Quantification Of CO Research Articles

A photobioreactor for production of algae biomass from gaseous emissions of an animal house

Sustainable approaches to circular economy in animal agriculture are still poorly developed. Here, we report an approach to reduce gaseous emissions of CO2 and NH3 from animal housing while simultaneously using them to produce value-added biomass. To this end, a cone-shaped, helical photobioreactor was developed that can be integrated into animal housing by being freely suspended, thereby combining a small footprint with a physically robust design. The photobioreactor was coupled with the exhaust air of a chicken house to allow continuous cultivation of a mixed culture of Arthrospira spec. (Spirulina). Continuous quantification of CO2 and NH3 concentration showed that the coupled algae reactor effectively purifies the exhaust air from the chicken house while producing algal biomass. Typical production rates of greater than 0.3 g/l*day dry mass were obtained, and continuous operation was possible for several weeks. Morphological, biochemical, and genomic characterization of Spirulina cultures yielded insights into the dynamics and metabolic processes of the microbial community. We anticipate that further optimization of this approach will provide new opportunities for the generation of value-added products from gaseous CO2 and NH3 waste emissions, linking resource-efficient production of microalgae with simultaneous sequestration of animal emissions.Key points• Coupling a bioreactor with exhaust gases of chicken coop for production of biomass.• Spirulina mixed culture removes CO2 and NH3 from chicken house emissions.• High growth rates and biodiversity adaptation for nitrogen metabolism.Graphical abstractTowards a sustainable circular economy in livestock farming. The functional coupling of a helical tube photobioreactor with exhaust air from a chicken house enabled the efficient cultivation of Spirulina microalgae while simultaneously sequestering the animals’ CO2 and NH3 emissions.

An emission based optical CO2 sensor fabricated on grating-like TiO2 substrates using HPTS

TiO2 is a widely used material in various applications, including photo-catalysis, sensing, and dye-sensitized solar cells. In this work, we presented a stable and sensitive CO2 sensor working on principle of emission signals of the HPTS dye immobilized on TiO2 substrates whose effectiverefractive indicesin the parallel and perpendicular grating orientations evidenced earlier. The HPTS exhibited 8.4-fold enhanced emission signal on the offered substrates with respect to the previously reported intensities recorded for the polymeric supports. The emission peaks of the HPTS exhibited CO2 induced intensity quenching when excited at 466 nm. Calibration sensitivity of the offered composites has been tested exposing the sensor materials to varying concentrations of the CO2 between 0.0 and 100.0 % pCO2 and correlating the measured fluorescence intensity with the corresponding CO2 levels. The dye revealed enhanced CO2 induced response exhibiting the I0/100 values of 11.9, 13.3, 11.2 and 6.5. We also recorded bi-exponential excited state lifetimes for the HPTS on four different test materials both in the absence and presence of the CO2. The emission based variations were followed as the analytical signal due to higher CO2-induced relative signal changes than that of the lifetime based variations. Herein we used the ion pair form of the HPTS in a protective chemical microenvironment and obtained considerable long term stability extending to16 mounts which can be attributed to the presence of the 1-butyl-3-methylimidazolium tetrafluoroborate as an internal buffering system in the sensing composition as well as the inert and robust structure of the substrate. The extremely high optical response, advantage of excitation with blue LEDs and long-term stability observed on grating-like TiO2 surfaces make the proposed system a promising design for the quantification of CO2 for further applications.

In Situ Raman Methodology for Online Analysis of CO2 and H2O Loadings in a Water-Lean Solvent for CO2 Capture.

Carbon capture represents a key pathway to meeting climate change mitigation goals. Powerful next-generation solvent-based capture processes are under development by many researchers, but optimization and testing would be significantly aided by integrating in situ monitoring capability. Further, real-time water analysis in water-lean solvents offers the potential to maintain their water balance in operation. To explore data acquisition techniques in depth for this purpose, Raman spectra of CO2, H2O, and a single-component water-lean solvent, N-(2-ethoxyethyl)-3-morpholinopropan-1-amine (2-EEMPA) were collected at different CO2 and H2O concentrations using an in situ Raman cell. The quantification of CO2 and H2O loadings in 2-EEMPA was done by principal component regression and partial least squares methods with analysis of uncertainties. We conclude with discussions on how this simultaneous online analysis method to quantify CO2 and H2O loadings can be an important tool to enable the optimal efficiency of water-lean CO2 solvents while also maintaining the critical water balance under operating conditions relevant to post-combustion CO2 capture.

Production of CO2 Hydrates in Aqueous Mixtures Having (NH4)2SO4 at Different Concentrations; Definition of Consequences on the Process Evolution, Quantification of CO2 Captured and Validation of Hydrates Production as Technique for Ammonium Removal from Waste Water

Carbon dioxide hydrates were formed in fresh water and in aqueous mixtures containing ammonium sulfate, at concentrations equal to 1.9, 6.3, and 9.5 wt%. The moles of hydrates formed were compared, to define the inhibiting strength of the electrolyte solution and the dependence of inhibition from concentration. The addition of salt strongly inhibited the process and the number of hydrates produced passed from 0.204–0.256 moles, obtained in fresh water, to 0.108–0.198 moles, obtained at the lowest concentration tested. The further addition of salt still lowered the production of the hydrates; at the highest concentration tested, only 0.092–0.177 moles were obtained. The pressure-temperature evolutions of the hydrates were then discussed and compared with the ideal process and with the experimental results obtained in demineralised water. Finally, further samples of CO2 hydrates, produced in the presence of 9.5 wt% salt in the aqueous phase (corresponding to 1.5 wt% NH4+), were recovered and dissociated in a separated environment. The liquid phase, resulting from their dissociation, was subjected to spectrophotometric analyses. Its NH4+ content was measured and compared with the initial concentration in water. Therefore, it was possible to quantify the capability of the system to remove the (NH4)2SO4 from the water (involved in hydrate formation) and to concentrate it in the remaining liquid phase. Considering the portion of water involved in hydrates formation, the concentration of ammonium passed from 1.5 wt% to 0.38–0.449 wt%.

Ratiometric dual-emission carbon dots coupled with smartphone for visual quantification of Co2+ and EDTA and biological sensing

Ratiometric fluorescence analysis provides the feasibility for visual quantitative sensing by presenting continuous color changes. Herein, dual-emission carbon dots (D-CDs) have been developed for ratiometric recognition of Co2+ and EDTA, along with successive fluorescence variation of yellow, purplish-pink, purple, light blue, and dark blue. D-CDs have been synthesized by microwave-assisted heating of tetracycline and manifest dual emissions at 562 nm and 610 nm under 450 nm excitation. Intriguingly, the emissions at 562 nm and 610 nm are quenched while a ratio rising emission emerges at 482 nm upon introducing Co2+, which displays ratiometric fluorescence emission characteristics (I482/I562) in the range of 0.25–400 µM with significant fluorescence varying from yellow, purplish-pink, purple, light blue, to dark blue. Subsequent addition of EDTA could ratiometric recover the fluorescence of D-CDs in the range of 50–130 µM with the fluorescence returning from dark blue, light blue, purple, purplish-pink, to yellow. More crucially, integrating continuous color changes and color recognizer APP in the smartphone, visual quantification of Co2+ and EDTA can be realized based on the ratio of blue value and red value (B/R) with linear ranges of 0–400 µM and 0–300 µM, respectively. Furthermore, proposed D-CDs could be extended as a visual biosensing platform for tracking Co2+ and EDTA in living cells, which have potentialapplication prospect in biosystem.

Suitability of a diamine functionalized metal-organic framework for direct air capture.

The increase in the atmospheric carbon dioxide level is a significant threat to our planet, and therefore the selective removal of CO2 from the air is a global concern. Metal-organic frameworks (MOFs) are a class of porous materials that have shown exciting potential as adsorbents for CO2 capture due to their high surface area and tunable properties. Among several implemented technologies, direct air capture (DAC) using MOFs is a promising strategy for achieving climate targets as it has the potential to actively reduce the atmospheric CO2 concentration to a safer levels. In this study, we investigate the stability and regeneration conditions of N,N'-dimethylethylenediamine (mmen) appended Mg2(dobpdc), a MOF with exceptional CO2 adsorption capacity from atmospheric air. We employed a series of systematic experiments including thermogravimetric analysis (TGA) coupled with Fourier transformed infrared (FTIR) and gas chromatography mass spectrometer (GCMS) (known as TGA-FTIR-GCMS), regeneration cycles at different conditions, control and accelerated aging experiments. We also quantified CO2 and H2O adsorption under humid CO2 using a combination of data from TGA-GCMS and coulometric Karl-Fischer titration techniques. The quantification of CO2 and H2O adsorption under humid conditions provides vital information for the design of real-world DAC systems. Our results demonstrate the stability and regeneration conditions of mmen appended Mg2(dobpdc). It is stable up to 50% relative humidity when the adsorption temperature varies from 25-40 °C and the best regeneration condition can be achieved at 120 °C under dynamic vacuum and at 150 °C under N2.

Real-Time Monitoring of Gas-Phase and Dissolved CO2 Using a Mixed-Matrix Composite Integrated Fiber Optic Sensor for Carbon Storage Application.

Novel chemical sensors that improve detection and quantification of CO2 are critical to ensuring safe and cost-effective monitoring of carbon storage sites. Fiber optic (FO)-based chemical sensor systems are promising field-deployable systems for real-time monitoring of CO2 in geological formations for long-range distributed sensing. In this work, a mixed-matrix composite integrated FO sensor system was developed with a purely optical readout that reliably operates as a detector for gas-phase and dissolved CO2. A mixed-matrix composite sensor coating consisting of plasmonic nanocrystals and hydrophobic zeolite embedded in a polymer matrix was integrated on the FO sensor. The mixed-matrix composite FO sensor showed excellent reversibility/stability in a high humidity environment and sensitivity to gas-phase CO2 over a large concentration range. This remarkable sensing performance was enabled by using plasmonic nanocrystals to significantly enhance the sensitivity and a hydrophobic zeolite to effectively mitigate interference from water vapor. The sensor exhibited the ability to sense CO2 in the presence of other geologically relevant gases, which is of importance for applications in geological formations. A prototype FO sensor configuration, which possesses a robust sensing capability for monitoring dissolved CO2 in natural water, was demonstrated. Reproducibility was confirmed over many cycles, both in a laboratory setting and in the field. More importantly, we demonstrated on-line monitoring capabilities with a wireless telemetry system, which transferred the data from the field to a website. The combination of outstanding CO2 sensing properties and facile coating processability makes this mixed-matrix composite FO sensor a good candidate for practical carbon storage applications.

Measuring in situ CO2 and H2O in apatite via ATR-FTIR

We present a new approach to determine in situ CO2 and H2O concentrations in apatite via attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Absolute carbon and hydrogen measurements by nuclear reaction analysis (NRA) and elastic recoil detection (ERD) are used to calibrate ATR-FTIR spectra of CO2 and H2O in apatite. We show that CO2 and H2O contents in apatite can be determined via linear equations (r2 > 0.99) using the integrated area of CO2 and H2O IR absorption bands. The main benefits of this new approach are that ATR-FTIR analyses are non-destructive and can be conducted on polished sample material surfaces with a spatial resolution of ~ 35 μm. Furthermore, the wavenumber of the phosphate IR absorption band can be used to determine the crystallographic orientation of apatite, which allows for accurate quantification of CO2 and H2O in randomly orientated apatite grains. The limit of quantification of H2O in apatite is ~ 400 ppm and ~ 100 ppm for CO2. Via two examples, one from a carbonatite and one from a metasedimentary rock, we show that this new technique opens up new possibilities for determining volatile concentrations and behavior in a wide range of hydrothermal, igneous, and metamorphic systems.

Neural-network-based estimation of regional-scale anthropogenic CO<sub>2</sub> emissions using an Orbiting Carbon Observatory-2 (OCO-2) dataset over East and West Asia

Abstract. Atmospheric carbon dioxide (CO2) is the most significant greenhouse gas, and its concentration is continuously increasing, mainly as a consequence of anthropogenic activities. Accurate quantification of CO2 is critical for addressing the global challenge of climate change and for designing mitigation strategies aimed at stabilizing CO2 emissions. Satellites provide the most effective way to monitor the concentration of CO2 in the atmosphere. In this study, we utilized the concentration of the column-averaged dry-air mole fraction of CO2, i.e., XCO2 retrieved from a CO2 monitoring satellite, the Orbiting Carbon Observatory-2 (OCO-2), and the net primary productivity (NPP) provided by the Moderate Resolution Imaging Spectroradiometer (MODIS) to estimate the anthropogenic CO2 emissions using the Generalized Regression Neural Network (GRNN) over East and West Asia. OCO-2 XCO2, MODIS NPP, and the Open-Data Inventory for Anthropogenic Carbon dioxide (ODIAC) CO2 emission datasets for a period of 5 years (2015–2019) were used in this study. The annual XCO2 anomalies were calculated from the OCO-2 retrievals for each year to remove the larger background CO2 concentrations and seasonal variability. The XCO2 anomaly, NPP, and ODIAC emission datasets from 2015 to 2018 were then used to train the GRNN model, and, finally, the anthropogenic CO2 emissions were estimated for 2019 based on the NPP and XCO2 anomalies derived for the same year. The estimated and the ODIAC CO2 emissions were compared, and the results showed good agreement in terms of spatial distribution. The CO2 emissions were estimated separately over East and West Asia. In addition, correlations between the ODIAC emissions and XCO2 anomalies were also determined separately for East and West Asia, and East Asia exhibited relatively better results. The results showed that satellite-based XCO2 retrievals can be used to estimate the regional-scale anthropogenic CO2 emissions, and the accuracy of the results can be enhanced by further improvement of the GRNN model with the addition of more CO2 emission and concentration datasets.

Impacts of Extreme Ambient Temperatures and Road Gradient on Energy Consumption and CO2 Emissions of a Euro 6d-Temp Gasoline Vehicle

The EU aims to substantially reduce its greenhouse gas emissions in the following decades and achieve climate neutrality by 2050. Better CO2 estimates, particularly in urban conditions, are necessary for assessing the effectiveness of various regional policy strategies. In this study, we measured the CO2 emissions of a Euro 6d-temp gasoline direct injection (GDI) vehicle with a three-way catalyst (TWC) and a gasoline particulate filter (GPF) at ambient temperatures from −30 °C up to 50 °C with the air-conditioning on. The tests took place both on the road and in the laboratory, over cycles simulating congested urban traffic, dynamic driving, and uphill driving towing a trailer at 85% of the maximum payloads of both the car and the trailer. The CO2 values varied over a wide range depending on the temperature and driving conditions. Vehicle simulation was used to quantify the effect of ambient temperature, vehicle weight and road grade on the CO2 emissions. The results showed that vehicle energy demand was significantly increased under the test conditions. In urban trips, compared to the baseline at 23 °C, the CO2 emissions were 9–20% higher at −10 °C, 30–44% higher at −30 °C, and 37–43% higher at 50 °C. Uphill driving with a trailer had 2–3 times higher CO2 emissions. In motorway trips at 50 °C, CO2 emissions increased by 13–19%. The results of this study can help in better quantification of CO2 and fuel consumption under extreme conditions. Additional analysis on the occurrence of such conditions in real-world operation is advisable.

Machine learning deciphers CO<sub>2</sub> sequestration and subsurface flowpaths from stream chemistry

Abstract. Endmember mixing analysis (EMMA) is often used by hydrogeochemists to interpret the sources of stream solutes, but variations in stream concentrations and discharges remain difficult to explain. We discovered that machine learning can be used to highlight patterns in stream chemistry that reveal information about sources of solutes and subsurface groundwater flowpaths. The investigation has implications, in turn, for the balance of CO2 in the atmosphere. For example, CO2-driven weathering of silicate minerals removes carbon from the atmosphere over ∼106-year timescales. Weathering of another common mineral, pyrite, releases sulfuric acid that in turn causes dissolution of carbonates. In that process, however, CO2 is released instead of sequestered from the atmosphere. Thus, understanding long-term global CO2 sequestration by weathering requires quantification of CO2- versus H2SO4-driven reactions. Most researchers estimate such weathering fluxes from stream chemistry, but interpreting the reactant minerals and acids dissolved in streams has been fraught with difficulty. We apply a machine-learning technique to EMMA in three watersheds to determine the extent of mineral dissolution by each acid, without pre-defining the endmembers. The results show that the watersheds continuously or intermittently sequester CO2, but the extent of CO2 drawdown is diminished in areas heavily affected by acid rain. Prior to applying the new algorithm, CO2 drawdown was overestimated. The new technique, which elucidates the importance of different subsurface flowpaths and long-timescale changes in the watersheds, should have utility as a new EMMA for investigating water resources worldwide.

A sealed-tube method for offline δ13 C analysis of CO2 via a Gas Bench II continuous-flow isotope ratio mass spectrometer.

The isotopic measurement of environmental sample CO2 via isotope ratio mass spectrometry (IRMS) can present many analytical challenges. In many offline applications, exceedingly few samples can be prepared per day. In such applications, long-term storage (months) of sample CO2 is desirable, in order to accumulate enough samples to warrant a day of isotopic measurements. Conversely, traditional sample tube cracker systems for dual-inlet IRMS offer a capacity for only 6-8 tubes and thus limit throughput. Here we present a simple method to alleviate these concerns using a Gas Bench II gas handling device coupled with continuous-flow IRMS. Sample preparation entails the cryogenic purification and quantification of CO2 on a vacuum line. Sample CO2 splits are expanded from a known volume to several sample ports and allowed to isotopically equilibrate (homogenize). Equilibrated CO2 splits are frozen into 3 mm outer diameter Pyrex break-seals and sealed under vacuum with a torch to a length of 5.5 cm. Sample break-seals are scored, placed into 12 mL Labco Exetainer® vials, purged with ultrahigh-purity helium, cracked inside the capped helium-flushed vials and subsequently measured via a Gas Bench equipped IRMS instrument using a CTC Analytics PAL autosampler. Our δ13 C results from NIST and internal isotopic standards, measured over a time period of several years, indicate that the sealed-tube method produces accurate δ13 C values to a precision of ±0.1‰ for samples containing 10-35 μgC. The tube cracking technique within Exetainer vials has been optimized over a period of 10 years, resulting in decreased sample failure rates from 5-10% to <1%. This technique offers an alternative method for δ13 C analyses of CO2 where offline isolation and long-term storage are desired. The method features a much higher sample throughput than traditional dual-inlet IRMS cracker setups at similar precision (±0.1‰).

A Novel Methodology for Online Analysis of Amine Solution Degradation Caused by Fly Ash

Two research goals were set for this study. (1) The first goal was to develop a reliable and cost-effective online analytical technique to measure amine solvent concentration, loading, and to quantify the amine degradation process based on Gas Chromatography (GC). (2) The second goal was the investigation of amine degradation in the presence of fly ash, which includes: the identification of proper chemistry of degradation; and, the identification and quantification of the degradation products of the amines. For this study, aqueous monoethanolamine (MEA) and aqueous methyldiethanolamine (MDEA) have been selected. To accomplish the first goal, an online analytical technique to quantify the amine solvent chemistry based on Gas Chromatography (GC) was developed and set up in the lab. An automatic liquid sample injection system was attached to the GC to study the impact of the concentration of fly ash on the degradation process of two well-known amines (MEA and MDEA) by measuring the concentrations of amine, water and carbon dioxide (CO2). The flow system was equipped with filters to avoid the introduction of large particles into the GC column. A solvent back-flush system was used to allow for automated cleaning of the particulate filters. GC was then calibrated for the amine and water using various concentrations of aqueous amines (MEA and MDEA), and various CO2 loaded aqueous MDEA solutions and aqueous solutions of ammonium bicarbonate (NH4HCO3) were used to calibrate the GC for quantification of CO2 using a Total Organic Carbon / Total Inorganic Carbon (TOC/TIC) analyzer. To accomplish the second goal, two kinds of fly ash samples were collected from a coal burning power plant. Fly ash samples collected from the power plant were analyzed by SGS Canada Inc. ASTM methods were used to estimate the ash percentage, moisture content and elemental composition of the fly ash (silica and other metal oxides). A lab scale experimental setup was designed and developed to observe the influence of fly ash on amine-based solvents (MEA or MDEA) degradation.

Sulfur quantum dot-based portable paper sensors for fluorometric and colorimetric dual-channel detection of cobalt

Sulfur quantum dots are promising alternatives for traditional heavy metal-containing quantum dots due to their benign chemical properties and low cytotoxicity. Herein, cysteine-decorated sulfur dots were prepared from facile modification of pristine sulfur dots and can be acted as a chemosensor for the fluorometric and colorimetric dual-channel detection of cobalt (Co2+) with high sensitivity and selectivity. Visual colors of the as-prepared chemosensor in the presence of Co2+ changed from blue to colorless under UV light and also can transform from colorless to yellow under sunlight based on the photoinduced electron transfer effect. The detection limit of cysteine-decorated sulfur dots toward Co2+ was determined as low as 0.16 μM with a wide detection range, which is lower than the permitted guideline level by Department of Environmental Protection for drinking water (1.7 μM). Furthermore, portable paper sensor-based cysteine-decorated sulfur dots were fabricated for Co2+ detection and showed superior detection ability. Aided by a common smartphone as detector, the rapid, on-site and accurate quantification of Co2+ in real water samples can be accomplished. Our research has provided a novel chemosensor based on sulfur dots for dual-channel detection of Co2+, which would expand applications of sulfur dots in environmental monitoring, diseases diagnosis, cell imaging, light-emitting diodes, etc. Cysteine-decorated sulfur dots were acted as a chemosensor for fluorometric and colorimetric dual channel detection of Co2+ based on the photoinduced electron transfer effect.

The validity of floating chambers in quantifying CO2 flux from headwater streams

AbstractThe amount of CO2 exiting headwater streams through degassing plays an important role in the global carbon cycle, yet quantification of CO2 degassing remains challenging because of the morphology of headwater streams and because of uncertainty about whether floating or suspended chambers provide valid measurements in moving water. We show that experiments using large and small floating chambers in flowing water over a moderate range of water velocities (0.13–0.23 m s−1) in a laboratory flume resulted in similar k600s to published field measurements with similar water velocities. We confirmed the flume experiments with paired stirred-still beaker experiments, where resulting k600s fell within the extrapolated trend of the flume experiments. We propose that the floating chambers can provide good estimates of CO2 degassing, particularly in shallow, low-velocity, morphologically complex headwater streams, permitting quantification of this important contributor to the global carbon cycle.

Seismic tuning of dispersive thin layers

ABSTRACTThe wedge model is commonly used to study the limits of seismic resolution where conventionally the thickness of sub‐resolution seismic layers can be determined from thin layer tuning curves. Tuning curves relate the layer temporal thickness to the wavelet frequency, but, to our knowledge, no systematic study has been done to date of the effects of velocity dispersion and attenuation on tuning. In this work, we study the tuning properties of a thin layer dispersing according to the standard linear solid model. We show that the first tuning curve is sensitive to the attenuation, relative polarity and magnitude of the two reflection coefficients at the top and base of the layer. We provide an analytic formula for the upper bound in the mismatch between the elastic and dispersive tuning curves. We conclude that highly attenuative thin layers can appear thicker or thinner than they actually are depending on polarity and relative magnitude of reflection coefficients at the layer interfaces. Our results are particularly relevant in the quantification of CO2 where knowledge of the temporal thickness of CO2 layers is reliant on their tuning curves.

Probing Interphase Reactions on Lithium with Operando Gas Chromatograph

Li battery chemistries exploit reactions that occur under very reducing conditions (~ 0 V vs. Li/Li+) at negative electrodes, which are held below the electrochemical stability window of known carbonate-based electrolyte systems (0.5-1 V vs. Li/Li+),1 resulting in solvent decomposition at the surface and leading to the formation of a solid electrolyte interphase (SEI). When formed on Li, however, this interphase is unable to fully protect the electrode, resulting in an SEI composition that changes over time.2 Due to this dynamic nature, its chemistry is challenging to characterize using conventional ex-situ surface analysis (e.g., Fourier transform infrared spectroscopy, FTIR; X-ray photoelectron spectroscopy, XPS).3, 4 Consequently, identifying the chemical mechanisms through which candidate systems for improving Li SEI stability operate – such as the use of highly fluorinated and/or concentrated electrolytes5 – remains difficult. Fortunately, interphase reactions are known to release gases that are easily detected by gas chromatography (GC) and mass spectrometry (MS),6 using which we are able to construct a time-resolved picture of the SEI chemistry. Here we show that these experiments can provide valuable insight into the dynamic chemical reaction pathways on Li, yielding an updated picture of factors that contribute to a good SEI.Our experimental approach consists of a custom-designed electrochemical cell coupled to a GC instrument, which, by sampling the cell headspace periodically, enables operando quantification of CO2, CO, H2 and C1-2 products evolved at Li electrodes. By comparing gas evolution between rest and polarization regimes, we identified a significant increase in the rate of formation of all observed gases when the electrodes are polarized. Using electrodes that we identified to be gas-inert, such as LiFePO4, we identified that the deposition reaction, i.e., Li+ reduction, accounts for nearly all of the gas-releasing interphase reactions, implying that the SEI is only formed electrochemically when Li is plated. We next explored the nature of these reactions by quantifying how the evolution rate of each gas scales with current density, which enabled the distinction between gases that were formed in chemically-limiting reactions and gases that were formed from electrochemically-limiting steps. Because our experiments are able to quantify the abundance of each gas product, we also identified and quantified the branching of specific interphase reactions that occur on Li with conventional carbonate-based electrolyte systems. Then, by rationally tuning the electrolyte (i.e., changing the salt species and/or introducing fluorinated solvents), we discovered and quantified how each component drives specific interphase reactions, and how the ensuing SEI chemistry affects the Faradaic efficiency of the Li electrode over time. In particular, we observed that pathways that promote decarbonylation and/or decarboxylation (i.e., release of CO/CO2) of the solvent upon reduction correlate with higher Faradaic efficiencies. By varying salt concentration, we further explored how interphase formation pathways are affected by the solvation structure of the electrolyte in the contact-ion and solvent-separated regimes. Thus, our experiments provide a mechanistic picture of how organic solvent-derived products affect SEI chemistry and stability, which can be as important as known ionic phases like LiF.5 1. Gauthier, M.; Carney, T. J.; Grimaud, A.; Giordano, L.; Pour, N.; Chang, H.-H.; Fenning, D. P.; Lux, S. F.; Paschos, O.; Bauer, C.; Maglia, F.; Lupart, S.; Lamp, P.; Shao-Horn, Y., The Journal of Physical Chemistry Letters 2015, 6 (22), 4653-4672.2. Lin, D.; Liu, Y.; Cui, Y., Nature Nanotechnology 2017, 12 (3), 194.3. Aurbach, D.; Markovsky, B.; Shechter, A.; Ein‐Eli, Y.; Cohen, H., Journal of The Electrochemical Society 1996, 143 (12), 3809-3820.4. Dedryvère, R.; Gireaud, L.; Grugeon, S.; Laruelle, S.; Tarascon, J. M.; Gonbeau, D., The Journal of Physical Chemistry B 2005, 109 (33), 15868-15875.5. Suo, L.; Xue, W.; Gobet, M.; Greenbaum, S. G.; Wang, C.; Chen, Y.; Yang, W.; Li, Y.; Li, J., Proceedings of the National Academy of Sciences 2018, 115 (6), 1156-1161.6. Xu, K., Chemical Reviews 2014, 114 (23), 11503-11618.

Chromogenic-Functionalized Silica Nanoflower Composites for the Detection of Carbon Dioxide

Herein, we report the fabrication of chromogenic nanocomposites through the functionalization of silica nanoflowers for the detection as well as the quantification of CO2 using an optical spectrosc...

Microbial Degradation of Plastic in Aqueous Solutions Demonstrated by CO2 Evolution and Quantification

The environmental accumulation of plastics worldwide is a consequence of the durability of the material. Alternative polymers, marketed as biodegradable, present a potential solution to mitigate their ecological damage. However, understanding of biodegradability has been hindered by a lack of reproducible testing methods. We developed a novel method to evaluate the biodegradability of plastic samples based on the monitoring of bacterial respiration in aqueous media via the quantification of CO2 produced, where the only carbon source available is from the polymer. Rhodococcus rhodochrous and Alcanivorax borkumensis were used as model organisms for soil and marine systems, respectively. Our results demonstrate that this approach is reproducible and can be used with a variety of plastics, allowing comparison of the relative biodegradability of the different materials. In the case of low-density polyethylene, the study demonstrated a clear correlation between the molecular weight of the sample and CO2 released, taken as a measure of biodegradability.

Fabrication of triazine based colorimetric and electrochemical sensor for the quantification of Co2+ ion

Triazine based Schiff base was synthesized by sonochemical method and it was explored for the robust selective and sensitive determination of Co2+ by both colorimetry and electrochemical sensing. Selectivity studies were carried out with different metal ions and found that the proposed chemosensor has significant selectivity for the detection of Co2+ with the colour change from yellow to blue owing to the formation of complex with Co2+.The colorimetric sensitivity studies of BNHNTA shows maximum detection value of 0.05 µM towards the quantification of Co2+. In addition the amperometric studies exhibit selective electrochemical sensing of Co2+ by BNHNTA and the detection limit was calculated to be 0.03 µM. The HOMO-LUMO diagram clearly shows mechanism of charge transfer from ligand to metal (LMCT) between the triazine and Co2+ ion. In addition to that, Density functional theoretical (DFT) study provides the structural insights about cobalt (II) complex, which confirms the square pyramidal geometry of the formed complex. Theoretical studies confirm the formation of 1:1 receptor-metal ion complex in detecting Co2+ ion. High resolution mass spectrometry (HRMS) measurements confirm the above complex structure. Job's plot measurements also justify the same.