Hydrogen Reduction Research Articles

A wireless sensor network IoT platform for consumption and quality monitoring of drinking water

Generally, municipal water supply companies use manual collection and laboratory analysis for water quality testing. However, these methods have limitations such as lack of real-time information, inability to sample the entire water supply, and high costs. Therefore, continuous, real-time water quality monitoring is crucial for public health protection and ensuring that the whole water supply network is monitored. This paper proposes an Internet of Things (IoT) platform for the measurement of consumption and the quality of drinking water in rural or semi-rural environments. Data collected through temperature, flow, potential of hydrogen (pH), turbidity, and Oxidation Reduction Potential (ORP) sensors is exchanged with a database through a long-range wireless communication protocol. Two mobile applications and one desktop application were also developed, with the purpose of being used by simple users, technicians, and network administrators respectively. The presented implementation process includes the design of the hardware surrounding the ESP32 microcontroller and its mounted peripherals, as well as the software run by the microcontroller and the mobile devices. A prototype system was built and tested under controlled conditions, successfully recognizing an increase in water turbidity and its unsuitability when contaminated with different agents. This method may prove to be a financially advantageous solution for rural, semi-rural, and even urban environments when used with groups of data collection nodes, helping significantly in the upkeep and surveillance of the water supply network.

Iron enrichment and alumina recovery from bauxite residue through hydrogen reduction followed by alkaline leaching and CaO circulation

ABSTRACT The alumina industry faces a significant challenge in effectively utilising bauxite residue due to its hazardous nature. A potential solution involves recovering iron and alumina from the bauxite residue, leading to a substantial reduction in residue volume and also drawing some material value. This study involved the production of self-hardened calcite pellets from the bauxite residue, which were then subjected to hydrogen reduction and subsequently leached with a sodium carbonate solution for alumina extraction. In an effort to establish a circular material flow, the leaching residue, which contains most of calcium and metallic iron, was reintegrated into the process to produce self-hardened pellets. Analytical techniques such as X-ray diffraction, electron probe microanalysis, X-ray fluorescence, and inductively coupled plasma-mass spectroscopy were employed for comprehensive microstructural, chemical, and elemental evaluations of the samples. The integrated process yielded a final alumina recovery rate exceeding 62%, a substantial improvement compared to the process lacking calcium looping. The incorporation of leaching residue recycling played a crucial role in significantly reducing calcium consumption throughout the integrated process, reaching approximately 70%. This research signifies a promising approach to efficiently recover valuable components from bauxite residue while mitigating environmental concerns and optimising resource utilisation.

Evolutionary trends and photothermal catalytic reduction performance of carbon dioxide by MOF-derived MnOx

Metal oxide catalysts derived from MOFs can inherit the excellent performance from their parent MOFs, possess abundant surface defects and high stability, and have attracted widespread interest in multiphase catalysis. In this study, we used Mn-MOF as a precursor and systematically investigated the evolution of MnOx catalysts by setting different calcination temperatures and times. XRD, SEM, TEM, Fourier transform infrared spectroscopy (FTIR), N2 adsorption–desorption analysis, XPS, H2-TPR, CO2-TPD, electrochemical characterization, and other methods were used to investigate the structural characteristics, microstructure, surface properties, and photoelectric properties of the catalysts. The catalytic performance of the catalysts was also investigated through photocatalytic carbon dioxide hydrogenation reduction tests. Research has shown that calcination temperature and time have a significant impact on the phase structure and surface properties of MnOx, and the physicochemical properties of derived MnOx can be controlled by controlling calcination temperature and time. Among them, MnOx-500 has a wider light absorption range, better electron transfer performance, richer oxygen vacancies, and excellent separation performance of photo generated charge carriers, resulting in higher photocatalytic CO2 hydrogenation and reduction performance. Its CO yield and selectivity reached 7420 μmol/g/h and above 99 %, respectively. This study provides valuable references for the preparation, optimization, and utilization in CO2 photothermal catalytic conversion of MnOx catalysts derived from MOFs.

Dichloromethane -methanol fraction of Mahonia nepalensis containing Berberine, Jatrorrhizine, and tetrahydroberberine as corrosion inhibitor for mild steel

A potentially superior alternative source of environmentally acceptable corrosion inhibitors for metallic materials is plant extracts. This study reports on the use of compounds separated from Mahonia nepalensis (MN) bark extract as an environmentally friendly corrosion inhibitor for mild steel (MS) in 1 M H2SO4. The organic layer was separated from MN bark extracts and then Berberine, Jatrorrhizine, and Tetrahydroberberine were identified and quantified by Liquid column mass spectroscopy (LC-MS) in dichloromethane (DCM) −Methanol fraction of Mahonia nepalensis. The DCM − Methanol fraction of extract was characterized by Ultra violet − visible spectroscopy (UV–Vis) and Fourier Transform Infrared (FTIR). The DCM-Methanol fractions in 1 M H2SO4 were applied to study corrosion inhibition of MS by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed above 91 % inhibition efficiency (IE) for DCM-Methanol fraction containing 2.12 ppm berberine, jatrorrhizine, and tetrahydroberberine at room temperature indicating that it is an effective and cheap candidate for the corrosion prevention of MS in industry. The potentiodynamic polarization demonstrated a reduction in current density without affecting the reaction mechanism but reduced the hydrogen reduction indicated by suppression in cathodic current. Based on polarization curves and open circuit potential, it exhibited mixed inhibitory behavior. Similarly, EIS analysis revealed a drop in double-layer capacitance accompanied by an increase in charge transfer resistance. EIS and a scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX) ascertain the adsorption of inhibitor molecules forming a protective layer on the MS surface.

Microstructure and magnetic properties of Fe-Al2O3 nanocomposites prepared by a versatile facile combustion-based route

Fe-Al2O3 nanocomposites with Al2O3 nanoparticles uniformly dispersed have been successfully prepared via a versatile facile and scalable combustion-based route with two steps. Firstly, the homogenous mixed oxide precursor composed with α-Fe2O3, γ-Fe2O3 and Al2O3 was prepared by solution combustion synthesis. Subsequently, Fe-Al2O3 nanocomposites with Al2O3 nanoparticles evenly dispersed were prepared by hydrogen reduction of the mixed oxide precursor. The effects of the various reduction temperatures on the phase composition, morphology, grain size and magnetic properties of the Fe-Al2O3 nanocomposites were investigated in details. The results show that the Fe-Al2O3 nanocomposites prepared at as low as 400 °C present a connected network structure with an average grain size of about 17 nm, which have a saturation magnetization of 125.3 emu/g, and a coercivity of 721.2 Oe. With the increase of reduction temperature, the average grain size, and saturation magnetization of the Fe-Al2O3 nanocomposites increase gradually, while the coercivity decrease. When the reduction temperature is increased to 500 °C and 600 °C, the grain size increases to about 27 nm and 37 nm, the saturation magnetization increases to 153.6 emu/g and 177.1 emu/g, and the coercivity decreases to 634.6 Oe and 467.8 Oe, respectively.

Polycrystalline magneto-optical transparent Pr2Zr2O7 pyrochlore ceramic for Faraday rotation.

To design an innovative magneto-optical material aimed at a large Verdet constant coincides with the development trend of state-of-the-art modern optical devices. In this work, a magneto-optical transparent Pr2Zr2O7 ceramic with pyrochlore structure was successfully fabricated by vacuum sintering plus hydrogen reduction for the first time to our knowledge. The two- and three-dimensional images observed on the laser scanning confocal microscopy reveal that the grain-boundary dent depth of the polished Pr2Zr2O7 ceramic is only ∼1.6 µm upon thermal etching at a high temperature of 1675°C for 2 h, showing excellent heat-resistance ability. The crystal-clear Pr2Zr2O7 ceramic has a high in-line transmittance of ∼71.6% at 780 nm (∼92.3% of the theoretical value), a high refractive index of ∼2.1, and an effective magnetic moment of ∼5.28 µ B. In the visible region, the O2- polarizability and optical basicity of the Pr2Zr2O7 compound generally retain constants around 2.37 ± 0.07 Å3 and 0.965 ± 0.015, respectively. The magneto-optical transparent Pr2Zr2O7 ceramic exhibits high Verdet constants of -336 ± 4, -208 ± 3, -108 ± 1, and -48 ± 2 rad·T-1·m-1 at 515, 635, 780, and 1064 nm, respectively, which were ∼1.55-fold higher than the commercial Tb3Ga5O12 single crystal. Our developed new-type ceramic material has excellent potential application for Faraday rotation.

High-throughput screening of a transition metal single-atom electrocatalyst for the CH3NO2 reduction reaction

The hydrogenation reduction of nitro compounds involves the wide application of functional amines as important chemical intermediates in the fine chemical industry. However, the development of low-cost, mild reaction conditions and high-performance catalysts for the reduction of nitro compounds is challenging. In this study, the potential of electrocatalysts in which 26 transition metal atoms are anchored to the surface of N-doped graphene (TMN4@G) was explored to determine the mechanism of the electrocatalytic CH3NO2 reduction reaction (CNORR) via density functional theory. First, the stability of TMN4@G was evaluated to screen out the catalyst which is stable at 300 K via ab initio molecular dynamics. Second, the Gibbs free energy with all possible reaction pathways of the CNORR was calculated to search for high-performance catalysts. These results demonstrate that monodentate adsorbed CdN4@G, FeN4@G, CoN4@G and bidentate adsorbed MoN4@G exhibit excellent catalytic activity. The overpotential of MoN4@G is only 0.357 V. Finally, Finally, the role of central metal atom on the catalytic activity of single-atom catalysts in CNORR and the impact of hydrogen evolution reaction on the adsorption of CH3NO2 were further discussed. We hope that this theoretical simulation provides an effective scheme for the reduction of nitro compounds under mild conditions.

Hierarchical macro/mesoporous γ-Al2O3 as column matrix for development of low specific activity 99Mo/99mTc generator via 100Mo (γ, n)99Mo reaction

Abstract 99mTc, the daughter product of 99Mo, is a γ-emitting radionuclide with essential diagnostic applications in nuclear medicine. In this paper, an accelerator-based method (100Mo (γ, n)99Mo) for production of 99Mo and 99mTc has been explored. Approximately 68.3 MBq of 99Mo was successfully produced by the irradiation of 100Mo metallic target for 40 h using electron beam with energy of 50 MeV and current of 0.2 μA at electron linear accelerator (Institute of Modern Physics, Chinese Academy of Sciences, IMPCAS). Different types of 99Mo/99mTc generators were prepared using hierarchical macro/mesoporous γ-Al2O3 (HMMA) as column adsorbent, and their performances were evaluated for over one week. 99Mo/99mTc generator with a column (3 mL, 4.2 × 0.95 cm) packed with 0.6 g HMMA exhibited excellent eluting performance. 99mTc could be collected within 4.0 mL of saline solution with high purity, and the elution efficiency could reach >85 %. Furthermore, 99Mo breakthrough in the eluates was negligible (<2 × 10−3 %) and concentration of impurity (<10 ppm) was acceptable. Finally, the enriched 100Mo was eluted from the spent 99Mo/99mTc generator using 1.0 mol/L ammonium hydroxide, and then reduced by high-temperature hydrogen reduction process with a total recovery of 95.3 %. This work demonstrated that the preparation of 99Mo via 100Mo (γ, n)99Mo reaction and isolating 99mTc using HMMA column chromatography have a potential in application.

Plasma‐Catalytic CO2 Methanation Over Supported Ni–Co Catalysts Prepared by Solution Combustion Synthesis

ABSTRACTIncorporating suitable promoters into nickel‐based catalysts for carbon dioxide methanation proves to be a successful strategy for enhancing catalyst structure, optimizing surface properties, mitigating deactivation, and ultimately boosting catalytic performance. This study focuses on the synthesis of Co‐modified Ni/CaCO3 catalysts using the solution combustion synthesis method. The catalytic activity of the afforded catalysts has been evaluated for CO2 methanation in a dielectric barrier discharge reactor operating at a gaseous hourly space velocity of 11,320 h−1 and an H2:CO2 ratio of 4:1. The catalyst exhibits optimal performance at a Ni:Co ratio of 13:2, achieving a CO2 conversion rate of 57.5% and CH4 selectivity of 92.4%. Characterization techniques such as X‐ray diffraction, transmission electron microscopy, X‐ray photoelectron spectroscopy, programmed temperature‐raising hydrogen reduction, carbon dioxide desorption, and in situ plasma DRIFTS are employed to evaluate the catalysts. The results indicate that the addition of Co to Ni‐based catalysts leads to an increase in moderately basic sites, thereby enhancing the catalytic activity and stability of catalysts for CO2 methanation. Notably, the combination of the plasma and the Ni–Co catalyst offers a novel pathway for CO2 methanation, featuring higher energy efficiency and superior synergistic effects compared to monometallic catalysts.

Preparation and Catalytic Properties of Gold Single-Atom and Cluster Catalysts Utilizing Nanoparticulate Mg-Al Layered Double Hydroxides.

Au single atoms and clusters were stabilized on Mg-Al layered double hydroxide nanoparticles (LDH NPs), and the obtained Au@LDH NPs were supported on SiO2 and CeO2. After hydrogen reduction, Au single atoms were found together with Au clusters on LDH/SiO2. In contrast to Au single-atom catalysts which are deposited in metal vacancies of oxide supports, the LDH NPs stabilize very small Au species despite the absence of metal vacancies. The obtained Au(0)@LDH/SiO2 catalyzed aerobic oxidation of alcohols, and Au single atoms maintained after the reaction. Given that only Au NPs were observed on bulk LDH, the abundant surface OH group of LDH NPs would contribute to stabilize Au, resulting in higher activity than Au/LDH-bulk. After calcination to transform LDH to mixed metal oxide (MMO), the obtained Au(0)@MMO/SiO2 also exhibited high catalytic activity. Moreover, Au(0)@LDH/CeO2 exhibited higher activity and excellent selectivity for hydrogenation of 4-nitrostyrene to 4-aminostyrene than conventional Au catalysts such as Au/CeO2 and Au/TiO2. We demonstrated that Au size can be minimized using LDH NPs, exhibiting high catalytic performance. The basic surface OH groups of LDH would be also beneficial for deprotonation of alcohols and heterolytic dissociation of H2 in the catalytic reactions.

Chiral Pd(II) Nanofiber Promoting Electron Transfer of g-C3N4 for Efficient Photocatalytic Hydrogen Production.

The rapid transfer and separation of photogenerated electrons is very important for the improvement of photocatalytic efficiency. Here, chiral induced spin selectivity effect (CISS effect) was developed to accelerate electron transfer for efficient photocatalytic hydrogen production. A chiral and achiral racemic supramolecular Pd(II) complex nanofiber was fabricated via supramolecular self-assembly of chiral L-Py or its racemes with Pd(II) and used to modify carbon nitride (g-C3N4). The obtained chiral photocatalyst L-Py-Pd/g-C3N4-4 and achiral photocatalyst Rac-Pd/g-C3N4-4, show enhanced photocatalytic activities with hydrogen evolution rates of 2476 and 1339 μmol g-1 h-1, respectively, while that of pure g-C3N4 is 30.5 μmol g-1 h-1. Chiral photocatalyst has 85 % higher activity than achiral one and is 82.5-fold of pure g-C3N4, due to better suppression of the recombination of photogenerated electron-hole pairs in the interface of g-C3N4 contact with chiral molecule. Spectral tests and photoelectrochemical tests proved that the chiral supramolecular Pd(II) complex can act both as an electron spin filter and hydrogen reduction catalytic center to enhance photocatalytic efficiency. This work offers a new route to facilitate electron transfer by the CISS effect for photocatalytic hydrogen evolution.

Atomic‐Level Structural Responses of Chang'e‐5 Ilmenite to Space Weathering

AbstractSpace weathering records provide insights to better understand the formation and evolution of the lunar regolith. Ilmenite has contrasting responses to different space weathering processes. However, the atomic‐scale structural modification of ilmenite induced using different space weathering processes remains poorly understood. Here, we investigate the effects of spacing weathering on lunar ilmenite grains returned from Chang'e‐5 (CE‐5) mission using a combination of transmission electron microscopy and thermodynamic modeling approaches. Experimental results show that melt shock induces the formation of twining structures and vein‐like Si‐Ca‐rich nanostructures in the outermost and sub‐outermost layers of ilmenite, respectively. In contrast, solar wind causes the formation of multilayered nanostructures surrounding the ilmenite grains. These structures are characterized by an outermost amorphous Si‐rich vapor deposited layer, a middle layer rich in titanium (Ti) oxides and zero‐valent iron (Fe0) nanoparticles, and an innermost layer hosting crystallographic orientation defect. The Ti oxides were identified as poorly crystallized anatase. Thermodynamic calculations indicate that the disruptive sputtering of solar wind and the reduction of hydrogen under lunar surface pressure conditions can promote ilmenite transformation into Fe0 and Ti oxides; nevertheless, the pressure increase associated with melt shock can lead to a rise in the decomposition temperature of ilmenite. In other words, solar wind irradiation plays a more significant role in promoting nanoparticle (such as anatase and Fe0) formation as compared to melt shock. Thus, unlike the chemical alteration of ilmenite induced by the solar wind irradiation, melt shock mainly causes physical changes in ilmenite grains.

Mechanisms of Thermal Decomposition in Spent NCM Lithium-Ion Battery Cathode Materials with Carbon Defects and Oxygen Vacancies.

Resource recovery from retired electric vehicle lithium-ion batteries (LIBs) is a key to sustainable supply of technology-critical metals. However, the mainstream pyrometallurgical recycling approach requires high temperature and high energy consumption. Our study proposes a novel mechanochemical processing combined with hydrogen (H2) reduction strategy to accelerate the breakdown of ternary nickel cobalt manganese oxide (NCM) cathode materials at a significantly lower temperature (450 °C). Particle refinement, material amorphization, and internal energy storage are considered critical success factors for the accelerated decomposition of NCM cathode materials. In our proposed approach, NCM cathode materials can develop active sites with carbon defects (Cv) and oxygen vacancies (Ov), which improve the reduction and breakdown of H2. The adsorbed H2 on the surface of NCM decomposes into H* and combines with oxygen to form OH species, which can be facilitated by Ov via the enhanced charge transfer. The introduced Cv can enhance H2 cracking and generate *C-H species to promote the thermal decomposition of NCM. The presence of defects proves to foster the preferential reduction of Mn(IV) by H2, leading to a lower activation energy for the NCM decomposition (from 139 to 110 kJ/mol) with less H2 consumption. Life cycle assessment suggests a reduction of 4.42 kg CO2 eq for the recycling of every 1.0 kg of retired batteries. This study can promote material circularity and minimize the environmental burden of mining technology-critical metals for a low-carbon transition.

Enhanced catalytic performance of ethyl-levulinate to γ-valerolactone: Effect of copper loading on Ni/KIT-5 catalyst

A facile wet impregnation method was employed to prepare a bimetallic Ni–Cu catalyst on a mesoporous KIT-5 support, keeping the nickel loading constant (5 wt%) while varying the copper wt.% (xCu, where x = 8, 10, 12, 14). Several physico-chemical techniques, including X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), temperature-programmed desorption of ammonia (NH3-TPD), temperature-programmed reduction of hydrogen (H2-TPR), and X-ray photoelectron spectroscopy (XPS), were utilized for catalyst characterization. An environmentally friendly NiCu bimetallic-supported catalyst system was developed in response to many problems, including metal leaching, sintering, and cost. A mesoporous KIT-5 silica support with a large surface area was used. The hydrogenation of ethyl levulinate to gamma-valerolactone was studied utilizing a high-pressure stirred reactor and a range of reaction temperatures (120–160 °C), hydrogen pressures (10–30 bar), and reaction periods. Various catalysts were used in the investigation. Among all tested catalysts, the 12Cu–5Ni/KIT-5 one shows excellent activity. The best GVL yield is 84% at a conversion of 100% after 8 h of treatment at 150 °C and 25 bar H2 pressure; the promotion is also 76.1%. Optimization of reaction conditions was shown to correlate the physicochemical parameters of the catalyst with its activity.

Low-vanadium and high-activity SCR catalyst for low-temperature denitrification: Influence of vanadium precursor and surface vanadium concentration

Nitrogen oxides (NOx), as the main pollutants of air pollution, cause serious harm to the ecological environment and human health. SCR technology is widely used as the most effective method for treating NOx. The core of SCR technology is SCR catalyst. The reaction temperature of traditional commercial catalysts is difficult to reach the optimal operating temperature range, so expanding the temperature window of V2O5/TiO2 catalysts to the low-temperature region while reducing vanadium loading is a key issue to be solved. A series of V2O5/TiO2 catalysts with different vanadium precursors and different vanadium loadings were prepared by solid-phase synthesis method. The physicochemical properties of the catalyst were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, temperature programmed desorption of ammonia and temperature programmed reduction of hydrogen. The denitrification activity of the catalyst was evaluated in a fixed bed reactor. The catalysts prepared with vanadyl oxalate (VOC2O4·xH2O) and vanadyl acetylacetonate (VO(acac)2) as vanadium precursors with a vanadium loading of 5% exhibited the highest denitrification activity, with a stable NOx conversion of 100% within the temperature range of 200–350 °. Compared with the catalysts prepared with ammonium metavanadate (NH4VO3) and vanadyl sulfate (VOSO4·xH2O) as the vanadium precursors, the maximum activity temperature of VOC2O4-V5Ti and VO(acac)2-V5Ti shifted towards the low-temperature region by about 150 °. Furthermore, the denitrification activity of catalyst with a low vanadium content (1%) prepared using VO(acac)2 precursor was even higher than that of catalyst with a high vanadium content (6%) prepared using NH4VO3 precursor. Using VOC2O4 and VO(acac)2 as vanadium precursors could effectively regulate the active sites and polymeric states on the catalysts, and promote the interaction of V atoms with different valence states to form more reductive V species (V4+), thus exhibiting excellent SCR reactivity. This study provided an effective method for the preparation of low-vanadium and high-activity denitrification catalysts at low temperatures.

Modulation of the cobalt species state on zincosilicate to maximize propane dehydrogenation to propylene

Dispersing metals from nanoparticles into clusters or single atoms often exhibits unique properties such as the inhibition of structure-sensitive side reactions. Here, we reported the use of ion exchange (IE) methods and direct hydrogen reduction to achieve high dispersion of Co species on zincosilicate. The obtained 2Co/Zn-4-IE catalyst achieved an initial propane conversion of 41.4% at a temperature of 550 °C in a 25% propane and 75% nitrogen atmosphere for propane dehydrogenation. Visualization of the presence of Co species within specific rings (alpha-α, beta-β and delta-δ) was obtained by aberration-corrected scanning transmission electron microscopy. A series of Fourier transform infrared spectra confirmed the anchoring of Co by specific hydroxyl groups in zincosilicate and the specific coordination environment of Co and its presence in the rings essentially as a single site. The framework Zn for the modulation of the microenvironment and the presence of Co species as Lewis acid active sites (Co-O4) was also supported by density functional theory calculations.

Structural and photoelectrochemical properties of fibrous silica-titania (FST) photocatalyst for water splitting

Photoelectrochemical (PEC) water splitting is an ecologically friendly technique that uses effective photoanodes to generate hydrogen (H2). The microemulsion approach was used to develop a distinctive form displaying fibrous silica-titania (FST) photoanode. We examined the photocatalytic attributes of FST, hematite (Fe2O3), and zinc oxide (ZnO). XRD, N2 adsorption-desorption, FESEM, TEM, FTIR, XPS, UV–vis/DRS, and EIS were used to investigate the FST, Fe2O3, and ZnO. By using these techniques, a bicontinuous concentric lamellar arrangement with an ample surface area has been developed within FST. Characterization results demonstrate that FST has superior catalytic activity when compared to Fe2O3 and ZnO. The FST photoanode has an improved photocurrent density of 11.75 mA/cm2 and a 14.1% Solar-to-hydrogen (STH %) efficacy, which is greater than ZnO and Fe2O3, which performed at 4.7 mA/cm2 and 2.8 mA/cm2 with 5.6% and 3.36% STH efficiency, respectively. Moreover, we also compared the Solar-to-hydrogen (STH %) effectiveness of FST with different of TiO2 photoanodes. We absorbed that the band gap is decreased when Ti is added to the silica matrix, which facilitates the formation of Si–Ti bonds. FST displays a remarkable closeness of its conduction band (CB) to the hydrogen reduction potential in comparison to ZnO and Fe2O3, allowing for quick electron transfer and rapid production of H2. The geometry of FST design provides a novel way for producing robust and exceptionally productive photoanodes for PEC water splitting.

Effect of Water Vapor Partial Pressure on the Structure of Blue Tungsten Reduction Products in Hydrogen

This study investigates the structural evolution of blue tungsten reduction products when exposed to hydrogen under controlled water vapor partial pressures. The reduction of WO₂.₉ was achieved through hydrogen atom diffusion at 1050 °C. The Results indicate that, at low water vapor partial pressure, the reduction process of blue tungsten initiates on the surface and progresses inward, creating surface cracks on the clusters. These cracks enable water vapor to interact with the reduced tungsten (W) at their base, leading to the formation of needle-like WO₂.₇₂ phases that grow outward. Under high water vapor partial pressure, the morphology of the acicular WO2.72 phase changes to a stacked structure. Additionally, W-OH bonds were identified in the reduction products, with the WO₂.₇₂ growth angles observed at approximately 12° relative to the tungsten particles, closely matching the interfacial model prediction of 13.41°. The results of this paper will provide theoretical support for the structural evolution of intermediate products during hydrogen reduction of blue tungsten.

Desulfurization Behavior of Magnetite Pellets Reduced by Isothermal Pure Hydrogen

The desulfurization behavior of magnetite pellets reduced by pure hydrogen at isothermal temperature is studied, the mechanism of self‐oxidation desulfurization is put forward, and the thermodynamic theoretical calculation and experimental verification of this mechanism are carried out. The feasibility of the reaction between iron sulfide and Fe3O4 is analyzed by HSC Chemistry 6.0 software. Additionally, a thermal gravimetric analyzer is used to further study the thermal behavior of pellet material under Ar atmosphere from 400 to 1400 K. The results show that the removal of sulfur in the isothermal reduction process of pure hydrogen does not depend on hydrogen phase diffusion and reduction temperature. During the heating process, self‐oxidation desulfurization occurs in the system, and the self‐desulfurization reaction is more inclined to Fe3O4 + FexSy → FeS + SO2. Under the experimental conditions, the temperature range of self‐oxidation desulfurization under conventional thermal field and microwave field is 700–1100 and 370–1140 K, respectively, and the desulfurization rate is 92.9% and 95.8%, respectively. The key to improving desulfurization by microwave radiation is that iron sulfide has good wave‐absorbing characteristics.

Synthesis and Optimization of Foam Copper-Based CoMnOx@Co3O4/CF Catalyst: Achieving Efficient Catalytic Oxidation of Paraxylene.

This study successfully developed a foam copper (CF)-based CoMnOx@Co3O4/CF composite catalyst, achieving efficient thermal catalytic oxidation of paraxylene through multifactor optimization of synthesis conditions. At a Co:Mn molar ratio of 2:1 and a calcination temperature of 450 °C, the catalyst exhibited outstanding catalytic performance, with a T90 temperature as low as 246 °C, significantly lower than that of catalysts synthesized under other conditions. Additionally, BET, XPS, Raman, EPR, and H2-TPR test results indicate that the catalyst possesses a high specific surface area, abundant oxygen vacancies, a distribution of multivalent Co and Mn species, and a lower hydrogen reduction temperature, all of which contribute to the high catalytic activity of CoMnOx@Co3O4/CF. Furthermore, in situ DRIFTS confirmed that the oxidation of paraxylene on CoMnOx@Co3O4/CF follows the Mars-Van Krevelen (MvK) mechanism. The proposed reaction pathway begins with the oxidation of the methyl group on paraxylene, followed by the opening of the benzene ring and further oxidation to CO2 and H2O. The innovative structural design and excellent catalytic performance of this catalyst provide new insights and solutions for the industrial treatment of VOCs.