N-doped ordered mesoporous carbons (NOMC) were prepared with mixed solution of urea and sucrose as carbon source and nitrogen source. SBA-15 was adopted as the hard template. The effect of urea to ...sucrose molar ratio on NOMC was investigated. NOMC samples were characterized by techniques such as BET, TEM, XPS and TG. The catalytic performances of NOMC catalysts were evaluated for the pyrolysis of 1-chloro-1,1-difluoroethane (HCFC-142b, CH3CClF2) to vinylidene fluoride (VDF, CH2=CF2). The catalytic reactions were carried out at 400 °C and space velocity of 600 h−1 (based on HCFC-142b). The results indicate that NOMC exhibits a stable activity at 400 °C with high HCFC-142b conversion and selectivity to VDF. The textural parameters of NOMC play a major role in VDF selectivity and N species over the carbon surface are responsible for NOMC catalytic performance. Compared with the temperatures of industrial manufacture of VDF at 650–700 °C, the NOMC catalysts provide a promising pathway to produce VDF at much lower temperatures (below 400 °C).
NOMC catalyzes the dehydrochlorination of HCFC-142 b at 400 °C efficiently with high HCFC-142b conversion and VDF selectivity. Display omitted
•N-doped ordered mesoporous carbons were prepared with urea and sucrose as precursors.•NOMC catalyzes the dehydrochlorination of HCFC-142 b at 400 °C efficiently.•Pyridinic N and pyrrolic N are responsible for the dehydrochlorination of HCFC-142b.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Visible light communication (VLC) is an advanced and high-efficiency wireless communication technology. As one of the most important light sources in VLC, conventional white light emitting diode ...(WLED) based on Y
Al
O
:Ce
(YAG:Ce) phosphor limits the system transmitting rate severely due to its narrow modulation bandwidth. Considering the short fluorescent lifetime of quantum dots (QDs), QD-LEDs with wide modulation bandwidths were designed here to improve the transmitting rate of VLC. CdSe/ZnS core/shell QDs and related luminescent microspheres (LMS) were implemented as light conversion materials for the QD-LEDs. Compared with conventional phosphor WLED, the proposed QD-LED and QD-WLED reached maximum improvement on modulation bandwidth at 74.19% and 67.75% respectively. Furthermore, mathematical modeling of smearing was analyzed to establish the relationship between fluorescent lifetime and modulation bandwidth. Our findings will provide an effective solution of white LEDs for high speed VLC.
A defect-rich activated carbon featured superior catalytic performance and stability for acetylene hydrochlorination as metal-free catalysts. Raman and density functional theory calculations results ...indicate that the defective site on activated carbon is the active site for acetylene hydrochlorination. The catalytic performance of activated carbons is linearly correlated with the amount of surface defects.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Cu/C2N, Co/C2N, Ni/C2N and C2N were designed by DFT for CO2 capture and CO2RR.•M/C2N (M = Cu, Co, Ni) have good CO2 adsorption performance.•The three material systems of Cu/C2N, ...Co/C2N and Ni/C2N have lower energy barriers than the original C2N, which is more favorable for the CO2RR reaction.•Cu/C2N surface is more inclined to adsorb CO2 and then combine with H atoms to form OCHO.•Co/C2N and Ni/C2N surfaces are more inclined to hydrogenate CO2 to COOH in one step.
The capture and further conversion of carbon dioxide into useful fuels and value-added chemicals is critical to addressing the growing problem of global warming and promoting sustainable human development. In this work, the adsorption and activation of CO2 on the surface of single-atom-doped C2N monolayers and the first-step reaction mechanism of CO2RR were investigated by density functional theory (DFT). The catalyst structure, CO2 adsorption configuration and electronic properties of CO2 activation on C2N surfaces decorated with transition metal single atoms of Cu, Co, and Ni were discussed. Cu/C2N, Co/C2N and Ni/C2N all have good CO2 adsorption performance by calculations. The calculation results of the first hydrogenation reaction of CO2RR show that the three materials of Cu/C2N, Co/C2N and Ni/C2N have lower energy barriers than the pristine C2N, which suggests that they are more favorable for the CO2RR reaction to proceed. The Cu/C2N surface is more inclined to adsorb CO2 and then combine with H atoms to form OCHO, but the Co/C2N and Ni/C2N surfaces are more inclined to hydrogenate CO2 to COOH in one step. The difference in the mechanism of the three material systems may be due to the difference of electrons and density of states on the 4s orbital of the outermost electron number of the doped transition metal atoms Cu, Co, Ni.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•M/CeO2 (M=Pt, Ag, Au) was prepared and used for photodegradation of MO.•Structure, morphology and optical properties of M/CeO2 were investigated.•The various factors on the photocatalytic ...degradation efficiency of MO were studied.•The active species of photodegradation are hydroxyl and superoxide radicals.•Photocatalytic mechanism based on work function and electron transfer was discussed.
In this paper, M/CeO2 (M=Pt, Ag, Au) photocatalysts were prepared and used for visible light degradation of methyl orange (MO) with H2O2 as a sacrificial reagent. Utilizing X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), N2 physical adsorption (BET), X-ray photoelectron spectroscopy (XPS), photocurrent characterization and electrochemical impedance spectroscopy, etc., the structure, morphology, chemical state, and optical properties of the catalyst were investigated. The effects of the amount of catalyst, the initial concentration of methyl orange, the pH value of the solution and the number of reuses on the photocatalytic degradation efficiency of MO were studied. The results showed that under optimized reaction condition of 15 mg 2Pt/CeO2 catalyst, the initial concentration of MO was 20 mg/L, pH=5, the reaction time was 195 min and the amount of H2O2 was 0.2 mL, the degradation percentage of MO reached 75.8%. The main active species of photodegradation are hydroxyl radicals and superoxide radicals, which was determined by free radical capture experiments and combined electron spin resonance (ESR). The photocatalytic mechanism based on work function difference and electron transfer was also discussed in detail.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A defective nanodiamond-graphene material (ND@G) exhibits superior catalytic activity in acetylene hydrochlorination with an acetylene conversion of 50%, selectivity to vinyl chloride of up to 99.5% ...at 220 °C, and a C2H2 gas hourly space velocity of 300 h-1, which is the first example of a metal-free catalyst with comparable performance to that of the 0.25% Au/C catalyst.
Methanol is considered an attractive hydrogen carrier for fuel cells via steam reforming reaction. The industrial Cu/ZnO/Al2O3 catalyst is widely used for its excellent activity in various reactions. ...The function of aluminum was deemed to be indispensable for catalytic activity and stability. However, the promotion mechanism of aluminum on the Cu/ZnO catalyst for methanol steam reforming reaction remains ambiguous. Herein, a series of aluminum-modified Cu/ZnO-xAl and Cu/ZnO + xAl catalysts with various loadings were fabricated. Systematic characterizations (e.g., XRD, TEM, H2-TPR, CO2–N2O titration, CO2-TPD, and XPS) prove that incorporation of Al3+ ions into the ZnO lattice remarkably boosts the activity and stability due to enhanced Cu–ZnO synergy. The properties and chemical environment of Cu NPs were comprehensively investigated, and the Cu surface areas, oxygen vacancies, and ZnO x sites were quantitatively measured. The correlation between turnover frequency and catalyst structure proves that the aluminum-induced Znδ+ or ZnO x sites at the interface between Cu and ZnO play a dominant role in enhancing catalytic performance. This insight into Cu–ZnO synergy induced by aluminum may contribute to the design of high-performance catalysts in the future.
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Ordered mesoporous nitrogen doped carbon catalyst containing ruthenium nanoparticles (Ru-N-OMC) was directly synthesized by using RuCl3/SBA-15 as a hard template. Ruthenium particles with a narrow ...size distribution in the range of 1.5–2.5 nm are uniformly semi-embedded in the carbon matrix without aggregation and pore blocking. Urea was used as nitrogen source carbonized with sucrose, resulting in about 3 wt% nitrogen doped carbon catalyst and more than 70% nitrogen was quaternary N species. The doping nitrogen and Ru nanoparticles are both active sites for acetylene hydrochlorination. Compared with Ru-OMC catalyst without nitrogen, this Ru-N-OMC catalyst shows a better performance and stability in the acetylene hydrochlorination for vinyl chloride monomer production.
N and Ru NPs were doped in the mesoporous carbon framework via a one-step carbonization method, which shows high activity and stability in the acetylene hydrochlorination. Display omitted
•Nitrogen and uniformed semi-embedded Ru nanoparticles can be doped in one-step.•More than 70% graphitic N doped in the framework.•Active sites are N species and Ru nanoparticles.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In this work, transition metal atoms (TM=Co, Ni, Mo) doped with B defect (M-VB-BN) and N defect (M-VN-BN) boron nitride (BN) monolayer was constructed and used for the synthesis of ammonia with N2 ...and *H as raw materials (TM=Co, Ni, Mo). Based on the density functional theory (DFT), the structure of these six modified materials was optimized, and the simulation calculation of the N2 reduction reaction (N2RR) was carried out. It shows that the type of defects and TM will affect the reaction path. For Co-VB-BN and Ni-VB-BN, the most potential path is the alternate mechanism; Mo-VN-BN is most inclined to the enzymatic mechanism. In particular, for Co-VN-BN, Ni-VN-BN and Mo-VB-BN, the N2RR does not proceed from beginning to end according to any of the three basic mechanisms. It is manifested as a mixed mechanism in which the enzymatic mechanism and the associative mechanism are interleaved. In general, N defect is more suitable for N2RR than B defect. Among the six structures, Mo-VN-BN exhibits the highest catalytic activity, and its energy barrier for rate-determining step is only 0.24 eV. These findings can provide a certain reference for the selection of defect sites and transition metals in the study of two-dimensional BN material catalysts.
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•B defect (M-VB-BN) and N defect (M-VN-BN) BN monolayer (M=Co, Ni, Mo) was constructed.•M-VB-BN and M-VN-BN were used for the synthesis of ammonia with N2 and *H as raw materials.•N2RR does not proceed from beginning to end according to any of the three basic mechanisms.•N defect is more suitable for N2RR than B defect.•Mo-VN-BN shows the lowest energy barrier for rate-determining step.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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