Inexpensive Metal Research Articles

Addressing Low-Cost Methane Sensor Calibration Shortcomings with Machine Learning

Quantifying methane emissions is essential for meeting near-term climate goals and is typically carried out using methane concentrations measured downwind of the source. One major source of methane that is important to observe and promptly remediate is fugitive emissions from oil and gas production sites but installing methane sensors at the thousands of sites within a production basin is expensive. In recent years, relatively inexpensive metal oxide sensors have been used to measure methane concentrations at production sites. Current methods used to calibrate metal oxide sensors have been shown to have significant shortcomings, resulting in limited confidence in methane concentrations generated by these sensors. To address this, we investigate using machine learning (ML) to generate a model that converts metal oxide sensor output to methane mixing ratios. To generate test data, two metal oxide sensors, TGS2600 and TGS2611, were collocated with a trace methane analyzer downwind of controlled methane releases. Over the duration of the measurements, the trace gas analyzer’s average methane mixing ratio was 2.40 ppm with a maximum of 147.6 ppm. The average calculated methane mixing ratios for the TGS2600 and TGS2611 using the ML algorithm were 2.42 ppm and 2.40 ppm, with maximum values of 117.5 ppm and 106.3 ppm, respectively. A comparison of histograms generated using the analyzer and metal oxide sensors mixing ratios shows overlap coefficients of 0.95 and 0.94 for the TGS2600 and TGS2611, respectively. Overall, our results showed there was a good agreement between the ML-derived metal oxide sensors’ mixing ratios and those generated using the more accurate trace gas analyzer. This suggests that the response of lower-cost sensors calibrated using ML could be used to generate mixing ratios with precision and accuracy comparable to higher priced trace methane analyzers. This would improve confidence in low-cost sensors’ response, reduce the cost of sensor deployment, and allow for timely and accurate tracking of methane emissions.

Recent Progress on Cobalt‐Based Heterogeneous Catalysts for Hydrogen Production from Ammonia Borane

AbstractAmmonia borane (NH3BH3, AB) is a quintessential exemplar of chemical hydrogen storage materials and has been widely used in hydrogen evolution. Although expensive metal catalysts (such as Rh, Ru, Pt, Ag, etc.) exhibit high activity in the hydrolysis of ammonia borane, inexpensive metals are more economical. Cobalt (Co), in particular, is not only relatively inexpensive and readily available, but also possesses high activity and selectivity. Compared to other catalysts, cobalt‐based catalysts have better durability and can maintain catalytic activity for a longer period of time, making them favored by researchers. These catalysts demonstrate excellent stability, hydrogen evolution rate, and turn over frequency. This article summarized previous progress in low price metal cobalt‐based catalysts for hydrogen precipitation from ammonia borane, focusing on cobalt‐based catalysts supported on various supports, especially those supported on carbon materials, metal oxides, MOFs, and nickel foams. The characteristics of high‐performance catalytic systems are analyzed in detail. The development prospects of Co catalysts for hydrogen production from ammonia borane were also discussed. In summary, this review compiles various supported and other types of cobalt based catalysts in recent years, and also identifies the existing problems with these catalysts, providing a reference for developers to study these catalysts. It is believed that through careful regulation of the electronic and spatial structures of Co based catalysts, well‐designed Co based non precious metal catalysts will play a significant role in the decomposition of ammonia borane.

“One‐Stone, Two‐Birds”: Zinc‐Rich Metal–Organic Frameworks as Precursors for High‐Entropy Zn‐Air Battery Electrocatalysts with Hierarchical Pore Structures

AbstractThe active sites of inexpensive transition metal electrocatalysts are sparse and singular, thus high‐entropy alloys composed of non‐precious metals have attracted considerable attention due to their multi‐component synergistic effects. However, the facile synthesis of high‐entropy alloy composites remains a challenge. Herein, we report a “one‐stone, two‐birds” method utilizing zinc (Zn)‐rich metal–organic frameworks as precursors, by virtue of the low boiling point of Zn (907 °C) and its high volatility in alloys, high‐entropy alloy carbon nanocomposite with a layered pore structure was ultimately synthesized. The experimental results demonstrate that the volatilization of zinc can prevent metal agglomeration and contribute to the formation of uniformly dispersed high‐entropy alloy nanoparticles at slower pyrolysis and cooling rates. Simultaneously, the volatilization of Zn plays a crucial role in creating the hierarchically porous structure. Compared to the zinc‐free HEA/NC‐1, the HEA/NC‐5 derived from the precursor containing 0.8 Zn exhibit massive micropores and mesopores. The resulting nanocomposites represent a synergistic effect between highly dispersed metal catalytic centers and hierarchical adsorption sites, thus achieving excellent electrocatalytic oxygen reduction performance with low catalyst loading compared to commercial Pt/C. This convenient zinc‐rich precursor method can be extended to the production of more high‐entropy alloys and various application fields.

"One-Stone, Two-Birds": Zinc-Rich Metal-Organic Frameworks as Precursors for High-Entropy Zn-Air Battery Electrocatalysts with Hierarchical Pore Structures.

The active sites of inexpensive transition metal electrocatalysts are sparse and singular, thus high-entropy alloys composed of non-precious metals have attracted considerable attention due to their multi-component synergistic effects. However, the facile synthesis of high-entropy alloy composites remains a challenge. Herein, we report a "one-stone, two-birds" method utilizing zinc (Zn)-rich metal-organic frameworks as precursors, by virtue of the low boiling point of Zn (907 °C) and its high volatility in alloys, high-entropy alloy carbon nanocomposite with a layered pore structure was ultimately synthesized. The experimental results demonstrate that the volatilization of zinc can prevent metal agglomeration and contribute to the formation of uniformly dispersed high-entropy alloy nanoparticles at slower pyrolysis and cooling rates. Simultaneously, the volatilization of Zn plays a crucial role in creating the hierarchically porous structure. Compared to the zinc-free HEA/NC-1, the HEA/NC-5 derived from the precursor containing 0.8 Zn exhibit massive micropores and mesopores. The resulting nanocomposites represent a synergistic effect between highly dispersed metal catalytic centers and hierarchical adsorption sites, thus achieving excellent electrocatalytic oxygen reduction performance with low catalyst loading compared to commercial Pt/C. This convenient zinc-rich precursor method can be extended to the production of more high-entropy alloys and various application fields.

Supported Nickel Nanoparticles as Catalyst in Direct sp3 C-H Alkylation of 9H-Fluorene Using Alcohols as Alkylating Agent.

Herein, we report an inexpensive first-row transition metal Ni heterogeneous catalytic system for the Csp3-mono alkylation of fluorene using alcohols as alkylating agents via borrowing hydrogen strategy. The catalytic protocol displayed versatility with high yields of the desired products using various types of primary alcohols, including aryl/hetero aryl methanols, and aliphatic alcohols as alkylating agents. The catalyst Ni NPs@N-C was synthesized via high-temperature pyrolysis strategy, using ZIF-8 as the sacrificial template. The Ni NPs@N-C catalyst was characterized by XPS, HR-TEM, HAADF-STEM, XRD and ICP-MS. The catalyst is stable even in the air at room temperature, displayed excellent activity and could be recycled 5 times without appreciable loss in its activity.

Mn-enhanced performance of the Ni-CaO/γ-Al2O3 dual function material for CO2 capture and in situ methanation

The CH4 yield over dual functional materials (DFMs) remains low and requires further improvement. In this work, we first examined the influence of Mn on the performance of the Ni-CaO/γ-Al2O3 DFM for CO2 capture and in situ methanation. Our results showed that the MnNi-DFM-3 (MnNi-CaO/γ-Al2O3 DFM) exhibited the best performance at 350 °C, with a CH4 yield of 0.56 mmol/g which is 4 times higher than that of the Ni-DFM-1 (Ni-CaO/γ-Al2O3 DFM) (0.14 mmol/g). Nanoscale characterization revealed that highly scattered Mn3O4 acted as a barrier preventing the agglomeration of Ni-based catalysts. Furthermore, our density functional theory (DFT) analysis demonstrated that the introduction of Mn enhanced the activation of CO2, promoted the dissociation of H2 and intermediates, and reduced the activation energy needed to produce carboxylic acid intermediates on the Ni catalyst. The prepared MnNi-DFM is promising to be a cheap efficient material for CO2 capture and in situ methanation. This work opens up a new pathway for enhancing the performance of DFMs using inexpensive transition metals.

Photoinduced Ligand-to-Copper Charge Transfer for Aryl Decarboxylative Allylation, Thiolation, and Bromination.

Herein, aryl decarboxylative allylation, thiolation, and bromination reactions via photoinduced ligand-to-copper charge transfer are described. Utilizing inexpensive copper metal, the transformations of various aryl carboxylic acids enable the rapid synthesis of the corresponding alkene, thioether, and aryl bromide derivatives under visible light irradiation, which offers significant synthetic value. The reaction conditions are mild and straightforward, exhibiting a broad substrate compatibility. Furthermore, this method can be applied for the late-stage modification of complex drug molecules.

Hydrothermal synthesis of nanostructured Zn2SnO4 ternary metal oxide semiconductor for toxic gas sensing application and its characterization study

Purpose The study aims to develop an inexpensive metal oxide semiconductor gas sensor with high sensitivity, excellent selectivity for a specific gas and rapid response time. Design/methodology/approach This study synthesized Zn2SnO4 nanostructures using a hydrothermal method with a 1 M concentration of zinc chloride (ZnCl2) as the zinc source and a 0.7 M concentration of tin chloride (SnCl4) as the tin source. Thick films of nanostructured Zn2SnO4 were then produced using screen printing. The structural properties of Zn2SnO4 were confirmed using X-ray diffraction, and the formation of Zn2SnO4 nanoparticles was verified by transmission electron microscopy. Scanning electron microscopy was used to analyse the surface morphology of the fabricated material, while energy dispersive spectroscopy provided insight into the chemical composition of the thick film. These fabricated thick films underwent testing for various hazardous gases, including nitrogen dioxide, ammonia, hydrogen sulphide (H2S), ethanol and methanol. Findings The nanostructured Zn2SnO4 thick film sensor demonstrates a notable sensitivity to H2S gas at a concentration of 500 ppm when operated at 160°C. Its selectivity, response time and recovery time were assessed and documented. Research limitations/implications The primary limitations of this research on metal oxide semiconductor gas sensors include poor selectivity to specific gases, limited durability and challenges in achieving detection at room temperature. Practical implications The nanostructured Zn2SnO4 thick film sensor demonstrates a strong response to H2S gas, making it a promising candidate for commercial production. The detection of H2S is crucial in various sectors, including industries and sewage plants, where monitoring this gas is essential. Social implications Currently, heightened global apprehension about atmospheric pollution stems from the existence of perilous toxic and flammable gases. This underscores the imperative need for monitoring such gases. Toxic and flammable gases are frequently encountered in both residential and industrial environments, posing substantial hazards to human health. Noteworthy accidents involving flammable gases have occurred in recent years. It is crucial to comprehend the presence and composition of these gases in the surroundings for precise detection, measurement and control. Thus, there has been a significant push for extensive research and development in diverse sensor technologies using various materials and methodologies to monitor and regulate these gases effectively. Originality/value In this research, Zn2SnO4 nanostructures were synthesized using a hydrothermal method with ZnCl2 at a concentration of 1 M for zinc and SnCl4 at a concentration of 0.7 M for tin. Thick films of nanostructured Zn2SnO4 were then fabricated via screen printing technique. Following fabrication, all thick films were subjected to testing with various toxic gases, and the results were compared to previously published data. The analysis indicated that the nanostructured Zn2SnO4 thick film sensor demonstrated outstanding performance concerning gas response, gas concentration, selectivity and response time, particularly towards H2S gas.

The one-pot synthesis of defect-rich bimetallic MOFs for efficient photocatalytic Fenton degradation of organic pollutants

The efficient and straightforward treatment of organic contaminants in water remains a significant challenge. This study presents the synthesis of a defective NH2-MIL-88Fex/Cuy photo-Fenton catalyst via a simple one-pot hydrothermal method. The incorporation of the inexpensive metal Cu enhances the valence cycles of Cu2+/Cu+ and Fe3+/Fe2+ under the photo-Fenton system, thereby compensating for the rapid consumption rate of ·OH radicals. Degradation tests demonstrated that NH2-MIL-88Fe0.5/Cu0.5 can degrade 99.99 % of methylene blue within 30 min under visible light irradiation. Free radical trapping experiments and Electron Paramagnetic Resonance (EPR) confirmed that ·OH radicals play a predominant role in the catalytic system. Density Functional Theory (DFT) calculations verified the improved binding energy of the catalyst materials following the introduction of structural defects. The degradation pathway and mechanism of methylene blue were elucidated. This study offers a novel approach for designing photo-Fenton catalysts and holds significant promise for practical applications in wastewater treatment.

Alkene Isomerization Catalyzed by a Mn(I) Bisphosphine Borohydride Complex.

An additive-free manganese-catalyzed isomerization of terminal alkenes to internal alkenes is described. This reaction is implementing an inexpensive nonprecious metal catalyst. The most efficient catalyst is the borohydride complex cis-[Mn(dippe)(CO)2(κ2-BH4)]. This catalyst operates at room temperature, with a catalyst loading of 2.5 mol %. A variety of terminal alkenes is effectively and selectively transformed into the respective internal E-alkenes. Preliminary results show chain-walking isomerization at an elevated temperature. Mechanistic studies were carried out, including stoichiometric reactions and in situ NMR analysis. These experiments are flanked by computational studies. Based on these, the catalytic process is initiated by the liberation of "BH3" as a THF adduct. The catalytic process is initiated by double bond insertion into an M-H species, leading to an alkyl metal intermediate, followed by β-hydride elimination at the opposite position to afford the isomerization product.

Development of Fe-Doped Ni2P-POx Electrocatalyst for Oxygen Evolution Reaction

Water electrolysis is extensively researched as a next-generation energy storage method to overcome the intermittency of renewable energy. Electricity generated from renewable sources such as solar and wind power can be converted into pure green hydrogen through water electrolysis. Despite the potential of green hydrogen as a renewable energy storage/carrier medium, the high overpotential resulting from the slow kinetics of oxygen evolution reaction (OER) and the use of expensive noble metals make cost-competitive hydrogen production a significant challenge. Anion exchange membrane water electrolysis (AEMWE) is one method for hydrogen production, offering economic advantages over proton exchange membrane systems as it allows for the use of relatively inexpensive transition metal catalysts like Ni, Fe, and Co due to its alkaline environment.Nickel phosphide (Ni2P)-based catalysts have emerged as highly promising candidates to accelerate the electrocatalytic OER. In particular, the introduction of Fe into Ni2P has been found to induce charge transfer, optimizing the electronic structure and accelerating the OER process. OER catalysts based on transition metal phosphides often exhibit a core-shell structure with phosphide at the core and oxide at the shell during OER measurements. This core-shell structure enhances OER performance through the oxide shell, complementing the deficient electrical conductivity of the phosphide core, resulting in superior catalytic activity and durability. From this perspective, transition metal phosphates are also being studied as electrocatalysts for OER. Phosphates, such as PO3 -, not only promote oxygen adsorbate adsorption but also induce a distorted local metal center geometry that favors OH- adsorption and further oxidation.To address these challenges, this study develops a facile and scalable synthesis of iron-doped nickel phosphide-phosphate (Fe-doped Ni2P-POx) nano-hybrid system as a superior noble-metal free OER powder-catalyst. The utilization of self-filling and pyrolysis approaches facilitates economically viable production of the highly porous phosphide catalyst with a high specific surface area and rough surfaces. X-ray diffractometer, X-ray photoelectron spectroscopy, and electron paramagnetic resonance elucidates the electronic structure modulation, resulting in phosphide-phosphate nano-hybrid structures. Consequently, the catalyst demonstrates excellent OER activity in 1 M KOH, with a significantly low overpotential of 283 mV at 20 mA cm-2, a small Tafel slope of 28.4 mV dec-1, and a superior exchange current density of 8.22 mA cm-2, surpassing state-of-the-art PGM catalysts. Furthermore, its durability over 20 hours indicates its excellent stability, mass transport properties, and mechanical robustness in alkaline media, underscoring its potential as an efficient OER catalyst to facilitate electrocatalytic hydrogen production. Figure 1

Advancing Low-Cost Flow Battery Chemistries

Pumped-hydroelectric presently dominates U.S. grid electricity storage capacity resources, but the past decade has brought increasing levels of electrochemical energy storage (EES) installations.1 Policymakers have recognized the need for longer-duration systems as more EES gets added to the grid and sought systems that can provide durations of 8+ hours.2 , 3 Although Li-ion presently dominates EES deployments, the average duration of U.S. utility-based-systems are relatively short at 3 hours.4 Redox flow batteries (RFBs) have an advantage over Li-ion systems at long durations due to their system architecture. The marginal cost of another hour of RFB duration asymptotes to the cost of additional active materials and their storage containers, as opposed to the cost of additional Li-ion cells, packs, and modules.Leading vanadium RFBs have made cost reductions by improving the power density of their energy conversion stacks,5 , 6 but eventually are limited by the relatively high cost of their vanadium active materials. Vanadium RFB suppliers are actively seeking to reduce this cost through business innovations. Yet, from a technical perspective, switching to lower cost active materials can also permit economically feasible long duration RFB systems.7 RTX Technology Research Center has previously reported on the low cost active material chemistries including the sulfur/manganese (S-Mn) chemistry and ligand-coordinate metals (LCM, e.g. chromium/iron).8 , 9 S/Mn uses active materials based on low-cost sulfur, a waste product of fossil fuel production, and inexpensive manganese, an element presently used commercially in disposable primary cells. LCM chemistries use mass-produced organic ligands and inexpensive metal centers like iron, chromium, and titanium, and can rely on more neutral, and benign, electrolyte pH conditions that offer wider electrochemical stability windows. Along with these benefits, LCM chemistries bring new challenges such as managing pH in an environment where small absolute concentration changes have outsized effects. This abstract will focus on the progress made advancing low-cost chemistries toward industrial relevance via thousands of hours of operation and in full-sized cell/stack form-factors. Acknowledgements: The work presented herein was funded by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR000994. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. References Chalamala, B., DOE Global Energy Storage Database. Sandia National Laboratories: 2020.Padilla, M., Joint Long Duration Storage Request for Offers. Energy, S. V. C., Ed. Silicon Valley Clean Energy: 2020.Albertus, P.; Manser, J. S.; Litzelman, S., Long-Duration Electricity Storage Applications, Economics, and Technologies. Joule 2020, 4 (1), 21-32.Linga, V. Duration of utility-scale batteries depend on how they're used; EIA: U.S. EIA 'Today in Energy', March 25, 2022, 2022.Sun, C. N.; Mench, M. M.; Zawodzinski, T. A., High Performance Redox Flow Batteries: An Analysis of the Upper Performance Limits of Flow Batteries Using Non-aqueous Solvents. Electrochimica Acta 2017, 237, 199-206.Perry, M. L.; Darling, R. M.; Zaffou, R., High Power Density Redox Flow Battery Cells. ECS Transactions 2013, 53 (7), 7-16.Wadia, C.; Albertus, P.; Srinivasan, V., Resource constraints on the battery energy storage potential for grid and transportation applications. Journal of Power Sources 2011, 196 (3), 1593-1598.Yang, Z.; Gerhardt, M. R.; Fortin, M.; Shovlin, C.; Weber, A. Z.; Perry, M. L.; Darling, R. M.; Saraidaridis, J. D., Polysulfide-Permanganate Flow Battery Using Abundant Active Materials. Journal of The Electrochemical Society 2021, 168 (7), 070516.Saraidaridis, J.; Yang, Z., Electrolyte Takeover Strategy for Performance Recovery in Polysulfide-Permanganate Flow Batteries. Journal of The Electrochemical Society 2021, 168 (11), 110556.

Ultrafine PtFeMo intermetallic compound nanowires for efficient oxygen reduction reaction in proton exchange membrane fuel cells

To advance the application of proton exchange membrane fuel cells (PEMFCs), it is crucial to develop high-performance oxygen reduction reaction (ORR) catalyst. Pt-based alloy nanowires exhibit excellent ORR activity due to their unique one-dimensional structure, but transition metals undergo spontaneous leaching under the harsh operating condition, often leading to decreased activity. Herein, ultrafine PtFeMo intermetallic compound nanowires were successfully synthesized as a high-performance ORR catalyst for PEMFC. The average diameter of the nanowires was 2.1 nm and the incorporation of inexpensive and high melting point metal Mo improved both catalytic performance and structural stability. The as-prepared ultrafine PtFeMo intermetallic compound nanowires exhibited mass activity of 2.56 A mgPt−1 for ORR, which is higher than that of disordered PtFeMo alloy nanowires (1.36 A mgPt−1) and commercial Pt/C (0.24 A mgPt−1) in rotating disk electrode test. And it exhibited peak power density of 2716 mW cm−2 under 250 kPa H2-O2 single-cell and mass activity of 0.62 A mgPt−1 under 100 kPa H2-O2 single-cell test in PEMFC. After long-time durability test, the intermetallic compound nanowires maintained their original structure, composition and electrocatalytic performance well, highlighting the importance of Mo incorporation and ordered phase structure generation.

Efficient adsorptive separation of nitrotoluene isomers via a stable and low-cost metal–organic framework with descending affinity order of meta-/ortho-/para-isomers

Obtaining purified nitrotoluenes from their mixture is significant but challenging due to their similar molecular sizes and physical properties. To overcome this challenge, here we report a stable, inexpensive and green-synthesized aluminium-based metal–organic framework (MIL-160) to separate the nitrotoluene mixtures. The appropriate pore size and pore environment permitted MIL-160 to exhibit a rare meta-nitrotoluene (m-NT) preference and always maintain the meta- > ortho- > para-nitrotoluene (m- > o- > p-NT) adsorption order in dynamic breakthrough and pulse modes as well as batch-mode adsorption. Theoretical calculations revealed that the abundant H/O atoms in the confined nanospace provided strong binding sites for selectively capturing nitrotoluene isomers. Specifically, due to difference in shape matching, the strongest host–guest interactions occurred in m-NT@MIL-160, followed by o-NT@MIL-160, and last p-NT@MIL-160. Notably, breakthrough experiments confirmed that a variety of binary and ternary mixtures can be separated via continuous adsorption. The dynamic adsorption stage of ternary mixture directly produced 0.33 mmol g−1 of pure p-NT, and the eluent in the desorption stage contained a high content of m-NT. Additional dynamic adsorption model fitting results indicated that the outstanding dynamic separation performance was also achieved from kinetic factors. These results lay the foundation for the effective separation of nitrotoluene mixtures.

Density function theory investigation of bimetallic phthalocyanine as a potential sensor and scavenger for nitrogen-containing toxic gases

Urbanization and industrialization processes inevitably release a large amount of nitrogen-containing toxic gases (NTGs) such as NO, NO2, NH3 and HCN, posing a serious threat to the ecological environment. Therefore, it is necessary to develop new gas sensors to promptly detect the emission and leakage of these toxic gases. Herein, four bimetallic phthalocyanines (BMPc = FePdPc, FePtPc, MnPdPc and MnPtPc) were designed by introducing pairs of precious metal (Pd/Pt) and inexpensive metal (Fe/Mn) atoms into the phthalocyanine (Pc) monolayer. Subsequently, the adsorption behavior and sensing properties of these BMPc towards NTGs were investigated using density functional theory (DFT) method. The studied results show that the four BMPc exhibit excellent stability and display chemical adsorption for these target gases due to the synergistic effect of bimetallic active centers, with adsorption energy greater than −0.70 eV. The adsorption strength follows the order NO > NO2 > NH3 > HCN, which is further confirmed by electronic properties such as charge density difference and density of states. Additionally, the analyses of work function, bandgap, and sensing response demonstrate the superior sensitivity of BMPc towards NO, NO2, NH3, and HCN. Meanwhile, the MnPtPc monolayer presents suitable adsorption strength for HCN at 298 K, resulting in a short recovery time of only 0.68 s. When the temperature is increased to 348 K, FePdPc and MnPdPc exhibit high reversibility for HCN, while MnPtPc displays favorable performance for NH3. Therefore, MnPtPc is identified as a recyclable HCN gas-sensing material at room temperature, while FePdPc, FePtPc, and MnPdPc are regarded as reusable gas-sensing materials for HCN at high temperature, with their sensing properties remaining unaffected in a humid environment. By contrast, the prolonged recovery times of NOx (x=1, 2) adsorption systems make these four BMPc more suitable as efficient scavengers for NOx. This study provides a new strategy for designing and developing phthalocyanine-based gas sensors and scavengers for the NTGs and other harmful substances.

Constructing local nanomolecular trap in a scalable, low-cost, and ultramicroporous metal–organic framework for efficient capture of greenhouse gases SF6 and CO2

The capture of sulfur hexafluoride (SF6) and carbon dioxide (CO2) is an important but challenging task for reducing greenhouse gas emission and thereby diminishing negative impacts of global climate change. Herein, we integrated local nanomolecular traps into an inexpensive cobalt-based metal–organic framework (MOF, namely GNU-3) with suitable pore sizes and functional pore surfaces for capturing greenhouse gases. Activated GNU-3a showed good adsorption and separation properties for SF6 and CO2. Especially for SF6, GNU-3a displayed the high SF6/N2 (10:90, v/v) selectivity of 317.6 and SF6 uptake capacity of 2.63mmol/g at 298 K and 1.0 bar. Grand canonical Monte Carlo simulations and first-principles dispersion-corrected density functional theory calculations identified that gas molecules were favorably trapped in polyaromatic ring functionalized channel centers and nanomolecular traps of pore walls by the strong hydrogen bond interactions. Excellent breakthrough results recommend practical separating properties of GNU-3a for binary SF6/N2 and CO2/N2 mixtures, and ternary SF6/CO2/N2 mixtures. Moreover, benefitting from superior features of cheap raw materials and large-scale synthesis, GNU-3 is expected to be applied to practical industrial scenarios. This work may provide insights into constructing prospectively industrial porous MOF adsorbents with optimal pore structures for greenhouse gas capture.

Transition metal catalysts coordinated with electrochemistry for preparation of graphene

It is still crucial to produce mass high-quality graphene through simple and low-cost methods for its wide applications. Herein, a simple and fast method by combining inexpensive transition metal catalysts with electrochemistry to exfoliate natural flake graphite is reported. The electrode is prepared in a sandwich structure, where the titanium mesh will enwrap the nickel net coated with graphite powder. This method can quickly achieve the large-scale preparation of graphene within 15 min. The quality of graphene with large lateral size and few layers has been characterized by XRD, SEM, TEM, Raman, and AFM. The possible electrochemical exfoliation mechanism has been proposed. Oxygen evolution reaction occurs at the anode due to the transition metal catalysts, and hydrogen ions (H+) are generated along with oxygen, H+ and SO42− ions will form a local strong acid. The formation of strong acidic H2SO4 in-situ around electrode will oxidize the edge of the graphite, allowing the intercalation of SO42−, H2O, SO2 and O2 into the graphite sheets, which will inflate the graphite and exfoliate of graphite into graphene. This strategy is reliable, environmentally friendly, and suitable for industrial production.

Fundamental insights and recent advances in catalytic oxidation processes using ozone for the control of volatile organic compounds.

The development of technologies for highly efficient treatment of emissions containing low concentrations of volatile organic compounds (VOCs) remains an important challenge. Catalytic oxidation with ozone (catalytic ozonation) is useful for the oxidative decomposition of VOCs, particularly aromatic compounds, under ambient temperature conditions. Only inexpensive transition metal oxides are required as catalysts, and Mn-based catalysts are widely used for catalytic ozonation. This review describes the oxidation reaction mechanisms, reaction pathways of aromatic hydrocarbons, and dependence of the catalytic ozonation activity on the reaction conditions. The reasons why Mn oxides are effective in catalytic ozonation are also explained. The structure of the catalytic active sites and the types of supporting materials contributing to the reaction are also discussed in detail, with the aim of establishing a VOC control technology. In addition, recent progress in catalytic oxidation processes using ozone as an oxidant has been outlined, focusing on catalyst materials and reaction conditions.

Spotlight on Zinc: Exploring the Visible Light Responsiveness of Zinc Complexes.

Group 12 element zinc(II)-based d10 complexes have long been known for their inherent colorlessness, which has limited their applications in visible light-driven photophysical and photochemical applications, despite the attractiveness of inexpensive and low-toxicity zinc metal. Based on precedents with nickel(0) and copper(I) complexes, which also adopt the d10 electronic configuration, achieving a visible light response from zinc(II) complexes seems feasible; however, investigations and proactive design strategies specifically tailored to zinc remain lacking. In this context, the present invited concept paper highlights zinc's potential for visible light responsiveness and evaluates how molecular designs can achieve this capability. After delineating the differences between zinc and other d10 metal centers, we review recent developments in zinc complexes that exhibit visible light absorption and compare these complexes with previously reported colorless complexes to identify key distinctions. This study provides critical insights into the molecular design guidelines that are pivotal for harnessing the emerging potential of zinc for visible light responses.

Spectrally selective radiation infrared stealth based on a simple Mo/Ge bilayer metafilm

In this paper, we propose and demonstrate a spectrally selective radiation infrared stealth metafilm based on a simple bilayer structure. Specifically, we use the common inexpensive metal Mo instead of traditional precious metals and achieve selective thermal radiation in the infrared band. In the atmospheric window band, the absorptivity is relatively low, which can well achieve the purpose of infrared stealth, while in the non-atmospheric window band, the absorptivity acutely increases, with a high absorptivity of 94.89 % at 6.04 μm, which can achieve better radiation heat dissipation. The experimental results are consistent with the simulation. The average emissivity in the 8–14 μm atmospheric window band is 0.32, while in the 5–8 μm non-atmospheric window band is 0.80, which proves the possibility of its practical application. Meanwhile, the metafilm proposed by us can be easily fabricated and can be widely used in the control of infrared thermal radiation, thermal management, and thermal camouflage, which has a very promising application prospect.