CO2 Elimination Research Articles

Total oxidation of carbon monoxide, VOC and reduction of NO2 with catalytic ceramic filter media

This paper deals with the effect of catalyst loading on the activity and selectivity of CuOx−MnOy catalysts on alumina-silicate supports (fiber material-Al2O3(44)/SiO2(56)). A special focus lies on the oxidation of CO, on mixtures of VOC from 1-butene, isobutane, n-butane, propane, ethene, and ethane, as well as on CO oxidation in the presence of NO2. The catalysts are prepared through wet impregnation of the filter section with an aqueous solution of copper and manganese nitrate. The rate of CO oxidation for small carbon monoxide concentrations of up to 1 vol.% is independent of catalyst loading in the filter material. In contrast, at a carbon monoxide concentration of around 3 vol.%, it is found that the rate of CO oxidation increased rapidly with increasing catalyst loading of the filter material. The highest catalytic activity of over 93% CO elimination is achieved at 290 °C for 1 vol.% CO and smaller catalyst loading and for 3 vol.% CO with higher catalyst loading. In long-term stability tests, complete CO conversion is measured without deactivating the catalyst at 390 °C for at least 100 h. The highest catalytic activity for VOC elimination of 90% is achieved in the temperature range of 350–420 °C. During the CONO2 reaction with and without O2, a constant decrease in the CO oxidation rate is observed, while the NO2 reduction rate remained constant at a temperature below 300 °C.

Effect of single-port inflatable mediastinoscopy simultaneous laparoscopic-assisted radical esophagectomy on respiration and circulation

Background and purposeWe previously developed a new surgical method, namely, single-port inflatable mediastinoscopy simultaneous laparoscopic-assisted radical esophagectomy. The purpose of this study was to evaluate the effect of carbon dioxide inflation on respiration and circulation using this approach.MethodsFrom April 2018 to October 2020, 105 patients underwent this novel surgical approach. The changes in respiratory and circulatory functions were reported when the mediastinal pressure and pneumoperitoneum pressure were 10 and 12 mmHg, respectively. Data on blood loss, operative time, and postoperative complications were also collected.Results104 patients completed the operation successfully, except for 1 patient who was converted to thoracotomy because of intraoperative injury. During the operation, respectively, the heart rate, mean arterial pressure, central venous pressure, peak airway pressure, end-expiratory partial pressure of carbon dioxide and partial pressure of carbon dioxide increased in an admissibility range. The pH and oxygenation index decreased 1 h after inflation, but these values were all within a safe and acceptable range and restored to the baseline level after CO2 elimination. Postoperative complications included anastomotic fistula (8.6%), pleural effusion that needed to be treated (8.6%), chylothorax (0.9%), pneumonia (7.6%), arrhythmia (3.8%) and postoperative hoarseness (18.2%). There were no cases of perioperative death.ConclusionsWhen the inflation pressure in the mediastinum and abdomen was 10 mmHg and 12 mmHg, respectively, the inflation of carbon dioxide from single-port inflatable mediastinoscopy simultaneous laparoscopic-assisted radical esophagectomy did not cause serious changes in respiratory and circulatory function or increase perioperative complications.

Simultaneous production of hydrogen and carbon nanotubes from biogas: On the effect of Ce addition to CoMo/MgO catalyst

In this study, hydrogen and carbon nanotubes (CNTs) are simultaneously produced via a synergistic combined process of CO2 methanation (METH) and chemical vapor deposition (CVD) processes using biogas as a feedstock. METH process could upgrade CO2 containing biogas into CH4-rich gas which then decomposed into H2 and forming CNTs over CoMo/MgO catalyst by CVD process. The effects of Ce addition to CoMo/MgO were investigated. Comprehensive characterization confirms that all as-synthesized samples composed of well-aligned multi-walled carbon nanotubes (MWCNTs) with a narrow size distribution. The Ce addition improved CoMo dispersion on MgO, resulting in smaller and uniform CNTs. The small addition of Ce into CoMo/MgO catalyst could enhance the production CNTs yield. The higher Ce addition would, however, result in the CNTs yield decreased, attributed to a high basicity of CeO2 surface and a large coverage of CeO2 on the catalyst surface. The IG/ID increased with increased Ce addition, while the surface area monotonically decreased, attributed to a decrease in defects of nanotubes. In addition, this wisely combined process could result in a remarkable 100%CO2 elimination, while high CH4 conversion of 90% was obtained. The H2 production yield could gain more than 30 vol% with respect to H2 in the feed stream. The H2 yield and purity in the effluent gas stream were approximately 90%.

Quantification of Amino Acid Enantiomers Using Electrospray Ionization and Ultraviolet Photodissociation.

The enantioselectivity of tryptophan (Trp) for amino acids, such as alanine (Ala), valine (Val), and serine (Ser), was investigated using ultraviolet (UV) photoexcitation and tandem mass spectrometry. Product ion spectra of cold gas-phase amino acid enantiomers that were hydrogen-bonded to Na+(L-Trp) were measured using a variable-wavelength UV laser and a tandem mass spectrometer equipped with an electrospray ionization source and a cold ion trap. Na+(L-Trp), formed via amino acid detachment, and the elimination of CO2 from the clusters were observed in the product ion spectra. For photoexcitation at 265 nm, the relative abundance of Na+(L-Trp) compared to that of the precursor ion observed in the product ion spectrum of heterochiral Na+(L-Trp)(D-Ala) was larger than that observed in the product ion spectrum of homochiral Na+(L-Trp)(L-Ala). A difference between the Val enantiomers in the relative abundance of the precursor and product ions was observed in the case of photoexcitation at 272 nm. The elimination of CO2 was not observed for L-Ser for the 285 nm photoexcitation, which was the main reaction pathway for D-Ser. Photoexcited Trp chiral recognition was applied to identify and quantify the amino acid enantiomers in solution. Ala, Val, and Ser enantiomers in solution were quantified from their relative abundances in single product ion spectra measured using photoexcitation at 265, 272, and 285 nm, respectively, for hydrogen-bonded Trp within the clusters.

Visible-light photoredox-catalyzed selective carboxylation of C(sp3)−F bonds with CO2

Visible-light photoredox-catalyzed selective carboxylation of C(sp3)−F bonds with CO2

Morphology controllable synthesis of Pd/CeO2–ZrO2 catalysts and its structure-activity relationship in three-way catalytic performance

CeO2–ZrO2 mixed oxides with controlled morphologies (i.e., nanorod, nano-polyhedral and disordered shape) were synthesized through either hydrothermal or coprecipitation method, and the corresponding supported Pd/CeO2–ZrO2 catalysts were also prepared by conventional impregnation. The obtained catalysts were subjected to systematic structural/physio-chemical characterizations as well as three-way catalytic performance evaluations. The results showed that CeO2–ZrO2 mixed oxides presented different exposed crystal planes: namely disordered CZ-di mainly exposed (111) crystal planes, nanorod CZ-ro mainly exposed (111) crystal planes and few (100) crystal planes, while nano-polyhedral CZ-po exposed both (111) and (100) crystal planes. Clear structure-activity relationship could be demonstrated between the TWC (Three-way catalysts) performance of Pd/CeO2–ZrO2 and such different microstructures, as (100) and (111) crystal planes exposed by CZ-ro and CZ-po were beneficial for the surface oxygen vacancies formation, thus increasing the Pd-support interaction and effectively decreasing the light-off temperature of HC and NO elimination. On the other hand, the disordered CZ-di retained more lattice oxygen content, leading to better catalytic activity of CO elimination for the corresponding Pd/CZ-di catalyst.

Dimethylcarbene versus Direct Propene Formation in Dimethylketene Photodissociation.

Highly reactive carbenes are usually produced by photolysis of ketenes, diazoalkanes, or diazirines. Sequential kinetic pathways for deactivation of nascent carbenes usually involve bimolecular reactions in competition with isomerization producing stable products such as alkenes. However, the direct photolytic production of stable products, effectively bypassing formation of free carbenes, has been postulated for over 50 years but remains very poorly understood. Often termed "rearrangement in the excited state" (RIES), examples include 1,2-hydrogen migration within photoexcited carbene precursors yielding alkenes and the Wolff rearrangement in photogenerated carbonyl-substituted carbenes producing ketenes. In this study, the two competing CO elimination channels from photoexcited gaseous dimethylketene, producing dimethylcarbene and propene, were studied as a function of electronic excitation energy, under collision-free conditions, by using photofragment translational energy spectroscopy with vacuum ultraviolet photoionization of the products. A significant fraction of the dimethylcarbene → propene isomerization exothermicity (∼300 kJ/mol) was released as propene + CO translational energy, indicating that propene is formed prior to or concurrent with CO elimination. An increase in the propene yield with increasing excitation energy suggests that the effective potential energy barrier for this channel lies ∼24 kJ/mol above the energetic threshold for dimethylcarbene formation via C═C bond fission. Possible mechanisms for direct propene elimination are discussed in light of the observed energy dependence for the competing pathways.

Influence of γ-radiation on thermal destruction of a cross-linked acrylic polymer

The effect of γ-radiation dosage on the thermal stability of the cross-linked acrylic polymer "Carbomer-140" (СRB) was investigated. The DTA, TGA, and DTG curves show multistage processes occurring in different temperature ranges on heating CRB from 25 °C to 500 °C. The rates of thermal decomposition of CRB were determined in the temperature ranges of 40–110 °C, 180–260 °C, 260–330 °C, and 330–500 °C. In combination with results of electronic structure calculations, potential thermal destruction reactions were proposed for the indicated temperature ranges. The main reactions for thermal decomposition of CRB are formation of ketones and cyclic anhydrides with formation of unsaturated bonds in the macromolecule due to elimination of H2O, CO2, and CO, respectively, from the polymer chain. An increase in the radiation dose applied to CRB leads to a decrease in the post-radiation thermal stability of the polymer. During radiolysis, double bonds are formed and accumulate in the polymer, contributing to the thermal destruction of CRB. As a result, the higher the radiation dose, the higher the rate of post-radiation thermal destruction.

Influence of the Carboxylic Function on the Degradation of d-Galacturonic Acid and Its Polymers.

Past investigations have shown high browning potential during the caramelization of sugar acids in comparison to reducing sugars. However, no approaches to elucidate the chemical mechanisms have been made. Therefore, this study aims to clarify the reasons for the high browning potential by measuring the mutarotation velocity and the elimination of CO2 during the heat treatment of uronic acids. Performed polarimetric experiments show that the mutarotation velocity of d-galacturonic acid exceeds that of d-galactose by a factor of nearly 4.5. However, the ring opening velocity is not the only parameter that differs between the two carbohydrate structures. Measurements of the release of CO2 of heated d-galacturonic acid at 60 °C show a steady increase, and after 48 h, 6% of degraded d-galacturonic acid has eliminated CO2. CO2 release was also found during the heating of pectin, indicating a decarboxylation reaction during thermal degradation. One of the degradation reactions postulated for the release of CO2 leads to α-ketoglutaraldehyde, which is responsible for the formation of several chromophoric substances.

Gas Containment Systems for Stationary and Mobile Applications

While green hydrogen production should remain the main target toward Zero Emissions Society, it would be prudent to maximize the utilization of easily accessible energy carries available already today in abundance.Compressed Natural Gas (CNG) represents a widely available energy carrier. Approximately 4.000 CNG/LNG car filling stations are available, thus enabling CNG to be used as fuel for commercial and personal vehicles based on the SOFC technology. Employing SOFC up to 30% higher efficiency can be achieved in comparison with conventional combustion engines. The SOFC based vehicles fueled by CNG can thus represent a perfect intermediate solution toward CO2 reduction and elimination of NOx emissions. Decentral power and heat generation via SOFC in combination with CNG offers yet another pathway to reach CO2 targets set by the European Union. Conditions for continued, more rapid growth of SOFC technology are favorable as global demand seeks different clean emissions heat and power generation solutions. Worthington as a center of excellence is focused on the design and production of high-pressure cylinders and onboard fueling systems for mobile applications, like vehicle integration, gas transport containers and stationary storage solutions. Ensuring easier fuel storage and transport, application and commercialization of SOFC based systems for mobile application can be accelerated.Worthington Industries is a global value-added steel processing company with headquarters in Columbus, Ohio, USA and production sites in Austria, Poland, and Portugal dedicated to pressure cylinder solutions for sustainable mobility. In addition to an overview of our approach to advancement of SOFC utilization, we intend to cover, as well, the availability of gas street components, system integration, safety, maintenance and product lifetime of proposed onboard fueling systems.

FTIR spectroscopic evidence for new isomers of 3-aminopyrazine-2-carboxylic acid formed in argon matrices upon UV irradiations

The UV-induced photochemistry and molecular structure of 3-aminopyrazine-2-carboxylic acid were studied in argon matrices by Fourier-transform infrared spectroscopy and B3LYP/6–311++G(2d,2p) calculations. Out of seventeen possible isomers of this molecule located on the singlet potential energy surface the most stable one, APA1 comprising intramolecular O–H···N and N–H···O hydrogen bonds, was detected experimentally in the matrix after deposition. Two new conformers APA2 and APA3 were generated upon irradiation with λ = 280 nm by trans/cis-COOH isomerization and at λ = 360 nm by COOH group rotamerization, respectively, whereas an amino-imino tautomerization leading to IPA1 and IPA2 structures occurred at λ = 305 nm. The reverse reactions were also observed upon irradiation of the matrices at 265, 230 and 400 nm. Simultaneously with the photoisomerizations, a cleavage of the pyrazine ring along with CO2 elimination was observed leading to the formation of carbodiimide and cyanamide derivatives.

Obesity Blunts the Ventilatory Response to Exercise in Men and Women.

Rationale: Obesity presents a mechanical load to the thorax, which could perturb the generation of minute ventilation (V̇e) during exercise. Because the respiratory effects of obesity are not homogenous among all individuals with obesity and obesity-related effects could vary depending on the magnitude of obesity, we hypothesized that the exercise ventilatory response (slope of the V̇e and carbon dioxide elimination [V̇co2] relationship) would manifest itself differently as the magnitude of obesity increases.Objectives: To investigate the V̇e/V̇co2 slope in an obese population that spanned across a wide body mass index (BMI) range.Methods: A total of 533 patients who presented to a surgical weight loss center for pre-bariatric surgery testing performed an incremental maximal cycling test and were studied retrospectively. The V̇e/V̇co2 slope was calculated up to the ventilatory threshold. Patients were examined in groups based on BMI (category 1: 30-39.9 kg/m2, category 2: 40-49.9 kg/m2, and category 3: ≥50 kg/m2). Because the respiratory effects of obesity could be sex and/or age specific, we further examined patients in groups by sex and age (younger: <50 yr and older: ≥50 yr). Differences in the V̇e/V̇co2 slope were then compared between BMI category, age, and sex using a three-way ANOVA.Results: No significant BMI category by sex by age interactions was detected (P = 0.75). The V̇e/V̇co2 slope decreased with increases in BMI (category 1, 29.1 ± 4.0; category 2, 28.4 ± 4.1; and category 3, 27.1 ± 3.3) and was elevated in women (28.9 ± 4.1) compared with men (26.7 ± 3.2) (BMI category by sex interaction, P < 0.05). No age-related differences were observed (BMI category by age interaction, P = 0.55). The partial pressure for end-tidal CO2 was elevated at the ventilatory threshold in BMI category 3 compared with BMI categories 1 and 2 (both P < 0.01).Conclusions: These findings suggest that obesity presents a unique challenge to augmenting ventilatory output relative to CO2 elimination, such that the increase in the exercise ventilatory response becomes blunted as the magnitude of obesity increases. Further studies are required to investigate the clinical consequences and the mechanisms that may explain the attenuation of exercise ventilatory response with increasing BMI in men and women with obesity.

Mortality Associated Factors of Patients with Mechanical Ventilation Treated at the Intensive Care Unit of a Second Level Hospital at Piedras Negras Coahuila Mexico

Introduction: The mechanical ventilation is the cornerstone of treatment for patients with acute respiratory failure and is one of the pivotal therapies in critical care medicine. The epidemiology of mechanical ventilation in México is scarce and usually a transpolated of the information in high specialty centers. The mechanical ventilation has the aim of assisting in the elimination of CO2 (carbon dioxide) and / or favoring the adequate exchange of oxygen while the patient is unable to do so or due to conditions external to the respiratory system. Quality indicators of attention are a quantitative measure that are used to assess important aspects of clinical practice. Objective: Describe the epidemiology and mortality factors in mechanically ventilated patients treated at second level ICU in Piedras Negras, Coahuila México. Material and Methods: retrospective study from December 2016 to December 2019 all patients treated with MV. We collected general demographic characteristics, quality indicators and complications, severity of disease and mortality. Results: 164 patients were enrolled. Female 54.8%, main diagnoses Sepsis 30.5%, and DKA 13.4%, mean age 44.1 SD ± mean SOFA 7.2 SD ± 6.2, mean SAPS3 50.6 SD ± 20.2, ICU LOS 4.5 SD ± 5.1, Hospital LOS 11.7 SD ± 10.2 p&lt;0.0001. ICU and Hospital mortality 14 % and 23.8%. The factors associated with ICU mortality were: Age, MV hours, Respiratory SOFA, and Hepatic SOFA and with Hospital mortality: Age, Neurological SOFA, Unstable at admission, SOFA and SAPS 3. Conclusions: MV is a primordial need of critical care patients, our mortality was reported lower than expected but quality of attention indicators most be improved in order to maintain this trend. This study has several limitations in population and applicability but contributes with primordial information about MV critical care patients treated at México.

Chemical effects of anisole and toluene addition to n‑heptane on PAH characteristics in laminar premixed flames by LIF measurement and kinetic model

Anisole is a candidate renewable fuel that displays satisfying combustion characteristics, but its sooting characteristics are not well known. The goal of this study is to investigate the chemical effects of anisole and toluene on PAH formation in n-heptane laminar premixed flames, using LIF measurement and chemical kinetic simulation. To focus on chemical effects, the equivalence ratios, dilution ratios, and flame temperatures were kept nearly unchanged when anisole and toluene were blended separately into n-heptane flame. LIF experimental results indicated that PAH formation was promoted with the addition of anisole and toluene, and the effect of toluene was stronger than the promotional effect of anisole. The chemical kinetic model predicted the observed PAH tendencies well in the LIF experiments. Based on this model, reaction pathway and sensitivity analyses were performed to interpret the chemical effects. Results revealed that, due to their different molecular structures, the difference in chemical effects between anisole and toluene was notable in PAH growth processes. Anisole decomposed first via the O-CH3 bond dissociation reaction, and then proceeded to a CO elimination reaction to yield an important PAH precursor, C5H5, which contributed to PAH formation via styrene and indene reaction networks. In the toluene added flame, PAH formation was enhanced because of ring expansion reaction on the dehydrogenated branch of the toluene.

Cobalt Metal ALD: Understanding the Mechanism and Role of Zinc Alkyl Precursors as Reductants for Low-Resistivity Co Thin Films

In this work, we report a new and promising approach toward the atomic layer deposition (ALD) of metallic Co thin films. Utilizing the simple and known CoCl2(TMEDA) (TMEDA = N,N,N′,N′-tetramethylethylenediamine) precursor in combination with the intramolecularly stabilized Zn aminoalkyl compound Zn(DMP)2 (DMP = dimethylaminopropyl) as an auxiliary reducing agent, a thermal ALD process is developed that enables the deposition of Zn-free Co thin films. ALD studies demonstrate the saturation behavior of both precursors and linearity depending on the applied number of cycles as well as temperature dependency of film growth in a regime of 140–215 °C. While the process optimization is carried out on Si with native oxide, additional growth studies are conducted on Au and Pt substrates. This study is complemented by initial reactivity and suitability tests of several potential Zn alkyl-reducing agents. For the CoCl2(TMEDA)–Zn(DMP)2 combination, these findings allow us to propose a series of elemental reaction steps hypothetically leading to pure Co film formation in the ALD process whose feasibility is probed by a set of density functional theory (DFT) calculations. The DFT results show that for reactions of the precursors in the gas phase and on Co(111) substrate surfaces, a pathway involving C–C coupling and diamine formation through reductive elimination of an intermediate Co(II) alkyl species is preferred. Co thin films with an average thickness of 10–25 nm obtained from the process are subjected to thorough analysis comprising atomic force microscopy, scanning electron microscopy, and Rutherford backscattering spectrometry/nuclear reaction analysis as well as depth profiling X-ray photoemission spectroscopy (XPS). From XPS analysis, it was found that graphitic and carbidic carbon coexist in the Co metal film bulk. Despite carbon concentrations of ∼20 at. % in the Co thin film bulk, resistivity measurements for ∼22 nm thick films grown on a defined SiO2 insulator layer yield highly promising values in a range of 15–20 μΩ cm without any postgrowth treatment.

Lung function and stress echocardiography in pulmonary arterial hypertension: a cross-sectional study.

The mechanism of exercise limitation in idiopathic pulmonary arterial hypertension (IPAH) is not fully understood. The role of hemodynamic alterations is well recognized, but mechanical, ventilatory and gasometric factors may also contribute to reduction of exercise capacity in these individuals. To investigate whether there is an association between ventilatory pattern and stress Doppler echocardiography (SDE) variables in IPAH patients. Single-center prospective study conducted in a Brazilian university hospital. We included 14 stable IPAH patients and 14 age and sex-matched controls. Volumetric capnography (VCap), spirometry, six-minute walk test and SDE were performed on both the patients and the control subjects. Arterial blood gases were collected only from the patients. The IPAH patients and control subjects were compared with regard to the abovementioned variables. The mean age of the patients was 38.4 years, and 78.6% were women. The patients showed hypocapnia, and in spirometry 42.9% presented forced vital capacity (FVC) below the lower limit of normality. In VCap, IPAH patients had higher respiratory rates (RR) and lower elimination of CO2 in each breath. Therewas a significant correlation between reduced FVC and the magnitude of increases in tricuspid regurgitation velocity (TRV). In IPAH patients, VCap showed similar tidal volumes and a higher RR, which at least partially explained the hypocapnia. The patients with IPAH showed hypocapnia, probably related to their higher respiratory rate with preserved tidal volumes; FVC was reduced and this reduction was positively correlated with cardiac output.

A DFT study on carbon dioxide reduction of low-valent diuranium complex supported by a polypyrrolic macrocycle

To mitigate carbon emission and satisfy the ever-increasing energy demands, a flourishing area of research is to design and develop innovating actinide-containing catalysts, which enables CO2 reduction at modest condition. In this regard, a polypyrrolic diuranium(III) complex (1) was examined using relativistic DFT. The reaction of 1 with CO2 is exothermic. The onwards 1-OCO → 1-OOC transformation was found kinetically feasible. Furthermore, the hydrogenation and CO elimination reactions were also calculated. The proposed mechanism indicates that both U(III) centers having high reducing ability provide two electrons with the assistance of the U-U bonding and cooperatively catalyze the CO2 cleavage.

Numerical Model to Analyze the Physicochemical Mechanisms Involved in CO2 Absorption by an Aqueous Ammonia Droplet.

CO2 is the main anthropogenic greenhouse gas and its reduction plays a decisive role in reducing global climate change. As a CO2 elimination method, the present work is based on chemical absorption using aqueous ammonia as solvent. A CFD (computational fluid dynamics) model was developed to study CO2 capture in a single droplet. The objective was to identify the main mechanisms responsible for CO2 absorption, such as diffusion, solubility, convection, chemical dissociation, and evaporation. The proposed CFD model takes into consideration the fluid motion inside and outside the droplet. It was found that diffusion prevails over convection, especially for small droplets. Chemical reactions increase the absorption by up to 472.7% in comparison with physical absorption alone, and evaporation reduces the absorption up to 41.9% for the parameters studied in the present work.

Design Aspects of Doped CeO2 for Low-Temperature Catalytic CO Oxidation: Transient Kinetics and DFT Approach.

CO elimination through oxidation over highly active and cost-effective catalysts is a way forward for many processes of industrial and environmental importance. In this study, doped CeO2 with transition metals (TM = Cu, Co, Mn, Fe, Ni, Zr, and Zn) at a level of 20 at. % was tested for CO oxidation. The oxides were prepared using microwave-assisted sol–gel synthesis to improve catalyst’s performance for the reaction of interest. The effect of heteroatoms on the physicochemical properties (structure, morphology, porosity, and reducibility) of the binary oxides M–Ce–O was meticulously investigated and correlated to their CO oxidation activity. It was found that the catalytic activity (per gram basis or TOF, s–1) follows the order Cu–Ce–O > Ce–Co–O > Ni–Ce–O > Mn–Ce–O > Fe–Ce–O > Ce–Zn–O > CeO2. Participation of mobile lattice oxygen species in the CO/O2 reaction does occur, the extent of which is heteroatom-dependent. For that, state-of-the-art transient isotopic 18O-labeled experiments involving 16O/18O exchange followed by step-gas CO/Ar or CO/O2/Ar switches were used to quantify the contribution of lattice oxygen to the reaction. SSITKA-DRIFTS studies probed the formation of carbonates while validating the Mars–van Krevelen (MvK) mechanism. Scanning transmission electron microscopy-high-angle annular dark field imaging coupled with energy-dispersive spectroscopy proved that the elemental composition of dopants in the individual nanoparticle of ceria is less than their composition at a larger scale, allowing the assessment of the doping efficacy. Despite the similar structural features of the catalysts, a clear difference in the Olattice mobility was also found as well as its participation (as expressed with the α descriptor) in the reaction, following the order αCu > αCo> αMn > αZn. Kinetic studies showed that it is rather the pre-exponential (entropic) factor and not the lowering of activation energy that justifies the order of activity of the solids. DFT calculations showed that the adsorption of CO on the Cu-doped CeO2 surface is more favorable (−16.63 eV), followed by Co, Mn, Zn (−14.46, −4.90, and −4.24 eV, respectively), and pure CeO2 (−0.63 eV). Also, copper compensates almost three times more charge (0.37e−) compared to Co and Mn, ca. 0.13e− and 0.10e−, respectively, corroborating for its tendency to be reduced. Surface analysis (X-ray photoelectron spectroscopy), apart from the oxidation state of the elements, revealed a heteroatom–ceria surface interaction (Oa species) of different extents and of different populations of Oa species.

Striped catfish (Pangasianodon hypophthalmus) use air-breathing and aquatic surface respiration when exposed to severe aquatic hypercarbia.

We investigated the extent to which the facultative air-breathing fish, the striped catfish (Pangasianodon hypophthalmus), uses air-breathing to cope with aquatic hypercarbia, and how air-breathing is influenced by the experimental exposure protocol and level of hypercarbia. We exposed individuals to severe aquatic hypercarbia (up to Pw CO2 = 81 mmHg) using step-wise and progressive exposure protocols while measuring gill ventilation rate, heart rate, mean arterial blood pressure, and air-breathing frequency, as well as arterial blood pH and PCO2 . We confirm that P. hypophthalmus is tolerant of hypercarbia. Under both protocols gill ventilation rate, heart rate, and mean arterial blood pressure were maintained near control levels even at very high CO2 levels. We observed a marked amount of individual variation in the PwCO2 at which air-breathing was elicited, with some individuals not responding at all. The experimental protocol also influenced the onset of air-breathing. Air-breathing began at lower Pw CO2 in the step-wise protocol (23 ± 4.1 mmHg) compared with the progressive protocol (46 ± 7.8 mmHg). Air-breathing was often followed by aquatic surface respiration, at higher PCO2 (71 ± 5.2 mmHg) levels. On average, the blood PCO2 was approximately 43% lower (46 ± 2.5 mmHg) than water Pw CO2 (~81 mmHg) at our highest tested CO2 level. While this suggests that aerial CO2 elimination is an effective, and perhaps critical, respiratory strategy used by P. hypophthalmus to cope with severe hypercarbia, this observation may also be explained by a long lag time required for equilibration.