Humidified CO2 Research Articles

Gas-phase electrochemical CO2 reduction on silver-copper BTC MOF in a zero-gap membrane electrode assembly

Bimetallic AgCu-BTC MOFs, derived from Cu-BTC (HKUST-1), have been synthesized by fast co-precipitation method and evaluated for CO2 reduction reaction (CO2RR) using humidified CO2 gas in a zero-gap configuration. Three compositions with varying Ag content – AgCu-1 (9.4 at.%), AgCu-2 (12.5 at.%), and AgCu-3 (16.5 at.%) – were characterized by SEM-EDS, PXRD, FTIR, and XPS. These structural analyzes confirmed the formation of a low-crystalline AgCu-BTC MOF with Ag+1 ions coordinated to the BTC framework. Electrochemical tests (CV and LSV) revealed that AgCu-3 MOF, with the highest Ag content (16.5 at.%), exhibited a more positive onset potential at -0.65 V vs Ag/AgCl compared to HKUST-1 MOF, indicating enhanced CO2RR activity, owing to Ag incorporation. Constant potential (CP) experiments showed that AgCu-3 MOF predominantly produced CO and H2, achieving faradaic efficiency of approximately 65 % for CO production and 5 % for H2 production. Moreover, lowering the relative humidity (RH%) in the inlet CO2 gas stream from 80% to 20% increased CO production by 2-fold from 6.2 µmol s-1 cm-2 to 13 µmol s-1 cm-2, simultaneously suppressing the hydrogen evolution reaction (HER). This reduction in humidity resulted in an increased local concentration of CO2 at the catalyst site, leading to an enhanced CO2RR rate. However, substantial morphological changes have been observed in the AgCu-3 MOF after the CP experiment under humid CO2 reduction conditions.

Cobalt substitution slows forsterite carbonation in low-water supercritical carbon dioxide.

Cobalt recovery from low-grade mafic and ultramafic ores could be economically viable if combined with CO2 storage under low-water conditions, but the impact of Co on metal silicate carbonation and the fate of Co during the carbonation reaction must be understood. In this study, in situ infrared spectroscopy was used to investigate the carbonation of Co-doped forsterite ((Mg,Co)2SiO4) in thin water films in humidified supercritical CO2 at 50 °C and 90 bar. Rates of carbonation of Co-doped forsterite to Co-rich magnesite ((Mg,Co)CO3) increased with water film thickness but were at least 10 times smaller than previously measured for pure forsterite at similar conditions. We suggest that the smaller rates are due to thermodynamic drivers that cause water films on Co-doped forsterite to be much less oversaturated with respect to Co-doped magnesite, compared to the pure minerals.

Comparing Commercially Available Gas Diffusion Layers in the Electrochemical CO2 Reduction Reaction

One of the most urgent challenges of our society is the continuously rising level of CO2 in the atmosphere, caused by anthropogenic emission, including different point sources (e.g., cement factories, automobiles, airplanes). The electrochemical CO2 reduction reaction (CO2RR) can be an alternative route for the chemical- and energy industries to convert CO2 into useful products (e.g., carbon monoxide, methane, ethylene), hence providing a value-added approach for CO2 neutralization1.In our work we employed a zero gap electrolyzer cell (active area = 8 cm2), where the catalyst coated electrodes are separated by only a Grade-T Sustainion® X37-50 anion exchange membrane (AEM). As the cathode we used Ag nanoparticle coated gas diffusion layers and as the anode we used Iridium Black coated Ti frit. During the experiments, an anolyte was recirculated continuously through the anode side and humidified CO2 was fed to the cathode side. Beyond the cell structure and membrane, the applied catalyst coated gas diffusion layer (GDL) is one of the most critical elements, determining the efficiency of CO2RR. In this work we compared commercially available GDLs in the CO2RR. All GDLs are used in identical electrochemical cells, under the same experimental conditions2.Our goal was to provide a comprehensive conclusion of the most frequently used commercially available GDLs in CO2RR. We studied the effect of the microporous layer (MPL), the PTFE content, the thickness, and the structure of the selected GDLs. One-hour long chronoamperometric measurement revealed some trends and important differences - in case of five of the tested GDLs (Sigracet 28BC, Sigracet 39BB, Freudenberg H23C6, Toray H60 MPL and Elat LT 1400W), the CO partial current density exceeded 500 mA cm−2 already at 3.0 V cell voltage. To unravel which structural parameters affect the electrolyzer performance the most, the results were compared along a few selected properties (Figure 1.): (A) whether they contained MPL or not, (B) the PTFE content, (C) the overall thickness, and (D) the structure of the GDL.<Figure 1.> Figure 1. Comparing commercially available gas diffusion layers in the CO2RR. Partial current densities for CO and H2 production during one-hour long chronoamperometric CO2RR measurements at ΔU = 3.0 V, applying different GDL based cathode GDEs with Ag catalyst. The electrolyte solution was 0.1 M CsOH, humidified CO2 was fed to the cathode at a flow rate of 12.5 cm3 cm−2 min−1 and the temperature of the electrolyzer cell was 60 °C. The error bars represent the deviations of two consecutive analyses during the same measurements.Long-term electrolysis experiments (100 hours) were performed with two GDLs, the Sigracet 39BB and the Toray H60 MPL. Throughout the long-term electrolysis, a stable total current density and CO formation selectivity was measured in both cases. Throughout our study, to understand the differences among their electrochemical behavior, of the various GDLs, we characterized their wetting properties and microstructure before the electrochemical measurements. The structure and morphology of the GDLs were characterized with SEM, micro-CT and contact angle measurements. References (1) Samu, A. A.; Kormányos, A.; Kecsenovity, E.; Szilágyi, N.; Endrödi, B.; Janáky, C. Intermittent Operation of CO2 Electrolyzers at Industrially Relevant Current Densities. ACS Energy Lett. 2022, 1859–1861(2) Samu, A. A.; Szenti, I.; Kukovecz, Á.; Endrődi, B.; Janáky, C. Systematic Screening of Gas Diffusion Layers for High Performance CO2 Electrolysis. Commun. Chem. 2023, 6 (1), 1–9 Supported by the KDP-2021 program of the Ministry for Innovation and Technology from the source of the National Research, Development and Innovation fund. Figure 1

Visualizing the Effect of Temperature on Carbonate Salt Production in CO2 Electrolysis

Carbon dioxide (CO2) electrolysis is a novel and promising technology to tackle anthropogenic climate change by reducing our dependency on fossil fuels and creating a sustainable carbon cycle. However, current CO2 electrolysis suffers from low CO2 reduction reaction (CO2RR) selectivity and rapid gas diffusion electrode (GDE) degradation and flooding due to carbonate precipitation. As the hydrophilic precipitate accumulates in the porous structure of the cathode GDE, the liquid anolyte invades the pores, blocking the catholyte from reaching the catalyst layer. This effect promotes the adverse hydrogen evolution reaction and thus decreases the CO2RR selectivity (1). Current literature focuses on limiting carbonate precipitate formation as opposed to understanding the factors affecting its growth (2). While carbonate precipitation is dependent on the specific electrolyte in a flow cell, the impact of parameters, such as operating temperature and GDE porosity, on the nature of carbonate precipitation still need to be investigated (3).In this study, we examine the relationship between cell temperature with carbonate precipitate accumulation. A zero-gap alkaline membrane electrode assembly (MEA) was used with potassium carbonate as the anolyte and humidified CO2 as the catholyte. Electrochemical impedance spectroscopy was used to calculate the activation, ohmic, and mass transport losses of the cell before and after a constant current density phase where faradaic efficiency was measured to quantify the CO2RR selectivity degradation due to salt accumulation. Furthermore, to characterize precipitate growth, the cathode GDEs were imaged before and after electrochemical testing using scanning electron microscopy (SEM) and wavelength dispersive spectroscopy (WDS). To quantify precipitate-driven flooding over operation time, identical MEAs were imaged using operando X-ray synchrotron radiography over a range of temperatures. Through-plane images of the operating cell were processed to find the electrolyte thickness in the cathode GDE as a function of time. Radiography results revealed progressive, cyclical flooding as well as preferential gas pathways. Moreover, after four hours of constant current operation and at a cell temperature of 60℃, the catalyst layer exhibited large amounts of uniformly distributed precipitates, while the GDE contained large, localized precipitate crystals. This indicates that at high temperatures, carbonate precipitates significantly block the catalyst layer and cause flooding into the substrate layer. This work provides new insight into the effect of temperature on carbonate precipitate buildup, deepening the understanding of the mechanism responsible for precipitate degradation. M. E. Leonard, L. E. Clarke, A. Forner-Cuenca, S. M. Brown, and F. R. Brushett, ChemSusChem, 13 (2020).Y. Xu et al., ACS Energy Lett, 6, 809–815 (2021).E. R. Cofell, U. O. Nwabara, S. S. Bhargava, D. E. Henckel, and P. J. A. Kenis, ACS Appl Mater Interfaces, 13, 15132–15142 (2021).

Enabling Ambient Stability of LiNiO2 Lithium-Ion Battery Cathode Materials via Graphene–Cellulose Composite Coatings

Nickel-rich layered oxides are widely used as cathode materials for energy-dense lithium-ion batteries. These chemistries, based on the parent compound LiNiO2 (LNO), are highly sensitive to ambient environments and are known to readily react with moisture and carbon dioxide. As a result, impurities such as lithium hydroxides and lithium carbonates are formed at the LNO surface, compromising electrochemical behavior. Here, we address this issue by coating LNO cathode particles with a hydrophobic barrier layer composed of graphene and ethyl cellulose (GrEC). This coating limits contact between atmospheric moisture and the LNO surface, which minimizes the generation of lithium impurities. This scheme is evaluated by exposing coated LNO to humidified CO2 for 24 h as an accelerated ambient degradation test. Subsequent spectroscopy, microscopy, and electrochemical characterization show no detectable signatures of carbonates on the LNO surface, thus verifying that the GrEC coating prevents ambient degradation. By demonstrating this methodology for the ultimate nickel-rich chemistry, this approach can likely be generalized to a wide range of ambient-sensitive battery materials.

Controlling product selectivity in hybrid gas/liquid reactors using gas conditions, voltage, and temperature.

For the conversion of CO2 into fuels and chemical feedstocks, hybrid gas/liquid-fed electrochemical flow reactors provide advantages in selectivity and production rates over traditional liquid phase reactors. However, fundamental questions remain about how to optimize conditions to produce desired products. Using an alkaline electrolyte to suppress hydrogen formation and a gas diffusion electrode catalyst composed of copper nanoparticles on carbon nanospikes, we investigate how hydrocarbon product selectivity in the CO2 reduction reaction in hybrid reactors depends on three experimentally controllable parameters: (1) supply of dry or humidified CO2 gas, (2) applied potential, and (3) electrolyte temperature. Changing from dry to humidified CO2 dramatically alters product selectivity from C2 products ethanol and acetic acid to ethylene and C1 products formic acid and methane. Water vapor evidently influences product selectivity of reactions that occur on the gas-facing side of the catalyst by adding a source of protons that alters reaction pathways and intermediates.

Ag Dendrites on W/C as Enhanced Active and Stable Electrocatalysts for Scalable Solar-Driven CO2rr

The electrochemical conversion of solar energy into competent chemicals is the most efficient technique to ensure clean and sustainable energy source for society in the future. In fact, solar cells can electrochemically produce electricity without pollution by converting CO2 into a variety of chemicals. The carbon dioxide reduction reaction (CO2RR) is an environmentally friendly approach to produce useful hydrocarbons such as carbon monoxide (CO), methane, ethylene, formates, etc and alcohols and remove exhausted CO2, which is a greenhouse gas. Conventionally, studies on the CO2RR have been conducted by using liquid-phase H-cells and a CO2-saturated electrolyte. However, it resulted in a low current density because the low solubility of CO2 in the liquid electrolyte occurs mass transfer limitation. To improve of the current density related to the CO2RR, two types of gas-fed CO2RR electrolyzers containing gas diffusion layer (GDL) electrodes have been proposed. The first type of CO2RR devices use a liquid electrolyte, the electrolyte increases CO2RR performance through controlling the cathode conditions, such as pH and anion concentration. The second type of CO2RR devices is zero-gap electrolyzers that use an anion exchange membrane (AEM) and humidified CO2 gas. AEM transmits carbonate and hydroxide ion, inducing favorable environmental for CO2RR. These zero-gap CO2 electrolyzers are attracting attention as the most promising system owing to several advantages such as extremely low ohmic resistance, scalable and stackable configuration, and commercial applicability, as affirmed by using a system consisting of a fuel cell and water electrolyzer. Among the products of the CO2RR, CO is particularly attractive as aspect of its economic benefits and large demand. Ag-based materials exhibit the most electrochemical performance for producing CO. and high selectivity. To enhance the catalytic activity of Ag-based catalysts, various approaches have been studied to change the surface electronic structure of Ag such as alloy formation, anion-based modification, shape control, near-surface structure and engineering. However, catalyst designs that do not consider the gas phase reactions cannot enough utilize their catalytic activity although recent progress has made in the development of Ag-based catalysts for the CO2RR. Therefore, considerable efforts must be preoccupied with the development of highly active, stable, and gas-transferable structured catalysts for gas-fed CO2RR electrolyzers with incoporating a GDL. Additionally, aming for the realization of clean technology for producing CO, we demonstrate the practicalbility of sunlight-driven CO2RR on a large scale using commercial silicon-based solar cells and zero-gap electrolyzers. Silicon-based solar cells are still the preferred commercially applicapable options for producing large amounts of electrical power from solar energy because of their scalability. In this study, we report a 3D silver dendrite on W/C (as denoted WC@AgD) catalyst with abundant nanograin boundaries that show enhanced CO2RR performance and stability. WC@AgD exhibited marked catalytic activity with a maximum CO partial current density of 400 mA cm-2 and durability for 100 h at 150 mA cm-2. We also fabricated an solar-to-CO (STC) conversion device combined with a silicon-based solar cell of 120 cm2 area and a zero-gap CO2 electrolyzer with an area of 10 cm2. The stand-alone photovoltaic-electrochemical system achieved a solar-to-CO efficiency (ηSTC) of 12.1 % at 1A under AM 1.5 G illumination and realistic outdoor conditions. The device design and electrode configuration extended viable route for implementing large-scale installations for solar-driven production of chemicals. Figure 1

Fabrication of Low Loading Ag Electrodes for CO2 Reduction Reaction in Zero-Gap Electrolyzer

In recent years, there has been intense effort directed towards catalyst development and electrode design for electrochemical carbon dioxide reduction reaction (CO2RR) with an objective of achieving high production rate (current density) of desirable products including CO, CH3OH, CH4 and C2+ hydrocarbons. Silver electrocatalyst is reported to exhibit remarkable CO selectivity and high current density, both of which are requisite parameters for CO2RR electrolyzer scale up. Silver is still moderately priced and reduction of Ag loading in CO2RR electrode is one of the technological goals for electrolyzer development.Most of the prior studies on Ag electrodes for CO2RR have utilized Ag nanoparticles, which are typically spray coated on a substrate from Ag or Ag-ionomer suspension resulting in high-Ag loading (> 1 mg/cm2 loading) and hence low mass specific activity (MSA) < 150 mA.mg-1 Ag. In this work, we developed a combined approach for Ag deposition using pulse electrodeposition (PE) and spray coating (SC) with an aim of decreasing Ag loading and increasing MSA. Such electrodes were found to exhibit high current densities and CO selectivity even with low Ag loading (< 0.5 mg/cm2).Specifically, several different gas diffusion electrodes (GDE) prepared by pulse electrodeposition of silver, spray coating of Ag nanoparticles, and combination of the two were prepared by coating of Sigracet gas diffusion layer (GDL). Commercial IrO2 electrode and the fabricated silver electrode were utilized as the anode and cathode, respectively. The anode and the cathode were separated by a polymer electrolyte membrane, which was Sustainion® X37-50 Grade 60- an anion exchange membrane. 10 mM KHCO3 electrolyte was re-circulated at the anode using a pump while humidified CO2 gas was flowed through the cathode. CO2RR tests are performed in a zero-gap electrolyzer setup, at a temperature of 25 °C.The main findings are summarized in the Figure below. The electrode prepared by pulse electrodeposition (PE) exhibits a low areal current density (~30 mA/cm2) but high mass-specific activity of 302 mA.mg-1 Ag. However, the selectivity for CO is low. On the other hand, spray coated (SC) electrodes yield higher CO selectivity and higher areal current density but mass specific activity is lower. By depositing silver sequentially, either pulse electrodeposition (PE) followed by spray coating (SC), i.e. the SC+PE electrode, or SC followed by PE (PE+SC electrode), both the mass-specific and areal current density increased drastically while CO selectivity remained high (99%). In particular, the current densities of the PE and SC electrodes are improved by 2 and 4.5 times, respectively, from 31 and 70 mA.cm-2 up to 136 mA.cm-2 on the SP+PE electrode, at the cell voltage of -3 V. Also, the CO selectivity of the electrodes is improved from 25 % (PE sample) and 81 % (SC sample) up to 99 % on the SC+PE electrode. The optimized electrode provided a catalyst layer with high surface coverage of silver on the GDL substrate at low Ag loadings (<0.5 mg/cm2). Further optimization of electrode is underway including modification of silver deposition and incorporation of ionomer to increase current density while maintaining the CO selectivity and durability of GDE. Details of the electrode fabrication and characterization as well as performance evaluation will be presented at the meeting. Figure 1

Methodical Approach to Inactivate Any Microbial Element like SARS-CoV2.

The proposed paper discusses Far UVC could assassinate microbes without harming healthy tissues. The plasma ion generation will increase the ion (O2−) generation in abundance along with hydrogen ion (H+), and at the same time, the negative hydroxyl radical (OH−) formed will merge with the positive (H+) ion of the virus to break the structure of it. The silver nanoparticle which is present in the diffuser with thermostat support is very effective for destroying the microbial elements by heating the gel present within the diffuser. The gel will mix in the environment, and it will also increase the activity of T cell generation and act as an immunoglobulin booster in the human body while inhaling it. In the proposed device, we are using warm humidified CO2 strategic therapy in low dose which is able to suppress any microbial element like SARS-CoV2.

Abstract 443: Blackcurrant Extract Inhibits Oxidative Stress In Cultured Cardiomyocyte Cells

Background: Cardiovascular disease (CVD) affects a large sector of the U.S. population; accounting for millions of adult men and women impacted by its high annual incidence of mortality and morbidity. An underlying cellular link to the pathophysiological process of CVD is oxidative stress. Oxidative stress occurs when there is an imbalance of reactive oxygen species, reactive nitrogen species, and a deficiency in antioxidants. In particular, flavonoids found in fruits and berries have antioxidant properties that may quell oxidative stress activities at the cellular level. Mounting evidence suggests that flavonoids in the form of berry extracts may offer health benefits. Methods: Blackcurrant and various berry extracts (aronia berry, tart cherry, elderberry, cranberry, and a berry blend) were investigated in cultured cardiomyocyte (HL-1) cell line-to determine their effects on oxidative stress. Cells were maintained in Claycomb medium at 37°C in humidified 5% humidified CO 2. A menadione-induced oxidative stressor was applied to generate oxidative stress in the HL-1 cells. A CellROX TM green reagent assay was used as a detection method of oxidative stress. The effects of berry extracts on cell viability within the HL-1 cells were also investigated. Results: Blackcurrant extract was found to be superior compared to all of the other berry extracts in suppressing oxidative stress in the HL-1 cells. N-acetyl-cysteine (NAC) used as a control, also had similar antioxidant effects as blackcurrant extract in the HL-1 cells under menadione-induced oxidative stress conditions. Additionally, NAC demonstrated significance for increased cell viability and cardio protection, while blackcurrant extract showed modest cellular protection. These results indicate that blackcurrant extract has potent antioxidant and modest cardioprotective properties comparable to NAC in HL-1 cells. Conclusion: Blackcurrant extract rich in flavonoids showed promising effects as an antioxidant with cardioprotective benefits. This may have significant implications for improving CV health in the human model. Further studies are warranted to determine the role of the bioactive components of blackcurrant and application to CV health.

Simultaneous collision-induced transitions in H2O+CO2 gas mixtures

A collision induced absorption (CIA) band has been measured near 6000 cm−1 in a spectrum of humidified CO2 recorded by cavity ring down spectroscopy (CRDS) at low pressure (<1 atm). This absorption adds a contribution to the H2O+CO2 continuum mostly originating from far wings of the CO2 and H2O resonance lines broadened by collisions with H2O and with CO2, respectively. The observed CIA corresponds to a simultaneous excitation of 12CO2 and H2O colliding molecules in the ν3 antisymmetric and ν1 symmetric stretching mode, respectively. CRDS spectra recorded near 5940 cm−1 with a highly enriched 13CO2 sample provide a confirmation of the assignment since the measured CIA isotopic spectral shift (of about −68 cm−1) coincides with that between the ν3 bands of 12CO2 and 13CO2. The integrated binary coefficient of the two CIA is evaluated and found to be on the order of 2.3 × 10−3 cm−2amagat−2. Classical molecular dynamics simulations (CMDS) of the considered CIA are also presented, based on the dominant dipole induction mechanism associated with the vibrational matrix elements of the dipole of CO2 (ν3) and isotropic polarizability of H2O (ν1). The results of the calculations are found in good agreement with the observations, thus further validating the attribution of the observed CIA structure to the above mentioned double transitions.

Warm humidified CO2 insufflation improves pericardial integrity for cardiac surgery: a randomized control study.

Flooding the surgical field with dry cold CO<inf>2</inf> during open-chamber cardiac surgery has been used to mitigate air entrainment into the systemic circulation. However, exposing epithelial surfaces to cold, dry gas causes tissue desiccation. This randomized controlled study was designed to investigate whether the use of humidified warm CO<inf>2</inf> insufflation into the cardiac cavity could reduce pericardial tissue damage and the incidence of micro-emboli when compared to dry cold CO<inf>2</inf> insufflation. Forty adult patients requiring elective open-chamber cardiac surgery were randomized to have either dry cold CO<inf>2</inf> insufflation via a standard catheter or humidified warm CO<inf>2</inf> insufflation via the HumiGard device (Fisher & Paykel Healthcare, Panmure, Auckland, New Zealand). The primary endpoint was biopsied pericardial tissue damage, assessed using electron microscopy. We assessed the percentage of microvilli and mesothelial damage, using a damage severity score (DSS) system. We compared the proportion of patients who had less damage, defined as DSS<2. Secondary endpoints included the severity of micro-emboli, by visual assessment of bubble load on transesophageal echocardiogram; lowest near infrared spectroscopy; total de-airing time; highest cardio-pulmonary bypass sweep speed; hospital length of stay and complications. A higher proportion of patients in the humidified warm CO<inf>2</inf> group displayed conserved microvilli (47% vs. 11%, P=0.03) and preserved mesothelium (42% vs. 5%, P=0.02) compared to the control group. There were no differences in the secondary outcomes. Humidified warm CO<inf>2</inf> insufflation significantly reduced pericardial epithelial damage when compared to dry cold CO<inf>2</inf> insufflation in open-chamber cardiac surgery. Further studies are warranted to investigate its potential clinical benefits.

Characterization of the H2O+CO2 continuum within the infrared transparency windows

Absorption spectra of humidified CO2 have been recorded at room temperature by cavity enhanced absorption techniques (CRDS and OFCEAS): (i) in three spectral ranges of the 1.6 µm window (5720–6045 cm−1; 6390–6460 cm−1 and 6570–6665 cm−1), (ii) in four narrow spectral intervals of the 2.3 µm window (4243–4255 cm−1; 4301.3–4302 cm−1; 4421.5–4440 cm−1 and 4518–4535 cm−1), and (iii) around 2853 cm−1. All these spectral ranges are situated in transparency windows of both H2O and CO2. The binary absorption coefficients (BCO2−H2O+BH2O−CO2)are retrieved from low pressure spectra (<1 atm) recorded with different molar fractions of water vapor in CO2 after subtracting the H2O and CO2 local monomer contributions and the self-continuum contribution of each species (i.e. H2OH2O and CO2CO2). Experimental room temperature binary coefficients are then compared to the only available empirical model based on line shape profiles with χ-factors. This model well reproduces our experimental values on the low- and high-frequency edges of the 1.6 µm window and gives a relatively good agreement for the 2853 cm−1 data point. Larger differences are observed in the 2.3 µm window where the calculated values are underestimated by a factor of 3. Around 6000 cm−1, an additional absorption peak is observed which is tentatively interpreted as a collision induced absorption band due to the simultaneous excitation of the H2O and CO2 molecules.

Improving Catalytic Activity in the Electrochemical Separation of CO2 Using Membrane Electrode Assemblies

The direct electrochemically driven separation of CO2 from a humidified N2, O2, and CO2 gas mixture was conducted using an asymmetric membrane electrode assembly (MEA). The MEA was fabricated using a screen-printed ionomer bound Pt cathode, an anion exchange membrane (AEM), and ionomer bound IrO2 anode. Electrocatalyst materials were physically and chemically characterized prior to inclusion within the electrode. Electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) measurements using a rotating disk electrode (RDE) were used to quantify the catalytic activity and determine the effects of the catalyst-to-ionomer ratio. Catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface analysis, and (dynamic light scattering) DLS to evaluate catalyst structure, active surface area, and determine the particle size and bulk particle size distribution (PSD). The electrocatalyst layer of the electrodes were fabricated by screen printing a uniformly dispersed mixture of catalyst, dissolved anionic ionomer, and a solvent system onto an electrode supporting gas diffusion layer (GDL). Pt-IrO2 MEAs were fabricated and current-voltage relationships were determined using constant-current measurements over a range of applied current densities and flow rates. Baseline reaction kinetics for CO2 separation were established with a standard set of Pt-IrO2 MEAs.

Port-Site Metastasis (PSM): Definition, clinical contexts and possible preventive actions to reduce risk

The "port-site metastasis" represents a tumor recurrence that develops in the abdominal wall within the scar tissue of the insertion site of one or more trocars, after laparoscopic surgery, not associated with peritoneal carcinomatosis. This last aspect is central because in the literature some isolated cases are reported, but most cases are associated with peritoneal carcinomatosis. The first case in the literature dates back to 1978 and in the literature, the incidence varies from 1% to 21%, although most published research reports a very small number of patients. Currently, the incidence in a specialized cancer center is consistent with the incidence of recurrence on a laparotomy scar. Possible mechanisms for cell implantation at the port site are direct implantation into the wound during forced, unprotected tissue retrieval or from contaminated instruments during tumor dissection; the effect of gas turbulence in lengthy laparoscopic procedures, and embolization of exfoliated cells during tumor dissection or hematogenous spread. Probably, however, the triggering mechanism is necessarily multifactorial. To date, the only significant prognostic factor in patients diagnosed with port-site metastasis is the interval between laparoscopy and the diagnosis of the port site: in fact, patients who develop the port site within 7 months after surgery have a generally worse prognosis, as well as port-site metastasis are more frequent in advanced cancers and the presence of ascites. To reduce the risk, the following measures are proposed in the literature: 1) Select the patient who does not have a metastatic oncologic condition or friable cancerous masses or lymph node spread or attached external or intracystic vegetations, preferring well-localized, benign or low-malignant or otherwise intact tumors; 2) Use wound protectors and use of protective bags (or endo bag) for tissue retrieval; 3) Peritoneal washing with heparin, to prevent free cell adhesion, or washing with cytocidal solutions. Evaluate the utility of using Povidone-iodine, Taurolidine (which has anti-adhesion activity and decreases proangiogenic factors), and chemotherapy products; 4) Avoid removing pneumoperitoneum with trocars in place; 5) Avoiding direct contact between the solid tumor and the port site; 6) Prefer laparoscopy to laparotomy, if possible; 7) Avoid the use of gas or direct CO2 insufflation, although in literature the point is controversial and deserves more attention and study, as the initial hypothesis that CO2 increased the invasion capacity of tumor cells (in vitro and in vivo) has been refuted several times. Insufflation of hyperthermic CO2 and humidified CO2 leads to a better outcome in patients with a malignant tumor who undergo a laparoscopic procedure compared with normal CO2 pneumoperitoneum; 8) Comply with surgical protocols and techniques by updating one's surgical skills, as it has been demonstrated, as already reported here, the presence of cancerous cells on instruments, washing systems and trocars (in particular, on the trocars of the first operator). Suturing all layers of the abdominal wall decreases the risk of the port site; 9) Avoid excessive manipulation of the tumor mass during the surgical/operative procedure.

Pneumoperitoneum induced mesothelial cell changes in a laparoscopic mouse model

BackgroundCO2 pneumoperitoneum (PP) during laparoscopic surgery, can cause hypoxia and desiccation in the peritoneal mesothelial cell, resulting in a time-dependent retraction and bulging of these cells, an acute inflammatory reaction and enhanced adhesion formation. Since hypoxia is prevented by adding 4% of oxygen (O2) to the CO2 PP, the aim of this study was to evaluate the effect of adding 4% O2 to the CO2 PP on mesothelial cell morphology. MethodsIn a standardized laparoscopic mouse model (n=8 mice per group), a control group with a 30- or 60-min PP with humidified CO2 + 4% of O2 (groups I and II) was compared to a hypoxic group with 30- or 60-min humidified pure CO2 (groups III and IV) and a desiccation group with 60-min of dry CO2 PP (group V). The effect upon the peritoneum morphology was evaluated by scanning electron microscopy (SEM) of abdominal wall peritoneal biopsies. Biopsies, taken immediately (n=4) and 24 hrs (n=4) after surgery, were compared to a group without PP (group VI, n=4). SEM pictures were blindly scored for cell retraction, deletion of microvilli, fibrin deposition, holes in the epithelial layer and visibility of cell borders using a semi-quantitative scoring system. ResultsPP Hypoxia (CO2 PP) has a deleterious effect upon mesothelial morphology, immediately (holes: p= 0.04) and 24 hrs later (cell retraction: p=0.005; total score: p=0.03) . Desiccation has also a deleterious effect immediately (microvilli p=0.0090; fibrin deposition p=0.05) and 24 hrs after surgery (cell retraction: p=0.0036; holes: p=0.0004; microvilli: p< 0.0001, fibrin deposition: p=0.0225; borders: p=0.0007). This deleterious effect increases with duration of CO2 PP, affecting cell retraction (p=0.016), holes (p=0.0441), and the total score (p=0.0488). The addition of 4% of O2 to the CO2 PP failed to reach statistical significance. ConclusionsThese data confirm that CO2 PP and dry gas have a deleterious effect on mesothelial cell morphology. Humidification of the insufflation gas reduces this deleterious effect. The hypothesis of a protective effect of adding O2 failed to reach significance.

Gold-like activity copper-like selectivity of heteroatomic transition metal carbides for electrocatalytic carbon dioxide reduction reaction

An overarching challenge of the electrochemical carbon dioxide reduction reaction (eCO2RR) is finding an earth-abundant, highly active catalyst that selectively produces hydrocarbons at relatively low overpotentials. Here, we report the eCO2RR performance of two-dimensional transition metal carbide class of materials. Our results indicate a maximum methane (CH4) current density of −421.63 mA/cm2 and a CH4 faradic efficiency of 82.7% ± 2% for di-tungsten carbide (W2C) nanoflakes in a hybrid electrolyte of 3 M potassium hydroxide and 2 M choline-chloride. Powered by a triple junction photovoltaic cell, we demonstrate a flow electrolyzer that uses humidified CO2 to produce CH4 in a 700-h process under one sun illumination with a CO2RR energy efficiency of about 62.3% and a solar-to-fuel efficiency of 20.7%. Density functional theory calculations reveal that dissociation of water, chemisorption of CO2 and cleavage of the C-O bond—the most energy consuming elementary steps in other catalysts such as copper—become nearly spontaneous at the W2C surface. This results in instantaneous formation of adsorbed CO—an important reaction intermediate—and an unlimited source of protons near the tungsten surface sites that are the main reasons for the observed superior activity, selectivity, and small potential.

Improving the Chemical Stability of BaCe0.9Y0.1O3-d (BCY10) Towards Humidification and Carbonation By Microstructural Design

Protonic ceramic fuel cells are rapidly gaining interest as a promising technology for energy conversion. These devices use proton-conducting electrolytes allowing them to operate at considerably lower temperatures (e.g., 400 – 600 °C) than those of the oxide-ion-conducting counterparts (e.g., > 600 °C). This decrease in temperature can bring significant benefits, including shorter start-up times, lower energy inputs to heat the cell up to the operating temperature and greater longevity [1].Owing to its very high equilibrium constant for hydration, yttrium-doped barium cerate, BaCe1−xYxO3−δ (BCY), stands out as being an interesting electrolyte material to use at lower temperatures, due to its high proton conduction under these conditions (e.g., ∼ 10−3 S cm−1 at 400 °C under humidified atmospheres, p H2O ∼ 10−2 atm). Nonetheless, this composition has been, typically, discarded for real world applications due to its very poor chemical stability towards carbonate or hydroxide formation at low temperatures. In this respect, the presence of amorphous intergranular phases in BaCeO3 polycrystalline materials can be highly reactive to acidic atmospheres and have been suggested to be a likely cause of the structural disintegration of this composition [1,2].To try to overcome this limitation, we report a potential solution based on the modification of BaCe0.9Y0.1O3−δ (BCY10) composition by the introduction of small amounts of NiO (1 vol%) during the sintering process. While the addition of transition metals has been widely adopted for enhancing the sinterability of these materials [1], such behaviour has not been previously tested as a method to improve the chemical stability and lifetime of this material.To accomplish this goal, four different samples were pelletised and sintered: the undoped samples, BCY10 sintered at 1450 °C (BCY1450) and 1600 °C (BCY1600); and the NiO-modified samples, sintered at 1450 °C (Ni-BCY1450) and 1350 °C (Ni-BCY1350). All materials were characterised for phase composition by X-ray diffraction (XRD), and for microstructure by scanning electron microscopy, coupled with chemical analysis by Energy Energy-dispersive X-ray spectroscopy (SEM/EDS).The XRD results reveal all samples to be single phase, indexed as the orthorhombic perovskite BaCe0.9Y0.1O3- d. Nevertheless, slight changes of the cell volume were noted upon Rietveld refinement of the XRD data, suggesting that nickel is incorporated in the perovskite structure of BCY10. From the SEM results, it was possible to observe that all samples showed different average grain sizes. Particularly, the NiO-modified samples showed considerably higher grain sizes and levels of densification than that observed for the unmodified BCY10 samples.Electrochemical Impedance Spectroscopy (EIS) was utilised to evaluate the electrical properties of bulk samples in wet O2 (p H2O = 0.033 atm) in the temperature range 100 – 600 °C. It was found that the bulk response is similar for all samples under study, with no notable dependence from any compositional differences. Conversely, the specific grain boundary conductivity, a factor where the grain boundary response is normalised as a function of microstructural differences, was found to be higher in the case of the BCY1450 and Ni-BCY1350 samples, followed by Ni-BCY1450 and BCY1600.To evaluate the chemical stability, fresh samples were exposed to a humidified CO2 atmosphere (p H2O = 0.033 atm) at 400 °C for 30 days and EIS was used to record impedance data. The results revealed that the unmodified BCY10 samples suffered a substantial drop in total conductivity in this timeframe, while the NiO-modified samples (Ni-BCY1350 and Ni-BCY1450) remained stable through the tests.This result is important as it reveals that the simple addition of 1vol% of NiO not only offers its typical role of decreasing the sintering temperature from 1450 to 1350 °C, but also is sufficient for dramatically improving the stability of BCY10 against humidification and carbonation. The work offers a significant advance to the knowledge of this family of materials at low temperatures, potentially opening a way to use a previously discarded proton-conducting perovskite material in real world applications. Acknowledgements The authors acknowledge to FCT for the PhD grant SFRH/BD/130218/2017 and the projects, PTDC/CTM-CTM/2156/2020, PTDC/QUI-ELT/3681/2020, POCI-01-0247-FEDER-039926, POCI-01-0145-FEDER-032241, UIDB/00481/2020 and UIDP/00481/2020 and CENTRO-01-0145-FEDER-022083 - Centro Portugal Regional Operational Programme (Centro2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF).

Combination Effect of Tamoxifen and Ascorbic Acid Treatment on Breast Cancer Cells (MCF-7) and Cervical Cancer Cells (HeLa)

Breast cancer and cervical cancer are among the leading causes of death among women in the world. The development of drug resistance in both cancer cells, has reduced the efficacy of chemotherapeutic drugs in cancer treatment. The current study was aimed to evaluate cell viability of human breast cancer cells, MCF-7 and cervical cancer cells, HeLa upon combination treatment of ascorbic acid and tamoxifen. The cell viability was performed using MTT assay incubated for 72 hours in humidified CO 2 incubator. The concentration of tamoxifen and ascorbic acid that reduced 50% of cells population (IC 50 ) was determined from dose response curve. IC 50 concentration was used to determine cell viability in treated cells. CompuSyn software was used to evaluate the combination effects towards both cells upon treatment and results were calculated as combination index (CI). Data were analysed using IBM SPSS Statistics 24. Statistical analysis was performed using independent t-test. The IC 50 value of tamoxifen and ascorbic acid on MCF-7 cells were 14.53 µg/ml and 15.8 µg/ml respectively whereas the IC 50 value of tamoxifen and ascorbic acid on HeLa cells were 11.09 µg/ml and 202.3 µg/ml respectively. Combination of tamoxifen and ascorbic acid exerted greater growth reduction in both cells compared to tamoxifen alone. The results indicated ascorbic acid synergizes the cytotoxic effect of tamoxifen at lower concentrations towards MCF-7 cells with the CI less than 1. However, the combination of tamoxifen and ascorbic acid exerted antagonistic effect in HeLa cells when CI were more than 1. DOI : http://dx.doi.org/10.17576/JSKM-2021-1902-12

A phase I, nonrandomized controlled trial demonstrating the novel technique of cytoreductive surgery and hyperthermic intraperitoneal chemotherapy utilizing warm humidified carbon dioxide insufflation

The aim of this work was to report on the safety and feasibility of warm humidified CO2 (WHCO2 ) insufflation during cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Ten consecutive patients with histologically confirmed peritoneal cancer were enrolled in this phase I pilot nonrandomized controlled trial. They were alternately assigned to CRS and HIPEC with WHCO2 versus standard procedure. WHCO2 was delivered at 10L/min, a pressure of 4.5bar, 37ºC and 98% relative humidity during CRS using the HumiGardTM system. HIPEC was performed with an open abdomen using the Coliseum technique at 42ºC for 60min. All patients were admitted to the intensive care unit and commenced on total parenteral nutrition postoperatively. Surface and core temperatures were measured every 30min using an infrared camera and nasopharyngeal probe, respectively. Clinicopathological, intra- and postoperative details were collated between groups, and median surface and core temperatures were statistically compared. Surface and core temperatures were generally higher in the WHCO2 group. Core temperature at 120 and 180min was significantly higher in the WHCO2 versus the non-WHCO2 group (p=0.028 and 0.008, respectively). There was a significant linear relationship between core and surface temperature at 30, 60, 90, 120, 150 and 180min (p=0.033, 0.004, 0.007, 0.021, 0.009 and 0.006, respectively). The peritoneal cancer index was lower but the estimated blood loss was higher in the non-WHCO2 than the WHCO2 group. WHCO2 in CRS and HIPEC appears to be safe and feasible. An appropriately powered phase II trial will be required to determine if WHCO2 is associated with improved intra- and postoperative outcomes.