CO Molar Ratio Research Articles

Dual Metal Sites Coengineered Graphitic Carbon Nitride as Green Electrocatalyst for Highly Selective Overall Water Splitting—A Sustainable Approach

The development of efficient, low‐cost, non‐noble metal‐oxide‐based nanohybrid materials for overall water splitting is a critical strategy for enhancing clean energy use and addressing environmental issues. In this study, an interfacial engineering strategy for the development of bimetallic Co–Ni nanoparticles on graphitic carbon nitride (g‐C3N4) using ultrasonication followed by coprecipitation is conveyed. These nanoparticles demonstrate high efficacy as bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline conditions. Co–Ni nanoparticles on graphitic carbon nitride demonstrate an increased surface area via ultrasonication and subsequent coprecipitation. The g‐C3N4 combined with Co–Ni nanoparticles leads to the development of bifunctional catalysts that exhibit significant efficiency in both HER and OER, and their interfacial properties are investigated for the first time. The chemical composition and morphology of g‐C3N4 integrated with Co–Ni nanoparticles significantly influence the modulation of redox‐active sites and the facilitation of electron transfer, resulting in improved splitting efficiency. The interactions between the Co–Ni bimetal and g‐C3N4 demonstrate exceptional electrochemical performance for water splitting. Consequently, the 20% 20–Co–Ni–graphitic carbon nitride electrode demonstrated superior HER performance, comparable to the other electrodes. In the results, it is indicated that an increased molar ratio of Co and Ni incorporated in graphitic carbon nitride significantly improves HER performance.

A Multiple-physics coupled model for nanoconfined CO2-CH4 mixture transport behavior: Implications for CO2 geological storage in ultra-tight formation

Considerable efforts have been made to examine the feasibility of CO2-enhanced gas recovery (CO2-EGR), a promising approach for improving gas recovery by using CO2 to displace in-situ CH4 in ultra-tight gas reservoirs rich in nanopores. However, most research has focused on either single-component gas flow physics or competitive adsorption of multiple gas components in nanopores. The flow behavior of nanoconfined CO2-CH4 mixtures remains an area of knowledge gap. This work establishes a theoretical framework for CO2-CH4 mixture flow capacity by coupling mixture flow in the bulk region with surface diffusion in the adsorption area. Results indicate that: a) Total mixture flow conductance increases rapidly at pressures below ∼10 MPa, with CO2 contributing over 99 % to surface diffusion conductance; b) Increasing CO2 molar ratio from 0.2 to 0.8 can lead to a 167 % enhancement in total mixture conductance; c) Variations in CO2-CH4 competitive adsorption characteristics have little impact on total conductance.

Growth behavior of anisotropic monometallic MOFs derivatives with the high absorbing and thermal properties

The growth behavior and morphological characteristics of metal-organic frameworks (MOFs) should be considered as important factors in understanding their structure. Therefore, MOFs with atypical shapes, heterogeneous structures or abnormal properties that grow anisotropic can serve as components and templates for further directed assembly or conversion into MOF derivatives with excellent performance in electromagnetic wave absorption. Cobalt (Co) and nickel (Ni) metals have good magnetic properties and are common materials for the preparation of monometallic MOF-derived. In this study, various MOF materials with anisotropic properties, such as rod-like, flower-like, and braided, were prepared by adjusting the molar ratio of Co and Ni solvent to the organic ligand. Due to the rich inter-facial polarization and strong magnetic coupling network of the magnetic composites, Ni-MOF-b (Ni-MOF with braided shape) was prepared for the first time when the molar ratio of nickel nitrate to linker was 1:1.2. The Ni-C-b was obtained after pyrolysis of Ni-MOF-b, the minimum reflection loss of Ni-C-b was –50.7 dB at 4.0 mm. In addition, the thermal conductivity of the film prepared with Ni-C-b as filler is 2.2 W/mK. The film with integrated good heat dissipation and wave absorbing properties provides a research idea for the design of multifunctional integrated film.

Cu–Co bimetallic organic framework as effective adsorbents for enhanced adsorptive removal of tetracycline antibiotics

In this study, the removal effect of a new MOF-on MOF adsorbent based on Cu–Co bimetallic organic frameworks on tetracycline antibiotics (TCs) in water system was studied. The adsorbent (Cu-MOF@Co-MOF) were synthesized by solvothermal and self-assembly method at different concentrations of Co2+/Cu2+. The characterization results of SEM, XRD, XPS, FTIR and BET indicated that the MOF-on MOF structure of Cu-MOF@Co-MOF exhibited the best recombination and physicochemical properties when the molar ratio of Co2+: Cu2+ is 5:1. In addition, the Cu-MOF@Co-MOF have a high specific surface area and bimetallic clusters, which can achieve multi-target synergistic adsorption of TCs. Based on above advantages, Cu-MOF@Co-MOF provided a strong affinity and could efficiently adsorb more than 80% of pollutants in just 5 to 15 min using only 10 mg of the adsorbent. The adsorption capacity of tetracycline and doxycycline was 434.78 and 476.19 mg/g, respectively, showing satisfactory adsorption performance. The fitting results of the experimental data were more consistent with the Langmuir isotherm model and pseudo-second-order kinetic model, indicating that the adsorption process of TC and DOX occurred at the homogeneous adsorption site and was mainly controlled by chemisorption. Thermodynamic experiments showed that Cu-MOF@Co-MOF was thermodynamically advantageous for the removal of TCs, and the whole process was spontaneous. The excellent adsorption capacity and rapid adsorption kinetics indicate the prepared MOF-on MOF adsorbent can adsorb TCs economically and quickly, and have satisfactory application prospects for removing TCs in practical environments. The results of the study pave a new way for preparing novel MOFs-based water treatment materials with great potential for efficient removal.

Circular fuel production through steam reforming of waxy crude sludge: Enhancing syngas production using transition bimetallic catalyst

Waxy crude sludge (WCS) is an ignitable and hazardous semi-solid mixture containing petroleum, water, and heavy metals. Due to its high hydrocarbon content, WCS is a promising feedstock for syngas production. The carbon and hydrogen conversions were found to depend on temperature, primarily due to endothermic reactions. Ni and Cu metals were successfully doped onto dolomite to synthesize mono-metallic and bi-metallic catalysts to enhance the steam reforming. Notably, bimetallic Ni-Cu/dolomite catalysts exhibited high H2 and CO conversions. The 5 %Ni-5 %Cu/dolomite catalyst achieved the highest conversion yield, with total CO and H2 conversions of 21.15 % and 28.93 %, respectively, resulting in a H2 to CO molar ratio of 1.36 and a lower heating value (LHV) of 5.35 MJ/m3. These findings indicate that the surface-active site of dolomite-supported Ni-Cu catalysts exhibit enhanced activity and reduced carbon deposition. The study also demonstrated that using bimetallic catalysts with inexpensive mineral supports like dolomite is a viable solution for generating syngas from waxy sludges encountered during petroleum drilling operations. Additionally, this process aligns with the principles of the circular economy, facilitating energy generation and efficient hydrogen production.

Noble metal (Pt, Pd and Rh) promoted Ni-Co/Mg(Al)O catalysts for steam reforming of tar impurities from biomass gasification

Steam reforming is a promising approach to remove biomass gasification tar impurities. Noble metal promotion (Pt/Pd/Rh), Ni+Co loading (20–40 wt%) and calcination temperature (600–800 °C) effects were investigated with hydrotalcite-derived Ni-Co/Mg(Al)O catalysts for bio-syngas tar steam reforming. Fresh catalysts were characterized by XRD, ICP-MS, XRF, N2-physisorption, H2-chemisorption and TPR. Small-diameter metal particles were achieved (5.1–5.8 nm) below a Ni+Co loading threshold (above 30 wt%). Model bio-syngas activity tests were performed (CH4/H2/CO/CO2 molar ratio = 10/35/25/25, 700 °C, steam-to-carbon = 3.0) with and without tar addition (toluene/1-methylenaphthalene, 10 g/Nm3). Tar elimination was achieved with all samples. Enhanced reforming activity accompanied by strong tar active site inhibition effects were found for the Rh promoted catalyst. Noble metal promoted samples were effectively reduced in the bio-syngas environment (H2/CO/CH4) without any pre-reduction (in situ activation by the action of the syngas) with Rh > Pt > Pd. Coke characterization was conducted with TPO-MS and Raman spectroscopy. High-dispersion 20NiCo/30NiCo samples were strongly deactivated through active site inhibition and coke formation. High-temperature calcination (800 °C) reduced the deactivation effects of the coke deposition, attributed to enhanced Mg(Al)O-assisted coke gasification.

Biogas upgrading by intensified methanation (SESaR): Reaction plus water adsorption - desorption cycles with Ni-Fe/Al2O3 catalyst and LTA 5A zeolite

This work is conducted within the framework of the Power to Gas (PtG) technologies, focusing on the topic of “biogas upgrading”. The objective is to enhance the CH4 content of biogas streams by utilizing the CO2 present in these streams through the Sabatier reaction, thereby producing a renewable alternative to natural (fossil) gas. Referred to as “SESaR”(Sorption Enhanced Sabatier Reaction), this process employs a catalytic fixed-bed reactor, featuring selective water adsorption using LTA 5A zeolites, as an innovative approach to traditional methanation reactors. The catalyst used comprises Ni-Fe (7.5:2.5 wt/wt) as the active metallic phase supported on γ-Al2O3. Experimental work has been divided in two sets of trials. The first set focuses on the hydrogenation of CO2 as single reactant (H2 also supplied in the inlet with 4:1 = H2:CO2 molar ratio). The second set of experiments was carried out with a synthetic gas mixture representative of a sweetened biogas stream (molar ratio CH4:CO2 = 7:3). Maximum intensification behavior for CO2 conversion was found at 350 °C, also showing that CH4 presence in the inlet gas has negligible influence on the conversion of CO2. Selectivity to CO is minimized at temperatures exceeding 300 °C and remains constant after three consecutive cycles of methanation, water adsorption, and desorption. The Fe-Ni catalyst has demonstrated sustained performance throughout the experimental cycles, exhibiting no significant loss of activity.

Experimental and kinetic modelling studies for the design of fixed bed methanol reactor over CuZA catalyst

Direct conversion of CO2 via hydrogenation to value-added chemicals is a vital approach for utilising CO2 emitted into the atmosphere. In this paper, a critical analysis of reaction kinetic modelling studies is explored in a fixed bed reactor to improve methanol yield for different H2 to CO2 ratios by simulating a lab-scale reactor for adiabatic and isothermal conditions. The feed inlet temperature and pressure variations are applied to study the effect of both configurations on methanol production. The results show that the isothermal configuration yields 2.76% more methanol yield compared to the adiabatic reactor. The effect of H2 to CO2 molar ratios of 3, 6 and 9 on the performance of the catalyst and the influence of CO and CO2 hydrogenation is investigated with model simulations. The overall methanol yield is increased from 19.03% to 36.41% with increase in H2 to CO2 molar ratio from 3 to 9. Experiments are performed using commercial copper-based catalyst for different temperatures of 210, 230 and 250 °C at a pressure of 40 bar for H2/CO2 of 3 and GHSV of 720 h−1 as well as at optimal temperature of 250 °C and 50 bar with varying H2/CO2 of 3, 6, 9 for 3 g and 6 g catalyst. The maximum methanol yield of 2.53% and space time yield of 13.59 mg/gcat.h is obtained at H2/CO2 ratio of 9.

Adsorption behavior of CO2/H2S mixtures in calcite slit nanopores for CO2 storage: An insight from molecular perspective

It is acknowledged that injecting CO2 into oil reservoirs and saline aquifers for storage is a practical and affordable method for CO2 sequestration. Most CO2 produced from industrial exhaust contains impurity gases such as H2S that might impact CO2 sequestration due to competitive adsorption. This study makes a commendable effort to explore the adsorption behavior of CO2/H2S mixtures in calcite slit nanopores. Grand Canonical Monte Carlo (GCMC) simulation is employed to reveal the adsorption of CO2, H2S as well as their binary mixtures in calcite nanopores. Results show that the increase in pressure and temperature can promote and inhibit the adsorption capacity of CO2 and H2S in calcite nanopores, respectively. CO2 exhibits stronger adsorption on calcite surface than H2S. Electrostatic energy plays the dominating role in the adsorption behavior. Electrostatic energy accounts for 97.11% of the CO2-calcite interaction energy and 56.33% of the H2S-calcite interaction energy at 10 MPa and 323.15 K. The presence of H2S inhibits the CO2 adsorption in calcite nanopores due to competitive adsorption, and a higher mole fraction of H2S leads to less CO2 adsorption. The quantity of CO2 adsorbed is lessened by approximately 33% when the mole fraction of H2S reaches 0.25. CO2 molecules preferentially occupy the regions near the pore wall and H2S molecules tend to reside at the center of nanopore even when the molar ratio of CO2 is low, indicating that CO2 has an adsorption priority on the calcite surface over H2S. In addition, moisture can weaken the adsorption of both CO2 and H2S, while CO2 is more affected. More interestingly, we find that pure CO2 is more suitable to be sequestrated in the shallower formations, i.e., 500–1500 m, whereas CO2 with H2S impurity should be settled in the deeper reservoirs.

Fe-Co-Ni trimetallic Prussian blue analogs with tunable electrochromic energy storage properties

Prussian blue (PB) and its analogs (PBAs) have become a research hotspot in the fields of electrochemical energy storage and electrochromism due to their good reversible redox activity, and reversible color change response in different redox states. Herein, a series of trimetallic PBAs (Co/NiHCF with Co to Ni molar ratios of 1:0, 3:1, 1:1, 1:3, and 0:1) are synthesized by a facile co-precipitation method. In particular, the impact of Co to Ni molar ratio on the lithium storage and electrochromic properties of Co/NiHCF materials are systemically investigated. All five samples possess good crystallinity but the particle size decreases with the reduction of Co/Ni molar ratio. The color change, redox reaction potential, and lithium storage activity of the samples can be readily controlled by adjusting the molar ratio of Co to Ni. The lithium storage activity of the samples strengthens with the increase of Ni content in Co/NiHCF, accompanied by a decrease in redox potentials. With the increase of Ni content, the color of the Co/NiHCF film in the oxidation state changes from purple-red to orange, and finally to yellow; in the reduction state, the color of the film changes from green to light green and then to colorless. All the samples exhibit superior rate capability, excellent cycling stability, and short switching time (in the range of 1.6 to 4.3 s). The present work demonstrates a facile strategy for readily tunning the lithium storage activity, redox reaction potentials, and realizing rich color changes of PBA-based bifunctional materials.

Probing the exchange of CO2 and O2 in the shallow critical zone during weathering of marl and black shale

Abstract. Chemical weathering of sedimentary rocks can release carbon dioxide (CO2) and consume oxygen (O2) via the oxidation of petrogenic organic carbon and sulfide minerals. These pathways govern Earth's surface system and climate over geological timescales, but the present-day weathering fluxes and their environmental controls are only partly constrained due to a lack of in situ measurements. Here, we investigate the gaseous exchange of CO2 and O2 during the oxidative weathering of black shales and marls exposed in the French southern Alps. On six field trips over 1 year, we use drilled headspace chambers to measure the CO2 concentrations in the shallow critical zone and quantify CO2 fluxes in real time. Importantly, we develop a new approach to estimate the volume of rock that contributes CO2 to a chamber, and assess effective diffusive gas exchange, by first quantifying the mass of CO2 that is stored in a chamber and connected rock pores. Both rock types are characterized by similar contributing rock volumes and diffusive movement of CO2. However, CO2 emissions differed between the rock types, with yields over rock outcrop surfaces (inferred from the contributing rock volume and the local weathering depths) ranging on average between 73 and 1108 tCkm-2yr-1 for black shales and between 43 and 873 tCkm-2yr-1 for marls over the study period. Having quantified diffusive processes, chamber-based O2 concentration measurements are used to calculate O2 fluxes. The rate of O2 consumption increased with production of CO2, and with increased temperature, with an average O2:CO2 molar ratio of 10:1. If O2 consumption occurs by both rock organic carbon oxidation and carbonate dissolution coupled to sulfide oxidation, either an additional O2 sink needs to be identified or significant export of dissolved inorganic carbon occurs from the weathering zone. Together, our findings refine the tools we have to probe CO2 and O2 exchange in rocks at Earth's surface and shed new light on CO2 and O2 fluxes, their drivers, and the fate of rock-derived carbon.

Coupling of high-temperature proton exchange membrane fuel cells with methanol steam reforming: Modeling and simulation for an integrated coupled for power generation system

This study established a zero-dimensional numerical model integrating methanol steam reforming (MSR) and high-temperature proton exchange membrane fuel cells (HT-PEMFC), systematically investigating the effects of parameters such as steam-methanol (S/C) ratio, reformer reaction temperature, methanol catalytic combustion ratio, fuel cell number, and anode stoichiometry on the thermal, mass, electrical, and efficiency performance parameters of the integrated system. The results confirmed that the integrated system can achieve thermal self-sustained operation without the need for additional heat from methanol catalytic combustion. Improved insulation quality enables the attainment of thermal self-sufficiency at lower operating conditions. The molar ratio of CO in the reformate increases with a decrease in the S/C ratio and an increase in the reformer reaction temperature. The system achieves maximum output power and efficiency when S/C equals 1.25 and the reformer temperature is 513 K, with increases of 8.6 % and 37.1 %, respectively. The system efficiency is highly sensitive to the anode stoichiometry of the fuel cell, showing an 11.7 % improvement as the stoichiometry decreases from 2.0 to 1.2. Based on these results, three improvement measures were proposed to enhance the performance of MSR and HT-PEMFC integrated systems: improving system insulation to lower thermal self-sufficiency conditions, optimizing the stoichiometry of the bipolar plates for significant efficiency improvement, and selecting appropriate operating parameters for system components to enhance overall performance. This study quantitatively demonstrates the potential of these measures to improve system performance, providing valuable insights for the design and optimization of integrated systems.

Controllable fabrication of CoNi bimetallic alloy for high-performance electromagnetic wave absorption.

With the coming era of artificial intelligence (AI) dominated by high-tech electronics, developing high-performance microwave absorption materials (MAMs) is imperative to solve the problem of increasing electromagnetic inference and pollution. Herein, a metal-organic framework (MOF)-derived CoNi bimetallic alloy (CoNi/C) with an irregular rod-like structure is prepared by a thermal reduction method. Introducing the CoNi alloy facilitates the balance between conduction loss and polarization loss and forms good impedance matching, leading to excellent microwave absorption performance. Interestingly, the optimization of absorption performance can be further achieved by controllably modulating the molar ratio of Co and Ni (Co2+/Ni2+). As expected, the obtained CoNi/C delivers excellent microwave absorption performance with a minimum reflection loss (RLmin) of -50.80 dB at 10.40 GHz and an effective absorption bandwidth (EAB) of 3.28 GHz (8.91-12.19 GHz) with a filler loading of 50 wt% at 2.0 mm. In addition, the CoNi/C can reach a maximum EAB of 4.77 GHz (12.99-17.76 GHz) at a low thickness of 1.5 mm, spanning nearly the entire Ku band. The CoNi3/C also exhibits an impressive RLmin of -44.84 dB at 3.28 GHz in the S band. This work offers a novel strategy to modulate the magnetic/electric properties of MOF-derived MAMs.

Performance Study of Ni/Si-MCM-41 Catalysts, Synthesized with Different Silica Sources, and their Application on Methane Dry Reform to Produce Green Hydrogen

The present work carried out an extensive and deepened study regarding the physicochemical characteristics of two Si-MCM-41-type supports, synthesized employing two distinct silica precursors, tetraethyl orthosilicate (TEOS) and rice husk ash (RHS), with the dispersion of nickel on the surface of the catalytic support. The direct influence of the active phase dispersion was analyzed, making a relationship with the formation of coke and with its performance on methane dry reform (DRM). The catalysts were prepared with 5, 10, and 20% (m/m) of Ni by wet impregnation method (with excess solvent), calcined at 800 ºC for 6 h, and characterized by the techniques of scanning electron microscopy and energy dispersive spectroscopy (SEM/ EDS), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET)/Barret-JoyerHalenda (BJH), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), temperature-programmed ammonia desorption (TPD-NH3), and H2-temperature-programmed reduction (TPR). The DRM experiments were carried out at 800 °C for 24 h with a 1:1 CH4:CO2 molar ratio. Analyzes of gaseous products were performed in gas chromatography (GC) and the coke produced was estimated by temperature-programmed oxidation (TPO). The best reaction results were obtained for catalysts with 20% nickel, which were selective and stable within 24 h of reaction. Comparing the TEOS and RHS catalysts for 20% Ni, the DRM results were very similar. The catalysts on RHS support demonstrated a significant low formation of coke, which can be considered negligible in a 24 h reaction.

Synergistic effect between In2O3 and ZrO2 in the reverse water gas shift reaction.

Efficient activation of CO2 at low temperature was achieved through the interface effect between In2O3 and ZrO2 by their geometric and electronic effects. The results show that 75In2O3-25ZrO2 (In2O3 : ZrO2 molar ratio of 3 : 1), as a catalyst for the reverse water gas shift reaction, can achieve 28% CO2 conversion with 96% CO selectivity at 400 °C, 0.1 MPa, a H2 : CO2 molar ratio of 3 : 1 and a gas hourly space velocity of 10 000 mL g-1 h-1. In situ FTIR experiments provide a basis for clarifying the pivotal role of formate (facilitated at In2O3-ZrO2 interface) in this reaction.

Raman spectroscopic characterization of the CO2-N2 gaseous system at 24–300°C and 2–40 MPa and applications

ABSTRACT CO2 and N2 are important gas components of deep-sourced geological fluids. To establish a quantitative method for the study of these fluids, we used a high-pressure optical cell, a heating–cooling stage, and a laser Raman spectrometer to examine pure CO2 and N2 gases and nine CO2-N2 gaseous mixtures at 24–300°C and 2–40 MPa. The results show that the CO2 Fermi diad split and the peak area ratios of the ν 1 band of N2 to the upper band of CO2 are considered to be the best for determining pressure and composition, respectively. The quantitative Raman analysis method developed in this study for the determination of the C N2/C CO2 molar ratio was verified by measuring those in synthetic N2-CO2-H2O fluid inclusions. The developed method has also been applied to the analysis of natural fluid inclusions in quartz from Donghai for the determination of both the C N2/C CO2 molar ratio and pressure.

Effect of doping Ni on microstructures and properties of CoxNi1-xHCF based seawater battery

Prussian blue analogues (PBAs) have been proven to be a kind of seawater battery cathode due to the accommodation of electrons upon the intercalation of Na+ in seawater. In the current work, Ni-doped cobalt hexacyanoferrate (CoxNi1-xHCF) was fabricated by using co-precipitation method at room temperature. Results have shown that with increasing the molar ratio of Co: Ni, the specific capacity of the cathode initially increases and then decreases. The best battery properties were obtained when the molar ratio of Co: Ni was 1:2. The specific capacity was up to 76.5 mAh·g−1 at 0.1 A g−1, the capacity retention was up to 63.5 % at a current density of 10 A g−1, and the capacity retention of 81 % was obtained after 100 cycles. The introduction of Ni2+ increases the specific surface area leading to the additional active sites for the redox reaction. At the same time, the specific capacity decreased due to the Ni doping. The enhanced electrochemical performance of CoxNi1-xHCF cathode for seawater battery was achieved by considering the synergistic effects of specific surface and elemental composition. Furthermore, seawater battery was successfully assembled by matching the Co0.86Ni0.14HCF cathode with Mg anode, which demonstrates the promising application of PBAs for seawater batteries.

Bimetallic MOFs/MXene derived CoNi@C@Ti3C2Tx/TiO2 nanocomposites for high-efficiency electromagnetic wave absorption

Constructing intricately designed multiple heterogeneous interfaces offers an effective strategy for exploring lightweight and efficient microwave absorbing materials (MAMs). Herein, the CoNi@C@Ti3C2Tx/TiO2 (CNCTT) nanocomposites with multiple heterogeneous interfaces were synthesized using the straightforward solvothermal method, electrostatic self-assembly, and subsequent heat treatment process, utilizing bimetallic CoNi-MOF-74@few-layered Ti3C2Tx MXene as the precursor. The modulation of composition, microstructure, and electromagnetic wave absorption (EMWA) properties of the CNCTT nanocomposites was comprehensively investigated by simply controlling the ratio of magnetic metal sources. Hierarchical porous structure simultaneously promotes interfacial polarization by quaternary CoNi/C/MXene/TiO2 interfaces, enhances magnetic loss by the CoNi nanoparticles coupling network, enlarges conduction loss by the graphite carbon layer/MXene/TiO2 triple-network, and optimizes impedance matching with the synergistic effect of dielectric loss and magnetic loss. Significantly, it is observed that the C3N3CTT nanocomposite, with the molar ratio of Co:Ni is 3:3 and a filler loading of 30 wt%, demonstrates an impressive minimum reflection loss (RLmin) of −70.26 dB at 15.92 GHz and an effective absorbing bandwidth (EAB, RL < −10 dB) of 4.19 GHz with an absorption layer thickness of 1.7 mm. Furthermore, the RLmin remains notable −40.50 dB with an expanded EAB of 5.17 GHz at a thickness of 1.8 mm. This endeavor can provide significant insights into the potential applications of MOF-derived composites in the realm of efficient electromagnetic wave absorption.

Preparation of various Co/Cu and Co/Fe molar ratios and gel-modified nanomaterials as anodes for Li-ion batteries

Co-based binary metal oxides with higher theoretical capacity have attracted increasing attention as anodes for lithium-ion batteries (LIBs). In this study, Co-based bimetallic oxides were prepared by optimizing different molar ratios of Cu/Co and Fe/Co using an electroconversion method. The purity and microstructure of the synthesized powders were investigated, and their lithium storage properties were studied by assembling half-cells. Cu/Co oxide exhibited three different microstructures, while Fe/Co oxide showed a nanoparticle morphology. The electrochemical performance results revealed that the optimal molar ratio of Co: Cu was 2:1, and the optimal molar ratio of Fe: Cu was 5:1. Particularly, Fe: Cu = 5:1 exhibited the best electrochemical stability and higher specific capacitance. Therefore, Fe3O4/Co3O4 (Fe: Cu = 5:1) was used as the raw material for modification, and a hydrogel method was employed with sodium alginate (SA) serving as the fixing agent and carbon source to prepare microspheres. Taking advantage of the natural freezing conditions in the winter of Northeast China, the dried microspheres were subjected to calcination to obtain Fe3O4/Co3O4/SA with enhanced conductivity. Even at a current density of 2 A/g, Fe3O4/Co3O4/SA still maintained a discharge capacity of around 280 mAh/g, demonstrating excellent cycling stability and rate capability.

Hydrothermal Graphite as a Trigger for High-Temperature Orogenic Gold Mineralization at Haoyaoerhudong, Northern China

Abstract Carbonaceous materials are a key factor controlling mineralization processes in many world-class gold deposits. Haoyaoerhudong is the largest carbonaceous metasediment-hosted gold deposit on the north margin of the North China craton. Gold-bearing orebodies are hosted in carbonaceous slates and schists belonging to Mesoproterozoic rift-related successions. Typical hydrothermal minerals are pyrrhotite, quartz, biotite, graphite, apatite, titanite, and native gold. The ore mineralogy, combined with microthermometry and Raman spectra on fluid inclusions, has demonstrated three stages of hydrothermal activity: (I) quartz-biotite ± sulfide stage associated with gold mineralization (315°–510°C; ~4.8 wt % NaCl equiv; H2O-NaCl-CO2 ± CH4 ± N2 system); (II) quartz-sulfide stage, including quartz-sulfide stringers (IIa, 250°–334°C; ~5.4 wt % NaCl equiv; H2O-NaCl-CH4 ± CO2 ± N2 system) and fractured quartz-sulfide ores (IIb, 234°–308°C; ~4.1 wt % NaCl equiv; H2O-NaCl-N2 ± CH4 system); and (III) post-ore quartz-calcite stage (70°–219°C; ~4.8 wt % NaCl equiv; H2O-NaCl system). The molar ratios of CO2 and CH4 progressively decreased from stage I to II, consistent with the occurrence of graphite in alteration zones. Microscopic observation and Raman spectra suggest that the fine-grained graphite from altered schist (Gr-1/2) and coarse-sized graphite from gold-bearing veins (Gr-3/4) are of high crystallinity and exhibit characteristics indicating a hydrothermal origin. The δ13C values of graphite, varying from −27.1 to −26.0‰ Vienna-Pee Dee Belemnite (V-PDB), suggest that the carbon was of biogenetic origin. Apatite Sr isotopes (87Sr/86Sr: 0.708293–0.708842) and titanite Nd isotopes (εNdt: –11.76 to –14.84) also indicate contributions from carbonaceous rocks during mineralization. Thermodynamic modeling demonstrates that graphite may have precipitated at Haoyaoerhudong due to cooling and reduction of the H2O-CO2-CH4 fluids at high temperatures. Graphite precipitation would significantly consume CO2 and effectively destabilize Au bisulfide complexes, facilitating the codeposition of pyrrhotite, graphite, and native gold at high temperatures (≥379°C). We infer that deposition of hydrothermal graphite is a crucial process for mesothermal-hypothermal mineralization in sediment-hosted orogenic gold deposits.