Oxidation State Modulation of Bismuth for Efficient Electrocatalytic Nitrogen Reduction to Ammonia

Electrocatalytic nitrogen reduction reaction (NRR) is a promising strategy for ammonia (NH₃) production under ambient conditions. However, it is severely impeded by the challenging activation of the NN bond and the competing hydrogen evolution reaction (HER), which makes it crucial to design electrocatalysts rationally for efficient NRR. Herein, the rational design of bismuth (Bi) nanoparticles with different oxidation states embedded in carbon nanosheets (Bi@C) as efficient NRR electrocatalysts is reported. The NRR performance of Bi@C improves with the increase of Bi⁰/Bi³⁺ atomic ratios, indicating that the oxidation state of Bi plays a significant role in electrochemical ammonia synthesis. As a result, the Bi@C nanosheets annealed at 900  ° C with the optimal oxidation state of Bi demonstrate the best NRR performance with a high NH₃ yield rate and remarkable Faradaic efficiency of 15.10  ± 0.43% at − 0.4 V versus RHE. Density functional theory calculations reveal that the effective modulation of the oxidation state of Bi can tune the p-filling of active Bi sites and strengthen adsorption of *NNH, which boost the potential-determining step and facilitate the electrocatalytic NRR under ambient conditions. This work may offer valuable insights into the rational material design by modulating oxidation states for efficient electrocatalysis.     

Hydrothermal synthesis of α-SnWO4: Application to lithium-ion battery and photocatalytic activity

The high capacity anode material is required to replace the most commonly used anode - graphite to keep up the global demand to achieve the goal. Multi-metal oxide has gained keen attention for its higher theoretical capacity and relatively stable than a single metal oxide. α-SnWO₄ has a theoretical capacity of 850 mAh g^?1 which is greater than graphite (372 mAh g^?1). α-SnWO₄ has been synthesized through low-temperature hydrothermal method using tin chloride and sodium tungstate as a precursor in acidic medium (succinic acid) at 200 °C for 12 h. The obtained product has been characterized using various analytical tools such as XRD, FT-IR, UV-DRS, BET, PL, SEM, and HR-TEM. XRD analysis shows the orthorhombic phase with a crystallite size of ~25 nm α-SnWO₄has been examined as an electrode material for Li-ion battery (LIB) and displays an initial discharge capacity of 985 mAh g^?1. Columbic efficiency close to 100% has been observed for 100 cycles. The stability of the electrode material was studied at different C-rates. Band-gap calculated using UV-DRS (Eg = 1.9 eV) shows that α-SnWO₄ is a good candidate for photocatalytic degradation. Results of the photocatalytic experiment using methylene blue (MB) as a model pollutant in an aqueous medium shows good results. The above applications show that α-SnWO₄ is multifunctional materials for diverse applications.     

Microscopic Methods for Identification of Sulfate-Reducing Bacteria from Various Habitats

This paper is devoted to microscopic methods for the identification of sulfate-reducing bacteria (SRB). In this context, it describes various habitats, morphology and techniques used for the detection and identification of this very heterogeneous group of anaerobic microorganisms. SRB are present in almost every habitat on Earth, including freshwater and marine water, soils, sediments or animals. In the oil, water and gas industries, they can cause considerable economic losses due to their hydrogen sulfide production; in periodontal lesions and the colon of humans, they can cause health complications. Although the role of these bacteria in inflammatory bowel diseases is not entirely known yet, their presence is increased in patients and produced hydrogen sulfide has a cytotoxic effect. For these reasons, methods for the detection of these microorganisms were described. Apart from selected molecular techniques, including metagenomics, fluorescence microscopy was one of the applied methods. Especially fluorescence in situ hybridization (FISH) in various modifications was described. This method enables visual identification of SRB, determining their abundance and spatial distribution in environmental biofilms and gut samples.     

Efficient sunlight and UV photocatalytic degradation of Methyl Orange,Methylene Blue and Rhodamine B,using Citrus×paradisi synthesized SnO2 semiconductor nanoparticles

In this work, tin dioxide (SnO2) Nanoparticles (NPs) were synthesized through green synthesis, using Citrus × paradisi extract as a stabilizing (capping). The extract concentrations used were 1, 2 and 4% in relation to the aqueous solution. The resulting SnO2 NPs were used for the degradation of Methyl Orange (MO), Methylene Blue (MB) and Rhodamine B (RhB), under both solar and UV radiation. The NPs were characterized via Attenuated Total Reflectance Infrared Spectroscopy (ATR-IR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM-SAED), the Brunauer-Emmett-Teller (BET) theory, Ultraviolet to Visible spectroscopy (UV–Vis), and Photoluminescence spectroscopy (PL); while the photocatalytic degradation was evaluated using UV-VIS. The results showed that the Citrus × paradisi extract is a good medium for the formation of SnO2 NPs. These NPs presented quasi-spherical morphology, particle sizes of 4–8 nm, with a rutile phase crystalline structure, and with banned gap of 2.69 at 3.28 eV. The NPs had excellent photocatalytic properties under solar radiation, degrading 100% of the OM in 180 min. Furthermore, under UV radiation, 100% degradation of the three dyes was achieved in a short time; 20 min for MO, and 60 min for MB and RhB. Therefore, green synthesis is a feasible medium for the formation of SnO2 NPs with good photocatalytic properties.     

Enhancement effect of zero-valent iron nanoparticle and iron oxide nanoparticles on dark fermentative hydrogen production from molasses-based distillery wastewater

This study investigates the effect of two different iron compounds (zero-valent iron nanoparticle: nZVI and iron oxide nanoparticles: nIO) and pH on fermentative biohydrogen production from molasses-based distillery wastewater. The nZVI and nIO of optimum particle sizes of 50 nm and 55 nm respectively were synthesized and applied for fermentative hydrogen (H₂) production. The addition of nIO & nZVI at (0.7 g/L, pH: 6) resulted in the highest H₂ yield, H₂ production rate, H₂ content and COD reduction. Moreover, the kinetic parameters of H₂ production potential (P) and H₂ production rate (R_m) increased to 387 mL, and 22.2 mL/h, respectively for nZVI, these values were 363 mL and 21.8 mL/h for nIO. The results obtained indicated the positive effect of nZVI and nIO addition on enhanced fermentative H₂ production. The addition of nZVI & nIO resulted in 71% and 69.4% enhancement in biohydrogen production respectively.     

Type-II AsP/Sc2CO2 van der Waals heterostructure: an excellent photocatalyst for overall water splitting

In this work, we explore the application potential of AsP/M₂CO₂ (M = Sc, Zr) van der Waals heterostructures in photocatalytic water splitting through the first-principles calculations. The calculated results show that AsP/Zr₂CO₂ heterostructure possesses an unfavorable type-Ⅰ band alignment, whereas AsP/Sc₂CO₂ exhibits a desirable type-Ⅱ band alignment, which is beneficial for separating the photogenerated electron-hole pairs. Also, the band edge positions of AsP/Sc₂CO₂ heterostructure stride the redox potential of water, ensuring favorable reaction kinetics. Besides, the strong optical absorption of AsP/Sc₂CO₂ heterostructure in both visible and ultraviolet regions (especially up to 10⁻⁶ cm⁻¹ at about 250 nm) makes it possible to utilize solar energy effectively. Meanwhile, AsP/Sc₂CO₂ heterostructure has an exciton binding energy as low as 0.09 eV, which quantitatively illustrates the high separation efficiency of photogenerated charge carrier. Thus, the type-Ⅱ band alignment, suitable band edge position, strong light absorption, and low exciton binding energy together indicate that AsP/Sc₂CO₂ heterostructure is a potential photocatalytic material. In addition, the obvious redshift phenomenon in the optical spectrum of AsP/Sc₂CO₂ heterostructure shows that biaxial strain can improve its light capture capability. Also, the interconversion between type-Ⅱ and type-Ⅰ can be achieved by applying different strains. All these findings suggest that the novel AsP/Sc₂CO₂ heterostructure has significant application prospects in next-generation photovoltaic and photocatalytic devices.     

The p-n heterojunction constructed by NiMnO3 nanoparticles and Ni3S4 to promote charge separation and efficient catalytic hydrogen evolution

Using sunlight to catalyze water to produce H₂ is a key technology to solve the problem of energy shortage. In this research, perovskite-type NiMnO₃ and Ni₃S₄ was recombined through secondary hydrothermal treatment. The optimal hydrogen evolution for composite materials NiMnO₃/Ni₃S₄is 3.76 μmol mg^?1 h^?1, that 3.7 and 4 times more than that of two monomer materials, respectively. After four cycles of catalytic experiments, proving the high efficiency and stability of the composite catalyst. The characteristics of fluorescence spectroscopy and electrochemistry have confirmed the existence of p-n heterostructures, the excellent catalytic performance is related to the built-in electric field (accelerating the separation and utilization of photocharges) generated by the combination of NiMnO₃ and Ni₃S₄. Strengthening the performance of the catalyst by constructing a heterostructure is an effective modification strategy and has positive application value in the fields of sensors and optoelectronics.     

Composition-tunable PtCu porous nanowires as highly active and durable catalyst for oxygen reduction reaction

To accelerate the commercialization of fuel cells, many efforts have been made to develope highly active and durable Pt-based catalyst for oxygen reduction reaction (ORR). Herein, PtCu porous nanowires (PNWs) with controllable composition are synthesized through an ultrasound-assisted galvanic replacement reaction. The porous structure, surface strain, and electronic property of PtCu PNWs are optimized by tuning composition, which can improve activity for ORR. Electrochemical tests reveal that the mass activity of Pt_0.5Cu_0.5 PNWs (Pt/Cu atomic ratio of 1:1) reaches 0.80 A mg_Pt^?1, which is about 5 times higher than that of the commercial Pt/C catalyst. Notably, the improved activity of the porous nanowire catalyst is also confirmed in the single-cell test. In addition, the large contact area with the carrier and internal interconnection structure of Pt_0.5Cu_0.5 PNWs enables them to exhibit much better durability than the commercial Pt/C catalyst and Pt_0.5Cu_0.5 nanotubes in accelerated durability test.     

A machine learning‐based operational control framework for reducing energy consumption of an amine‐based gas sweetening process

This study proposes a data‐driven operational control framework using machine learning‐based predictive modeling with the aim of decreasing the energy consumption of a natural gas sweetening process. This multi‐stage framework is composed of the following steps: (a) a clustering algorithm based on Density‐Based Spatial Clustering of Applications with Noise methodology is implemented to characterize the sampling space of all possible states of the operation and to determine the operational modes of the gas sweetening unit, (b) the lowest steam consumption of each operational mode is selected as a reference for operational control of the gas sweetening process, and (c) a number of high‐accuracy regression models are developed using the Gradient Boosting Machines algorithm for predicting the controlled parameters and output variables. This framework presents an operational control strategy that provides actionable insights about the energy performance of the current operations of the unit and also suggests the potential of energy saving for gas treating plant operators. The ultimate goal is to leverage this data‐driven strategy in order to identify the achievable energy conservation opportunity in such plants. The dataset for this research study consists of 29 817 records that were sampled over the course of 3 years from a gas train in the South Pars Gas Complex. Furthermore, our offline analysis demonstrates that there is a potential of 8% energy saving, equivalent to 5 760 000 Nm³ of natural gas consumption reduction, which can be achieved by mapping the steam consumption states of the unit to the best energy performances predicted by the proposed framework.