Interest in the low-cost production of clean hydrogen is growing. Anion exchange membrane water electrolyzers (AEMWEs) are considered one of the most promising sustainable hydrogen production ...technologies because of their ability to split water using platinum group metal-free catalysts, less expensive anode flow fields, and bipolar plates. Critical to the realization of AEMWEs is understanding the durability-limiting factors that restrict the long-term use of these devices. This article presents both durability-limiting factors and mitigation strategies for AEMWEs under three operation modes,
i.e.
, pure water-fed (no liquid electrolyte), concentrated KOH-fed, and 1 wt% K
2
CO
3
-fed operating at a differential pressure of 100 psi. We examine extended-term behaviors of AEMWEs at the single-cell level and connect their behavior with the electrochemical, chemical, and mechanical instability of single-cell components. Finally, we discuss the pros and cons of AEMWEs under these operation modes and provide direction for long-lasting AEMWEs with highly efficient hydrogen production capabilities.
Understanding the durability-limiting factors of anion exchange membrane water electrolyzers operating under pure water-, KOH- and K
2
CO
3
-fed conditions.
•Rapid two-phase flow and micro oxygen bubble dynamics are in-situ visualized.•Bubble detachment diameters and frequencies increase with current density.•GDL structures and morphologies has a great ...impact on micro bubble detachments.•Slug flow tends to form at high current densities and low flow velocities.
Bubble dynamics and two-phase flow phenomena are closely related to the performance of proton exchange membrane electrolyzer cells (PEMECs). This paper reports an in-situ study of the oxygen bubble behavior and associated multiphase evolutions in the anode side of PEMECs with titanium (Ti) felt liquid gas diffusion layers (LGDLs) by a high-speed visualization system. The micro oxygen bubble dynamics was captured and analyzed at different locations and virous operating conditions. The results show that the bubble detachment frequency and detachment diameter greatly increase with the operating current density. Additionally, they are significantly impacted by the local pore structure and morphology of Ti felt LGDLs. In the flow channels, there exist only several discrete micro bubbles at a low current density (0.04 A/cm2) and a large flow velocity (133 mm/s). At a current density (0.2 A/cm2) and a flow velocity (67 mm/s), a number of gas slugs are formed in the follow channels, in addition to discrete micro bubbles. At a high current density (1 A/cm2) and a flow velocity (67 mm/s), more bubbles appear in the channel, and the flow field is dominated by slug or annular flows. These investigations can help to better understand the two-phase flow and bubble detachment mechanism, and provide a foundation for electrochemical reaction, multiphase flow studies and optimize the design of gas diffusion layers and flow fields for PEMECs in the future.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Liquid/gas diffusion layers (LGDLs), which are located between the catalyst layer (CL) and bipolar plate (BP), play an important role in enhancing the performance of water splitting in proton ...exchange membrane electrolyzer cells (PEMECs). They are expected to transport electrons, heat, and reactants/products simultaneously with minimum voltage, current, thermal, interfacial, and fluidic losses. In this study, the thin titanium-based LGDLs with straight-through pores and well-defined pore morphologies are comprehensively investigated for the first time. The novel LGDL with a 400 μm pore size and 0.7 porosity achieved a best-ever performance of 1.66 V at 2 A cm −2 and 80 °C, as compared to the published literature. The thin/well-tunable titanium based LGDLs remarkably reduce ohmic and activation losses, and it was found that porosity has a more significant impact on performance than pore size. In addition, an appropriate equivalent electrical circuit model has been established to quantify the effects of pore morphologies. The rapid electrochemical reaction phenomena at the center of the PEMEC are observed by coupling with high-speed and micro-scale visualization systems. The observed reactions contribute reasonable and pioneering data that elucidate the effects of porosity and pore size on the PEMEC performance. This study can be a new guide for future research and development towards high-efficiency and low-cost hydrogen energy.
Gas bubble dynamics and two-phase flow have a significant impact on the performance and efficiency of proton exchange membrane electrolyzer cells (PEMECs). It has been strongly desired to develop an ...effective experimental method for in-situ observing the high-speed/micro-scale oxygen bubble dynamics and two-phase flow in an operating PEMEC. In this study, the micro oxygen bubble dynamic behavior and two-phase flow are in-situ visualized through a high-speed camera coupled with a specific designed transparent PEMEC, which uses a novel thin liquid/gas diffusion layer (LGDL) with straight-through pores. The effects of different operating conditions on oxygen bubble dynamics, including nucleation, growth, and detachment, and two-phase flow have been comprehensively investigated. The results show that temperature and current density have great effects on bubble growth rate and reaction sites while the influence of flow rate is very limited. The number, growth rate, nucleation site, and slug flow regime of oxygen gas bubbles increase as temperature and/or current density increases, which indicates that an increase in temperature and/or current density can enhance the oxygen production efficiency. Further, a mathematical model for the bubble growth is developed to evaluate the effects of temperature and current density on the bubble dynamics. A mathematical model has been established and shows a good correlation with the experimental results. The studies on two-phase flow and high-speed micro bubble dynamics in the microchannel will help to discover the true electrochemical reaction at micro-scale in an operating PEMEC.
•Rapid micro oxygen bubble generation and growth are in-situ visualized.•Bubble growth rate and reaction sites are increased with the current density.•A model shows a good agreement with the experiment results.•Annular flow is more easily to form under high current densities.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Novel TT-LGDLs with different surface treatments are investigated for the first time.•Superior PEMEC performance with a value of 1.63V at 2.0A/cm2 and 80°C is obtained.•Ohmic losses is reduced from ...0.0925Ωcm2 to 0.0700Ωcm2.•Hydrogen production rate can be greatly increased by 28.2%.•Au thin film surface treatment on titanium material shows good stability.
A proton exchange membrane electrolyzer cell (PEMEC) is one of the most promising devices for high-efficiency and low-cost energy storage and ultrahigh purity hydrogen production. As one of the critical components in PEMECs, the titanium thin/tunable LGDL (TT-LGDL) with its advantages of small thickness, planar surface, straight-through pores, and well-controlled pore morphologies, achieved superior multifunctional performance for hydrogen and oxygen production from water splitting even at low temperature. Different thin film surface treatments on the novel TT-LGDLs for enhancing the interfacial contacts and PEMEC performance were investigated both in-situ and ex-situ for the first time. Surface modified TT-LGDLs with about 180nm thick Au thin film yielded performance improvement (voltage reduction), from 1.6849V with untreated TT-LGDLs to only 1.6328V with treated TT-LGDLs at 2.0A/cm2 and 80°C. Furthermore, the hydrogen/oxygen production rate was increased by about 28.2% at 1.60V and 80°C. The durability test demonstrated that the surface treated TT-LGDL has good stability as well. The gold electroplating surface treatment is a promising method for the PEMEC performance enhancement and titanium material protection even in harsh environment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Bispecific antibodies (BsAbs) have demonstrated significant therapeutic impacts for the treatment of a broad spectrum of diseases that include oncology, auto-immune, and infectious diseases. However, ...the large-scale production of clinical batches of bispecific antibodies still has many challenges that include having low yield, poor stability, and laborious downstream purification processes. To address such challenges, we describe the optimization of the controlled Fab arm exchange (cFAE) process for the efficient generation of BsAbs.
The process optimization of a large-scale good manufacturing practice (GMP) cFAE strategy to prepare BsAbs was based on screening the parameters of temperature, reduction, oxidation, and buffer exchange. We include critical quality standards for the reducing agent cysteamine hydrochloride.
This large-scale production protocol enabled the generation of bispecific antibodies with >90% exchange yield and at >95% purity. The subsequent downstream processing could use typical mAb procedures. Furthermore, we demonstrated that the bispecific generation protocol can be scaled up to ∼60 L reaction scale using parental monoclonal antibodies that were expressed in a 200 L bioreactor.
We presented a robust development strategy for the cFAE process that can be used for a larger scale GMP BsAb production.
The rapid advancement of modern technology has significantly driven progress in various IT-related activities, resulting in a substantial increase in internet penetration rates, particularly among ...college students. The utilization of the internet has become one of the most essential tools in our modern society. However, internet addiction (IA) has emerged as a serious concern, particularly among college students, adversely affecting academic performance and having significant psychological and psychiatric implications. The aim of the current study was to determine the impact of physical exercise, gender and academic year on IA among college students. In the present study, we investigated internet usage, engagement in sports activities, and academic performance among college students from Western, Middle, and Eastern regions of Chinese universities. It's noteworthy that most of the respondents were freshmen. Our findings indicate that freshmen students were more susceptible to experiencing IA. Approximately 75% of students engaged in leisure sports activities, revealing an inverse correlation between sports activity and IA. This correlation aligns with the level of sports involvement, emphasizing the potential benefits of physical activity in mitigating IA. However, our study did not uncover any correlation between geographic location and the occurrence of IA, nor did it find differences between medical and non-medical students. Furthermore, our study revealed no significant variations in IA among students from different ethnic backgrounds. The underlying mechanism of IA is being currently determined. Our data suggest that physical exercise, gender, and academic year have a significant impact on IA among college students.
Noble metal electrocatalysts are highly preferred for the oxygen evolution reaction (OER) in a proton exchange membrane water electrolysis cell (PEMWE) due to their exceptional catalytic activity and ...stability. This study proposes a novel thin electrode (NTE) design to enhance the performance of noble metal electrocatalysts for the OER in PEMWE. The NTE utilizes a thin porous transport layer for the direct deposition of Iridium (Ir). Unlike conventional gas diffusion electrodes with deep porous structures that underutilize the catalyst due to limited triple-phase boundary conditions, the flat NTEs with straight-through pores overcome this restriction. The paper compares two deposition methods, electroplating and sputter coating. The in-situ electrochemical properties of NTEs with varying Ir loadings (0.06–1.01 mg cm−2) are investigated. The electroplated NTE demonstrates excellent mass activity, achieving 5.05 A mg−1 at 1.6 V and 80 °C. The NTE exhibits a simple fabrication process and low cost while significantly improving catalyst mass activity. Additionally, the NTE reduces electrode thickness from hundreds of micrometers to only 25 μm. This concept holds great promise for the future advancement of compact and high-efficiency PEMWE electrodes, resulting in reduced cost, volume, and mass of both the electrode itself and the overall system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Based on the X-ray cocrystal structure of the Tang−Ghosh heptapeptide inhibitor 1 (OM00-3), a series of macroheterocyclic analogues were designed and synthesized. Analogues containing dithia, dioxa, ...oxathia, and carbathia macrocycles were synthesized by methods relying on ring-closing olefin metathesis for the dioxa analogues and by alkylation of thiolates or bisthiolates for the others. Molecular modeling suggested that the incorporation of piperidine units appended to the macrocycles improved interactions through additional H-bonds and introduced further rigidity. These were synthesized in enantiomerically pure form using enzyme-catalyzed desymmetrization and diastereomer separation. Inhibitory activity on β-site amyloid precursor protein cleaving enzyme (BACE) was observed with several macroheterocyclic inhibitors and structure−activity relationship (SAR) correlations were deduced. Cocrystal structures of two synthetic analogues revealed interesting and unexpected binding interactions.
DNA-encoded libraries (DELs) can be considered as one of the most powerful tools for the discovery of small molecules of biological interest. However, the ability to access large DELs is contingent ...upon having chemical transformations that work in aqueous phase and generate minimal DNA alterations and the availability of building blocks compatible with on-DNA chemistry. In addition, accessing scaffolds of interest to medicinal chemists can be challenging in a DEL setting because of inherent limitations of DNA-supported chemistry. In this context, a squaramide formation reaction was developed by using a two-step process. The mild and high-yielding reaction tolerates a wide array of functional groups and was shown to be safe for DNA, thereby making this methodology ideal for DELs.
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