Evolution Of Carbon Monoxide Research Articles

0D/2D S-scheme heterojunction of cadmium selenide and covalent triazine frameworks with enhanced photocatalytic activity for hydrogen evolution, carbon dioxide reduction and terpene dehydrogenation

The step-scheme (S-scheme) heterojunction shows the merits of controlling the directional transfer of photogenerated charge carriers and realizing a strong redox potential for photocatalytic hydrogen evolution and carbon dioxide reduction. In this paper, a zero/two-dimensional (0D/2D) S-scheme heterojunction composed of cadmium selenide quantum dots and covalent triazine frameworks (CdSe/CTF) is designed and fabricated by an electrostatic self-assembly approach. Compared with pristine CTF and CdSe quantum dots, the photocatalytic activities of CdSe/CTF composites for hydrogen evolution, carbon dioxide reduction and terpene oxidation are significantly enhanced. The hydrogen evolution rate of CdSe/CTF hybrid photocatalyst immobilized with platinum nanoparticles as cocatalyst reached 19.0 mmol g−1 h−1 under visible-light irradiation, and the apparent quantum yield is 9.8 % at 420 nm. The CdSe/CTF hybrid also exhibited more superior photocatalytic activity in carbon dioxide reduction with a carbon monoxide evolution rate of 1.48 mmol g−1 h−1, and presented higher photocatalytic reactivity in the selective oxidation of α-terpinene to p-cymene. The remarkable enhancement of photocatalytic performance for CdSe/CTF composite is mainly attributed to the facilitated separation and transfer of photoexcited charge carriers of 0D/2D S-scheme heterojunction. This work provides an in-depth insight of utilizing semiconducting polymers as a suitable platform to sustainably transform inexhaustive solar energy to storable chemical energy.

Effect of Alkali and Alkaline Earth Metallic Species on Gas Evolution and Energy Efficiency Evolution in Pyrolysis and CO2-Assisted Gasification

Abstract In this study, the same moles of alkali and alkaline earth metallic species were introduced into pine wood to investigate their effects on biomass pyrolysis and carbon dioxide-assisted gasification. First, thermogravimetric analysis was conducted to examine the pyrolytic behavior of pine wood loaded with alkali and alkaline earth metallic species. A semi-batch fixed bed platform was used to quantify gaseous product parameters, including gas mass flowrate, gas yield, recovered energy, energy efficiency, and net carbon dioxide consumption. Thermogravimetric results indicated that the loading of alkali and alkaline earth metallic species promoted the thermal decomposition of pine wood at low temperatures, but an inhibitory effect was observed at high temperatures. In terms of pyrolysis, adding alkaline earth metals increased syngas yields, and recovered energy, as well as energy efficiency, whereas alkali metals had the opposite effect. For the gasification, the loading of alkali metals showed a stronger catalytic than the pine wood loaded with alkaline earth metals. Based on the evolution of carbon monoxide, the effects of alkali and alkaline earth metallic species on enhancing the biochar's gasification reactivity were in the sequence of sodium > potassium > calcium > magnesium. In addition, the addition of alkali metals exhibited a stronger capacity for carbon dioxide consumption, which contributed to the management of the greenhouse gas. Considering only energy efficiency, adding alkaline earth metals in biomass pyrolysis is an optimal choice due to the higher overall energy efficiency obtained in less time.

Photocatalytic selective C-C bond cleavage of biomass-based monosaccharides and xylan to co-produce lactic acid and CO over an Fe-doped GaN catalyst

The utilization of photocatalysis for the simultaneous production of valuable fine chemicals and fuels from biomass-derived feedstocks holds significant promise; however, its practical implementation remains constrained. In this study, we present the development of an Fe-doped gallium nitride (GaN) catalyst treated by calcination (Fe@GaN-X) for the selectively conversion of biomass-based monosaccharides and xylan into lactic acid and carbon monoxide (CO). Fe@GaN-400 exhibited broader visible light absorption, lower resistance, and reduced photoluminescence intensity in comparison to pristine GaN, thereby affording exceptional photocatalytic activity (lactic acid yield: 71.38%; CO evolution rate: 385.74 μmol g−1 h−1). When monosaccharides and xylan were used as substrates, the Fe@GaN-400 system demonstrated outstanding photocatalytic activity, particularly in the case of xylan system (CO evolution rate = 923.21 μmol g−1 h−1). Additionally, the experimental results revealed the generation of distinctive reactive species, encompassing holes (h+), superoxide anion (·O2-), hydroxyl radical (·OH) and singlet oxygen (1O2) within this catalytic system. Remarkably, the ·O2- and h+ exhibit heightened selectivity towards CO and lactic acid, respectively. This work establishes a novel pathway for the co-production of fine chemicals and fuels through the photocatalytic conversion of biomass.

Kinetic Study of Heterogeneous Photocatalytic CO2 Reduction: Development of a General Formula for Relations between Activity and Reaction Conditions

Recently, the development of technologies for CO2 emission reduction has been extensively investigated to achieve the global 2 °C climate stabilization target. This study demonstrates that the photocatalytic activity and selectivity toward carbon monoxide (CO) evolution for the selective photocatalytic conversion of CO2 to CO, using H2O as an electron donor, are significantly dependent on the reaction conditions, such as additive concentration, CO2 partial pressure, and reaction temperature. The systematic experiments performed in this study revealed that the CO formation rate was proportional to the increase in the CO2 partial pressure and inversely proportional to the proton (H+) concentration in the reaction solution. Based on these results, a quantitative expression for the formation rate of CO with CO2 partial pressure and pH as variables was developed using kinetics, considering the equilibria of surface hydroxyl groups. This study confirmed that the derived mathematical expressions matched well with the experimental results of three different photocatalysts, whose activities and selectivities were completely different. Moreover, based on these expressions, a theoretical method is proposed to determine the kinetic constant and activation energy for the reduction of adsorbed CO2 molecules. The developed mathematical expression for photocatalytic CO2 conversation in water contributes to the development of CO2 recycling technologies.

Virtuous utilization of carbon dioxide in pyrolysis of polylactic acid

Polylactic acid has been adopted as a strategic alternative to petroplastics because of its biodegradability. The waste generation rate could be proportional to its use, considering the short lifespan of polylactic acid. However, a practical disposal or recycling protocol for polylactic acid waste has not yet been developed. Thus, this study suggests a promising thermochemical platform for valorizing polylactic acid waste into energy resources (syngas). Specifically, carbon dioxide-assisted pyrolysis has been suggested to impart environmental features to polylactic acid disposal. Before the pyrolysis tests, the polylactic acid waste sample was characterized by Fourier transform-infrared spectrometer and thermogravimetric analyses, which showed that polylactic acid contained a substantial amount of additives and impurities (∼13 wt%). The impurity containing polylactic acid was converted into pyrogenic gases and biocrudes through pyrolysis process. The pyrolysis was performed under carbon dioxide condition and led to enhanced carbon monoxide formation from simultaneous homogeneous reactions between CO2 and volatile organic compounds evolved from thermal degradation of polylactic acid. CO2 was reduced and the volatile compounds were oxidized. The evolution of carbon monoxide from pyrolysis under carbon dioxide condition was 2 times higher than that from nitrogen condition. The concentration of carbon monoxide from the pyrolysis of polylactic acid waste with respect to plastics and biomass was considerably higher. This observation indicates that the susceptibility of carbon dioxide to the homogeneous reaction is highly sensitive. To seek a way to hasten the homogeneous reaction, silica supported nickel catalysts were applied. The evolution of carbon monoxide from catalytic pyrolysis under carbon dioxide condition was 4.5 times higher than inert atmosphere.

Potassium and Sulfur Dual Sites on Highly Crystalline Carbon Nitride for Photocatalytic Biorefinery and CO2 Reduction

The co-production of high-value-added chemicals and fuels by coupling biomass photooxidation with carbon dioxide (CO2) photoreduction has attracted wide interest. Nevertheless, there still lacks comprehensive studies. Herein, we synthesized a highly crystalline carbon nitride with potassium and sulfur dual sites (K/S@CN-x) by a salt-template-assisted incorporation method. The incorporation of K/S and high crystallinity resulted in the photocatalytic performance by significantly enhancing the visible-light absorption and accelerated photogenerated charge separation/transfer. Thus, in K/S@CN-0.5, the carbon monoxide (CO) evolution rate (16.27 μmol g–1 h–1) and lactic acid yield (78.07%) were 4.80 times and 1.15 times, respectively, those of CN. Furthermore, density functional theory calculations were performed to investigate the role of K and S dual sites in photocatalytic reactions. Our findings provide unique routes for synthesizing highly crystalline photocatalysts with dual sites and demonstrate the feasibility of photocatalytic selective oxidation of biomass coupled with CO2 reduction.

Optimized full CO2 photoreduction process by defective spinel atomic layers.

The impact of defects on the carbon dioxide (CO2) photoreduction property is sometimes contradictory. Herein, we employ two-dimensional materials, possessing high-density and high-uniformity active sites, as ideal models to thoroughly investigate the influence of defects on three main processes during CO2 photoreduction. As an example, oxygen-deficient ZnGa2O4 atomic layers are successfully fabricated, verified by the electron spin resonance spectra, X-ray photoelectron spectroscopy spectra and X-ray absorption near edge structure spectra. UV-vis diffuse reflectance spectra, photoluminescence spectra, surface photovoltage spectroscopy, N2 adsorption-desorption isotherm plots and density functional theory calculations indicate that the presence of oxygen defects helps to expand the photoabsorption, accelerate the carrier separation, and enhance the CO2 adsorption and protonation process. As a result, the carbon monoxide evolution rate of the defective ZnGa2O4 atomic layers was approximately 88 times higher than that of the ZnGa2O4 atomic layers under visible light irradiation. In other words, this work discloses that the introduction of defects on photocatalysts allows the optimization of the three primary processes, thus obtaining boosted CO2 photoreduction performance.

Electrocatalytic CO 2 Reduction over Bimetallic Bi-Based Catalysts: A Review

Electrocatalytic CO ₂ Reduction over Bimetallic Bi-Based Catalysts: A Review

Depletion of gaseous CO in protoplanetary disks by surface-energy-regulated ice formation

Empirical constraints of fundamental properties of protoplanetary disks are essential for understanding planet formation and planetary properties1,2. Carbon monoxide (CO) gas is often used to constrain disk properties3. However, estimates show that the CO gas abundance in disks is depleted relative to expected values4,5,6,7, and models of various disk processes impacting the CO abundance could not explain this depletion on observed ~1 Myr timescales8,9,10,11,12,13,14. Here we demonstrate that surface energy effects on particles in disks, such as the Kelvin effect, that arise when ice heterogeneously nucleates onto an existing particle can efficiently trap CO in its ice phase. In previous ice formation models, CO gas was released when small ice-coated particles were lofted to warmed disk layers. Our model can reproduce the observed abundance, distribution and time evolution of gaseous CO in the four most studied protoplanetary disks7. We constrain the solid and gaseous CO inventory at the midplane and disk diffusivities and resolve inconsistencies in estimates of the disk mass—three crucial parameters that control planetary formation.

Photomodification of benzyl germanane with group 6 metal carbonyls

Successful postmodification of germanene-based materials opens new applications in the chemistry of monoelemental two-dimensional materials. Here, we demonstrate the successful synthesis of germanane bearing benzyl group and its coordination with carbonyl metal complexes from the group 6. The photochemical reaction was used for in situ formation of reactive intermediates based on chromium, molybdenum and tungsten carbonyls and led to the attachment of the metal-carbonyl group to the benzyl group on the germanane surface. Successful functionalization was proven by various spectroscopic methods including FTIR, Raman and x-ray photoelectron spectroscopy as well as TG-MS measurements showing the evolution of carbon monoxide at elevated temperature. The homogeneous distribution of metals and morphology was also approved by microscopy method SEM/EDS and AFM. This work shows new possibilities in the chemistry of two-dimensional monoelemental materials like germanane giving the opportunity to homogenously distribute metal atoms over the sheet surface by coordination to the benzyl group.

Bi-Functional Paraffin@Polyaniline/TiO2/PCN-222(Fe) Microcapsules for Solar Thermal Energy Storage and CO2 Photoreduction.

A novel type of bi-functional microencapsulated phase change material (MEPCM) microcapsules with thermal energy storage (TES) and carbon dioxide (CO2) photoreduction was designed and fabricated. The polyaniline (PANI)/titanium dioxide (TiO2)/PCN-222(Fe) hybrid shell encloses phase change material (PCM) paraffin by the facile and environment-friendly Pickering emulsion polymerization, in which TiO2 and PCN-222(Fe) nanoparticles (NPs) were used as Pickering stabilizer. Furthermore, a ternary heterojunction of PANI/(TiO2)/PCN-222(Fe) was constructed due to the tight contact of the three components on the hybrid shell. The results indicate that the maximum enthalpy of MEPCMs is 174.7 J·g−1 with encapsulation efficiency of 77.2%, and the thermal properties, chemical composition, and morphological structure were well maintained after 500 high–low temperature cycles test. Besides, the MEPCM was employed to reduce CO2 into carbon monoxide (CO) and methane (CH4) under natural light irradiation. The CO evolution rate reached up to 45.16 μmol g−1 h−1 because of the suitable band gap and efficient charge migration efficiency, which is 5.4, 11, and 62 times higher than pure PCN-222(Fe), PANI, and TiO2, respectively. Moreover, the CO evolution rate decayed inapparently after five CO2 photoreduction cycles. The as-prepared bi-functional MEPCM as the temperature regulating building materials and air purification medium will stimulate a potential application.

Determining the dynamics of carbon monoxide formation during gas welding processes

This paper reports a study of the air medium where welding processes take place, with special attention paid to the evolution of carbon monoxide (CO) in the working medium in the process of gas welding. Plots were constructed and polynomial dependences were obtained to show a change in the concentration of carbon monoxide in the air of the working area during gas welding. It was confirmed experimentally that the concentration of carbon monoxide exceeds the permissible sanitary and hygienic indicators MPC (20 mg/m3) during gas welding. As a result of the experiment, the effectiveness of the use of an additional device was proven, namely an umbrella gas concentrator, in order to capture welding gases that are formed during gas welding. It was established that the MPC is exceeded under certain working conditions and welding wire. The carbon monoxide formation during gas welding was analyzed; these processes were compared with electric arc welding. The mathematical dependences derived make it possible to assess the risks of the welders’ work and conclude that the electric arc welding is characterized by a much higher rate of CO evolution from the beginning of the welding process (8.5 mg/s), that speed then decreases over 20 s by 2 times (to 4.5 mg/s). In 90 s, the speed becomes constant, to 2 mg/s. In comparison, gas welding has almost the same rate of CO formation, namely 0.3–0.9 mg/s. By changing the types of welding wires used in gas welding and taking into consideration the type of material that needs to be welded (including the period of its use), it is possible to influence the volume of CO emissions entering the working area and an employee’s respiratory area

Oxidation kinetics of graphite nanoparticles with copper oxide as oxygen carrier

The oxidation characteristics of graphite with copper oxide nanoparticles as oxidizer mixed in stoichiometric proportion were studied using a thermogravimetric analyzer. Progress of reactions was followed by measuring the mass loss, evolved gas analysis, and energy-dispersive X-ray spectroscopy. The samples were heated from room temperature conditions to 975 °C at four different heating rates of 5, 10, 15, and 20 °C min -1. The exhaust gas composition was quantified using a non-dispersive infrared analyzer. Experimental results indicate that the system requires a critical CO concentration buildup before the combustion process accelerates. The carbon dioxide production begins and peaks later than carbon monoxide. A total of three peaks occur in both carbon monoxide and carbon dioxide evolution. An Arrhenius dependence for the peak separation times with respect to the starting peak or trough temperature was observed. This work experimentally identifies the various regimes of oxidation chemistry for this fuel oxidizer combination over the entire combustion process via the trajectory of CO and CO2 evolution with temperature. The paths in this trajectory are then mapped onto the mass loss profiles. Modulated TGA experiments were also conducted to obtain the activation energy during the combustion process that shows overlapping mass loss regions. This activation energy is obtained over a wide range of temperatures using this model free-approach. The activation energies obtained using the modulated TGA experiments were also compared to those obtained using the Flynn–Wall–Ozawa method. This work provides new insights into the oxidation kinetics of graphitic carbon with solid copper oxide as an oxidizer.

Effect of Nitrogen on the Plasma Decarburization of Chromium-Containing Steel

Abstract—To study the kinetics of the processes occurring in the region where a plasma torch interacts with high-chromium Kh18N10-steel-type iron melts, we investigate the influence of the partial nitrogen pressure in a plasma-forming gas on the decarburization when the melts are processed by an oxidizing plasma in a laboratory setup at a variable oxidation potential. A computer program for processing experimental data is developed. It takes into account the process of inert gas dilution of evolved carbon monoxide and dioxide with allowance for the true character of gas evolution. The kinetic parameters of the plasma decarburization of the high-chromium melts are determined, and the influence of the partial pressures of oxygen and nitrogen in the plasma-forming gas on the process kinetics is detected. The mechanisms of limiting the interaction at various stages of the process are proposed. The influence of nitrogen on the oxidative decarburization in a plasma furnace is studied. The presence of nitrogen in the plasma-forming gas composition is shown to decrease the rate and degree of carbon removal from the melts.

Acetic Acid Adsorption and Reactions on Ni(110).

Acetic acid adsorption and reactions at multiple surface coverage values on Ni(110) were studied with temperature-programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRAS) at 90-500 K. The experimental measurements were interpreted with density functional theory (DFT) calculations that provided information on adsorbate geometries, energies, and vibrational modes. Below the monolayer saturation coverage of 0.36 ML at 90 K, acetic acid adsorbs mostly molecularly. Above this coverage, a physisorbed layer is formed with dimers and catemers, without detectable monomers. Dimers and catemers desorb as molecular acetic acid at 157 and 172 K, respectively. Between 90 and 200 K, the O-H bond in acetic acid breaks to form bridge-bonded bidentate acetate that becomes the dominant surface species. Desorption-limited hydrogen evolution is observed at 265 K. However, even after the acetate formation, acetic acid desorbs molecularly at 200-300 K due to recombination. Minor surface species observed at 200 K, acetyls or acetates with a carbonyl group, decompose below 350 K and generate adsorbed carbon monoxide. At 350 K, the surface likely undergoes restructuring, the extent of which increases with acetic acid coverage. The initial dominant bridge-bonded bidentate acetate species formed below 200 K remain on the surface, but they now mostly adsorb on the restructured sites. The acetates and all other remaining hydrocarbon species decompose simultaneously at 425 K in a narrow temperature range with concurrent evolution of hydrogen, carbon monoxide, and carbon dioxide. Above 425 K, only carbon remains on the surface.

CO as a therapeutic agent: discovery and delivery forms.

Carbon monoxide (CO) as one of the three important endogenously produced signaling molecules, termed as "gasotransmitter," has emerged as a promising therapeutic agent for treating various inflammation and cellular-stress related diseases. In this review, we discussed CO's evolution from a well-recognized toxic gas to a signaling molecule, and the effort to develop different approaches to deliver it for therapeutic application. We also summarize recently reported chemistry towards different CO delivery forms.

Decorating g-C3N4 with alkalinized Ti3C2 MXene for promoted photocatalytic CO2 reduction performance

Photocatalytic reduction of carbon dioxide (CO2) under visible light irradiation for producing high-value fuel has attracted tremendous attention in recent years. In this study, titanium carbide MXene (Ti3C2) was used as a noble metal-free co-catalyst by simply mixing graphitic carbon nitride (g-C3N4) and alkalized Ti3C2. The carbon monoxide evolution rate of the optimized composite (5%TCOH-CN) from photocatalytic reduction of CO2 was 5.9 times higher than that of pure g-C3N4. Alkalized Ti3C2 was responsible for the superior photocatalytic activity due to its excellent electrical conductivity and large CO2 adsorption capacity. Furthermore, the separation of the photo-induced electron–hole pairs was greatly enhanced because of the large Fermi level difference between alkalized Ti3C2 and pure g-C3N4. This work demonstrates the potential of MXenes as noble metal-free co-catalyst for photocatalysis processes such as carbon dioxide reduction reaction and nitrogen reduction reaction.

New Reaction of Dimethylformamide with Acrylic Acid

A new homogeneous reaction of dimethylformamide (DMF) with acrylic acid was studied. The reaction afforded previously unknown 3-[2-carboxyethyl(dimethyl)azaniumyl]propanoate and carbon monoxide. The product structure was determined by 1H and 13C NMR spectroscopy, X-ray diffraction, and elemental analysis, and evolution of gaseous carbon monoxide was confirmed by GC/MS. The kinetic parameters of the described reaction and its overall order were determined.

Improvement of functional performance of concrete in livestock buildings through the use of complex admixtures

When examining concrete in livestock buildings, signs of corrosion and destruction of concrete floors and walls were found. Experimental studies have identified main critical points that directly affected concrete continuity. Excessive moisture, use of corrosive acidic or alkaline disinfectants and presence of natural excretions of animals (urine and feces) were found in livestock buildings. To solve this problem, admixtures were proposed: yellow iron oxide pigment and liquid glass which improve strength characteristics of concrete, its heat resistance and reduce penetrability. It was proved by the conducted studies that introduction into concrete of admixtures in quantities from 0.5 % to 2 % has resulted in a 2.8 times smaller depth of chloride penetration as compared to the control specimens. This was due to a decrease in water absorption by concrete when introducing iron oxide, cuprous sulphate, peracetic acid and sodium silicate which reduced pore size in samples. It was proposed as an innovation to assess thermal stability of concrete using the method of temperature-programmed desorption mass spectrometry (TPMS) based on the dependence of evolution of carbon monoxide and carbon dioxide from samples of carbonate-containing substances on the sample temperature. Microbiological studies have identified microbes of Penicillium and Fusarium species, bacteria Escherichia coli and Pseudomonas aeruginosa, which cause corrosion of concrete in livestock buildings. Numerous experiments have shown that the proposed admixtures added to the concrete (based on yellow iron oxide pigment (1.5‒2.0 wt. %), peracetic acid (0.2‒0.3 wt. %), liquid glass (2‒3 wt. %) and cuprous sulfate (0.5‒1.0 wt. %) had antimicrobial properties and thus prospects for their use in animal husbandry

Effects of two different agents, H3PO4 and NaCl, to increase the flame-retardant properties of cellulose fibers

After flame-retardant treatment by the two different agents, the thermal behaviors of Lyocell fibers are discussed. In this research, H3PO4 and NaCl reduced the degradation rate and increased the char yield of the Lyocell fibers, and also increased the limiting oxygen index with the char yield increased. After treatment, the integral procedure decomposition temperature and the activation energy of Lyocell fibers are significantly increased by various concentration factors. These phenomena were indicated by the dehydration, rearrangement, formation of carbonyl groups, the evolution of carbon monoxide and dioxide, and carbonaceous residue formation. These effects were indicating the slow pathway of flame retardancy for the Lyocell fibers and are attributed to the two different flame-retardant agent treatments.