CO2 Atmosphere Research Articles

The impact of customized surface topography and porosity created by additive manufacturing technology on gingival fibroblasts.

The purpose of this study was to analyze gingival fibroblast proliferation on additively manufactured polymethylmethacrylate (PMMA) groups with different surface characteristics namely no treatment group (NTG) and customized 250µm diameter porosity (AM-250G) group. 3D-printed NTG was compared for its influence on growth of cells to a additively manufactured surface with porosity (AM-250G). For each group (NTG, AM-250G) 20 samples of material were tested. Fibroblast cells, at a concentration of 2.5×104cells/mL, were seeded into 48 plates separately into two groups (NTG, AM-250G). These were cultured in Dulbecco's Modified Eagle's Medium (DMEM) supplemented with 10% fetal bovine serum (FBS) at 37°C and 5% CO2 atmosphere. For cell proliferation MTT assay was conducted at 24, 48, and 72h. Cell proliferation was quantified through optical density (OD) measurements of the cell supernatant, and surface analysis was conducted using a scanning electron microscope (SEM). Data normality was confirmed by the Shapiro-Wilk test, with a significance level set at p<0.05. Statistical analysis was conducted using an independent Student's t-test at each time point. A significant difference in cell proliferation was observed at 24h, with the NTG group showing higher cell numbers compared to AM-250G group. Qualitative analysis of cell culture was performed using scanning electron microscopy to compare to the NTG and the porosity (AM-250G) groups after 24, 48, and 72h of fibroblast tissue attachment. No significant differences were observed between the groups at the 48 and 72-h intervals. At 24h, the NTG surface demonstrated superior cell proliferation compared to the surface with porosity (AM-250G). However, significant differences in cell growth on both materials at 48 and 72h, suggesting that both surface types eventually support similar levels of cell proliferation, with an increase of extensive spread and elongation of fibroblasts cells proliferation on the surface with porosity.

Promise and Peril: Stellar Contamination and Strict Limits on the Atmosphere Composition of TRAPPIST-1 c from JWST NIRISS Transmission Spectra

Abstract Attempts to probe the atmospheres of rocky planets around M dwarfs present both promise and peril. While their favorable planet-to-star radius ratios enable searches for even thin secondary atmospheres, their high activity levels and high-energy outputs threaten atmosphere survival. Here we present the 0.6–2.85 μm transmission spectrum of the 1.1 R ⊕, ∼ 340 K rocky planet TRAPPIST-1 c obtained over two JWST NIRISS/SOSS transit observations. Each of the two spectra displays 100–500 ppm signatures of stellar contamination. Despite being separated by 367 days, the retrieved spot and facula properties are consistent between the two visits, resulting in nearly identical transmission spectra. Jointly retrieving for stellar contamination and a planetary atmosphere reveals that our spectrum can rule out hydrogen-dominated, ≲300× solar metallicity atmospheres with effective surface pressures down to 10 mbar at the 3σ level. For high mean molecular weight atmospheres, where O2 or N2 is the background gas, our spectrum disfavors partial pressures of more than ∼10 mbar for H2O, CO, NH3, and CH4 at the 2σ level. Similarly, under the assumption of a 100% H2O, NH3, CO, or CH4 atmosphere, our spectrum disfavors thick, &gt;1-bar atmospheres at the 2σ level. These nondetections of spectral features are in line with predictions that even heavier, CO2-rich atmospheres would be efficiently lost on TRAPPIST-1 c given the cumulative high-energy irradiation experienced by the planet. Our results further stress the importance of robustly accounting for stellar contamination when analyzing JWST observations of exo-Earths around M dwarfs, as well as the need for high-fidelity stellar models to search for the potential signals of thin secondary atmospheres.

Mechanistic Insights into CO2 Adsorption of Li4SiO4 at High Temperature.

The development of materials with high adsorption capacity for capturing CO2 from industrial exhaust gases has proceeded rapidly in recent years. Li4SiO4 has attracted attention due to its low cost, high capture capacity, and good cycling stability for direct high-temperature CO2 capture. Thus far, the CO2 adsorption mechanism of Li4SiO4 is poorly understood, and detailed phase transformations during the CO2 adsorption process are missing. Here, aided by in situ X-ray diffraction and in situ Raman spectroscopy, we find that Li4SiO4 reacts with CO2 to form Li2SiO3 and Li2CO3 in CO2 atmosphere at 973 K, with no detectable involvement of crystalline Li2O during the adsorption process. Moreover, we observe a formation of stepped structures in the Li4SiO4 surface after CO2 adsorption by scanning electron microscopy. To illustrate the formation of stepped structures, we propose a modified double-shell mechanism, suggesting a possible two-dimensional nucleation and growth of Li2CO3. This work provides a deeper understanding of the CO2 adsorption mechanism and paves a way for further optimization of Li4SiO4-based adsorbents.

Experimental study on the influence of CO2 injection on coal spontaneous combustion characteristics and molecular functional groups

The study aims to investigate changes in the spontaneous combustion characteristics of coal and its microscopic reaction mechanisms in a CO2 atmosphere. Programmed heating experiments and thermogravimetric analysis were conducted to examine index gas and combustion parameters in both air and CO2 atmospheres. Molecular functional group changes were analyzed via in situ infrared experiments, and their correlation with index gases was assessed using the grey correlation method. The results revealed that CO2 injection during the initial heating stage increased the production of CO, CH4, and C2H4. However, beyond 160 °C, CO2 effectively reduced the oxidation activity of functional groups and significantly inhibited the production of indicator gas. The characteristic temperature range of coal samples exhibited a 'lag' phenomenon under the influence of CO2, resulting in a prolonged combustion stage with reduced mass loss and heat discharge. Following CO2 injection, the -OH concentration significantly decreased, while C=O gradually increased. Additionally, the concentrations of -COOH, aliphatic hydrocarbons, and aromatic hydrocarbons initially increased with rising temperature and then declined. The contribution of these groups to gas generation followed the sequence of oxygen-containing functional groups > aliphatic hydrocarbons > -OH > aromatic hydrocarbons.

Isolation and characterization of the dimetal decacarbonyl dication [Ru2(CO)10]2+ and the metal-only Lewis-pair [Ag{Ru(CO)5}2]+ .

The reaction of Ag+ with Ru3(CO)12 in a CO atmosphere under concommittant irradiation with UV-light yields a salt of the metal-only Lewis-pair [Ag{Ru(CO)5}2]+. Switching the silver cation for a more process-selective deelectronator yields a salt of the homoleptic transition metal carbonyl cation [Ru2(CO)10]2+, which fills the gap between the known cations [Ru(CO)6]2+ and [Ru3(CO)14]2+. The amount of π-backdonation in this series was studied by a combination of vibrational spectroscopy and computed relaxed force constants.

Development of a superhydrophobic and superoleophilic halloysite nanotube/phenyltriethoxysilane-coated melamine sponge sorbent material with high performance in supercritical CO2 atmosphere for the selective and effective oil spill cleanup and oil-water separation.

In this study, activated halloysite nanotube (HNT) and phenyltriethoxysilane (PTES) were utilized for the first time to fabricate modified HNT materials and coat them onto melamine sponge (MS) substrate in the supercritical carbon dioxide (scCO2) atmosphere. The successful coating of MS substrate was confirmed using SEM, EDS, XPS, and contact angle measurements. The drainage technique applied in the CO2 medium achieved the uniform coating of both the inner and outer surfaces of the MS. Water and oil contact angles of the fabricated sorbent material (MS-PTES) were measured as 167.1° and 0°, respectively. MS-PTES sorbent having superhydrophobic and superoleophilic properties demonstrated sorption capacities ranging from 47.6g/g to 132.2g/g for 13 different pollutants, including various petroleum products, oils, and organic solvents. Moreover, the MS-PTES sorbent material showed outstanding separation efficiency (99.99%) for the diesel-water mixture using a continuous separation process. It also displayed high selectivity for oil and organic solvent pollutants under acidic, saline, and alkaline conditions, along with excellent reusability, chemical stability, robustness, and mechanical flexibility. MS sorbent material coated with HNT-modified PTES nanoparticles, produced in the scCO2 atmosphere using the drainage technique, represents a promising solution for the removal of petroleum derivatives, oils, and organic solvents from water.

CoII-organic 'soft' metallo-supramolecular polymer nanofibers for efficient photoreduction of CO2.

Coordination-driven metallo-supramolecular polymers hold significant potential as highly efficient catalysts for photocatalytic CO2 reduction, owing to the covalent integration of the light harvesting unit, catalytic center and intrinsic hierarchical nanostructures. In this study, we present the synthesis, characterization, and gelation behaviour of a novel low molecular weight gelator (LMWG) integrating a benzo[1,2-b:4,5-b']dithiophene core with terpyridine (TPY) units via alkyl amide chains (TPY-BDT). The two TPY ends of the TPY-BDT unit efficiently chelate with metal ions, enabling the formation of a metallo-supramolecular polymer that brings together the catalytic center and a photosensitizer in close proximity, maximizing catalytic efficiency for CO2 reduction. The self-assembly of TPY-BDT with CoII ions yields a Co-TPY-BDT coordination polymer gel (CPG) with a 3D interconnected fibrous morphology, facilitating rapid electron transfer and efficient substrate diffusion. The Co-TPY-BDT CPG achieves an outstanding CO2 to CO conversion, producing 33.74 mmol g-1 of CO in 18 hours with ∼99% selectivity under visible light irradiation, using triethylamine (TEA) as a sacrificial electron donor. Remarkably, the Co-TPY-BDT CPG demonstrates significant catalytic activity even under low-concentration CO2 atmospheres (5% CO2, 95% Ar), producing 1.9 mmol g-1 of CO in 10 hours with a selectivity of 94.6%. Moreover, In situ diffuse reflectance Fourier transform (DRIFT) study, femtosecond transient absorption spectroscopy, and DFT calculations were employed to elucidate the CO2 to CO reaction mechanism.

Pre-Melting-Assisted Impurity Control of β-Ga2O3 Single Crystals in Edge-Defined Film-Fed Growth.

This study reveals the significant role of the pre-melting process in growing high-quality (100) β-Ga2O3 single crystals from 4N powder (99.995% purity) using the edge-defined film-fed growth (EFG) method. Among various bulk melt growth methods, the EFG method boasts a fast growth rate and the capability of growing multiple crystals simultaneously, thus offering high productivity. The pre-melting process notably enhanced the structural, optical, and electrical properties of the crystals by effectively eliminating impurities such as Si and Fe. Specifically, employing a 100% CO2 atmosphere during pre-melting proved to be highly effective, reducing impurity concentrations and carrier scattering, which resulted in a decreased carrier concentration and an increased electron mobility in the grown Ga2O3 single crystals. These results demonstrate that pre-melting is a crucial technique for substantially improving crystal quality, thereby promising better performance in β-Ga2O3-based device applications.

BIOTECHNOLOGICAL SYSTEM FOR THE SEARCH OF SUBSTANCES WITH POTENTIAL ACTIVITY AGAINST CORONAVIRUS

Aim. Development of a biotechnological system based on a non-pathogenic coronavirus strain for humans and a sensitive cell line to the selected strain aimed at identifying compounds with potential antiviral activity. Methods. The study was conducted on the cell lines CEF, CEFs, and ВНК-21, which are sensitive to the avian infectious bronchitis virus (IBV). Cell cultivation was performed in flasks and microplates with adhesive surfaces at 37 °C in a 5% CO2 atmosphere. To detach the cells from the growth surface, a Versene solution (0.02%) was used, and for trypsinization of CEF, a trypsin solution (0.25%) was applied. Growth media for all cell cultures were prepared based on a mixture of RPMI-1640 and DMEM in a 1:1 ratio, supplemented with 5% fetal serum. Results. The adaptation of the model virus IBV strain H120 to cultivation in ВНК-21 cell cultures was carried out using intermediate CEF and CEF cultures. In ВНК-21 cells, IBV induced a pronounced cytopathic effect and demonstrated high infectious titers, reaching 5.5 lg TCID50/mL. The use of intermediate CEF and CEF cell cultures facilitated the gradual adaptation of the virus to the new cultivation conditions due to the antigenic affinity between chicken embryo fibroblast cells and avian embryos. Conclusions: As a result of the conducted research, the vaccine virus IBV H-120 was successfully adapted to cultivation conditions in ВНК-21 cell cultures, using primary trypsinized chicken embryo fibroblast cells as an intermediate system. The obtained system "ВНК-21 cell culture + IBV H-120," cultivated at 37 °C in a 5% CO2 atmosphere, can be recommended for use in further biotechnological and virological studies, particularly for evaluating the antiviral activity of potential drugs against coronaviruses.

Design and Preparation of Activated Carbon with High Specific Surface Area and Porosity Through an Organic Activator Coupled with CO2 Activation

AbstractThe advancement of effective techniques for the production of activated carbon has been a prominent focus of research. Herein, this work designs and successfully prepares a nontoxic, environmentally friendly organic activator on the surface of carbon materials through in situ organic fermentation treatment method. The production of activated carbon via this novel organic activator is at a temperature of 850 °C under CO2 atmosphere for an activation time of 90 min, showing a specific surface area (SBET) of 1354 m2 g−1, an adsorption capacity of iodine (QI) of 1195 mg g−1, and a total pore volume (Vtot) of 0.855 cm3 g−1. Compared to the activated carbon prepared at high temperature under pure CO2, these results represent increases of 69.67%, 53.01%, and 93.44% in SBET, QI, and Vtot values, respectively. By means of thermogravimetric (TG) analysis and simultaneous thermal analysis‐Fourier transform infrared spectroscopy‐gas chromatography/mass spectrometry a suggested activation process and mechanism of the novel organic activators is proposed. This organic activator is not only used for semi‐coke (SC) based activated carbon preparation and saturated activated carbon (SAC) regeneration, but also attracts other industrial activated carbon production.

Synergistic atmospheric influence on the co-pyrolysis of antibiotic sludge and waste bicycle tires: Optimal drivers, products, and pathways

Effective management of antibiotic sludge (AS) is essential for disease prevention. This study investigated the co-pyrolysis of AS with polyurethane (PU) and rubber tires (RT), focusing on its key drivers, synergies, resulting products, and atmospheric (N2 versus CO2) dependency. Composite pyrolysis index indicated superior co-pyrolysis properties of AS with PU or RT in the CO2 atmosphere compared with those in the N2 atmosphere. The strongest synergistic effect occurred at an optimal ratio of 75 % AS to 25 % PU (AP31) or 25 % RT (AR31), regardless of the atmosphere. Real-time gas analysis revealed greater product diversity in N2 than in CO2, with AS-derived products predominating. The co-pyrolysis altered AS nitrogen groups, promoting pyrrolic-N and pyridinic-N formation, and accelerated organic sulfur decomposition. Experimental results combined with univariate and multivariate joint optimizations identified the co-pyrolysis pathways of AP31 (650 – 800 °C) and AR31 (600 – 800 °C), respectively, in the CO2 atmosphere as synergistically optimal for maximizing resource recovery while minimizing waste and pollutant generation. This study provides actionable insights into the synergistic co-pyrolysis of AS with PU or RT, facilitating optimized gas emissions, energy recovery, and resource reuse.

Stereoselective chemical N-glycoconjugation of amines via CO2 incorporation

Chemical N-glycoconjugation can provide a unique way to tailor the properties of the ubiquitous amines for further expending their diverse functions and applications. Nevertheless, effective methodology for glycoconjugation of amines remains largely underdeveloped. Inspired by a biotransformation pathway of amine-containing drugs in vivo, we have developed an effective protocol that enables one-step chemical N-glycoconjugation of amines in high stereoselectivity under mild conditions. This protocol involves conversion of the amine moiety into the corresponding carbamate anion under CO2 atmosphere and a subsequent SN2 type reaction with glycosyl halides. This work provides an example of using CO2 as the coupling unit in chemical glycoconjugation reactions. A case study on the resulting N-glycoconjugates of Crizotinib, an anticancer drug, demonstrates a quick cleavage of the glucosyl carbamate linkage, testifying that this N-glyconjugation method could serve as a general approach to procure novel prodrugs.

Structure-Reactivity- and Modelling-Relationships during Thermal Annealing in Biomass Entrained-Flow Gasification: The Effect of Temperature and Residence Time

Biomass entrained-flow gasification enables the sustainable production of chemicals and liquid fuels. For reliable and accurate gasifier operation and design, the analysis of biomass char reactivity represents one of the key studies. Therefore, the annealing-induced char reactivity loss needs to be investigated for biogenic feedstocks from microscopic to reactor level. In the present work, the influence of pyrolysis temperature and particle residence time on solid digestate char reactivity and structure is studied. Several char types are prepared in a pressurized entrained-flow reactor between 1200 °C and 1600 °C with varying residence times between 0.4–2.4 s. Isothermal char reactivity in O2 and CO2 atmosphere is measured by TGA and reactivities are determined. Strong char deactivation between 1200 °C and 1400 °C resulted from severe heat treatment, especially toward the CO2 reaction. At 1600 °C, the influence of residence time becomes less relevant since all measured reactivities are comparably low. Experimental data are fitted to a coal deactivation model and verified for biogenic residues with very good agreement. The results are further corroborated by char structure analysis using FT-IR, XRD, Raman spectroscopy, SEM-EDX and ETV-ICP-OES. The decrease in char reactivity is mainly attributed to graphitization and the formation of aromatic ring structures. Char deactivation is further promoted by the loss of catalytic mineral matter and by high concentrations of inhibiting elements like phosphorus.

Effect of irradiation on Co0.72Sr0.07Ni0.21Fe2O4 ferrite nanoparticles and their catalytic efficiency in water treatment

This study investigates the magnetic, thermal, and electrical properties of Co0.72Sr0.07Ni0.21Fe2O4 ferrite nanoparticles under different conditions, including as-prepared, irradiated (at a dose of 100 kGy in CO2 atmosphere), and aged (at 1000°C). The magnetic properties are analyzed using M-H loops, revealing that the aged sample exhibits the highest magnetization values. The observed decrease in magnetization after irradiation and increase after aging is consistent due to the presence of a new phase (γ-FeOOH) in the irradiated sample that XRD confirms. Electrical conductivity measurements demonstrate that the aging sample exhibits the highest electrical conductivity due to increased grain boundaries, while the irradiated sample shows increased conductivity attributed to oxygen vacancies. As well as the nanocomposite of PVP and Co0.72Sr0.07Ni0.21Fe2O4 nanoparticles aged (at 1000°C) is found to be effective in degrading the Toluidine Blue (TB) dye through catalytic oxidation and photodegradation mechanisms. The catalytic degradation of TB dye provides valuable insights into the potential application of these ferrite nanoparticles in environmental remediation and wastewater treatment. Also, nanocomposite demonstrated significant antimicrobial activity against five pathogenic bacterial strains commonly found in contaminated water, with superior effectiveness against Gram-negative bacteria, particularly Salmonella enterica and Pseudomonas aeruginosa, suggesting its potential as an effective water treatment agent. The novelty and the aims are to analyze the changes in magnetization and conductivity of the nanoparticles under different conditions, including as-prepared, irradiated, and aged samples. Additionally, the catalytic efficiency of the aged nanoparticles in degrading Toluidine Blue (TB) dye is examined, providing insights into their potential application in environmental remediation and wastewater treatment.

A sustainable process for Pb, Zn, and Fe from copper slag by salt roasting-magnetization roasting-magnetic separation

Copper slag is a byproduct in the copper smelting process, rich in Pb, Zn and Fe and is an important recyclable secondary resource. In this study, Pb, Zn and Fe in copper slag were successfully recovered by the novel process of salt roasting-magnetization roasting-magnetic separation. With the addition of 12.5 % CaCl2 and 20 % CaO, copper slag was roasted at 1000 ℃ under the CO2 atmosphere, and the recovery rate of Pb, Zn and Fe was up to 99.72 %, 75.31 % and 80.32 % respectively. Hence, this method of salt roasting-magnetization roasting-magnetic separation provides a new approach to the comprehensive utilization of copper slag.

Effect of CO2 and HClO4 Concentrations on CO2 Reduction Reaction Intermediates at Pt Polycrystalline Electrode

Introduction To achieve carbon neutrality, it is necessary to apply practical CO2 reduction and effective utilization technologies. Recently, there has been an expectation for the electrochemical reduction of CO2 (CO2 Reduction Reaction: CO2RR) using electricity derived from renewable energy. CO2RR with low overvoltage using a polymer electrolyte membrane is an actively researched next-generation technology. It is important to improve Faraday efficiency and analyze CO2RR mechanisms. Cu electrode catalysts are commonly used for CO2RR due to their high Faraday efficiency. However, a challenge remains in reducing the overvoltage of CO2RR to the level of hydrogen generation in normal PEM water electrolysis. Although Pt electrode catalysts have a significantly lower Faraday efficiency for CO2RR than Cu electrode catalysts, they have been reported to have low overvoltage1. Recent research has shown that the presence of water in the supplied CO2 and the alloy composition enhances Faraday efficiency2,3. To reduce CO2RR overvoltage, this study utilized a Pt electrode. Successful CO2RR requires the electrode catalyst surface to have coexisting surface-adsorbed hydrogen (Had) and CO2RR intermediate (COad). This study investigates the effect of electrolyte pH (perchloric acid concentration) and CO2 concentration on the COad and Had, utilizing a Pt polycrystalline electrode. Experimental Electrochemical measurements were carried out using a three-electrode cell. The counter electrode was a Pt mesh, and the reference electrode was a reversible hydrogen electrode (RHE). The working electrode was a φ3 mm Pt polycrystalline disk electrode that was mirror-polished with a 0.05 μm alumina suspension. Cyclic voltammetry (CV) measurements were performed with a sweep range of 0.05-1.0 V vs. RHE and a sweep rate of 50 mV/s or 10 mV/s. The results of the CV measurements are presented after IR correction. To evaluate CO2RR, the concentration of HClO4 was adjusted to 0.01-0.5 M as the electrolyte. The CO2 concentration was varied from 0-100 vol% and bubbled for 30 minutes before the CV measurements. For the electrochemical evaluation of CO2RR, the initial potential was kept at 0.05-0.4 V for 5 minutes before the CV measurements, and then the CV measurement was performed. Results and Discussion 1. CO2RR potential in HClO4 electrolyte saturated with 100% CO2 Figure 2 shows the results of CV measurements performed after holding the initial potentials at 0.05-0.4 V for 5 minutes before starting the CV measurements. The bubbling CO2 concentration during the measurements was 100%, and the HClO4 concentration was 0.1 M. In comparison to the CV peaks observed in the N2 atmosphere, peaks where the CO2RR reduction intermediate (COad) are reoxidized are observed at 0.6-0.7 V in the 100% CO2 atmosphere. The charge of these COad peaks remain constant at low initial holding potentials. However, it decreases significantly as the initial holding potential approaches 0.4 V. Under the measurement conditions of 100% CO2 atmosphere and 0.1 M HClO4 concentration, it can be seen that CO2 is reduced on the Pt electrode at a potential positive of 0 V vs. RHE because the COad peaks are seen between 0.05-0.3 V of the initial holding potentials. 2. Dependence of COad peak on bubbling CO2 concentration CV measurements were performed by changing the CO2 concentration bubbled in 0.1 M HClO4. Figure 3 shows the results of CV measurements at an initial potential hold of 0.05 V, where the CO2 concentration was changed from 0% to 100%. In the Hupd region, the amount of charge decreases in the CO2 atmosphere because CO2 is already surface-adsorbed as COad at 0.05 V, and the decrease is larger as the CO2 concentration increases. It is evident that the peaks of COad increase as the concentration of CO2 increases. Additionally, when the CO2 concentration is low, the peaks of COad are divided into at least two peaks, indicating the generation of COad with different adsorption structures during CO2RR. As the CO2 concentration increases, the peaks of COad appearing on the low potential side also increase. Additionally, the ratio of COad with different adsorption structures might change depending on the CO2 concentration bubbled. Acknowledgements This work was supported by JSPS KAKENHI Grant Number JP23K13835 and TEPCO Memorial Foundation.

(Invited) Preparation of Aucu Alloy Nanoparticles Via Ionic Liquid/Metal Sputtering for Electrocatalytic CO2 Reduction

Development of highly active electrocatalysts for carbon dioxide reduction has been intensively investigated for the efficient utilization of CO2 and the lowering of electric energy consumption. Among various strategies, alloy nanoparticles (NPs) have attracted significant interest due to their tunable catalytic properties, which can be adjusted by altering their chemical composition and particle size. Recently, we reported novel preparation methods of metal nanoparticles through the sputter deposition of metals onto room-temperature ionic liquids (RTILs), a technique we termed “RTIL/metal sputtering technique”. This method enabled the formation of metal and alloy NPs, such as Au, Ag, Pd, Pt, AuAg, AuCu, AuPt and AuRh,(1-6) with sizes in the nanometer ranges, in the absence of additional stabilizing agents. Here we report the preparation of AuCu alloy NPs via RTIL/metal sputtering and evaluate their electrocatalytic activity for CO2 reduction as a function of the alloy composition.The simultaneous sputtering of Au and Cu onto RTILs produced AuCu alloy NPs with the size ranging from 3 to 4 nm. Subsequent loading of these sputter-deposited AuCu NPs in RTIL on carbon black powders (CB) not only increased the AuCu NP size to 3-7 nm but also facilitated alloying between Au and Cu. The chemical composition of AuCu NPs was controlled by changing the area fraction of Au plates in Au-Cu binary targets used for sputtering. The XRD analysis revealed that thus-obtained AuCu NPs had the fcc structure, in which each peak shifted to a lower angle with an increase in the Au fraction.The prepared AuCu/CB powers were immobilized on glassy carbon electrodes and used for the electrocatalyst for CO2 reduction in a 0.5 M KHCO3 aqueous solution. Cyclic voltammetry revealed that cathodic currents were observed at potentials more negative than -1.2 V, with the current intensity being higher under a CO2 atmosphere compared to an N2 atmosphere. This confirms the CO2 reduction activity of AuCu nanoparticles. Constant potential electrolysis was carried out at -2 V vs. Ag/AgCl in a CO2 atmosphere. As CO2 reduction products, CO and HCOOH were formed. The selectivity of these products was remarkably influenced by the composition of AuCu alloy NPs: The HCOOH selectivity increased with a higher Cu ratio, while the CO selectivity showed a volcano-type relationship, reaching an optimum at the Au fraction in NPs of ca. 0.8. H2 was also produced as a byproduct, with its selectivity being minimized at the Au fraction of 0.6-0.9. In conclusion we demonstrated the importance of alloy composition in optimizing the electrocatalytic performance of AuCu NPs for CO2 reduction. References T. Torimoto, et al., Appl. Phys. Lett. 89, 243117 (2006) .K. Okazaki, et al, Chem. Commun. 691-693 (2008) .M. Hirano, et al., Chem. Chem. Phys. 15, 7286-7294 (2013).S. Suzuki, et al., 44, 4186-4194, (2015).S. Suzuki, et al., CrystEngComm, 14, 4922-4926 (2012)K. Akiyoshi, et. al, Phys. Chem. Chem. Phys., 24, 24335 (2022) .

(General Student Poster Award Winner, 3rd Place) Solar CO2 Reduction to Form Green Syngas Employing a Black Cu3VS4 Photocathode Utilizing a Whole Range of Visible Light

A photoelectrochemical cell as artificial photosynthesis is an attractive system for solar CO2 reduction in H2O to produce a mixture gas of H2 and CO, so called “green syngas.” Development of photocathodes with the response to long wavelength visible light and high selectivity for CO formation is necessary in terms of efficient solar energy conversion. Recently, we reported that a powder-based Cu3VS4 black photocathode was active for solar H2 production utilizing a whole range of visible light.1 This photocathode was a Cu(Ⅰ)-containing metal sulfide, which was a suitable material for solar CO2 reduction.2 Therefore, solar CO2 reduction using a Cu3VS4 photocathode is expected to be achieved by constructing a photoelectrochemical cell. In the present study, we developed a new photoelectrochemical cell employing a black Cu3VS4 photocathode for solar CO2 reduction to produce green syngas.The black metal sulfide was prepared by a solid-state-reaction (SSR) and a flux method using a mixture of chloride salts (flux).1 The powder-based Cu3VS4 photocathode was fabricated by a particle transfer method contacted with deposited Au as a conductive layer.1,3 A sputtered Au cocatalyst was loaded on the photocathode. Photocathodic properties were measured using a three-electrode system under CO2 atmosphere. The photocathode was irradiated with visible light and simulated sunlight using a 300 W Xe-lamp attached with a long-pass filter and a solar simulator, respectively. The amounts of evolved H2, CO and O2 were determined using an online gas-chromatograph.Single particle layers with Cu3VS4 (SSR, flux) particles were observed on the photocathodes by SEM images. Large Cu3VS4 (SSR) particles with a size of 5-8 µm contacted with deposited Au layer roughly, while fine contacts with the Au layer were constructed due to small Cu3VS4 (flux) particles with a size of 200-800 nm. The results of SEM-EDS mappings and XPS measurements indicated that the surfaces of Cu3VS4 (SSR, flux) particles were mostly covered with a sputtered Au cocatalyst and a deposited Au layer. Photoelectrochemical CO2 reduction to form a green syngas using the Cu3VS4 photocathodes proceeded under visible light irradiation. During the reaction, green syngas including 24% of CO was successfully obtained using a Cu3VS4 (flux) photocathode. The comparatively high selectivity for CO evolution was due to the 2-type Au functioning as efficient active sites. It was notable that a stability of the photocurrent was drastically improved by employing fine Cu3VS4 (flux) particles instead of large Cu3VS4 (SSR) particles. XRF analysis and SEM images of the photocathode revealed that a large amount of the Cu3VS4 (SSR) particles were peeled off from the Au-deposited substrate after the reaction, while the Cu3VS4 (flux) particles were not. Therefore, the good stability of the photocurrent on the Cu3VS4 (flux) photocathode was due to the good contacts between the photocatalyst particles and the deposited Au layer. The onset of the IPCE agreed well with that of an absorption edge of Cu3VS4, reaching up to 820 nm. In other words, the black photocathode produced a green syngas utilizing a whole range of visible light. Finally, a photoelectrochemical cell consisting of the Cu3VS4 photocathode and a BiVO4 photoanode was constructed. Solar CO2 reduction proceeded applying the bias at 1.0 V between the photocathode and the photoanode. H2 and CO steadily evolved accompanied by O2 evolution from water, reaching unity of the ratio of reacted electrons to holes. These results indicated that solar CO2 reduction to form a green syngas using the Cu3VS4 photocathode was successfully achieved utilizing water as an electron donor.Thus, it was concluded that a Cu3VS4 photocathode with the high selectivity for CO evolution and the response to long wavelength visible light was successfully developed. Our findings will contribute to development of a photoelectrochemical cell for an efficient solar energy conversion and a sustainable carbon neutrality.[1] H. Fukai, K. Nagatsuka, Y. Yamaguchi, A. Iwase, A. Kudo, ECS J. Solid State Sci. Technol. 2022, 11, 063002.[2] S. Yoshino, T. Takayama, Y. Yamaguchi, A. Iwase, A. Kudo, Acc. Chem. Res. 2022, 55, 966.[3] T. Minegishi, N. Nishimura. J. Kubota, K. Domen, Chem. Sci. 2013, 4, 1120. Figure 1

Acetylene Synthesis from CO2 and H2O Via Electrochemical Formation of Metal Carbides in High-Temperature Chloride Melt

Research on CO2 conversion into valuable materials has attracted much attention, aiming to realize carbon neutrality and carbon-negative emission technology. It has been reported that the unique physicochemical properties of high-temperature molten salt, such as high conductivity and wide electrochemical window, make it possible to obtain solid carbon directly from CO2 and metal carbides.In this study, we focused on the electrochemical formation of CaC2 from CO2 in high-temperature chloride melt. CaC2 is the raw material for acetylene, the starting material for various chemical products. This study demonstrated the selective formation of CaC2 from CO2 by an electrochemical process in NaCl-KCl-CaCl2-CaO melt at 823 K to produce C2H2 with high current efficiency. When the inert material for oxygen evolution in the high-temperature melts was used as the anode, the formation of acetylene and oxygen from carbon dioxide and water can be realized as the total reaction.2CO2 + H2O → C2H2 + 5/2O2 On the metal cathode, the CaC2 was formed through two reactions: the carbon electrodeposition from CO2-derived CO3 2− (Step 1) and the electrochemical reduction of Ca(II) ion on the carbon (Step 2). These two reactions could be controlled by conducting potentiostatic electrolysis under CO2 and Ar atmospheres, resulting in acetylene synthesis with a maximum current efficiency of 92%. The electrolysis on carbon electrodes revealed that the higher the crystallinity of carbon, the more selectively CaC2 was formed. The CaC2 formation was induced by the reduction of Ca(II) ions on the basal plane of the graphite layer rather than the edge plane. The unique interfacial phenomenon between high-temperature melt and a carbon electrode surface will contribute to realizing a highly efficient CO2 conversion process to acetylene. It was found that the electrochemical formation of CaC2 tends to proceed at the basal plane of the graphite layer. This reaction mechanism is entirely different from the interlayer reactions that tend to occur in LIBs and is unique to this electrolytic system at the carbon/molten salt interface. The obtained data will provide a highly efficient process for CO2 resource conversion and physicochemical insights into new carbon surface reactions.

Reduction Kinetics of Non-spherical Hematite Particle in CO Atmosphere with Multi-step Limited Reaction Zone Modification

Reduction Kinetics of Non-spherical Hematite Particle in CO Atmosphere with Multi-step Limited Reaction Zone Modification