High-purity Gas Research Articles

Surface plasmons on silver gratings transform pyrolytic carbon into luminescent graphitized carbon dots.

Plasmonic catalysis holds the promise of opening new reaction pathways that are inaccessible thermally or via direct UV-vis electronic transitions. Here, energetic carriers produced via the decay of surface plasmons excited by visible light at 532nm (2.33eV, green) on a Ag-grating-bearing pyrolytic carbon residue drive its transformation into light-emitting graphitized carbon dots. The pyrolytic carbon residue is detectable via high-magnification surface-enhanced Raman scattering but cannot be directly observed using optical, electron, atomic force, or helium ion microscopy. When a Ag-grating-bearing pyrolyzed residue is introduced into a high-purity O2-depleted gas environment (Ar, N2, and CO2) and excited with 532nm light, bright yellow luminescence emerges and is readily observed. Light emission is not observed without the pyrolytic carbon, without the excitation of plasmons, or in air or an Ar/O2 gas mixture. This process, driven by visible light and a nanostructured Ag surface bearing pyrolytic carbon, will be of interest to researchers involved in plasmonic catalysis, catalytic processes involving carbon, and luminescent plasmonic surfaces.

Thermal properties and decomposition of perovskite energetic materials (C6H14N2) NH4 (ClO4)3

(C6N2H14) NH4 (ClO4)3 (DAP-4) have attracted an increasing focus recently as an ammoniumperchlorate-based molecular perovskite energetic material with outstanding features. Microscopy, variable temperature X-ray diffraction, in situ infrared spectroscopy, differential scanning calorimetry-thermogravimetry simultaneous thermal analysis coupled with infrared spectroscopy and mass spectrometry (DSC-TG/FTIR/MS) techniques were used to systematically investigate DAP-4 thermal properties from -40 °C to 550 °C. The results revealed that DAP-4 have two solid-solid crystallization phase transitions with a non-characteristic melting process. The generated activation energies of HCN, CO, CH2NH2, CO2 and NO2 gas products are all lower than the macroscopic decomposition's of DAP-4. This finding strongly proves that DAP-4 is easy to form these gas products during thermal stimulus. The two stages decomposition mechanism accompanying a large of CH2NH2 and NH2C2H4 gases and kinetic model of DAP-4 were proposed under the condition of high-purity argon gas. This study provides new insight into the in-depth and accurate description thermal decomposition mechanism of DAP-4 as a potential energetic material.

Multifunctional and Ultrastable Co-MOF Effectively Separates Various Different Component Gas Mixtures.

Developing low-cost and multifunctional adsorbents for adsorption separation to obtain high-purity (>99.9%) gases is intriguing yet challenging. Notably, the ongoing trade-off between adsorption capacity and selectivity in separating multicomponent mixed gases still persists as a pressing scientific challenge requiring urgent attention. Herein, the ultrastable TJT-100 exhibits unique structural characteristics including uncoordinated carboxylate oxygen atoms, coordinated water molecules directed toward the pore surface, and sufficient Me2NH2+ cations in channels. TJT-100 exhibits a high adsorption capacity and exceptional separation performance, particularly notable for its high C2H2 capacity of 127.7 cm3/g and remarkable C2H2 selectivity over CO2 (5.4) and CH4 (19.8), which makes it a standout material for various separation applications. In a breakthrough experiment with a C2H2/CO2 mixture (v/v = 50/50), TJT-100 achieved a record-high C2H2 productivity of 69.33 L/kg with a purity of 99.9%. Additionally, TJT-100 demonstrates its effectiveness in separating CO2 from natural gas and flue gas. Its exceptional selectivity for CO2/CH4 (10.7) and CO2/N2 (11.9) results in a high CO2 productivity of 21.23 and 22.93 L/kg with 99.9% purity from CO2/CH4 (v/v = 50/50) and CO2/N2 (v/v = 15/85) mixtures, respectively.

Structural Modification Effect of Se-doped Porous Carbon for Hydrogen Evolution Coupled Selective Electrooxidation of Ethylene Glycol to Value-added Glycolic Acid.

The ethylene glycol oxidation reaction (EGOR) has attracted attention because ethylene glycol (EG), which exhibits large-scale production and a low market price, can be reformed into valuable glycolic acid (GCA) with the cogeneration of high-purity hydrogen gas during the reaction. In this study, a noble catalyst material of Pt nanoparticles supported on Se-doped porous carbon (Pt/SePC) is prepared and investigated for the selective electrochemical oxidation of EG to GCA. Pt/SePC achieved a maximum EG conversion of 94.6% and GCA selectivity of 84.4% and maintained this high performance with negligible degradation during durability tests. Furthermore, the EGOR required lower overpotential rather than the oxygen evolution reaction, thus the EGOR coupled with the hydrogen evolution reaction can reduce the cell overpotential to 0.60 V, which is much lower than that of water electrolysis (1.58 V). The effect of Se doping is investigated through experimental analyses and density functional theory (DFT) calculations, and they shows that Se modified the binding energy of Pt nanoparticles and the adsorption energy of reactants by lattice deformation and charge density modification. This study provides scientific insights and strategies for electrocatalyst design for the selective oxidation of polyols to value-added chemicals via the cogeneration of hydrogen gas.

Effect of atmospheric-pressure nitrogen plasma treatment at low temperature on fatigue properties of low-alloy steels

A device for parallel-plate-type atmospheric-pressure nitrogen plasma (APNP) treatment, which can generate plasma in a sealed environment with high-purity nitrogen gas, was developed. The objective of the present study was to use microstructural analyses to investigate the effect of APNP treatment at low temperatures on the fatigue properties of low-alloy steels. The APNP treatment was conducted at 473 K, which is lower than the common gas nitriding temperature. X-ray analyses revealed that a nitrogen–oxygen diffusion layer with high fatigue limit was formed on the steel by the APNP treatment at 473 K. Thus, the APNP treatment is an effective approach for increasing the fatigue limit of steels by increasing their surface hardness.

Microstructure and Pore Characteristics of a Double-Layered Pore Structure Powder Filter Fabricated by the WPS Process

In order to supply high-purity process gas in the semiconductor manufacturing process, a gas filter is used to remove particles that may be contained in the gas. However, because the gas filters currently in use have simple pore structures, there is a need to increase filtration efficiency through the development of filters with complex pore structures. In this study, a metal powder filter with double-layered pores was manufactured using a Wet Powder Spraying process (WPS) to increase the filtering efficiency of gas filters used in semiconductor manufacturing. The effects of the mixing ratio of spherical-shape and flake-shape powders and the rolling process on the filter’s characteristics were investigated. The filter’s performance, microstructure, and surface roughness were evaluated by measuring porosity and gas permeability. The results showed that as the ratio of flake-shaped powder decreased, the thickness of the coating layer and the porosity of the filter decreased. Additionally, it was observed that as the rolling process progressed, the non-uniform pore structure was oriented parallel to the cross-section of the filter regardless of the mixing ratio. Measurements found that the gas permeability of the uncoated filter support was the highest, and that gas permeability decreased as the proportion of spherical powder increased regardless of the average particle size of the mixed powder. Lower gas permeability was observed in rolled samples. A filtration efficiency of LRV 3 or higher was confirmed.

Research on the minimum detection limit for measuring high-purity gases by gas chromatography

Abstract At present, the application fields of high-purity gases (purity reached 99.999% and above) include the semiconductor manufacturing industry, chemical analysis, fuel cells, aerospace, medicine, etc., and the quality and purity requirements of high-purity gases are also getting higher and higher. As the only detector that can detect ppb-level trace impurities, the pulsed discharge helium ionization detector (PDHID) is the most used detector in the field of high-purity gases. The minimum detection limit of existing PDHID-related analysis methods is usually calculated theoretically. In order to verify the actual minimum detection limit of PDHID, a multi-group gas distribution system was used in this paper to dilute the permanent gas components in the high-purity gas, and the gas chromatograph with pulsed discharge helium ionization detector (GC-PDHID) was used to detect the obtained different concentrations of standard gases. The experimental results showed that PDHID possessed high sensitivity, good linearity, and a wide linear range. The actual minimum detection limit for the permanent gas components in the high-purity gas could reach the ng/g (ppb) level, which could realize the detection of ultra-low concentration samples, and further verify the actual minimum detection limit of PDHID. This experiment provides a reference basis for the analysis of trace gases in the gas industry, especially in industries such as high-purity and ultra-high-purity gases and gas for the electronics industry, and is of great significance in actual production work.

Insight into the mechanism of helium enrichment in natural gas from the Bohai Bay basin, China: Chemical and isotopic composition perspectives

Helium (He) is an important societal resource, yet its enrichment mechanism is unclear in the Bohai Bay Basin, despite the presence of He-rich (He > 0.1% v/v) gas. A comprehensive analysis of 112 sets of chemical and isotopic data from natural gases in the literature was conducted to further elucidate the source and accumulation mechanism of He in this basin. Natural gas is categorized into five groups based on CO2 and N2 abundances: N2 gas (CO2+N2 ≥ 95%, CO2 < N2), high-purity CO2 gas (CO2+N2 ≥ 95%, CO2 > N2), low-purity CO2 gas (50 ≤ CO2+N2 < 95%, CO2 > N2), low-purity HC gas (15 ≤ CO2+N2 < 50%) and high-purity HC gas (CO2+N2 < 15%). δ13C–CO2 (−8.3 to −3.0‰) and 3He/4He (1.66–6.45 Ra, where Ra is the atmospheric 3He/4He) suggest a mantle origin of CO2 in N2 and CO2 gases. The δ13C–CO2 of N2 gas (−8.3‰) is lighter than that of high-purity CO2 gas (−6.2 to −3.4‰), indicating CO2 dissolution and mineralization. A positive correlation between He and CH4 content in the N2 and high-purity CO2 gases suggests water-derived CH4 capture during CO2 migration. Similarly, the positive correlation between He and N2 content across all samples indicates water-derived N2 capture during gas migration. A mixture of mantle and crust-derived He is indicated by 3He/4He ratio (0.06–6.45 Ra). Two distinct types of He-rich gas were identified: He-rich N2 gas (3He/4He = 3.1–3.2 Ra) and He-rich HC gas (3He/4He = 0.36–0.48 Ra). He enrichment in N2 gas is attributed to water-derived He capture and concurrent loss of CO2 during mantle-derived CO2 migration. He-rich HC gas formation results from He-rich N2 gas dilution with hydrocarbons. The findings provide theoretical support for exploring He-rich natural gas in this basin and offer valuable insights into He enrichment mechanisms in comparable sedimentary basins globally.

Hollow-structured cobalt sulfide electrocatalyst for alkaline oxygen evolution reaction: Rational tuning of electronic structure using iron and fluorine dual-doping strategy

Utilizing renewable electricity for water electrolysis offers a promising way for generating high-purity hydrogen gases while mitigating the emission of environmental pollutants. To realize the water electrolysis, it is necessary to develop highly active and precious metal-free electrocatalyst for oxygen evolution reaction (OER) which incurs significant overpotential due to its complicated four-electron transfer mechanism. Hence, we propose a facile preparation method for hollow-structured Fe and F dual-doped CoS2 nanosphere (Fe-CoS2-F) as an efficient OER electrocatalyst. The uniform hollow and porous structure of Fe-CoS2-F enlarge the specific surface area and increase the number of exposed active sites. Furthermore, the Fe and F dual-dopants synergistically contributed to the adjustment of electronic structure, thereby promoting the adsorption/desorption of oxygen-containing reaction intermediates on active sites during the alkaline OER procedure. As a result, the prepared Fe-CoS2-F exhibits outstanding OER activity, characterized by a low overpotential of 298 mV to achieve a current density of 10 mA cm−2 and a Tafel slope as small as 46.0 mV dec−1. Based on computational theoretical calculations, the introduction of the dual-dopants into CoS2 structure reduce the excessively strong adsorption energy of reaction intermediate in the rate determining step, leading to effectively promoted electrocatalytic cycle for OER in alkaline environment. This study presents an effective strategy for preparing noble metal-free OER electrocatalysts with promising potential for large-scale industrial water electrolysis.

Biogas Upgrading Using a Single-Membrane System: A Review.

In recent years, the use of biogas as a natural gas substitute has gained great attention. Typically, in addition to methane (CH4), biogas contains carbon dioxide (CO2), as well as small amounts of impurities, e.g., hydrogen sulfide (H2S), nitrogen (N2), oxygen (O2) and volatile organic compounds (VOCs). One of the latest trends in biogas purification is the application of membrane processes. However, literature reports are ambiguous regarding the specific requirement for biogas pretreatment prior to its upgrading using membranes. Therefore, the main aim of the present study was to comprehensively examine and discuss the most recent achievements in the use of single-membrane separation units for biogas upgrading. Performing a literature review allowed to indicate that, in recent years, considerable progress has been made on the use of polymeric membranes for this purpose. For instance, it has been documented that the application of thin-film composite (TFC) membranes with a swollen polyamide (PA) layer ensures the successful upgrading of raw biogas and eliminates the need for its pretreatment. The importance of the performed literature review is the inference drawn that biogas enrichment performed in a single step allows to obtain upgraded biogas that could be employed for household uses. Nevertheless, this solution may not be sufficient for obtaining high-purity gas at high recovery efficiency. Hence, in order to obtain biogas that could be used for applications designed for natural gas, a membrane cascade may be required. Moreover, it has been documented that a significant number of experimental studies have been focused on the upgrading of synthetic biogas; meanwhile, the data on the raw biogas are very limited. In addition, it has been noted that, although ceramic membranes demonstrate several advantages, experimental studies on their applications in single-membrane systems have been neglected. Summarizing the literature data, it can be concluded that, in order to thoroughly evaluate the presented issue, the long-term experimental studies on the upgrading of raw biogas with the use of polymeric and ceramic membranes in pilot-scale systems are required. The presented literature review has practical implications as it would be beneficial in supporting the development of membrane processes used for biogas upgrading.

Michaelis-Menten kinetics during dry etching processes.

The chemical etching of germanium in Br2 environment at elevated temperatures is described by the Michaelis-Menten equation. The validity limit of Michaelis-Menten kinetics is subjected to the detailed analysis. The steady-state etching rate requires synergy of two different process parameters. High purity gas should be directed to the substrate on which intermediate reaction product does not accumulate. Theoretical calculations indicate that maximum etching rate is maintained when 99.89% of the germanium surface is covered by the reaction product, and 99.9999967% of the incident Br2 molecules are reflected from the substrate surface. Under these conditions, single GeBr2 molecule is formed after 30 million collisions of Br2 molecules with the germanium surface.

Accuracy validation of open-circuit respiration chambers for the assessment of energy metabolism and enteric methane emissions in pigs and small ruminants

Respiratory chambers are one of the main methods of obtaining data regarding animal energy metabolism and determine enteric methane emissions from livestock. The boom in research examining methane emissions has led to an increase in the number of facilities where such measurements can be performed. This has concerned various research groups, and emphasis has been placed on implementing a method for validating respiratory chambers according to international standards, thus ensuring that the results are traceable. This study aimed to validate the accuracy of two respiratory chambers for assessing animal energy metabolism and enteric methane emissions from livestock using international standards. The analyzers (oxygen, carbon dioxide, and methane), duct and air extraction system, and chamber were the three components used to validate the complete respiratory chamber system. The linearity and response time of the analyzers, stability of the plateau, and recovery of high-purity gases from the chambers were evaluated for the three components. The average variations in the gas measurements for the supplied reference gas were 1.77 and 1.30 % for the carbon dioxide and methane analyzers, respectively. Recovery test calculations after supplying high-purity carbon dioxide and methane into chambers revealed that the efficiency of gas recovery averages were 1.018 ± 0.0001 and 0.991 ± 0.0001 for chambers one and two, respectively. In conclusion, the respiratory chambers at the National Center of Disciplinary Research in Animal Physiology of INIFAP, Mexico designed for evaluating energy metabolism and enteric methane emissions in livestock, work with accuracy.

Single-Molecule Traps in Covalent Organic Frameworks for Selective Capture of C2H2 from C2H4-Rich Gas Mixtures.

Removing trace amounts of acetylene (C2H2) from ethylene (C2H4)-rich gas mixtures is vital for the supply of high-purity C2H4 to the chemical industry and plastics sector. However, selective removal of C2H2 is challenging due to the similar physical and chemical properties of C2H2 and C2H4. Here, we report a "single-molecule trap" strategy that utilizes electrostatic interactions between the one-dimensional (1D) channel of a covalent organic framework (denoted as COF-1) and C2H2 molecules to massively enhance the adsorption selectivity toward C2H2 over C2H4. C2H2 molecules are immobilized via interactions with the O atom of C=O groups, the N atom of C≡N groups, and the H atom of phenyl groups in 1D channels of COF-1. Due to its exceptionally high affinity for C2H2, COF-1 delivered a remarkable C2H2 uptake of 7.97 cm3/g at 298 K and 0.01 bar, surpassing all reported COFs and many other state-of-the-art adsorbents under similar conditions. Further, COF-1 demonstrated outstanding performance for the separation of C2H2 and C2H4 in breakthrough experiments under dynamic conditions. COF-1 adsorbed C2H2 at a capacity of 0.17 cm3/g at 2,000 s/g when exposed to 0.5 ml/min C2H4-rich gas mixture (99% C2H4) at 298 K, directly producing high-purity C2H4 gas at a rate of 3.95 cm3/g. Computational simulations showed that the strong affinity between C2H2 and the single-molecule traps of COF-1 were responsible for the excellent separation performance. COF-1 is also robust, providing a promising new strategy for the efficient removal of trace amounts of C2H2 in practical C2H4 purification.

Screening of novel halide perovskites for photocatalytic water splitting using multi-fidelity machine learning.

Photocatalytic water splitting is an efficient and sustainable technology to produce high-purity hydrogen gas for clean energy using solar energy. Despite the tremendous success of halide perovskites as absorbers in solar cells, their utility for water splitting applications has not been systematically explored. A band gap greater than 1.23 eV, high solar absorption coefficients, efficient separation of charge carriers, and adequate overpotentials for water redox reaction are crucial for a high solar to hydrogen (STH) efficiency. In this work, we present a data-driven approach to identify novel lead-free halide perovskites with high STH efficiency (ηSTH > 20%), building upon our recently published computational data and machine learning (ML) models. Our multi-fidelity density functional theory (DFT) dataset comprises decomposition energies and band gaps of nearly 1000 pure and alloyed perovskite halides using both the GGA-PBE and HSE06 functionals. Using rigorously optimized composition-based ML regression models, we performed screening across a chemical space of 150 000+ halide perovskites to yield hundreds of stable compounds with suitable band gaps and edges for photocatalytic water splitting. A handful of the best candidates were investigated with in-depth DFT computations to validate their properties. This work presents a framework for accelerating the navigation of a massive chemical space of halide perovskite alloys and understanding their potential utility for water splitting and motivates future efforts towards the synthesis and characterization of the most promising materials.

Supported Ruthenium Catalysts for Transformation of Aqueous Glycerol to Hydrogen Gas and Lactic Acid

Glycerol (GLY) is an attractive biobased platform chemical that produces precious fine chemicals with a wide range of industrial applicability and has the potential to produce high-purity H2 gas. Herein,...

Maximizing urea-/hydrazine-assisted electrolytic hydrogen production by defective nickel copper selenide nanostructures

Replacing the formidable oxygen evolution reaction (OER) with other oxidizable species is an appealing approach to attain highly efficient hydrogen (H2) generation with a lower potential. Accordingly, the kinetically favorable electrooxidation reaction of urea or hydrazine molecule can increase the return on energy profiteering and prevent pollutant emission. Thus, opening up an innovative direction to replace the sluggish OER and generate high-purity H2 gas via an energy-saving approach. Thus, constructing highly efficient and stable bifunctional electrodes/electrocatalysts is a key to realize economical and sustainable H2 production. In this work, we developed defect-enriched two-dimensional (2D) heterogeneous nickel copper selenide (D/Ni-Cu-Se) on a conductive Ni foam (NF) scaffold as an integrated bifunctional electrocatalytic electrode for energy-saving for H2 production. The self-supported D/Ni-Cu-Se/NF electrode with a regulated interfacial property and abundant metal defects is fabricated through a hydrothermal approach and a metal-defect engineering route. The thus-prepared electrode exhibits a high electrocatalytic performance for both hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) in a 1.0 M KOH electrolyte, achieving the catalytic current density of 10 mA cm−2 at a potential of 87.7 mV and 1.335 V vs. RHE, respectively. In relation, the two-electrode urea-water electrolyzer and hydrazine-water electrolyzer utilizing the bifunctional D/Ni-Cu-Se/NF as both the cathode and anode electrodes reveal a cell voltage of ∼ 1.395 V and 0.268 V at 10 mA cm−2 in 1.0 M KOH/0.33 M urea and 1.0 M KOH/0.25 M hydrazine, respectively, which is much less than that of conventional water electrolysis (1.572 V). The implemented electrolyzer systems consequently endow high long-term durability over 48 h of continuous electrolysis, indicating that the defect-rich D/Ni-Cu-Se/NF can serve as a potential bifunctional electrocatalyst with an outstanding electrolysis performance and excellent stability for H2 generation. Indeed, such a novel bifunctional electrode configuration and corresponding electrolysis performances are much desired for energy-saving electrolytic H2 production and pave the way for exploring highly efficient and robust electrodes.

Metal Doping in SrTiO3 Photocatalyst to Improve the Photocatalytic Activity for CO2 Conversion

Among various strategies toward finding new energy sources to replace conventional fossil fuels, photocatalytic conversion of CO2 into useful chemicals using water as an electron donor and a proton source has been increasingly attracting attentions because it can convert light energy to chemical energy. The photocatalytic conversion of CO2 involves photoabsorption (light harvesting), charge separation, and H2O oxidation, as well as the consumption of the photogenerated electrons for reduction. The evolution of H2 rather than CO is preferred when H2O is used as the electron donor, since the redox potential of CO2/CO (−0.51 V vs NHE, at pH 7) is more negative than that of H+/H2 (−0.41 V vs NHE, at pH 7) in an aqueous solution. Therefore, “high selectivity toward CO2 reduction” is one of the most important requirements for the photocatalytic system to achieve the CO2 conversion in water. Various mixed oxides including tantalum-based oxides, titanium-based oxides, gallium-based oxides, and niobium-based oxides were found to be excellent photocatalysts for the conversion of CO2 into CO in the presence of Ag cocatalyst. However, these materials show significant activity for CO evolution only when irradiated with deep region UV-light (λ < 300 nm). Therefore, a series of photocatalysts which can drive under the photoirradiation with UV-light at λ > 300 nm is strongly desired in the research area of the photocatalytic conversion of CO2. As continuous efforts to develop effective photocatalysts for the photocatalytic conversion of CO2 to CO in water, in this study, we investigated metal doping in the SrTiO3 photocatalyst, and evaluated the photocatalytic activity of the doped SrTiO3 photocatalysts for the conversion of CO2 to CO under UV-LED-light irradiation at 365 nm. SrTiO3 photocatalyst was prepared by a previously reported solid-state method (Journal of Power Sources, 2008, 183, 701−707). SrCO3 and TiO2 were ground for 15 min in a mortar and pestle, and the mixture was transferred to an alumina crucible to calcine at 1373 K for 10 h in air. The resulting powder was washed three times with hot ultrapure water and dried overnight at room temperature. M-doped SrTiO3 (M−SrTiO3, M = Al, Zn, Li, Mn, W, Ca, Y, and Mg) was synthesized via a flux method (ACS Applied Energy Materials, 2020, 3, 1468−1475.). Excess amount of SrCl2 flux was added to a mixture of the prepared SrTiO3 and a metal oxide as a doping source. The mixture was ground for 15 min in a mortar and pestle, transferred to an yttria crucible, and calcined at 1418 K for 15 h. The obtained powder was washed three times with hot ultrapure water, and dried overnight at 353 K. Photocatalytic activity of AgCo/M−SrTiO3 photocatalyst was evaluated by using an external-irradiation type reaction vessel in a quasi-flowing batch system. The photocatalyst powder was dispersed in 0.2 L of an aqueous NaHCO3 solution, and the dissolved air in the suspension was degassed by a flow of high-purity CO2 gas. CO2 gas was continuously bubbled into the reaction solution at a flow rate of 30 mL/min. The suspension was irradiated using a monochromatic UV-LED lamp at 365 nm (IRS-1000, CELL System Co., Ltd., Japan). The gaseous products in the outlet gas, e.g., CO, H2, and O2, were analyzed by gas chromatography (FID-GC with methanizer: CO, TCD-GC: H2 and O2). The attached figure shows a formation rate of CO (red), H2 (blue), and O2 (green) in the photocatalytic conversion of CO2 with H2O using the M−SrTiO3 photocatalysts (M = Al, Zn, Li, Mn, W, Ca, Y, and Mg) in the presence of AgCo cocatalyst. Zn−, Li−, Mn−, W−, Ca−, and Y−SrTiO3 showed extremely low photocatalytic activities for the conversion of CO2, whereas Al− and Mg−SrTiO3 produced certain amount of CO and O2. Mg−SrTiO3 exhibited the highest activity for CO2 conversion, which has been observed as a CO formation rate of ca. 20 μmol h−1. However, H2 evolution was thoroughly suppressed (0.055 μmol h−1) in the presence of AgCo/Mg−SrTiO3, where the selectivity toward CO evolution was higher than 99%. These results indicated that Mg-doping into SrTiO3 improved the photocatalytic activity for the conversion of CO2. Moreover, stoichiometric O2 evolution (8.9 μmol h−1) was found in the presence of AgCo/Mg−SrTiO3, suggesting that H2O acts as both an electron donor and a proton source for the photocatalytic conversion of CO2 in water. The apparent quantum efficiency (AQE) of AgCo/Mg−SrTiO3 photocatalyst in the photocatalytic conversion of CO2 under monochromatic UV-light irradiation (365 nm) was determined to be 0.05%. Figure 1

Water vapor concentration measurements in high purity gases by means of comb assisted cavity ring down spectroscopy

Water vapor concentration measurements in high purity gases by means of comb assisted cavity ring down spectroscopy

GC-ICP-MS for Process and Quality Control in Semiconductor Manufacturing

Gas chromatography (GC) coupled to inductively coupled plasma–mass spectrometry (ICP-MS) is a powerful and flexible analytical solution that is well-established for measuring organometallic compounds such as organotin, organomercury, and organolead in environmental samples, foodstuffs, and consumer products. GC–ICP-MS is also used for industrial applications, such as monitoring catalyst poisons and environmental contaminant elements in petrochemical processing and plastics manufacturing. The semiconductor industry uses a range of high-purity specialty gases and volatile liquids as precursors in wafer substrate production, and for processes such as plasma etching and deposition of thin films by chemical vapor deposition (CVD). Semiconductor manufacturers are constantly developing new integrated circuit (IC) chips with smaller sizes, higher speeds, lower power consumptions, and greater transistor densities. This trend means that contaminants must be controlled at even lower levels in process chemicals and precursors. In this article, we show how GC–ICP-MS, particularly using triple quadrupole or tandem ICP-MS (ICP-MS/MS), enables determination of the lowest levels of contaminants in the specialty gases and volatile liquids used to make the most advanced electronic devices.

Topologically Optimized Anode Catalyst Layers of Proton Exchange Membrane Water Electrolyzers

Climate change and global warming are ongoing global problems that will severely impact the environment if they are not addressed seriously. Replacing traditional fossil fuels with clean and sustainable energy from renewable energy sources, such as wind and solar, is necessary to reduce carbon emissions. However, these renewable energy sources are intermittent and thus require a system to help stabilize power generation. In this regard, hydrogen, the most sustainable form of clean energy, is proposed as a potential energy carrier. In such a system, water electrolyzers are used together with fuel cells. This allows hydrogen to be produced and stored in times of excess power generation. When there is demand and insufficient power generation, the produced hydrogen will be converted into electricity using fuel cells, resulting in a stable power grid. Although fuel cells have been improving significantly, water electrolyzers are an essential bottleneck for the widespread commercialization of the hydrogen economy.Due to the intermittency of renewable energy, the water electrolysis system applied to renewable energy should be able to turn on and off depending on renewable energy sources. As a result, low-temperature water electrolysis has gained widespread attention. Due to its potentially high-performance and high-purity hydrogen gas, the proton exchange membrane water electrolyzer (PEMWE) is one of the most promising technology for producing clean hydrogen. However, concerning widespread industrial use, PEMWE is affected by high costs due to its high loadings of expensive iridium-based catalysts. Therefore, it is necessary to improve its performance. As PEMWE technology grows, the working current density is inevitably higher. When the current density is higher, the amount of oxygen and hydrogen that must be removed from the cell must be more significant to deliver water to the reaction site efficiently. To meet the demands of the application, it is crucial to design an efficient electrode, especially at the anode, where the water must be supplied to the catalyst layer, and, at the same time, it is necessary to transfer oxygen gas from the reaction area to the flow channel.Topology optimization, an emerging tool to optimize physical systems, has recently been applied to systems with multi-physics. However, attempts to implement the approach in the system with reactions still lacked in the literature. Only a few studies were interested in utilizing such an approach in electrochemical energy device applications. Roy et al. [1] used topology optimization to develop the porous electrode. According to the findings, the developed electrode outperformed the traditional electrode. However, topology optimization is just a numerical approach. Our research group showed how a topologically optimized structure of porous reactors connected to the situation of the most uniform and minimum entropy generation [2]. To utilize topology optimization with PEMWE, a model for the anode catalyst layer is necessary. Although there are existing models to simulate the phenomena of PEMWE [3,4], to the best of our knowledge, studies have yet to look into how to model the phenomena inside the anode catalyst layer of the PEMWE.Therefore, the main goal of this study is to develop a model to simulate the physics of the anode and utilize it in topology optimization to search for the optimal structure of the anode catalyst layer. The optimization problem was formulated to maximize the cell performance by controlling the volume fractions of ionomer and catalyst materials. Figure 1a-c displays the heterogeneous structure obtained by topology optimization. The electrochemical reaction increased by approximately 40% compared to a case with the homogeneously distributed electrode. The topologically optimized structure was similar to the structure proposed by Dong et al. [5], where their ordered structure with Ir loading of 0.2 mg cm−2 can significantly decrease the overpotentials compared with conventional MEA with an Ir loading of 2 mg cm−2. Therefore, such a structure might be a way forward for high-performance PEMWE system. Acknowledgment The authors would also like to express their gratitude to Office of the Permanent Secretary, Ministry of Higher Education, Science, Research and Innovation (OPS MHESI) (Grant No. RGNS 65-084), Thailand Science Research and Innovation (TSRI) and King Mongkut’s University of Technology Thonburi. This work was partially supported by Grant-in-Aid for JSPS Fellows number 22J20603 and JSPS KAKENHI Grant number 21H04540 References [1] Roy, T., et al., Struct. Multidiscipl. Optim. 65 (2022) 171.[2] Charoen-amornkitt, P., et al., Int. J. Heat Mass Transf. 202 (2023) 123725[3] Lopata, J., et al., J. Electrochem. Soc., 168 (2021) 054518.[4] Lopata, J.S., et al., Electrochim. Acta, 424 (2022) 140625[5] Dong, S., et al., Nano Lett. (2022) (In Press) Figure 1