) water pollutants. The synthesized MIL-100(Fe) sample, MIL-100(FeSO 4 ), owned a crystalline microporous-mesoporous structure, with a large BET surface area of 1984 m 2 /g and total pore volume of 1.096 cm 3 /g. The equilibrium data best conformed to the Langmuir-Freundlich isotherm and pseudo-second order kinetic model, with the maximum adsorption capacity for MB and NPX of 568.1 mg/g and 148.8 mg/g, respectively. Thermodynamic analysis revealed the favorable energetics (Δ G < 0 and Δ S > 0), endothermic (Δ H > 0 for MB) and exothermic nature (Δ H < 0 for NPX) of the adsorption process. Negligible degradation of the adsorptive performance was recorded under high ionic strength solutions and simulated wastewaters. MIL-100(FeSO 4 ) demonstrated great regenerative potential by ethanol stripping for at least 5 regeneration cycles. The present findings provide an invaluable insight into the green synthesis technique of MIL-100(Fe), with high upscaling prospects. Imparted with different surface anionicity and electrically neutral functional sites, MIL-100(FeSO 4 ) has emerged to be a potent adsorbent for the successful treatment of both cationic and anionic water pollutants, even under high-strength water samples with complex water matrices.

Enhanced Photocatalytic Antibacterial Properties of TiO2 Nanospheres with Rutile/Anatase Heterophase Junctions and the Archival Paper Protection Application.

TiO2 has been generally studied for photocatalytic sterilization, but its antibacterial activities are limited. Herein, TiO2 nanospheres with rutile/anatase heterophase junctions are prepared by a wet chemical/annealing method. The large BET surface area and pore size are beneficial for the absorption of bacteria. The rutile/anatase heterojunctions narrow the bandgap, which enhances light absorption. The rutile/anatase heterojunctions also efficiently promote the photogenerated carriers’ separation, finally producing a high yield of radical oxygen species, such as •O2− and •OH, to sterilize bacteria. As a consequence, the obtained TiO2 nanospheres with rutile/anatase heterojunctions present an improved antibacterial performance against E. coli (98%) within 3 h of simulated solar light irradiation, exceeding that of TiO2 nanospheres without annealing (amorphous) and TiO2 nanospheres annealing at 350 and 550 °C (pure anatase). Furthermore, we design a photocatalytic antibacterial spray to protect the file paper. Our study reveals that the TiO2 nanospheres with rutile/anatase heterojunctions are a potential candidate for maintaining the durability of paper in the process of archival protection.

Study on the Preparation and Lipophilic Properties of Polyvinyl Alcohol (PVA) Nanofiber Membranes via Green Electrospinning.

As an environmentally friendly water-soluble polymer, polyvinyl alcohol (PVA) has attracted extensive attention because of its non-toxic, degradable, low cost, and good biocompatibility. Electrospinning is a kind of nanotechnology, and the nanofiber membrane prepared by it has the advantages of large surface area-to-volume ratios, nano- to micron-sized fibers, etc. Herein, a simple and facile one-step green electrospinning method was developed to fabricate various environmentally friendly PVA nanofiber membranes. The lipophilic properties of PVA membranes were investigated and optimized according different PVA concentrations. The PVA electrospun fiber prepared from the solution at a concentration of 10 wt% had the highest adsorption capacity for the adsorption of new and waste engine oils, and the waste engine oil adsorption capacity (12.70 g/g) was higher than that of new engine oil (11.67 g/g). It also has a relatively large BET surface area (12.05 m2/g), a pore volume (0.04 cm3/g), and an appropriate pore diameter (13.69 nm) and fiber diameter (174.21 nm). All electrospun PVA membranes showed excellent lipophilic properties due to their oil contact angles of much less than 30°. Therefore, PVA electrospun fibrous membranes have great application potential in the field of purifying engine oil due to the excellent lipophilic properties and oil absorption capacity.

Cooperation between microporous frameworks and micron-sized channel in crystals for excellent chromate removal

The vitrification process represents an effective method for high-level radioactive waste disposal, but CrO42- can form crystalline spinels within the glass to cause the secondary leak of radioactive waste. Porous materials are widely used for trapping CrO42-, but the unsatisfied adsorbing capacity and poor selectivity of reported materials make CrO42- enrichment to be a challenging issue. Herein, a rarely hollow single-crystalline MOF (1) with ordered macro-micropores of 13 μm and 8.6 Å was obtained, exhibiting high N2 adsorption of 339.2 cm3/g and large BET surface area of 1150 m2/g. Cooperation effect between microporous frameworks and micron-sized channels in crystals endows 1 with excellent chromate removal capacity of 609 mg/g, which is a record value known to date among the anion-exchange materials for CrO42- removal. The kinetic analysis revealed that such adsorption was a pseudo-second-order adsorption process. Framework 1 possessed high pH stability and irradiation resistance, can repeatedly absorb/desorb CrO42- to some degree. More importantly, sample 1 can maintain its high CrO42- adsorption capacity after 400 kGy β irradiation, offering the promising application for CrO42- disposal in high-level radioactive waste.

Facile fabrication of N-doped hierarchical porous carbons derived from soft-templated ZIF-8 for enhanced adsorptive removal of tetracycline hydrochloride from water

N-doped hierarchical porous carbons (NHPCs) were successfully prepared from soft-templated zeolitic imidazolate framework-8 (ZIF-8) precursors using sodium dodecylbenzene sulfonate (SDBS) as a template through facile one-step carbonization and applied in tetracycline hydrochloride (TCH) adsorption. The NHPC synthesized at 1000 °C with an SDBS/Zn2+ molar ratio of 0.075 exhibited the highest TCH adsorption (qm = 80.92 mg g−1) owing to its relatively large BET surface area (1067.41 m2 g−1) and pore volume (1.22 cm3 g−1) and the stronger surface interaction between TCH and NHPCs (HC1000–0.075). Compared with surfactant-free ZIF-8-derived carbon (HC), introduction of SDBS in the ZIF-8 precursor not only improved the pore structure of the carbon materials but also increased the nitrogen content and the number of surface functional groups. Adsorption kinetics and isotherms showed that the pseudo-second-order model and Sips model fit the TCH adsorption behavior on HC and HC1000–0.075 well. Adsorption experiments and characterizations revealed that the adsorption mechanism involved in TCH adsorption on HC1000–0.075 mainly depended on the synergistic effect of pore filling, H-bonding, π-π interactions, and weak electrostatic interactions. This study provides an effective and simple strategy for fabricating MOF-derived NHPCs as a promising adsorbent for the removal of antibiotics from water.

Hydrogen production by catalytic methane decomposition over rice husk derived silica

Methane decomposition (DeCH4) over solid catalysts is an interesting route for the production of hydrogen free of CO2 emissions. Moreover, it could lead to a negative carbon balance if biogas/biomethane is used as feedstock. However, it is limited by the huge amounts of carbon that are deposited over the catalyst causing its deactivation and hindering its regeneration, which makes necessary the development of low-cost and durable catalytic systems. This work reports the use of different silica materials fully produced from rice husk, i.e. without incorporating any external phase or component, as DeCH4 catalysts. The highest catalytic activity has been found for the silica samples showing large BET surface area and amorphous nature. These properties favor the generation of the actual DeCH4 active sites (-Si-C- species), shortening the induction time detected at the beginning of the reaction tests. The nano-silica materials produced from acid-washed rice husk exhibit a remarkable resistance against deactivation, affording an almost constant reaction rate at long times on stream. This fact is assigned to the presence of large mesopores that facilitate the growth of the carbons deposits towards the outer part of the catalyst particles. The results here reported show the great potential of rice husk-derived nano-silica to overcome several of the most relevant limitations that currently exist for the commercial deployment of hydrogen production by catalytic DeCH4, as a consequence of the low cost and durable activity of these sustainable materials.

Magnetic N-doped porous carbon for analysis of trace Pb and Cd in environmental water by magnetic solid phase extraction with inductively coupled plasma mass spectrometry

A novel magnetic N-doped porous carbon material (MNPC) was obtained by mixing urea, sucrose and Fe3O4@SiO2 and calcinating for carbonization. With g-C3N4 as intermediate template, the synthesized material has large BET surface area of 219.4 m2 g−1 and high nitrogen content of 9.4 wt%. With using MNPC material as sorbent, a new method by coupling magnetic solid phase extraction (MSPE) with inductively coupled plasma mass spectrometry (ICP-MS) was established for enrichment and determination of Cd(II) and Pb(II) in environmental waters. The conditions affecting MSPE were optimized including the effects of pH, sample volume, amount of sorbent usage, adsorption/desorption time and eluent type/concentration/volume. Under the optimized conditions, the developed MSPE-ICPMS method exhibited a good linear dynamic range of more than three orders of magnitude (2–5000 pg mL−1 for Cd(II) and 10–5000 pg mL−1 for Pb(II)) and a low detection limits of 0.49 and 3.1 pg mL−1 for Cd(II) and Pb(II), respectively. The relative standard deviations were in the range of 6.9%–7.3% for the target metal ions. The adsorption/desorption kinetics of the developed MSPE procedure was fast, and the total extraction procedure only cost 7 min (5 min for adsorption and 2 min for desorption) for each sample. The sorbent could be used for at least 5 times. The MSPE-ICPMS method has great potential for the determination of trace and even ultra-trace Cd(II) and Pb(II) in the environment waters.

Cure Characteristics and Mechanical Properties of Rubber Compound Reinforced with Activated Carbon from Coconut Husks as Alternative to Carbon Black

Selection of raw materials for rubber products is an important aspect of rubber engineering. One of the components often investigated is the filler material, wherein among the considerations include reinforcing capability, cost, and environmental impact. In this study, a greener alternative to carbon black (CB) was explored using activated carbon (AC) from coconut husk. Results showed that AC has lower fixed carbon content (33.64 wt%C) than CB (96.92 wt%C) due to the retained volatile organic components. AC also has a larger particle size distribution (&lt; 150μm) in terms of 80% passing than CB (which is 28-36 nm for technically specified particle size of commercial N330). However, AC exhibits larger BET surface area (423.66 m2/g) due to natural porosity of activated carbon materials as compared to CB (58.109 m2/g). Moreover, AC was found to be basic while CB has a neutral pH. Consequently, the tensile strength and complex modulus G* of the AC-compound (4.3 MPa and 75.36 kPa, respectively) are inferior to CB-compound (20.3 MPa and 87.41 kPa, respectively). This is thought to be mainly due to the larger particle size and porous structure of the activated carbon. Yet, the % elongation and hardness values are comparable. Processability may also be a concern in using activated carbon as a filler due to higher Mooney viscosity (45.8 M). Nonetheless, the scorch time and cure index of the two compounds were found to be comparable. Hence, the potential of complete replacement of carbon black with activated carbon is viable for rubber products with low tensile strength requirements, such as protective matting.

Fluorescent core-shell SiO2@vertical covalent organic frameworks nanosheets for sensing application

Fluorescent covalent organic frameworks (COFs) are attracting more and more attentions. However, it is very difficult to obtain COFs with strong fluorescence due to fluorescence quenching caused by interlaminar accumulation and intramolecular rotation. Here, the core-shell SiO2@COFTFP-TAPB (1,3,5-tri(4-aminophenyl)-benzene: TAPB, 1,3,5-triformylphloroglucinol: TFP) was prepared by assembling vertical COFTFP-TAPB through amine-aldehyde dehydration condensation reaction on -NH2-SiO2 nanospheres (NPs) for the first time. The 2D COFTFP-TAPB nanosheets with thickness of 25 nm and good crystallinity vertically stand on the surface of -NH2-SiO2 NPs based on the imine-linkage. Such core-shell structure results in larger BET surface area, effectively overcomes the interlaminar accumulation, and improves optical properties of COFTFP-TAPB. The core-shell SiO2@COFTFP-TAPB exhibits multiemission from the enol-imine form and keto-enamine form, which is sensitive to pH. After loading with glucose oxidase and urease, it could be used to detect glucose and urea successfully. The detection ranges are 0.23 μM-14 mM and 1.50 μM-90 mM, and the detection limits reaches 0.07 μM and 5.14 μM, respectively. The work provides a feasible idea to overcome the interlaminar accumulation and reaggregation of COFs during application.

A functionalized UiO-66 MOF acting as a luminescent chemosensor for selective and sensitive turn-on detection of superoxide and acetylacetone

A luminescent ZrIV based UiO-66 metal-organic framework (MOF) with sulphonamide functionality was successfully synthesized using solvothermal method and characterized using various instrumental tools. This newly synthesized Zr-MOF (UiO-66-NH–SO2–Ph-NO2, 1; UiO = University of Oslo) with 2-((4-nitrophenyl)sulfonamido)terephthalic acid (BDC–NH–SO2-Ph-NO2) ligand displayed high thermal stability up to 330 °C under N2 atmosphere and chemical stability in H2O, 1 (M) HCl, glacial acetic acid and NaOH solution (pH 8 to 10). The MOF showed a large BET surface area of 1073 m2 g−1. The thermally activated MOF (1′) showed highly selective and sensitive fluorescent switch-on properties for superoxide (O2•-) in MeOH and acetylacetone (ACAC) in DMF medium even in presence of its competitors. The detection limit (98 nM) of O2•- using this probe is much lower than the known MOF based chemo-sensor for O2•-. The uniqueness of this MOF (1′) is its ability to detect ACAC up to the limit of 1.23 ppm, which is similar as the previously published MOF chemo-sensors for ACAC. The mechanisms of both the sensing processes were investigated in detail.

Effects of the morphology and crystal-plane of TiO2 on NH3-SCR performance and K tolerance of V2O5-WO3/TiO2 catalyst

V2O5-WO3/TiO2 is the commercial NH3-SCR catalyst, the morphology and crystal-plane of its support can influence the denitration performance and K tolerance efficiently. TiO2 nano-rods (TiO2-NRs, mainly exposed the {100} facets) has larger BET surface area than those of TiO2 nano-octahedrons (TiO2-NOs, mainly exposed the {101} facets) and TiO2 nano-truncated octahedrons (TiO2-NTs, mainly exposed the {001} facets). The larger BET surface area was conducive to the dispersion of active species, thereby generating more active sites and enhancing the amount of V5+ ratio. Moreover, there was a stronger interaction between the active species (V2O5 and WO3) and TiO2-NRs support, which led to the increase of chemisorbed oxygen ratio and the improvement of surface acidity and redox ability. Furthermore, NH3-SCR reaction over V2O5-WO3/TiO2-NRs (i.e., VWTi-NRs) catalyst followed by both Langmuir-Hinshelwood (L-H) and Eley-Rideal (E–R) mechanisms. While it only followed by an L-H mechanism over V2O5-WO3/TiO2-NOs (i.e., VWTi-NOs) and V2O5-WO3/TiO2-NTs (i.e., VWTi-NTs) catalysts.

Synthesis and characterization of activated carbon of Moringa oleifera Lam pod and evaluation of its performance in the removal of oils and greases

Produced water treatment is crucial since its improper disposal can result in ecological damage. A widespread and effective technology for removing organic compounds in industrial effluents is adsorption. Approaches to treating real produced water using activated carbon with different activating agents lack discussions in the literature. The present study aimed to investigate the influence of acids, salts, and bases on the structure development of three activated carbon and their performance to remove oil and greases content (OGC) in produced water from an oil field. Moringa oleifera Lam was used as precursor material, and the influence of activating agents such as zinc chloride (ZnCl2), phosphoric acid (H3PO4), and sodium hydroxide (NaOH) was investigated. The adsorbents were characterized by elemental analysis (CHN), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and textural properties. The kinetic study showed that the pseudo-second-order kinetic model better represented the adsorbents. Among the activating agents, H3PO4 proved to be the most appropriate for producing an adsorbent with a large BET surface area, 1356.29 m2/g, and reaching an adsorption capacity equal to 294.41 mg/g. In addition, its chemical balance was described by Langmuir isotherm, suggesting chemical adsorption, while Freundlich isotherm adjusted well to experimental data of activated carbon with zinc chloride. Results indicated activated carbon with phosphoric acid or zinc chloride as alternative adsorbents for removal OGC since both had a percentage of oil and grease removal greater than 93%.

The Use of Low Cost Nanoporous Catalysts on the Catalytic Pyrolysis of Polyethylene Terephthalate.

This study evaluated the feasibility of low-cost nanoporous catalysts, such as dolomite and red mud, on the production of aromatic hydrocarbons via the catalytic pyrolysis of polyethylene terephthalate (PET). Compared to the non-catalytic pyrolysis of PET, catalytic pyrolysis over both dolomite and red mud produced larger amounts of aromatic hydrocarbons owing to their catalytic cracking efficiency and decarboxylation efficiency. Between the two catalysts, red mud, having a larger BET surface area and higher basicity than dolomite, showed higher efficiency for the production of aromatic hydrocarbons.

N, S Co-Doped Bagasse Mesoporous Carbon with Enhanced Electrochemical Performance

Nitrogen-sulfur co-doped interconnected honeycomb sheet-like biomass carbon (N, S-BC) from low-cost agriculture waste-bagasse, was prepared by a simple and effective strategy of one step heat treatment with thiourea as doping agent. The mesoporous structure of N, S-BC shows an average pore diameter of 6–25 nm, a sheet thickness of 5–7 nm, and a relatively large BET surface area of 1576.7 m2 g−1. The N, S-BC anode material exhibits better electrochemical performance than the un-doped BC and the N, S single-doped BC (N-BC and S-BC). The N, S-co-doping makes the first discharge specific capacity of BC increase 105.9%, the first coulomb efficiency increase 22.8%, and the reversible capacity increase 187.2% after 50 cycles. After 200 cycles, A relatively high reversible capacity of 572.8 mAh g−1 even can be observed at a high current density of 2 A g−1, which is 3.7 times that of BC and almost twice that of N-BC and S-BC. When using as LEDs lighting power supply, the brightness duration of N, S-BC cell shows longer than that of BC cell. The dynamic storage mechanism study results show that both the diffusion coefficient of lithium ions and capacitance contribution rate of N, S-BC are larger than those of BC. These enhanced electrochemical properties of N, S-BC are attributed to their high specific surface area, abundant uniform mesoporous structure of the honeycomb layer and defects, and the synergistic effect of diatomic doping. The one-step method of N, S co-doping technology for sheet-like porous biomass carbon could be used to synthesize high-performance lithium-ion battery electrode materials with cheap and readily available agricultural waste is used as precursors.

Facile synthesis of biomass-derived porous carbons incorporated with CuO nanoparticles as promising electrode materials for high-performance supercapacitor applications

Supercapacitors with large capacity, good stability and low cost are attractive to the development of energy storage technology. Herein, a new method for preparing biomass-derived carbon materials incorporated with CuO nanoparticles is proposed using cheap peanut shells as the carbon resource and copper acetate as the CuO precursor. The as-prepared CuO-AC sample retains a large BET surface area of 2640.55 m2/g with hierarchical micro-mesoporous structures. CuO nanoparticles with a particle size of 10–20 nm are formed and uniformly dispersed on the surface of the carbon skeleton. The synergetic effect of the double-layer capacitance of the porous carbon matrix and the Faraday capacitance introduced by CuO nanoparticles was successfully achieved, benefiting from which the CuO-AC electrode exhibits a high gravimetric specific capacitance up to 530 F/g at 1 A/g with prominent cycling stability of 92.5% after 10,000 cycles in the three-electrode system. CuO-AC was also used as the anode to assemble an asymmetric supercapacitor to investigate its practical application, showing that a high energy density of 11.7 W h/kg was reached at a power density of 628.73 W/kg. The large specific capacitance, high energy density and long cycle life of CuO-AC endow it a potential electrode material for supercapacitors.

Production of hydrogen-rich syngas from absorption-enhanced steam gasification of biomass with conch shell-based absorbents

In this study, steam gasification of pine sawdust is conducted in a fixed-bed reactor in the temperature range 650–700 °C with calcined conch shell (CS) serving as a starting absorbent. The CS is further subjected to hydration (HCS) and calcination (CHCS) to prepare a modified absorbent. It is found that the hydration-calcination treatment of CS causes smaller CaO crystal grains with a larger BET surface area and more porous surface. As a consequence, CHCS exhibits higher catalytic activity for tar reforming, faster reaction rate for CO2 absorption and better performance for H2 selectivity than CS. Elevating the temperature contributes to tar reduction but results in lower H2 content and higher CO2 content, while an increase in Ca/C leads to higher H2 content. And the H2 content can reach approximately 76% with the use of CHCS when temperature and Ca/C ratio are 650 °C and 2, respectively.

Controlled synthesis of electrospun hollow Pt-loaded SnO2 microbelts for acetone sensing

Challenges for ubiquitous diffusion of gas analytes into semiconducting metal oxides (SMOs) based sensing layers have necessitated the introduction of unprecedented synthesis techniques for thin, porous and high-performance gas sensing materials. In this work, electrospinning and calcination were employed to prepare unprecedented SiO2–SnO2 core–shell microbelts (hereinafter referred to as SiO2@SnO2 BLs) followed by etching away of SiO2 in NaOH solution (pH 12) to achieve hollow SnO2 BLs (hereinafter referred to as SnO2 HBLs) with mean crystal size of 14.01 nm, large BET surface area (143.5 m2‧g–1), high porosity (mean pore size of 5.7 nm), and shell thickness of 58.3 ± 11.4 nm. Sensitization of SnO2 HBLs with apoferritin-templated platinum nanoparticles (Pt NPs) enhanced their detection capability toward acetone. Response (defined as Ra/Rg, where Ra and Rg are sensor resistances in air and target gas, respectively) of Pt(0.12 %)_SnO2 HBLs toward 2 ppm acetone was up to 7.8 times higher compared to that of pristine SnO2 HBLs, and exhibited faster response (9.2 s). The Pt(0.12 %)_SnO2 HBLs based sensor indicated a promising long-term stability, and outstanding repeatability of response (Ra/Rg = 93.7 ± 0.89) toward 25 cycles of 2 ppm acetone exposure in a humid environment of 90 % relative humidity. This performance could be attributed to the unique morphology of HBLs, sensitization effects of catalytic Pt NPs, and enlargement of the electron-depleted layer resulting from a Schottky barrier between Pt NPs and SnO2 grains.

Design of Highly Sensitive and Selective H2s Gas Sensor Based on CuO-Cu7S4 Microflowers

Introduction CuxO (copper oxides, x=1, 2) as a p-type oxide semiconductor is widely used in photocatalysis, electrochemistry, solar energy conversion, gas sensors [1], and photoactivated splitting of water due to its non-toxicity, low cost, and facile controllable synthesis. In order to meet the increasing requirements of the above applications, various morphologies of CuxO such as nanocubes [2], nanowires [3], nanorods, nanoflowers, nanoparticles, nano-octahedrons, nanospheres, have been prepared by different methods. In this work, CuO-Cu7S4 microflowers were successfully synthesized through a simple hydrothermal route and used as sensing materials. In the comparative gas sensing test, the sensor fabricated from CuO-Cu7S4 (S/Cu = 27 mol%) microflowers exhibited the highest response to hydrogen sulfide, and the fast response and recovery time. CuO-Cu7S4 microflowers gas sensor showed not only superior hydrogen sulfide selectivity with other gases, but also ppb-level detection limit at 225 °C. The synergistic catalytic effect between CuO and Cu7S4, optimized structural parameters and marked resistive variation due to the formation of nanoscale p-p heterojunctions were regarded as the main reasons for the ultrasensitive and selective hydrogen sulfide detection. Method For device fabrication, a small amount of CuO-Cu7S4 microflowers were dissolved with a few drops of the deionized water in an agate mortar to form slurry and then coated uniformly on the ceramic tube (4 mm in length, 1.2 mm in external diameter and 0.8 mm internal diameter) with a pair of Au electrodes and Pt wires. The coating was calcined at 90 °C for 1 h in air using a muffle furnace. Then, a Ni-Cr alloy coil heater was inserted through the well-coated ceramic tube, which controlled the working temperature. The sensing measurement of the sensors was carried out on a static system. The resistance of sensing material was continuously recorded by digital multimeter and the sensing response (S) was defined as the percentage of relative variation in resistance (ΔR/Ra*100%), where ΔR represents the variation of resistance before and after contacting with target gases, while Ra represents the resistance of gas sensor in initial state. The response/recovery time was defined as the required time for the resistance to reach 90% of total resistance variation relative to the former equilibrium value upon exposure to/removal from target gases. Results and Conclusions In this work, the Cu7S4-CuO composites were synthesized by hydrothermal method, More importantly, the ppb-level detection limit indicated the potential application on the trace hydrogen sulfide detection. Such behaviors could be attributed to the existence of p-p heterojunctions, co-catalytic effect, the large BET surface areas and the synergistic combination between Cu7S4 and CuO.

Biomass-derived N/S dual-doped hierarchically porous carbon material as effective adsorbent for the removal of bisphenol F and bisphenol S

Biomass-derived heteroatom-doped porous carbon-based materials are emerging as low-cost adsorbents for removing common pollutants, although the adsorption performance is still unsatisfactory and the main adsorption mechanisms are still controversial. Herein, we report a facile and general method for fabricating biomass-derived N/S dual-doped hierarchically porous carbon adsorbent (MZ-NSPC). The MZ-NSPC material exhibits excellent adsorption capacity (295.8 mg/g for bisphenol F (BPF), 308.7 mg/g for bisphenol S (BPS)), short equilibrium time (30 min), and good reusability (the decline efficiency < 6.15% after five times). The remarkable adsorption performance originates from a large BET surface area, hierarchically porous structure, and N/S heteroatoms dual-doping. Combined with comparative experiments and density functional theory (DFT) calculations, we revealed that the doped N, S heteroatoms played a synergistic effect which promoted the adsorption performance and adsorption sites are mainly the oxidized-S and pyridinic-N. Importantly, for BPF, the proportion contribution of different mechanisms followed the order of hydrophobic interaction > π-π interaction > hydrogen bonding interaction. However, adsorption mechanism of BPS was mainly controlled by π-π interaction. This work not only promotes the development of low-cost and sustainable heteroatom-doped carbon-based materials, but also systematically studies adsorption mechanism of heteroatom-doped carbon-based materials for bisphenols.