Ag-MnOx/C composites were prepared using AgNO3 and KMnO4 as the precursors and Vulcan XC-72 as the support. The physical properties of the Ag-MnOx/C composites were investigated via X-ray diffraction ...(XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The activity and the stability of the series of Ag-MnOx/C composites toward the oxygen reduction reaction (ORR) in alkaline media were investigated through the electrochemical techniques. The results show that the main species MnO2 and Ag2O in the fresh sample convert into Mn3O4 and Ag(0), respectively, after the heat treatment in N2 at 300°C (Ag-MnOx/C-300). The Ag-MnOx/C-300 sample shows the highest activity toward the ORR, with the half-wave potential of the ORR shifting negatively only 0.035V compared to that on the commercial 40wt. % Pt/C (JM). The electron transfer number during the ORR on the Ag-MnOx/C composite increases with the value close to four after the heat treatment at 300°C, which is mainly attributed to the formation of Ag(0), rather than Mn3O4. The heat treatment brings about a better catalytic stability of the composite, and no obviously negative shift takes place for the half-wave potential of the ORR on the Ag-MnOx/C-300 composite after 1000 cycles accelerated aging test. The maximum power density of the zinc-air battery with the Ag-MnOx/C-300 air electrode reaches up to 130 mW cm−2, higher than those based on the Pd/C and Pt/C cathode catalysts, which shows that the Ag-MnOx/C-300 composite is a promising candidate as the catalyst for the air electrode.
Gas sweetening with an aqueous solution of diethanolamine is a crucial and common process in natural gas processing. However, the process, particularly in the solvent regeneration section, consumes a ...substantial amount of energy, significantly escalating the cost of gas. This paper presents a simulation and optimization of an existing natural gas refinery plant using a lean vapor compression method. The simulation results indicate that the current process requires 2.73 GJ/t
for solvent regeneration, with exergy destruction of 14,120.59 kW in the solvent regeneration section. The total annualized cost for the current process is 11.68 M$. A modified scheme is proposed to address the issue of high energy consumption and the associated costs. The proposed scheme demonstrates significant improvements in the aforementioned parameters. Specifically, energy for solvent regeneration, exergy destruction in the solvent regeneration section, total annualized cost, and cost of gas are reduced by 16.12 %, 25.04 %, 20.97 %, and 20 % compared to the current process, respectively. These improvements enhance the thermoeconomic indexes, making the proposed scheme a viable and cost-effective alternative to the current process.
•A noble-metal-free g-C3N4/α-Ni(OH)2 is fabricated through hydrothermal method.•α-Ni(OH)2 promotes the adsorption and activation of O2 and oxygen atoms.•g-C3N4/α-Ni(OH)2 reveals excellent ...photocatalytic NO removal without NO2 generation.•This find provides a fresh insight for the control of toxic byproduct.
Photocatalytic NOx removal is regarded as a promising technique for air purification in recent years. However, NOx removal process usually accompanies with toxic NO2 generation, leading to serious secondary pollutant and limiting its practical application. Herein, a noble-metal-free g-C3N4/α-Ni(OH)2 photocatalyst was fabricated through hydrothermal method. The introduction of α-Ni(OH)2 microspheres combines with g-C3N4, resulting in an enlarged surface area from 35 to 95 m2/g, while the unique structure of α-Ni(OH)2 broadens visible-light response range and accelerates photogenerated charge carriers transfer. More importantly, the H atoms of α-Ni(OH)2 improve the adsorption and activation of O2 and oxygen atoms to promote NO and NO2 oxidized to nitrate. Consequently, g-C3N4/α-Ni(OH)2 shows enhanced NO removal ratio of 51.3% without any toxic NO2 generation, indicating its great potential for air purification. Our results provide fresh insight into the design of highly efficient and safe photocatalyst for toxic byproduct control in the application of environmental remediation.
Oxygen reduction reaction (ORR) is becoming increasingly important with the development of fuel cells and metal-air batteries. Manganese oxides have been one of the focuses of recent research for ...Pt-alternative ORR catalysts. However, the structure-activity relationships of manganese oxides have not been well studied or understood. In the present work, we report a new finding that there is a strong dependence of the ORR activity of Mn3O4 on its morphology. By adopting different solvents in the wet-chemical synthesis, we are able to tailor the morphology of Mn3O4 from nanoparticles (NP-L, 12.5nm and NP-S, 5.95nm) to nanorods (NR, exposure of Mn3O4 (101)) and nanoflake (NF, exposure of Mn3O4 (001)). Surprisingly, surface-specific activity of NF toward the ORR was found to be one order of magnitude higher than NP-L. The morphology-activity relationships of Mn3O4 were further studied through a combination of electrochemical experiments and density functional theory (DFT) calculations. It was discovered that the formation of *OOH, concomitant with the first electron transfer, is the potential determining step, which is thermo-dynamically more facile on Mn3O4 (001) than (101) plane. The underlying mechanism could be ascribed to the strong interaction between O2 and Mn3O4 (001) surface as indicated by the DFT calculations. The study enlarges our understanding of Mn3O4 catalysis and provides clues for rational design of highly efficient transitional metal oxide electrocatalysts for the ORR.
•The efficient energy-dissipation binder is harnessed on silicon anodes.•A synergized static and dynamic strategy is used to release the stress.•The mechanism is clarified by in-situ IR and finite ...element simulations.•Unprecedented cycling performances are achieved at high areal capacity.
Although silicon has the highest theoretical capacity among the existing anode materials, its practical application is highly hindered by huge interface stress arising from large volume change upon cycling. Herein, an efficient energy-dissipation engineering was harnessed on high-capacity silicon anodes through a synergized “static” (chemically crosslinking) and “dynamic” (physically crosslinking) binder. In this dual network, the disassociation of non-covalent hydrogen bonds greatly facilitates the dispersion and release of unfavorable stress, while the permanent chemical bonding network enables a deformable network to sustain the electrode structure. Such a strategy effectively avoids both materials and electrodes deterioration and promises a better Si-based anode: a high areal capacity of 2 mAh cm−2 with capacity retention of 91.3% after 200 cycles. Meanwhile, the energy-dissipation mechanism was further clarified by temperature-dependent FTIR and finite element simulations.
•Ag nanoparticles were prepared using GO as reductant without any stabilizers.•A composite support with a 3D structure was constructed by GO and carbon black.•The Ag/GO/C composite shows enhanced ORR ...activity compared with Ag/GO.
A 3D graphene oxide/carbon sphere supported silver composite (Ag/GO/C) was synthesized using graphene oxide as the reducing agent. The reducing process of Ag+ was monitored by the ultra violet-visible (UV-vis) absorption spectrometer and the physical properties of the Ag/GO/C composite were characterized by Fourier transform infrared spectrometer (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the dispersive Ag nanoparticles are anchored uniformly on the surface of GO sheets with a mean size of about 6.9nm. With introducing carbon black, the Ag nanoparticles aggregated slightly. Compared with its counterpart Ag/GO, the Ag/GO/C composite showed a significantly enhanced activity towards the oxygen reduction reaction in alkaline media. The enhancement can be ascribed to the 3D composite support, which not only improves the electrical conductivity, but also enforces the mass transport in the catalyst layer facilitating the reactants access to the active sites. Moreover, the Ag/GO/C composite exhibits good tolerance to alcohols, carbonates and tetramethylammonium hydroxide. This work is expected to open a new pathway to use GO as a reducing agent to synthesize electrocatalysts without surfactants.
Stereocomplex (SC) crystallization can prominently improve the physico-chemical properties of poly(l-lactide)/poly(d-lactide) (PLLA/PDLA) blends, yielding a novel polylactide (PLA) material. However, ...the predominant formation of SC crystals in the melt-processing of high-molar-mass (high-MW, >100 kg/mol) enantiomeric PLA blends remains a huge challenge due to the competition between SC crystallization and homocrystallization. Herein, double-grafted copolymer having both PLLA and PDLA side chain has been designed and synthesized as an efficient crystallization promoter for the harvest of SC crystals in the high-MW PLLA/PDLA blends. The results show that, with the addition of such a copolymer, the blends can preferentially crystallize into SC crystals in both isothermal and non-isothermal conditions. Promisingly, the SC crystals can be exclusively formed by adding only small amounts (e.g., 0.5 wt%) of the copolymer, without the formation of any homocrystals. This interesting observation can be interpreted by the crucial role of the unique copolymer in suppressing the phase separation of the opposite PLA enantiomers upon melting as an efficient compatibilizer and then encouraging the generation of alternatingly arranged PLLA/PDLA chain clusters favored for SC nucleation and crystal growth. These findings provide new inspiration for the development of high-performance PLA with desirable SC crystallizability.
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A set of novel (AlTiCrVTa)Nx coatings are synthesized by DC magnetron sputtering to methodically investigate the effect of nitrogen content on the microstructure, mechanical and tribological ...properties and oxidation behavior of the coatings for the first time. As the nitrogen content increases, the coating structure transitions from amorphous to a simple fcc structure, accompanied by a change of preferred orientation from (200) to (111) and an enhancement in crystallinity. The coating morphology changes from featureless glassy to columnar crystals. The highest nanohardness of 38.1 GPa and the best wear rate of 4.9 × 10−7 mm3/Nm are achieved at 43.3 at.% nitrogen content. The friction coefficient exhibits a downward trend with rising nitrogen content, reaching the lowest value of 0.47 at 49.8 at.% nitrogen content. The oxidation tests reveal that the oxidation resistance deteriorates with increasing nitrogen content, caused by the looser structure and large-sized grain boundaries.
Carbon supported gold-iridium composite (AuIr/C) was synthesized by a facile one-step process and was investigated as the bifunctional catalyst for oxygen reduction reaction (ORR) and oxygen ...evolution reaction (OER). The physical properties of the AuIr/C composite were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Although the Au and Ir in the AuIr/C did not form alloy, it is clear that the introduction of Ir decreases the average Au particle size to 4.2nm compared to that in the Au/C (10.1nm). By systematical analysis on chemical state of metal surface via XPS and the electrochemical results, it was found that the Au surface for the Au/C can be activated by potential cycling from 0.12V to 1.72V, resulting in the increased surface roughness of Au, thus improving the ORR activity. By the same potential cycling, the Ir surface of the Ir/C was irreversibly oxidized, leading to degraded ORR activity but uninfluenced OER activity. For the AuIr/C, Ir protects Au against being oxidized due to the lower electronegativity of Ir. Combining the advantages of Au and Ir in catalyzing ORR and OER, the AuIr/C catalyst displays an enhanced catalytic activity to the ORR and a comparable OER activity. In the 50-cycle accelerated aging test for the ORR and OER, the AuIr/C displayed a satisfied stability, suggesting that the AuIr/C catalyst is a potential bifunctional catalyst for the oxygen electrode.
An AuIr/C composite shows enhanced oxygen reduction reaction and oxygen evolution reaction catalytic activity and stability compared with Au/C, Ir/C and their physical mixture (Au/C+Ir/C). Display omitted
Accurate identification and feature extraction of stratum images play a crucial role in geological exploration, resource prospecting, and mining operations. Traditional methods of stratum image ...identification largely rely on human experience and manual operations, which are inefficient and prone to errors. In recent years, deep learning technology has provided new methods for the identification and feature extraction of stratum images, but existing deep learning models still face challenges in computational efficiency, multi-scale feature extraction, and uneven sample distribution. This paper proposes a stratum image feature extraction network based on the pyramid model and constructs a lightweight stratum identification model for real-time recognition. By introducing a classification-regression network structure and anchor-based sample supervision rules, this study aims to improve the accuracy and efficiency of the model, providing an effective solution for real-time recognition of stratum images.
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