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Operating fuel cells in alkaline environments permits the use of platinum-group-metal-free (PGM-free) catalysts and inexpensive bipolar plates, leading to significant cost reduction. Of the PGM-free catalysts explored, however, only a few nickel-based materials are active for catalyzing the hydrogen oxidation reaction (HOR) in alkali; moreover, these catalysts deactivate rapidly at high anode potentials owing to nickel hydroxide formation. Here we describe that a nickel–tungsten–copper (Ni 5.2 WCu 2.2 ) ternary alloy showing HOR activity rivals Pt/C benchmark in alkaline electrolyte. Importantly, we achieved a high anode potential up to 0.3 V versus reversible hydrogen electrode on this catalyst with good operational stability over 20 h. The catalyst also displays excellent CO-tolerant ability that Pt/C catalyst lacks. Experimental and theoretical studies uncover that nickel, tungsten, and copper play in synergy to create a favorable alloying surface for optimized hydrogen and hydroxyl bindings, as well as for the improved oxidation resistance, which result in the HOR enhancement. The lack of efficient and cost-effective catalysts for H 2 oxidation reaction (HOR) hinders the application of anion exchange membrane fuel cells. Here, authors report a ternary nickel-tungsten-copper nanoalloy with marked HOR activity and stability that rivals the benchmark platinum catalyst.

Anion-exchange membrane fuel cells and Zn–air batteries based on non-Pt group metal catalysts typically suffer from sluggish cathodic oxygen reduction. Designing advanced catalyst architectures to improve the catalyst’s oxygen reduction activity and boosting the accessible site density by increasing metal loading and site utilization are potential ways to achieve high device performances. Herein, we report an interfacial assembly strategy to achieve binary single-atomic Fe/Co-N x with high mass loadings through constructing a nanocage structure and concentrating high-density accessible binary single-atomic Fe/Co–N x sites in a porous shell. The prepared FeCo-NCH features metal loading with a single-atomic distribution as high as 7.9 wt% and an accessible site density of around 7.6 × 10 19 sites g −1 , surpassing most reported M–N x catalysts. In anion exchange membrane fuel cells and zinc–air batteries, the FeCo-NCH material delivers peak power densities of 569.0 or 414.5 mW cm −2 , 3.4 or 2.8 times higher than control devices assembled with FeCo-NC. These results suggest that the present strategy for promoting catalytic site utilization offers new possibilities for exploring efficient low-cost electrocatalysts to boost the performance of various energy devices. An interfacial assembly strategy was developed to construct single-atom binary Fe/Co-Nx sites with a high accessible site density of 7.6 × 10 19 sites per gram which results in increased power densities in fuel cells and Zn/air batteries.

Hydroxide exchange membrane fuel cells offer possibility of adopting platinum-group-metal-free catalysts to negotiate sluggish oxygen reduction reaction. Unfortunately, the ultrafast hydrogen oxidation reaction (HOR) on platinum decreases at least two orders of magnitude by switching the electrolytes from acid to base, causing high platinum-group-metal loadings. Here we show that a nickel-molybdenum nanoalloy with tetragonal MoNi 4 phase can catalyze the HOR efficiently in alkaline electrolytes. The catalyst exhibits a high apparent exchange current density of 3.41 milliamperes per square centimeter and operates very stable, which is 1.4 times higher than that of state-of-the-art Pt/C catalyst. With this catalyst, we further demonstrate the capability to tolerate carbon monoxide poisoning. Marked HOR activity was also observed on similarly designed WNi 4 catalyst. We attribute this remarkable HOR reactivity to an alloy effect that enables optimum adsorption of hydrogen on nickel and hydroxyl on molybdenum (tungsten), which synergistically promotes the Volmer reaction. The lack of efficient and cost-effective catalysts for hydrogen oxidation reaction (HOR) hampers the application of hydroxide exchange membrane fuel cells. Here, authors reported bimetallic MoNi 4 and WNi 4 nanoalloys with marked HOR activity in alkali, among which MoNi4 outperforms the Pt/C catalyst.

Effecting the synergistic function of single metal atom sites and their supports is of great importance to achieve high-performance catalysts. Herein, we successfully fabricate polyoxometalates (POMs)-stabilized atomically dispersed platinum sites by employing three-dimensional metal-organic frameworks (MOFs) as the finite spatial skeleton to govern the accessible quantity, spatial dispersion, and mobility of metal precursors around each POM unit. The isolated single platinum atoms (Pt 1 ) are steadily anchored in the square-planar sites on the surface of monodispersed Keggin-type phosphomolybdic acid (PMo) in the cavities of various MOFs, including MIL-101, HKUST-1, and ZIF-67. In contrast, either the absence of POMs or MOFs yielded only platinum nanoparticles. Pt 1 -PMo@MIL-101 are seven times more active than the corresponding nanoparticles in the diboration of phenylacetylene, which can be attributed to the synergistic effect of the preconcentration of organic reaction substrates by porous MOFs skeleton and the decreased desorption energy of products on isolated Pt atom sites. It is of great significance to exert the synergistic effect between single atom and support. Here, the authors prepare polyoxometalates-stabilized single-atom site catalysts in confined space with enhanced activity for alkynes diboration.

Phosphors emitting visible and near-infrared persistent luminescence have been explored extensively owing to their unusual properties and commercial interest in their applications such as glow-in-the-dark paints, optical information storage, and in vivo bioimaging. However, no persistent phosphor that features emissions in the ultraviolet C range (200–280 nm) has been known to exist so far. Here, we demonstrate a strategy for creating a new generation of persistent phosphor that exhibits strong ultraviolet C emission with an initial power density over 10 milliwatts per square meter and an afterglow of more than 2 h. Experimental characterizations coupled with first-principles calculations have revealed that structural defects associated with oxygen introduction-induced anion vacancies in fluoride elpasolite can function as electron traps, which capture and store a large number of electrons triggered by X-ray irradiation. Notably, we show that the ultraviolet C afterglow intensity of the yielded phosphor is sufficiently strong for sterilization. Our discovery of this ultraviolet C afterglow opens up new avenues for research on persistent phosphors, and it offers new perspectives on their applications in terms of sterilization, disinfection, drug release, cancer treatment, anti-counterfeiting, and beyond.

Problem-Based-Learning (PBL) has been widely accepted in student-centered medical education. Since WeChat is the most popular communication app in China, we have chosen to use WeChat as new platform for online PBL in order to reduce the limitations of traditional PBL in dental practical clerkships. This study aims to demonstrate the feasibility and acceptability of online PBL using WeChat (WeChat-PBL) in a dental practical clerkship. A total of 72 students in a dental practical clerkship and 10 tutors participated in this study from June to August 2017. We created 10 WeChat groups to provide a communication platform for the PBL teaching, in which the students selected the PBL cases themselves from their practical clerkship. After each individual PBL case, group members were required to complete an evaluation on the PBL process itself. A final questionnaire survey was completed by the participants to summarize the long-term evaluation of the whole WeChat-PBL experience after the 3-month clerkship. Data from the PBL cases, WeChat messages, periodic evaluations, and long-term evaluations were collected for analysis. There were 45 cases presented in the WeChat-PBL within the 3-month clerkship. All students had positive reactions to the communication within the PBL groups. The results of the periodic evaluation showed that the students and tutors were quite satisfied with the process of WeChat-PBL and appreciated the group members' contributions and performance. The final questionnaire results indicated that the WeChat-PBL had achieved positive effects. The results of this study indicate the feasibility and acceptability of the app, WeChat, for problem-based learning in a dental practical clerkship.

Tissue-resident memory T cells (T RM cells) are critical for cellular immunity to respiratory pathogens and reside in both the airways and the interstitium. In the present study, we found that the airway environment drove transcriptional and epigenetic changes that specifically regulated the cytolytic functions of airway T RM cells and promoted apoptosis due to amino acid starvation and activation of the integrated stress response. Comparison of airway T RM cells and splenic effector-memory T cells transferred into the airways indicated that the environment was necessary to activate these pathways, but did not induce T RM cell lineage reprogramming. Importantly, activation of the integrated stress response was reversed in airway T RM cells placed in a nutrient-rich environment. Our data defined the genetic programs of distinct lung T RM cell populations and show that local environmental cues altered airway T RM cells to limit cytolytic function and promote cell death, which ultimately leads to fewer T RM cells in the lung. Kohlmeier and colleagues showed that the airway environment drove transcriptional and epigenetic changes that regulated the cytolytic functions of airway T RM cells and promoted their apoptosis due to amino acid starvation and activation of the integrated stress response.

Solar-driven water splitting to produce hydrogen may be an ideal solution for global energy and environment issues. Among the various photocatalytic systems, platinum has been widely used to co-catalyse the reduction of protons in water for hydrogen evolution. However, the undesirable hydrogen oxidation reaction can also be readily catalysed by metallic platinum, which limits the solar energy conversion efficiency in artificial photosynthesis. Here we report that the unidirectional suppression of hydrogen oxidation in photocatalytic water splitting can be fulfilled by controlling the valence state of platinum; this platinum-based cocatalyst in a higher oxidation state can act as an efficient hydrogen evolution site while suppressing the undesirable hydrogen back-oxidation. The findings in this work may pave the way for developing other high-efficientcy platinum-based catalysts for photocatalysis, photoelectrochemistry, fuel cells and water–gas shift reactions. Platinum is a widely studied catalyst for the reduction of protons to hydrogen in water splitting, but it also catalyses the competing hydrogen oxidation back-reaction, thus limiting efficiency. Here, the authors show that the back-reaction can be limited by tuning the platinum oxidation state.

Purpose This paper aims to study different possibilities for implementing easy-to-use and cost-effective micro-systems to detect and trace expelled gases from rotten food. The paper covers various radio-frequency identification (RFID) technologies and gas sensors as the two promoting feasibilities for the tracing of packaged food. Monitoring and maintaining quality and safety of food in transport and storage from producer to consumer are the most important concerns in food industry. Many toxin gases, even in parts per billion ranges, are produced from corrupted and rotten food and can endanger the consumers’ health. To overcome the issues, intelligent traceability of food products, specifically the packaged ones, in terms of temperature, humidity, atmospheric conditions, etc., has been paid attention to by many researchers. Design/methodology/approach Food poisoning is a serious problem that affects thousands of people every year. Poisoning food must be recognized early to prevent a serious health problem. Contaminated food is usually detectable by odor. A small gas sensors and low-cost tailored to the type of food packaging and a communication device for transmitting alarm output to the consumer are key factors in achieving intelligent packaging. Findings Conducting polymer composite, intrinsically conducting polymer and metal oxide conductivity gas sensors, metal–oxide–semiconductor field-effect transistor (MOSFET) gas sensors offer excellent discrimination and lead the way for a new generation of “smart sensors” which will mould the future commercial markets for gas sensors. Originality/value Small size, low power consumption, short response time, wide operating temperature, high efficiency and small area are most important features of introduced system for using in package food.

Lung resident memory CD8 T cells (TRM) are critical for protection against respiratory viruses, but the cellular interactions required for their development are poorly understood. Herein we describe the necessity of classical monocytes for the establishment of lung TRM following influenza infection. We find that, during the initial appearance of lung TRM, monocytes and dendritic cells are the most numerous influenza antigen-bearing APCs in the lung. Surprisingly, depletion of DCs after initial T cell priming did not impact lung TRM development or maintenance. In contrast, a monocyte deficient pulmonary environment in CCR2−/− mice results in significantly less lung TRM following influenza infection, despite no defect in the antiviral effector response or in the peripheral memory pool. Imaging shows direct interaction of antigen-specific T cells with antigen-bearing monocytes in the lung, and pulmonary classical monocytes from the lungs of influenza infected mice are sufficient to drive differentiation of T cells in vitro. These data describe a novel role for pulmonary monocytes in mediating lung TRM development through direct interaction with T cells in the lung.