Boost the Utilization of Dense FeN_(4) Sites for High-Performance Proton Exchange Membrane Fuel Cells

Iron-nitrogen-carbon(Fe-N-C)catalysts for the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs)have seriously been hindered by their poor ORR performance of Fe-N-C due to the low active site density(SD)and site utilization.Herein,we reported a melamine-assisted vapor deposition approach to overcome these hindrances.The melamine not only compensates for the loss of nitrogen caused by high-temperature pyrolysis but also effectively etches the carbon substrate,increasing the external surface area and mesoporous porosity of the carbon substrate.These can provide more useful area for subsequent vapor deposition on active sites.The prepared 0.20Mela-FeNC catalyst shows a fourfold higher SD value and site utilization than the FeNC without the treatment of melamine.As a result,0.20Mela-FeNC catalyst exhibits a high ORR activity with a half-wave potential(E_(1/2))of 0.861 V and 12-fold higher ORR mass activity than the FeNC in acidic media.As the cathode in a H_(2)-O_(2)PEMFCs,0.20Mela-FeNC catalyst demonstrates a high peak power density of 1.30 W cm^(-2),outstripping most of the reported Fe-N-C catalysts.The developed melamine-assisted vapor deposition approach for boosting the SD and utilization of Fe-N-C catalysts offers a new insight into high-performance ORR electrocatalysts.

Engineering asymmetric electronic structure of cobalt coordination on CoN_(3)S active sites for high performance oxygen reduction reaction

The efficacy of the oxygen reduction reaction(ORR) in fuel cells can be significantly enhanced by optimizing cobalt-based catalysts,which provide a more stable alternative to iron-based catalysts.However,their performance is often impeded by weak adsorption of oxygen species,leading to a 2e^(-)pathway that negatively affects fuel cell discharge efficiency.Here,we engineered a high-density cobalt active center catalyst,coordinated with nitrogen and sulfur atoms on a porous carbon substrate.Both experimental and theoretical analyses highlighted the role of sulfur atoms as electron donors,disrupting the charge symmetry of the original Co active center and promoting enhanced interaction with Co 3d orbitals.This modification improves the adsorption of oxygen and reaction intermediates during ORR,significantly reducing the production of hydrogen peroxide(H_(2)O_(2)).Remarkably,the optimized catalyst demonstrated superior fuel cell performance,with peak power densities of 1.32 W cm^(-2) in oxygen and 0.61 W cm^(-2) in air environments,respectively.A significant decrease in H_(2)O_(2) by-product accumulation was observed during the reaction process,reducing catalyst and membrane damage and consequently improving fuel cell durability.This study emphasizes the critical role of coordination symmetry in Co/N/C catalysts and proposes an effective strategy to enhance fuel cell performance.

Design and fabrication of metal spherical conformal thin film multisensor for high-temperature environment

Conformal thin-film sensors enable precise monitoring of the operating conditions of components in extreme environments.However,the development of these sensors encounters major challenges,especially in uniformly applying multiple film layers on complex metallic surfaces and accurately capturing diverse operational parameters.This work reports a multi-sensor design and multi-layer additive manufacturing process targeting spherical metallic substrates.The proposed high-temperature dip-coating and self-leveling fabrication process achieves high-temperature thin-film coatings with excellent uniformity,high-temperature electrical insulation,and adhesion properties.The fabricated Ag/Pt thin film thermocouple arrays and a heat flux sensor exhibit a maximum temperature resistance of up to 960℃,with thermoelectric potential outputs and hightemperature resistance closely mirroring those of wire-based Ag/Pt thermocouples.Harsh environmental testing was conducted using high-power lasers and a flame gun.The results show that the array of thin-film conformal thermocouples more accurately reflected temperature changes at different points on a spherical surface.The heat flux sensors achieve responses within 95 ms and with-stand environments with heat fluxes over 1.2 MW/m^(2).The proposed multi-sensor design and fabrication method offers promising monitoring applications in harsh environments,including aerospace and nuclear power.

Recent progress in co-detection of single-cell transcripts and proteins

Cellular heterogeneity is a universal property of living systems,and the interrogation of single cells facilitates in-depth understanding of distinct cellular states and functions in various biological processes.Co-analysis of transcripts and proteins from the same single cells opens the way to decipher complex RNA regulatory frameworks and phenotypes,facilitating the understanding of cellular fate and function regulations,discovery of novel cell types,and construction of a high-resolution cell atlas.Herein,we review the state-of-art advances in the development of methodologies for co-analysis of single-cell transcripts and proteins.First,imaging-based methods are summarized with particular emphasis on optical and mass spectrometry imaging.Next,sequencing-based approaches for high-throughput and sensitive co-analysis of single-cell transcripts and proteins are described,including droplet-,microwell-,and split-pool-based platforms.Subsequently,combined methods with more flexibility and universality are discussed.These methods commonly employ different strategies or reactions to convert transcripts and proteins of single cells into distinct signals simultaneously,which can be detected by different instruments or platforms.Lastly,some perspectives on the future challenges and development trends in this field are presented.

Deciphering molecular response of cell-cell interactions at the single-cell level by precise on-demand cell assembly

Multicellular systems rely on the interactions between cells to coordinate cell signaling and regulate cell functions [1]. Understanding the mechanism of cell–cell interactions (CCIs) is critical to many physiological and pathological processes, such as embryogenesis,differentiation, cancer metastasis, and immunological interactions.

High performance laser induced plasma assisted ablation by GHz burst mode femtosecond pulses

High performance laser micromachining based on the combination of GHz burst mode femtosecond pulses irradiation and laser induced plasma assisted ablation can open a new avenue for high-quality and high-efficiency micromachining of single crystalline sapphire.

A fully integrated electronic fabric-enabled multimodal flexible sensors for real-time wireless pressure-humidity-temperature monitoring

Real-time physiological information monitoring can predict and prevent disease, or improve treatment by early diagnosis. A comprehensive and continuous monitoring of human health requires highly integrated wearable and comfortable sensing devices. To address this need, we propose a low-cost electronic fabric-enabled multifunctional flexible sensing integration platform that includes a flexible pressure sensor for monitoring postural pressure, a humidity sensor for monitoring the humidity of the skin surface, and a flexible temperature sensor for visualizing the ambient temperature around the human body. Thanks to the unique rough surface texture, hierarchical structure, and robust electromechanical features of the MXene-modified nonwoven fabrics, the flexible pressure sensor can achieve a monitoring sensitivity of 1529.1 kPa~(-1) and a pressure range of 150 kPa, which meets the demand for human pressure detection. In addition, the unique porous structure of the fabric and the stacked multilayer structure of MXene enable the humidity sensor to exhibit extremely high monitoring sensitivity, even through clothing, and still be able to detect the humidity on the skin surface.Temperature sensors based on screen-printed thermochromic liquid crystals enable visual monitoring in the range of 0℃–65℃. Through further integration with flexible printed circuit board circuits, we demonstrate a proof-of-concept device that enables real-time monitoring of human physiological information such as physical pressure, humidity, and ambient temperature environment, suggesting that the device provides an excellent platform for the development of commercially viable wearable healthcare monitors.

Wearable multichannel-active pressurized pulse sensing platform Yunlong

With the modernization of traditional Chinese medicine(TCM),creating devices to digitalize aspects of pulse diagnosis has proved to be challenging.The currently available pulse detection devices usually rely on external pressure devices,which are either bulky or poorly integrated,hindering their practical application.In this work,we propose an innovative wearable active pressure three-channel pulse monitoring device based on TCM pulse diagnosis methods.It combines a flexible pressure sensor array,flexible airbag array,active pressure control unit,advanced machine learning approach,and a companion mobile application for human–computer interaction.Due to the high sensitivity(460.1 kPa^(−1)),high linearity(R^(2)>0.999)and flexibility of the flexible pressure sensors,the device can accurately simulate finger pressure to collect pulse waves(Cun,Guan,and Chi)at different external pressures on the wrist.In addition,by measuring the change in pulse wave amplitude at different pressures,an individual’s blood pressure status can be successfully predicted.This enables truly wearable,actively pressurized,continuous wireless dynamic monitoring of wrist pulse health.The innovative and integrated design of this pulse monitoring platform could provide a new paradigm for digitizing aspects of TCM and other smart healthcare systems.