Removal Of Oxygen Research Articles

Novel Phase YBa2Cu3O5 derived from the High Tc Superconductor YBa2Cu3O7-x

The orthorhombic unit cell of high Tc oxide superconductor YBa2Cu3O7–x is indicated by two-dimensional CuO2 planes spanned in a-b directions. Partial removal of oxygen, down to x > 1, creates an insulating state and randomly distributed oxygen vacancies. An attempt has been made to increase the concentration of vacancies up to some critical value when their ordering could take place, while balance with copper cations will still maintain the original tetragonal structure. Removal of two oxygen atoms per unit cell results in the YBa2Cu3O5 compound and formation of linear Cu1+– O chains. The novel phase is an insulator, and doping in a low (50 –200 mbar) oxygen atmosphere at T < 800 K converts it to a conducting state.

Formation of oxygen vacancy at surfaces of ZnO by trimethylaluminum

The two-dimensional electron gas (2DEG) is a group of electrons that can move freely in horizontal dimensions but are confined in the third direction. It has been reported that atomic layer deposition (ALD) of Al2O3 on various reducible n-type oxides can lead to the formation of 2DEG at the heterojunction interfaces, among which ZnO is known to provide promising properties. In this study, we have performed a theoretical analysis using density functional theory calculations combined with experimental investigations to elucidate the surface reactions of Al2O3 ALD on low-index nonpolar ZnO surfaces, specifically focusing on the formation of oxygen vacancies (VO). The trimethylaluminum precursor was observed to undergo sequential dissociation of CH3 ligands, leading to the removal of surface oxygen of ZnO in the form of dimethyl ether. In addition, by examining the electronic structure after the removal of oxygen, the localization of the charge density at the surface was confirmed. Experimentally, the carrier density of the 2DEG at the Al2O3/ZnO interface showed a strong dependence on the ALD process temperature of Al2O3, confirming the endothermic nature of the formation of the 2DEG. By examining the characteristics of the 2DEG induced by VO, insights into the fundamental comprehension of oxide-based 2DEG systems are provided.

Benefits of intratracheal and extrathoracic high-frequency percussive ventilation in a model of capnoperitoneum.

Abdominal inflation with CO2 is used to facilitate laparoscopic surgeries, however, providing adequate mechanical ventilation in this scenario is of major importance during anesthesia management. We characterized high-frequency percussive ventilation (HFPV) in protecting from the gas exchange and respiratory mechanical impairments during capnoperitoneum. In addition, we aimed to assess the difference between conventional pressure-controlled mechanical ventilation (CMV) and HFPV modalities generating the high-frequency signal intratracheally (HFPVi) or extrathoracally (HFPVe). Anesthetized rabbits (n = 16) were mechanically ventilated by random sequences of CMV, HFPVi, and HFPVe. The ventilator superimposed the conventional waveform with two high-frequency signals (5 Hz and 10 Hz) during intratracheal HFPV (HFPVi) and HFPV with extrathoracic application of oscillatory signals through a sealed chest cuirass (HFPVe). Lung oxygenation index ([Formula: see text]/[Formula: see text]), arterial partial pressure of carbon dioxide ([Formula: see text]), intrapulmonary shunt (Qs/Qt), and respiratory mechanics were assessed before abdominal inflation, during capnoperitoneum, and after abdominal deflation. Compared with CMV, HFPVi with additional 5-Hz oscillations during capnoperitoneum resulted in higher [Formula: see text]/[Formula: see text], lower [Formula: see text], and decreased Qs/Qt. These improvements were smaller but remained significant during HFPVi with 10 Hz and HFPVe with either 5 or 10 Hz. The ventilation modes did not protect against capnoperitoneum-induced deteriorations in respiratory tissue mechanics. These findings suggest that high-frequency oscillations combined with conventional pressure-controlled ventilation improved lung oxygenation and CO2 removal in a model of capnoperitoneum. Compared with extrathoracic pressure oscillations, intratracheal generation of oscillatory pressure bursts appeared more effective. These findings may contribute to the optimization of mechanical ventilation during laparoscopic surgery.NEW & NOTEWORTHY The present study examines an alternative and innovative mechanical ventilation modality in improving oxygen delivery, CO2 clearance, and respiratory mechanical abnormalities in a clinically relevant experimental model of capnoperitoneum. Our data reveal that high-frequency oscillations combined with conventional ventilation improve gas exchange, with intratracheal oscillations being more effective than extrathoracic oscillations in this clinically relevant translational model.

Avoiding Oxygen Removal for Photochemical Reactions – towards Water as the Solvent

AbstractOxygen removing protocols have long been the standard approach to perform photoreactions. By encapsulating photosensitizers and reactants in tailored supramolecular assemblies, preservation of photoreactivity even in the presence of molecular oxygen can be observed. Herein, we showcase some of the solutions that could render time‐consuming oxygen removal redundant in photochemical synthesis. A focus has been dedicated to aqueous solutions of supramolecular assemblies as potential reaction media. They present an attractive solution possibly useful not only for synthetic photochemical transformations, but also for water purification, bio‐applications or biocatalysis. The included media are membranes, hydrogels, deep eutectic solvents and peptide assemblies.

Steering the Reconstruction of Oxide-Derived Cu by Secondary Metal for Electrosynthesis of n-Propanol from CO.

As fuel and an important chemical feedstock, n-propanol is highly desired in electrochemical CO2/CO reduction on Cu catalysts. However, the precise regulation of the Cu localized structure is still challenging and poorly understood, thus hindering the selective n-propanol electrosynthesis. Herein, by decorating Au nanoparticles (NPs) on CuO nanosheets (NSs), we present a counterintuitive transformation of CuO into undercoordinated Cu sites locally around Au NPs during CO reduction. In situ spectroscopic techniques reveal the Au-steered formation of abundant undercoordinated Cu sites during the removal of oxygen on CuO. First-principles accuracy molecular dynamic simulation demonstrates that the localized Cu atoms around Au tend to rearrange into disordered layer rather than a Cu (111) close-packed plane observed on bare CuO NSs. These Au-steered undercoordinated Cu sites facilitate CO binding, enabling selective electroreduction of CO into n-propanol with a high Faradaic efficiency of 48% in a flow cell. This work provides new insight into the regulation of the oxide-derived catalysts reconstruction with a secondary metal component.

UV‐Light Generation in Micelles via Triplet‐Triplet Annihilation Upconversion – Towards Synthetic Applications

AbstractOver the last century UV‐light mediated processes gave access to synthetically valuable products. Some of the disadvantages encountered when performing such UV‐light triggered synthetic reactions are the necessity for special glassware (quartz), the environmentally unfriendly irradiation sources and the need for oxygen removal, often via time consuming freeze‐pump‐thaw cycles. In addition, the penetration of UV‐light into the reaction mixture is a challenge due to absorption effects and scattering. A solution to these disadvantages could be triplet‐triplet annihilation upconversion performed under micellar reaction conditions. Hereby, UV‐light can be generated in the reaction mixture using visible light irradiation. In addition, the aqueous micellar medium can allow for the process to occur without the need for oxygen removal. This concept has been sporadically demonstrated and holds a great promise for the development of UV‐light promoted photochemical reactions under milder and more benign reaction conditions that may eventually allow for the development of scale up protocols.

Influence mechanisms of torrefaction on syngas production from bio-waste molten salt thermal treatment

The production of high-value syngas from bio-wastes through thermal conversion is a promising way to achieve carbon neutrality. In order to reduce the cost of the process, molten salt thermal treatment has been used for bio-wastes syngas production. Moreover, the removal of oxygen and water induced by torrefaction can effectively enhance the energy density of biomass, and the effect of these changes on the quality of syngas was widely investigated. This study proposed to torrefy bio-wastes and then produce syngas in molten NaNO3-NaNO2-KNO3 at 300 ℃. Results showed that the evaluation indices of syngas were improved, while the cold gas efficiency reached 44.02 % for beech wood torrefied at 280 ℃, and the syngas quality is equivalent to the products obtained by gasification of bio-wastes. The gas yield of the torrefied bio-wastes was increased by 8.08–45.23 % compared to the raw bio-wastes. Na+ and K+ in the molten salt catalyzed the cracking of propyl chains and ring opening of aromatic rings in lignin, resulting in a prominent enhancement in CO yield. Meanwhile, torrefaction could change the solid structure, leading to a delay in gas production, and torrefaction could also increase graphitization degree of char (C–C/C = C up to 50.72 % for SB-280), thus preventing the reaction proceeding. This study provided a new approach to enhance the content and quality of syngas from bio-wastes at low temperatures.

Cooperation of Mn and P atoms in graphene for efficiently catalyzing CO oxidation at low temperature

Computational studies show that the co-doping of Mn and P atoms in graphene (MnP4-Gr) can provide high CO oxidation performance at room temperature. Results suggest that the configuration (CO+O2)* can be easily obtained due to the better adsorption of CO on the Mn atom and O2 on the P atom. (CO+O2)* is further found to undergo a fast Langmuir−Hinshelwood (LH) process and then left one atomic oxygen on P which is difficult to remove. Therefore, due to the more favorable adsorption of CO on the Mn atom and O2 on other P atoms, coupled with the speed of the LH process, the configuration (CO+4O)* of one atomic oxygen adsorbed on each P atom and CO on Mn atom is finally obtained. The whole reaction is determined by the atomic oxygen removal in (CO+4O)* with an energy barrier of 0.80 eV. It is predicted that the cooperation of Mn and P atoms is conducive to the fast LH process of MnP4-Gr and also the weaker binding between P and O in MnP4-Gr. Moreover, thermodynamic and kinetics analysis indicates that increasing temperature can accelerate CO oxidation and facilitate reaction in thermodynamics. Therefore, the insights reported in this paper will provide a new catalyst for low-temperature CO oxidation.

Poor Diet Leading to the Increasing Risk of Atherosclerosis in the World

Atherosclerosis Ischemic Cardiovascular Disease (ASICD), one of the leading causes of global deaths, is mainly caused due to the development of plaque on the inner walls of arteries of the human heart. Ischemia refers to the lack of enough oxygen (O2), nutrient delivery, and improper waste removal in the cardiac cells. About 90% of cardiovascular diseases in the present world are due to the formation of lipid/cholesterol-based plaques that can form under the lining of the smooth epithelial blood cells. In the US, a study published in the Journal of the American College of Cardiology estimated that poor diet is responsible for about 45% of Cardiovascular Disease. Atherosclerosis doesn’t cause much effect until and unless the plaque becomes unstable due to the accumulation of thrombus that shows Acute Coronary Syndrome. Acute Coronary Syndrome is the result of blockage of blood vessels leading to Myocardial Infarction (Unstable Angina Pectoris). Cardiac Cells require a sufficient amount of Oxygen to function properly. Thus, the demand and supply of oxygen to the cardiac cells should be properly balanced. Atherosclerosis Ischemic Cardiovascular syndrome can worsen if the person is more involved in exercise or emotional stress because at that time their body requires higher oxygen but blood flow gets disrupted due to the formation of plague. Later in the paper, we will discuss the New York Heart Association classification, followed by the top 3 poor diets that are considered to be increasing the cases of cardiovascular disease around the world.

Confined dual Lewis acid centers for selective cascade C-C coupling and deoxygenation.

The selective formation of C-C bonds, coupled with effective removal of oxygen, plays a crucial role in the process of upgrading biomass-derived oxygenates into fuels and chemicals. However, co-feeding reactants with water is sometimes necessary to assist binding sites in catalytic reactions, thereby achieving desirable performance. Here, we report the design of a CeSnBeta catalyst featuring dual Lewis acidic sites for the efficient production of isobutene from acetone via C-C coupling followed by deoxygenation. By incorporating Ce species onto SnBeta, which was synthesized through liquid-phase grafting of dealuminated Beta, we created confined dual Lewis acidic centers within Beta zeolites. The cooperative action of Ce species and framework Sn sites within this confined environment enabled selective catalysis of the acetone-to-isobutene cascade reactions, showcasing enhanced stability even without the presence of water.

The effect of temperature and oxygen partial pressure on the concentration of iron and manganese ions in La1/3Sr2/3Fe1-xMnxO3-δ.

The oxygen content was measured in cubic perovskite-type La1/3Sr2/3Fe1-xMnxO3-δ (x = 0.1, 0.17, 0.25, and 1/3) in the range of oxygen partial pressure from 10-22 to 0.5 atm at 750-950 °C with a step of 50 °C by coulometric titration. Gradual removal of oxygen from the oxides during the measurements was carried out until the stability limit was achieved and the reductive decomposition began. An increase in manganese content was shown to lead to a decrease in the stability of La1/3Sr2/3Fe1-xMnxO3-δ under reducing conditions. The obtained data on oxygen content were used for defect chemistry modeling in the oxides. The enthalpy of the Fe3+ to Fe4+ and Mn3+ to Mn4+ oxidation reactions (ΔHox0) was determined to be -103.2 ± 0.3 and -250 ± 2 kJ mol-1, respectively, for the x = 0.1 composition, and increased slightly with increasing manganese content. The large difference in ΔHox0 determines a strong distinction between the behavior of iron and manganese in perovskite-type oxides. An increase in manganese content in La1/3Sr2/3Fe1-xMnxO3-δ was found to lead to a decrease in the concentration of Fe4+ ions, but did not affect the concentration of Fe2+ ions. The impact of La/Sr ratio was evaluated by comparison of the obtained data with that for La0.5Sr0.5Fe1-xMnxO3-δ, and found to be different for iron and manganese. An increase in lanthanum fraction causes a decrease in the concentration of Fe2+ ions and an increase in the concentration of Mn2+ under reducing conditions.

Response surface methodology optimization of the effect of pH, contact time, and microbial concentration on chemical oxygen removal potential of vegetable oil industrial effluents.

The vegetable oil refinery industry generates highly polluted effluents during oil production, necessitating proper treatment before discharge to prevent environmental hazards. Treating such wastewater has become a major environmental concern in developing countries. Chemical oxygen demand (COD) is a key parameter in assessing the wastewater's organic pollutant load. High COD levels can lead to reduced dissolved oxygen in water bodies, negatively affecting aquatic life. Various technologies have been employed to treat oily wastewater, but microbial degradation has gained attention due to its potential to remove organic pollutants efficiently. This study aims to optimize the biodegradation treatment process for vegetable oil industrial effluent using response surface methodology (RSM). The wastewater's physicochemical properties were characterized to achieve this, and COD removal was analyzed. Furthermore, RSM was used to investigate the combined effects of pH, contact duration, and microbial concentration on COD removal efficiency. The result showed that the microbial strain used recorded a maximum COD removal of 92%. Furthermore, a quadratic model was developed to predict COD removal based on the experimental variables. From the analysis of variance (ANOVA) analysis, the model was found to be significant at p < 0.0004 and accurately predicted COD removal rates within the experimental region, with an R2 value of 90.99% and adjusted R2 value of 82.89%. Contour plots and statistical analysis revealed the importance of contact duration and microbial concentration on COD removal. PRACTITIONER POINTS: Response surface methodology (RSM) optimization achieved a significant chemical oxygen demand (COD) removal efficiency of 92% in vegetable oil industrial effluents. The study's success in optimizing COD removal using RSM highlights the potential for efficient and environmentally friendly wastewater treatment. Practitioners can benefit from the identified factors (pH, contact time, and microbial concentration) to enhance the operation of treatment systems. The developed predictive model offers a practical tool for plant operators and engineers to tailor wastewater treatment processes. This research underscores the importance of sustainable practices in wastewater treatment, emphasizing the role of microbial degradation in addressing organic pollutant loads.

Catalytic aqueous hydrodeoxygenation of palmitic acid with in-situ hydrogen donor

Algal bio-oil obtained from hydrothermal liquefaction of algae contains a large amount of water and long-chain fatty acids. High acidity and corrosiveness seriously restrict the application of algal bio-oil. The aqueous-phase catalytic upgrading was a promising approach to solve this problem, and the hydrogen donor was one of the most important parameters to the conversion of the algal bio-oil and the quality of the products. Catalytic transfer hydrogenation (CTH) reaction was an efficient, economical and green method for hydrogenation reaction, which can directly transfer hydrogen from the hydrogen donor to the reaction substrate. In this work, the CTH reaction of algal bio-oil model compound palmitic acid was investigated to deal with the problem of high oxygen content in the algal bio-oil. Several common hydrogen donors, included methanol, ethanol, formic acid, and isopropanol, as well as different reaction conditions were experimented to study the CTH process of palmitic acid. The results showed that, with the reaction conditions of 350 °C and 10 h, formic acid achieved the best oxygen removal, carbon retention and energy efficiency, the C16 selectivity reached the highest at 33.3 % as the formic acid addition ratio was 1:2, and the C15 selectivity reached the highest at 48.3 % as the formic acid addition ratio was 1:3. In general, the best ratio of formic acid added was 1:3, which showed the highest yield of C15 and above alkanes of 79.6 %. This result indicates that the catalytic transfer hydrogenation reaction of formic acid has practical value in improving the combustion performance of algal bio-oil.

Dissolved Oxygen Removal in Wines by Gas Sparging, Its Optimization and Chemical Impact

Sparging is a technique to remove an excess of dissolved oxygen from the wine with inerting gases before bottling to avoid negative consequences for its chemical and sensory properties. However, its effectiveness on these properties has not been studied in depth. This work investigates the effectiveness of different inerting gases (N2, CO2, and argon) in removing dissolved oxygen in different volumes of a model wine. The efficacy of these gases was also studied in white and red wine, as was their effect on the physicochemical characteristics. Sparging with N2 in the model wine gave the best results in terms of cost–benefits, and with CO2 the worst. The scaling in tanks of different sizes allowed us to establish that the N2 expenditure ranged between 0.09 L and 0.23 L of gas per liter of model wine, establishing an index (Lgas/Lwine) that can be very useful for wineries to remove the dissolved oxygen. Sparging treatments in white and red wine showed very similar results to the model wine. The effect on the chemical properties of the wines was, in some cases, different for white and red wine and for each gas used. The incorporation of oxygen and the subsequent sparging produced a significant loss of some volatile compounds of sensory interest and increased the content of others that have a negative sensory effect. In addition, it had a negative effect on the chromatic properties of red wines.

Determination of the efficiency of oxygen removal from water from the ratio of the concentrations of sodium sulfite and the iron catalyst

The main issue of corrosion activity is the removal of oxygen from water. Under certain conditions, inhibitors-passivators are effective. Other methods based on thermal and vacuum deaeration of water. These methods are energy-consuming and do not provide the necessary quality of water, so chemical reagents are used for deep deoxidation of water regardless of secondary pollution.&#x0D; In this work, distilled water with a certain concentration of oxygen was placed in a hermetic container. The calculated amount of sodium sulfite solution (sodium metabisulfite) was added to the water and after certain intervals the oxygen concentration in the water was recorded using an oxygen meter, the sensor of which was placed in the container before. In another series of experiments, calculated amounts of sodium sulfite and iron sulfate solutions were added to the water, the container was quickly closed and the oxygen concentration in the water was recorded at certain intervals.&#x0D; It has been shown that in distilled water at room temperature, sodium sulfite interacts very slowly with oxygen. In 1 hour, the rate of oxygen recovery increases from 27.7 % to 56.9 % when the sulfite concentration increases from 50 to 300 mg/dm3. It was established that iron (II) ions significantly accelerate the rate of oxygen reduction by sulfite already at an iron concentration of 0.1 mg/dm3 at a sulfite concentration of 50-300 mg/dm3. According to the integral kinetic curves of the 0th, 1st, 2nd, and 3rd orders, kinetic models of sulfite oxidation in distilled water with oxygen in the presence of iron ions were determined.&#x0D; It is shown that when the concentration of sulfite increases to 200, 300 mg/dm3, with an iron concentration of 0.5‑1.0 mg/dm3, the oxidation processes follow first-order reactions and their speed is determined by the oxygen concentration. When the concentration of iron and sulfite is reduced, the realization of oxidation processes according to the reactions of the 2nd and 3rd orders was noted, when the speed of the process depends not only on the concentration of oxygen, but also on the concentration of sulfite (2nd order) and iron ions (3rd order) .&#x0D; This work is aimed at solving the relevance of the problem of water deoxidation for water preparation in cooling systems. The direction of the research is very promising considering the satisfactory and effective results obtained and the inexpensive chemical reagents used. Further research will be aimed at finding ideal conditions for the reaction and finding optimal concentrations of reagents while ensuring maximum efficiency of the process, which in turn will bring mankind a solution to the problem of spending large amounts of money, chemical reagents and environmental pollution.

Utilization of 3-D Volume of Fluid Simulations to Understand Oxygen Evolution through Multilayer Porous Transport Layers for PEMWE Improvement

In this work, direct numerical modeling techniques were applied to 3-D generated porous transport layers (PTL), with the addition of a microporous layer (MPL), to understand the effect pore structure has on oxygen evolution. Proton Exchange Membrane Water Electrolyzers rely on PTLs to remove oxygen from the catalyst layer. Traditionally, an MPL is added to the PTL surface in contact with the catalyst layer. This creates a bilayer PTL, which is believed to improve oxygen removal, while maintaining liquid saturation. Two questions arise when creating a PTL sample for PEMWE application. First, how thick should the MPL be to achieve adequate oxygen removal? Second, is a bilayer PTL sufficient, or does a multilayer PTL result in improved oxygen removal?The objectives of this work are to observe the influence that the MPL has on oxygen transport, the effect of the MPL on oxygen removal when compared to a single layer PTL, determine an ideal MPL to PTL ratio, and identify if multilayer PTLs aid in oxygen removal. Each sample is created through an improved image processing technique that eliminates the need for interface communication when meshing. This process allows for multilayer PTL structures to be created as one geometry. Due to the improved imaging technique, meshing of these complex structures is possible. The Finite Volume Method combined with a volume of fluid model was used to simulate two phase flow, liquid water and gaseous oxygen, through all PTL samples. Each PTL/MPL combination has three different MPL thickness, which corresponds to a PTL/MPL ratio of 90:10, 80:20, and 70:30. Bilayer, trilayer, and quadlayer PTL samples were also studied. Oxygen bubble evolution, growth, and surface interaction through all sample microstructures was observed. In-plane and through-plane permeability, liquid saturation, and liquid/gas interfacial area were calculated from simulation results. Findings from this work will provide insight into ideal MPL thickness and number of MPL layers for improved oxygen removal inside PEMWEs.

(2022-2023 ECS Toyota Young Investigator Fellowship) Enhanced Water Electrolysis Using Layered Coaxial Nanowire Electrodes

Novel electrocatalytic approaches are urgently needed to increase the energy efficiency and decrease the cost of hydrogen production by PEM water electrolyzers. Recently, we developed a novel catalytic platform, the layered coaxial nanowire electrode (LCANE), which enables PEM water electrolyzers with higher energy efficiency and reduced usage of precious metal catalysts. Electrolyzers based on the LCANE approach use a thin film of IrO2-decorated Pt that is intimately interfaced with an ionomer membrane in the form of vertically-aligned coaxial nanowires. Each nanowire consists of a Pt shell encapsulating an ionomer core, with the Pt shell further decorated by IrO2 clusters. The top region of each nanowire bends to form a layer of in-plane aligned Pt/IrO2 nanowires, providing excellent in-plane electronic conductivity. This unique catalyst/electrode geometry offers several key advantages. By localizing ionomer within the nanowire core, the exterior surface of the catalyst remains free from ionomer, eliminating thin-film transport barriers and preventing catalyst poisoning by ionomer adsorption. The vertically aligned sections of the nanowires provide non-tortuous transport of reactants and products, with abundant pore space for facile access of water and removal of oxygen. Close integration of catalyst and ionomer provides improved proton access and eliminates stranding of catalyst. By incorporating catalyst in the form of a thin film and replacing some of the Ir with Pt, lower Ir loading (as low as 0.1 mg/cm2) is achieved without sacrificing surface area or performance.AcknowledgmentThis work was supported by the ECS-Toyota Young Investigator Fellowship and by the Laboratory Directed Research and Development program at Los Alamos National Laboratory.

1D One-Phase Modeling of the Anode Catalyst Layer/Porous Transport Layer Interface Affecting Proton Exchange Membrane Water Electrolysis

Optimizing the structure of the porous transport layer (PTL) is crucial for improving the performance of proton exchange membrane water electrolysis (PEMWE), particularly for cells with low anode catalyst loadings. A growing number of studies reveal that catalysts are normally not entirely utilized in PEMWE, whereas the degree of catalyst utilization strongly depends on the structure of the PTL. As the oxygen evolution reaction (OER) at the anode is the limiting reaction step in PEMWE, inefficient use of the anode catalyst layer (aCL) would result in higher activation losses and, thus, cause a waste of unused catalysts [1–3]. This phenomenon becomes more serious when catalyst loading is reduced to meet the eco-friendly requirement of $2 per kgH2 while conserving noble material resources [4].Schuler et al. [1, 5] combined commercial CCMs with different PTL configurations, and found that with different aCL/PTL interface properties, the activation overpotential could have a maximum deviation of 20 mA at 0.1 A/cm2. Peng et al. [2] manufactured an ultra-low Ir loading CCM with 0.03 mgIr/cm2. Optimizing the aCL/PTL interface showed that the activation overpotential can have a maximum deviation of 40 mV at 0.75 A/cm2. Previous studies concluded that the aCL/PTL interface is crucial for improving the catalyst utilization. Consequently, the triple-phase boundary (TPB) site concept at the aCL/PTL interface is gaining more and more attention: the catalysts can only be entirely activated at reaction sites with sufficient water supply, ionic and electronic conductivities, and oxygen removal pathways [3]. According to TPB, not all reaction sites on the aCL meet these requirements. Figure 1 shows the corresponding physical picture. At the contact point of aCL and PTL (S) offers much greater electronic conductivity compared to the pore area (P), where electron removal is limited by the aCL in-plane conductivity (i.e., 1.85×106 S/m vs. 65.8 S/m) [3]. However, beneath the contact area (S), mass transport of oxygen is limited, indicating the necessity of optimizing the aCL/PTL interface.Figure 1: Illustration of physical picture at aCL/PTL interface.In our contribution, we implement a one-dimensional, one-phase model to investigate the interplay between PTL geometry at the aCL/PTL interface and catalyst utilization. The PTL transports water toward the aCL and electrons and oxygen toward the cathode and anode bipolar plates, respectively [6]. To simplify the physical conditions, we assume sufficient water supply and ion removal for the reaction sites on the aCL. Therefore, mass transport and electron transport limitations are only influenced by the aCL/PTL interface properties. Oxygen is assumed to dissolve in water only so that bubble formation does not disturb the reaction sites. Additionally, an ideal heat management condition is assumed in the model to achieve an isothermal condition. Our simulation results are in good agreement with literature, enabling the prediction of activation overpotentials corresponding to the PTL structure at aCL/PTL interface. Moreover, our results illustrate the local aCL behavior, which can be used to optimize the porous structure at the aCL/PTL interface, maximizing catalyst utilization. With our model, we aim to screen for an optimum PTL structure for a given aCL, allowing us to improve PEMWE cell performance by minimization of activation losses.

Structure–Property Relationships with Functionalized Subphthalocyanines: Toward Photovoltaic Devices More Stable to Photooxidative Degradation Mediated by Singlet Oxygen

AbstractIn this work, the overarching goal of improving the photooxidative stability of organic components used in photovoltaic devices is addressed, focusing on the common problem of degradation mediated by singlet molecular oxygen. Through a systematic exploration of boron subphthalocyanines (SubPcs), the influence of donor and acceptor substituents on the SubPc's redox properties has been examined, including the SubPc's ability to (1) act as a photosensitizer for singlet oxygen generation and (2) deactivate singlet oxygen are examined. How singlet oxygen formation and removal are influenced by linking together three SubPcs in a compact structure and by linking a SubPc to another molecular unit of relevance for organic photovoltaics (indenofluorene‐extended tetrathiafulvalene) is also examined. Synthetic protocols rooted in acetylenic scaffolding, experimental and computational structure–property relationships (optical and redox properties, singlet oxygen quantum yields, and removal kinetics), and characteristics of a functional photovoltaic device using a SubPc molecule are presented, demonstrating that cyano functionalization results in remarkably enhanced organic photovoltaic device stability.

Primary processes in photophysics and photochemistry of a potential light-activated anti-cancer dirhodium complex.

Photophysics and photochemistry of a potential light-activated cytotoxic dirhodium complex [Rh2(µ-O2CCH3)2(bpy)(dppz)](O2CCH3)2, where bpy = 2,2'-bipyridine, dppz = dipyrido[3,2-a:2',3'-c]phenazine (Complex 1 or Rh2) in aqueous solutions was studied by means of stationary photolysis and time-resolved methods in time range from hundreds of femtoseconds to microseconds. According to the literature, Complex 1 demonstrates both oxygen-dependent (due to singlet oxygen formation) and oxygen-independent cytotoxicity. Photoexchange of an acetate ligand to a water molecule was the only observed photochemical reaction, which rate was increased by oxygen removal from solutions. Photoexcitation of Complex 1 results in the formation of the lowest triplet electronic excited state, which lifetime is less than 10ns. This time is too short for diffusion-controlled quenching of the triplet state by dissolved oxygen resulting in 1O2 formation. We proposed that singlet oxygen is produced by photoexcitation of weakly bound van der Waals complexes [Rh2…O2], which are formed in solutions. If this is true, no oxygen-independent light-induced cytotoxicity of Complex 1 exists. Residual cytotoxicity deaerated solutions are caused by the remaining [Rh2…O2] complexes.