The authors report first a new type of nitrogen‐triggered Zn single atom catalyst, demonstrating high catalytic activity and remarkable durability for the oxygen reduction reaction process. Both ...X‐ray absorption fine structure spectra and theoretical calculations suggest that the atomically dispersed Zn‐N4 site is the main, as well as the most active, component with O adsorption as the rate‐limiting step at a low overpotential of 1.70 V. This work opens a new field for the exploration of high‐performance Pt‐free electrochemical oxygen reduction catalysts for fuel cells.
The new nitrogen‐triggered Zn single‐atom catalyst shows high catalytic activity for the oxygen reduction reaction (ORR) process. The characterization and theoretical calculations suggest that the main active site is the dispersed Zn‐N4 moiety, with O adsorption as the rate‐limiting step at a low overpotential of 1.70 V. The single‐atom ZnNx/C catalyst is one of the most promising Pt alternatives for the ORR process.
Oxygen-containing groups on carbon materials can induce high catalytic activity for some reactions. Herein, on the basis of a series of metal-free single-layer graphene nanodisks (GNDs) with ...different surface contents of oxygen-containing groups for highly efficient electrocatalytic reduction reaction of CO2 (CO2RR) to produce formate (HCOO–), we find that the CO2RR catalytic performance is only positively correlated with the surface content of carboxyl groups. While significantly, the density functional theory calculations demonstrate that the observed high CO2RR catalytic activity originates not from the solo carboxyl or other oxygen-containing groups, but from the synergistic effect between carboxyl groups and adjacent other types of groups (namely, hydroxyl, epoxide, and carbonyl) on GNDs. Inspired by such new knowledge, we further find that if the GND catalyst can “alternate work with rest”, its electrocatalytic activity for CO2RR can be regenerated cyclically via a simple electro-oxidation method to regenerate the surface carboxyl groups, achieving a remarkable long-term durability for CO2RR. Such work deepens our understanding of the role of oxygen-containing groups in catalysis and provides a new strategy for the design and synthesis of high-performance metal-free carbon-based catalysts.
This open access book presents a series of complicated hydraulic phenomena and related mechanism of high-speed flows in head-head dam. According to the basic hydraulic theory, detailed experiments ...and numerical simulations, microscopic scale analysis on cavitation bubbles, air bubbles, turbulent eddy vortices and sand grains are examined systemically. These investigations on microscopic fluid mechanics, including cavitation erosion, aeration protection, air–water flow, energy dissipation and river-bed scouring, allow a deep understanding of hydraulics in high-head dams. This book provides reference for designers and researchers in hydraulic engineering, environment engineering and fluid mechanics.
Neuroinflammation and oxidative stress play important roles in early brain injury following subarachnoid hemorrhage (SAH). This study is the first to show that activation of apelin receptor (APJ) by ...apelin-13 could reduce endoplasmic reticulum (ER)-stress-associated inflammation and oxidative stress after SAH.
Apelin-13, apelin siRNA, APJ siRNA, and adenosine monophosphate-activated protein kinase (AMPK) inhibitor-dorsomorphin were used to investigate if the activation of APJ could provide neuroprotective effects after SAH. Brain water content, neurological functions, blood-brain barrier (BBB) integrity, and inflammatory molecules were evaluated at 24 h after SAH. Western blotting and immunofluorescence staining were applied to assess the expression of target proteins.
The results showed that endogenous apelin, APJ, and p-AMPK levels were significantly increased and peaked in the brain 24 h after SAH. In addition, administration of exogenous apelin-13 significantly alleviated neurological functions, attenuated brain edema, preserved BBB integrity, and also improved long-term spatial learning and memory abilities after SAH. The underlying mechanism of the neuroprotective effects of apelin-13 is that it suppresses microglia activation, prevents ER stress from overactivation, and reduces the levels of thioredoxin-interacting protein (TXNIP), NOD-like receptor pyrin domain-containing 3 protein (NLRP3), Bip, cleaved caspase-1, IL-1β, TNFα, myeloperoxidase (MPO), and reactive oxygen species (ROS). Furthermore, the use of APJ siRNA and dorsomorphin abolished the neuroprotective effects of apelin-13 on neuroinflammation and oxidative stress.
Exogenous apelin-13 binding to APJ attenuates early brain injury by reducing ER stress-mediated oxidative stress and neuroinflammation, which is at least partly mediated by the AMPK/TXNIP/NLRP3 signaling pathway.
Bismuth (Bi) has been known as a highly efficient electrocatalyst for CO
reduction reaction. Stable free-standing two-dimensional Bi monolayer (Bismuthene) structures have been predicted ...theoretically, but never realized experimentally. Here, we show the first simple large-scale synthesis of free-standing Bismuthene, to our knowledge, and demonstrate its high electrocatalytic efficiency for formate (HCOO
) formation from CO
reduction reaction. The catalytic performance is evident by the high Faradaic efficiency (99% at -580 mV vs. Reversible Hydrogen Electrode (RHE)), small onset overpotential (<90 mV) and high durability (no performance decay after 75 h and annealing at 400 °C). Density functional theory calculations show the structure-sensitivity of the CO
reduction reaction over Bismuthene and thicker nanosheets, suggesting that selective formation of HCOO
indeed can proceed easily on Bismuthene (111) facet due to the unique compressive strain. This work paves the way for the extensive experimental investigation of Bismuthene in many different fields.
Several studies underscore the potential of deep learning in identifying complex patterns, leading to diagnostic and prognostic biomarkers. Identifying sufficiently large and diverse datasets, ...required for training, is a significant challenge in medicine and can rarely be found in individual institutions. Multi-institutional collaborations based on centrally-shared patient data face privacy and ownership challenges. Federated learning is a novel paradigm for data-private multi-institutional collaborations, where model-learning leverages all available data without sharing data between institutions, by distributing the model-training to the data-owners and aggregating their results. We show that federated learning among 10 institutions results in models reaching 99% of the model quality achieved with centralized data, and evaluate generalizability on data from institutions outside the federation. We further investigate the effects of data distribution across collaborating institutions on model quality and learning patterns, indicating that increased access to data through data private multi-institutional collaborations can benefit model quality more than the errors introduced by the collaborative method. Finally, we compare with other collaborative-learning approaches demonstrating the superiority of federated learning, and discuss practical implementation considerations. Clinical adoption of federated learning is expected to lead to models trained on datasets of unprecedented size, hence have a catalytic impact towards precision/personalized medicine.
A real optimal Fe content: For N and Fe co‐doped carbon electrocatalysts for oxygen reduction reactions (ORRs) it is found that there is a real optimal trace Fe content (Peak II), which has never ...been observed before. The real optimal electrocatalyst shows superior high activity for ORR and possesses the best price/performance ratio ever.
Nanoparticles are important catalysts for petroleum processing, energy conversion, and pollutant removal. As compared to their bulk counterparts, their often superior or new catalytic properties ...result from their nanometer size, which gives them increased surface-to-volume ratios and chemical potentials. The size of nanoparticles is thus pivotal for their catalytic properties. Here, we use single-molecule fluorescence microscopy to study the size-dependent catalytic activity and dynamics of spherical Au-nanoparticles under ambient solution conditions. By monitoring the catalysis of individual Au-nanoparticles of three different sizes in real time with single-turnover resolution, we observe clear size-dependent activities in both the catalytic product formation reaction and the product dissociation reaction. Within a model of classical thermodynamics, these size-dependent activities of Au-nanoparticles can be accounted for by the changes in the adsorption free energies of the substrate resazurin and the product resorufin because of the nanosize effect. We also observe size-dependent differential selectivity of the Au-nanoparticles between two parallel product dissociation pathways, with larger nanoparticles less selective between the two pathways. The particle size also strongly influences the surface-restructuring-coupled catalytic dynamics; both the catalysis-induced and the spontaneous dynamic surface restructuring occur more readily for smaller Au-nanoparticles due to their higher surface energies. Using a simple thermodynamic model, we analyze the catalysis- and size-dependent dynamic surface restructuring quantitatively; the results provide estimates on the activation energies and time scales of spontaneous dynamic surface restructuring that are fundamental to heterogeneous catalysis in both the nano- and the macro-scale. This study further exemplifies the power of the single-molecule approach in probing the intricate workings of nanoscale catalysts.
For the goal of practical industrial development of fuel cells, inexpensive, sustainable, and high performance electrocatalysts for oxygen reduction reactions (ORR) are highly desirable alternatives ...to platinum (Pt) and other rare materials. In this work, sustainable fluorine (F)-doped carbon blacks (CB-F) as metal-free, low-cost, and high-performance electrocatalysts for ORR were synthesized for the first time. The performance (electrocatalytic activity, long-term operation stability, and tolerance to poisons) of the best one (BP-18F, based on Black Pearls 2000 (BP)) is on the same level as Pt-based or other best non-Pt-based catalysts in alkaline medium. The maximum power density of alkaline direct methanol fuel cell with BP-18F as the cathode (3 mg/cm2) is ∼15.56 mW/cm2 at 60 °C, compared with a maximum of 9.44 mW/cm2 for commercial Pt/C (3 mgPt/cm2). All these results unambiguously demonstrate that these sustainable CB-F catalysts are the most promising alternatives to Pt in an alkaline fuel cell. Since sustainable carbon blacks are 10 000 times less expensive and much more abundant than Pt or other rare materials, these CB-F electrocatalysts possess the best price/performance ratio for ORR to date.
Studying the characteristics of cavitation bubble microjets and shock waves is of great significance to reveal cavitation erosion mechanisms in hydraulic engineering. In this paper, a high-speed ...dynamic acquisition system and an electric pulse-induced cavitation bubble system are used to study the interaction between cavitation bubbles and different elastic boundaries from the perspective of microjets and shock waves. By analysing the difference in the microjet direction near different elastic materials, the relationship between the dimensionless critical distance of the microjet direction characteristics and the dimensionless elastic modulus of the boundary material is preliminarily established. Via quantitative analysis, the maximum velocity of the microjet near different elastic boundaries increases gradually and tends to stabilize with increasing dimensionless distance. Additionally, the shock wave intensity and propagation characteristics near different elastic boundaries are qualitatively analysed through images. The cavitation impact characteristics of the microjet and shock wave are compared. The elastic deformation characteristics of elastic materials under the penetration of microjets are the main influencing factors of cavitation erosion of elastic materials, while the effect of the shock wave on elastic materials is weak.
•High-speed imaging captures a spark-generated bubble near different elastic boundaries.•The effect of an elastic boundary on the bubble is complex.•The action of microjet penetration are the main factors affecting the cavitation erosion of elastic materials.•The cavitation erosion of shock waves to elastic materials is weak.•An elastic material can resist erosion within a certain distance from a bubble.
PDF
