Ammonia (NH
) is vital in modern agriculture and industry as a potential energy carrier. The electrocatalytic reduction of nitrate (NO
) to ammonia under ambient conditions offers a sustainable ...alternative to the energy-intensive Haber-Bosch process. However, achieving high selectivity in this conversion poses significant challenges due to the multi-step electron and proton transfer processes and the low proton adsorption capacity of transition metal electrocatalysts. Herein, we introduce a novel approach by employing functionalized multi-walled carbon nanotubes (MWCNTs) as carriers for active cobalt catalysts. The exceptional conductivity of MWCNTs significantly reduces charge transfer resistance. Their unique hollow structure increases the electrochemical active surface area of the electrocatalyst. Additionally, the one-dimensional hollow tube structure and graphite-like layers within MWCNTs enhance adsorption properties, thus mitigating the diffusion of intermediate and stabilizing active cobalt species during nitrate reduction reaction (NitRR). Using the MWCNT-supported cobalt catalyst, we achieved a notable NH
yield rate of 4.03 mg h
cm
and a high Faradaic efficiency of 84.72% in 0.1 M KOH with 0.1 M NO
. This study demonstrates the potential of MWCNTs as advanced carriers in constructing electrocatalysts for efficient nitrate reduction.
Two methods, viz., the hydrothermal (HT) and co-precipitation (CP) methods, were used to prepare CeO
2
–NiO composite oxides; with them as the supports, Au/CeO
2
–NiO catalysts were prepared by the ...colloidal deposition method and used in the preferential oxidation (PROX) of CO in H
2
-rich stream. Various characterization measures such as N
2
sorption, XRD, TEM, H
2
-TPR, Raman spectroscopy and XPS were used to clarify the influence of preparation method on the structure of CeO
2
–NiO support and the performance of Au/CeO
2
–NiO catalyst. The XPS and TEM results reveal that the CeO
2
–NiO(HT) support prepared by hydrothermal method displays a uniform rod-like shape and exposes preferentially the (110) and (100) planes of CeO
2
, whereas the CeO
2
–NiO(CP) support prepared by co-precipitation method is composed of nanorods and irregular nanoparticles dominated by (111) facets of CeO
2
. After deposition of gold, both the Au/CeO
2
–NiO(HT) and Au/CeO
2
–NiO(CP) catalysts are alike in the state and size distribution of deposited Au nanoparticles. The H
2
-TPR results indicate that the presence of Au strongly promotes the reduction of CeO
2
in the Au/CeO
2
–NiO catalyst. Raman spectra illustrate that the incorporation of Ni ions into CeO
2
remarkably increases the amount of oxygen vacancies in the CeO
2
–NiO supports, especially in CeO
2
–NiO(HT) prepared by hydrothermal method, which is beneficial to the dispersion and stabilization of gold species. The structure of CeO
2
–NiO support and catalytic activity of Au/CeO
2
–NiO in CO PROX is strongly related to the preparation method; Au/CeO
2
–NiO(HT) exhibits much higher activity than Au/CeO
2
–NiO(CP). The larger fraction of (110) and (100) CeO
2
facets in CeO
2
–NiO(HT) can promote the dispersion of gold species, formation of oxygen vacancies and migration of oxygen species, which are effective to enhance the redox capacity and activity of the obtained Au/CeO
2
–NiO(HT) catalyst for CO PROX in H
2
-rich stream.
Graphical Abstract
Au supported on CeO
2
–NiO nanorods prepared by hydrothermal method exhibits much higher catalytic activity for CO PROX in H
2
-rich stream.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The application of trimellitate (TMT) in the lubricating oil industry was seriously restricted because of its low viscosity index. In the work reported here, polycaprolactone (PCL) soft chain was ...embedded into the structure of TMT in order to improve the viscosity index. Characterization of the polymers was done by proton nuclear magnetic resonance (
H-NMR), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TG). Results supported our design and were consistent with the target product structure. Performance of the prepared materials was evaluated by standard ASTM methods. Noticeably, the viscosity index of the modified TMT increased from 8 to above 100, which greatly improved its viscosity-temperature performance. As the initiator, tetrabutyl titanate (TBT) can not only complete the ring-opening polymerization of caprolactam (ε-CL) at room temperature, but also generate nano-TiO
by-products with excellent anti-wear properties during the synthesis. Characterization of the nano-TiO
was done by scanning electron microscopy (SEM), FT-IR, TG and X-ray diffractometry (XRD). The friction and wear tests were conducted on a four-ball friction tester and the surface morphologies of worn surfaces were investigated by SEM. The experimental results clearly showed that the modified TMT showed better viscosity index and thermal stability as compared to the unmodified one. The modified nano-TMT base oil features excellent lubricant performance with good viscosity-temperature properties, thermal stability and anti-wear properties.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
This paper considers the effect of nonlinear atmospheric disturbances on wind power prediction. A Lorenz system is introduced as an atmospheric disturbance model. Three new improved wind forecasting ...models combined with a Lorenz comprehensive disturbance are put forward in this study. Firstly, we define the form of the Lorenz disturbance variable and the wind speed perturbation formula. Then, different artificial neural network models are used to verify the new idea and obtain better wind speed predictions. Finally we separately use the original and improved wind speed series to predict the related wind power. This proves that the corrected wind speed provides higher precision wind power predictions. This research presents a totally new direction in the wind prediction field and has profound theoretical research value and practical guiding significance.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The power system frequency is an important indicator that reflects the power system's operating status. Through real-time detection or prediction, it can effectively ensure stable power system ...operation. To provide a theoretical basis for the steady-state recovery of thepower system after major disturbances, a deep belief neural network model for predicting the power system's frequency response mode after major disturbances has been proposed. This model combines deep belief networks with deep neural networks. The feature extraction and learning abilities of deep belief networks were utilized to complete model training and learning. Deep neural networks were utilized to complete data classification and prediction. The load sudden variable is larger, the system frequency fluctuation is greater, the inertia time constant increases less, and the system frequency fluctuation is greater. In simulation testing with a training sample size of 2100 and a testing sample size of 900, the deep belief neural network took 3320 seconds, while the deep neural network took 11523 seconds. The prediction results' absolute error amplitude of this deep belief neural network is 0.025Hz. It meets the practical needs of frequency response mode prediction in power systems after major disturbances. The study analyzed the impact of load sudden changes and inertia time constants on system frequency, and successfully designed a frequency response mode prediction model for power systems after major disturbances.
Nano-micro calcium carbonate has a small particle size, uniform distribution, and good dispersion performance, offering great research value and development prospects. It has been widely used as a ...filler material for rubber, paper, ink, pigments, and coatings. Developing an efficient and controllable approach to preparing nano-micro calcium carbonate with adjustable morphology and controllable size has significant economic and environmental benefits. This study reports the controllable synthesis of nano-micro calcium carbonate meditated by additive engineering. The effects of various additives including inorganic acids, organic acids, alcohol, and surfactants on the particle size and morphology of the prepared materials were investigated. SEM, FT-IR and other characterization methods were used to analyze the prepared nano-micro calcium carbonate particle size, dispersion, and uniformity. The results showed that the particle size of calcium carbonate was 4~7 μm with a cubic structure. The particle size of calcium carbonate prepared by adding surfactant additives is in the range of 1~4 μm, and the crystal shape of calcium carbonate changes from calcite to vaterite after adding sodium dodecyl benzene sulfonate. With the aid of additives, the calcium carbonate particles dispersed more evenly. The mechanism of the controllable synthesis of nano-micro calcium carbonate mediated by additive engineering is elucidated and discussed. SDBS was found to be the best additive for preparing nano-micro calcium carbonate, and the synthesis conditions were explored and optimized.
•The research of wind speed prediction in this paper is conducive to the development of clean energy.•Use FCBF to select influencing factors, reducing the complexity of input variables.•The optimized ...VMD is used to decompose wind speed and fully mine its data characteristics.•The differential numerical analysis of VMD decomposition components gives full play to the role of data mining.•A novel system is established to provide high-precision short-term wind speed forecasting.
The uncertainty and instability of wind power make it difficult to develop wind energy, wind farm grid connection, and power system stability, so accurate forecasting of wind power is very important. How to reduce wind power forecast errors and improve wind power forecast accuracy has become an urgent problem to be solved. The combined model proposed in this paper uses fast filtering algorithm (FCBF) and variational mode decomposition (VMD) to extract features of wind resource data, and uses least squares support vector machine (LSSVM) to predict short-term wind speed. Finally, according to the point prediction results and the prediction error, the wind speed range is estimated. In this paper, three groups of wind speed data at different times and regions are used for experiments. The experimental results show that the prediction error of the model designed in this paper is significantly less than that of the comparison model. The results show that the prediction system proposed in this paper is superior to all comparative prediction schemes, which can reduce the fluctuation risk and improve the stability and security of wind power system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Biochar is considered as a promising candidate for emerging sustainable energy systems and environmental technology applications. However, the improvement of mechanical properties remains challenges. ...Herein, we propose a generic strategy to enhance the mechanical properties of bio-based carbon materials through inorganic skeleton reinforcement. As a proof-of-concept, silane, geopolymer, and inorganic gel are selected as precursors. The composites' structures are characterized and an inorganic skeleton reinforcement mechanism is elucidated. Specifically, two types of reinforcement of the silicon-oxygen skeleton network formed in situ with biomass pyrolysis and the silica-oxy-al-oxy network are constructed to improve the mechanical properties. A significant improvement in mechanical strength was achieved for bio-based carbon materials. The compressive strength of well-balanced porous carbon materials modified by silane can reach up to 88.9 kPa, geopolymer-modified carbon material exhibits an enhanced compressive strength of 36.8 kPa, and that of inorganic-gel-polymer-modified carbon material is 124.6 kPa. Moreover, the prepared carbon materials with enhanced mechanical properties show excellent adsorption performance and high reusability for organic pollutant model compound methylene blue dye. This work demonstrates a promising and universal strategy for enhancing the mechanical properties of biomass-derived porous carbon materials.
Here, 22-carbon tricarboxylic acid (C22TA) and its ester (C22TAE) were prepared via the Diels–Alder reaction of polyunsaturated fatty acids (PUFAs) and their esters (PUFAEs) as dienes with fumaric ...acid (FA) and dimethyl fumarate (DF) as dienophiles, respectively. The role of an iodine catalyst for the synthesis of C22TA and C22TAE in the Diels–Alder type reaction was investigated using a spectroscopic approach. The chemical structures of the products were characterized using proton nuclear magnetic resonance (1H-NMR) and electrospray ionization mass spectrometry (ESI-MS) analysis. Results showed that nonconjugated dienes can react with dienophiles through a Diels–Alder reaction with an iodine catalyst, and that iodine transformed the nonconjugated double bonds of dienes into conjugated double bonds via a radical process. DF was more favorable for the Diels–Alder reaction than FA. This was mainly because the dienophile DF contained an electron-withdrawing substituent, which reduced the highest and lowest occupied molecular orbital (HOMO–LUMO) energy gap and accelerated the Diels–Alder reaction. By transforming nonconjugated double bonds into conjugated double bonds, iodine as a Lewis acid increased the electron-withdrawing effect of the carbonyl group on the carbon–carbon double bond and reduced the energy difference between the HOMO of diene and the LUMO of dienophile, thus facilitating the Diels–Alder reaction.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Biomass-derived porous carbon materials have drawn considerable attention due to their natural abundance and low cost. In this work, nitrogen-doped porous carbons with high nitrogen content and large ...surface areas were designed and prepared from cottonseed hull and cattail. The two plant-based biomass compositions are similar, but the structures are very different, generating distinctly different property and performance of the prepared carbon materials. NRPC-112 has good electrochemical properties, while CN800 has good adsorption properties. By comparing the microstructure differences between the two starting materials, it was found that the structure of the raw materials would significantly affect the properties and performance of the materials. The work provided an important theoretical basis and reference for the selection of bio-resources for preparing carbon material. It is also important for choosing the appropriate synthesis method, process optimization, and application scenarios.
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