Proton‐exchange‐membrane fuel cells (PEMFCs) are of considerable interest for direct chemical‐to‐electrical energy conversion and may represent an ultimate solution for mobile power supply. However, ...PEMFCs today are primarily limited by the sluggish kinetics of the cathodic oxygen reduction reaction (ORR), which requires a significant amount of Pt‐based catalyst with a substantial contribution to the overall cost. Hence, promoting the activity and stability of the needed catalyst and minimizing the amount of Pt loaded are central to reducing the cost of PEMFCs for commercial deployment. Considerable efforts have been devoted to improving the catalytic performance of Pt‐based ORR catalysts, including the development of various Pt nanostructures with tunable sizes and chemical compositions, controlled shapes with selectively displayed crystallographic surfaces, tailored surface strains, surface doping, geometry engineering, and interface engineering. Herein, a brief introduction of some fundamentals of fuel cells and ORR catalysts with performance metrics is provided, followed by a detailed description of a series of strategies for pushing the limit of high‐performance Pt‐based catalysts. A brief perspective and new insights on the remaining challenges and future directions of Pt‐based ORR catalysts for fuel cells are also presented.
Some representative efforts in promoting the mass activity (MA) of Pt‐based oxygen reduction reaction catalysts through specific activity (SA) and electrochemically active surface area (ECSA) improvement (SA and MA are compared at 0.9 V vs RHE) are presented.
Plant-derived extracellular vesicles (PLEVs), as a type of naturally occurring lipid bilayer membrane structure, represent an emerging delivery vehicle with immense potential due to their ability to ...encapsulate hydrophobic and hydrophilic compounds, shield them from external environmental stresses, control release, exhibit biocompatibility, and demonstrate biodegradability. This comprehensive review analyzes engineering preparation strategies for natural vesicles, focusing on PLEVs and their purification and surface engineering. Furthermore, it encompasses the latest advancements in utilizing PLEVs to transport active components, serving as a nanotherapeutic system. The prospects and potential development of PLEVs are also discussed. It is anticipated that this work will not only address existing knowledge gaps concerning PLEVs but also provide valuable guidance for researchers in the fields of food science and biomedical studies, stimulating novel breakthroughs in plant-based therapeutic options.
•Plant-derived extracellular vesicles (PLEVs) are important for disease treatment.•Advances of PLEVs purification and surface modification engineering.•Latest progress in transporting bioactive substances as nano-therapeutic system.
Janus membranes (JMs) have attracted increasing attention in the fields of liquid manipulation owing to its interesting liquid-unidirectional transportation feature. Nonetheless, most of the ...currently available methods to fabricate JMs suffer from specific or complicated operations, impeding practical applications of JMs. Herein, a facile liquid/liquid (immiscible oil/water) interface-confined surface engineering strategy was first applied on hydrophilic cotton fabric membrane to construct JM with the aid of mussel-inspired chemistry. The water-infused fabric channels and the unique distribution of amphiphilic C18-NH2 at the oil/water interface enable the unilateral hydrophobicity transformation on fabric. As a result, the as-prepared membranes exhibited asymmetric chemistry, wettability, and surface morphology. The evaluation of water droplet behaviors across the membrane at the oil/water interface verified the water unidirectional transport feature of our JM. In addition, two collectors made by our JMs successfully demonstrated the excellent ability of water collection from both oil/water mixture and water-in-oil emulsion. The newly developed liquid/liquid interface-confined surface engineering strategy provides enormous potential for Janus membrane construction to manipulate liquid transportation towards smart applications.
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•Interface-confined surface engineering realized asymmetric surface modification.•Asymmetric surface modification can construct brand-new Janus membrane (JM).•The as-prepared JM possesses water-unidirectional transportation ability.•The JM devices successfully collect water under oil or from water-in-oil emulsion.
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Understanding how bacteria interact with surfaces with micrometer and/or sub-micrometer roughness is critical for developing antibiofouling and bactericidal topographies. A primary ...research focus in this field has been replicating and emulating bioinspired nanostructures on various substrates to investigate their mechanobactericidal potential. Yet, reports on polymer substrates, especially with very high aspect ratios, have been rare, despite their widespread use in our daily lives. Specifically, the role of a decrease in stiffness with an increase in the aspect ratio of nanostructures may be consequential for the mechanobactericidal mechanism, which is biophysical in nature. Therefore, this work reports on generating bioinspired high aspect ratio nanostructures on poly(ethylene terephthalate) (PET) surfaces to study and elucidate their antibacterial and antibiofouling properties. Biomimetic nanotopographies with variable aspect ratios were generated via maskless dry etching of PET in oxygen plasma. It was found that both high and low-aspect ratio structures effectively neutralized Gram-negative bacterial contamination by imparting damage to their membranes but were unable to inactivate Gram-positive cells. Notably, the clustering of the soft, flexible tall nanopillars resulted in cooperative stiffening, as revealed by the nanomechanical behavior of the nanostructures and validated with the help of finite element simulations. Moreover, external capillary forces augmented the killing efficiency by enhancing the strain on the bacterial cell wall. Finally, experimental and computational investigation of the durability of the nanostructured surfaces showed that the structures were robust enough to withstand forces encountered in daily life. Our results demonstrate the potential of the single-step dry etching method for the fabrication of mechanobactericidal topographies and their potential in a wide variety of applications to minimize bacterial colonization of soft substrates like polymers.
Selective exposure of high‐energy {221} facets with many surface dangling bonds, (111) terraces, and (110) steps (bottom picture) at the surface of octahedral SnO2 nanoparticles (top) through a ...simple hydrothermal synthesis route gives them enhanced gas‐sensing performance over particles with other shapes, whereby the sensing activity is proportional to the fraction of {221} facets among the exposed surfaces.
Towards natural gas purification, polymeric membranes generally face challenges of trade-off between permeability and selectivity, as well as CO2-induced plasticization effect. Previous works ...demonstrated that incorporating high-performing nanofillers and crosslinking the polymers are effective methods to overcome these two issues, respectively. In this work, we aimed to simultaneously improve permeability, selectivity and plasticization resistance of polymeric membranes by incorporating surface-engineered nanoporous fillers for CO2/CH4 separation. DD3R zeolite nanoparticles with high purity were synthesized and then surface-functionalized by 3-aminopropyl trimethoxysilane (APTMS) to serve as the filler. Mixed-gas permeation measurements showed that DD3R zeolites offered CO2-selective channels in 6FDA-DAM polyimide based on molecular sieving effect of zeolitic aperture. 30 wt% DD3R-APTMS zeolite imparted the membrane with CO2 permeability of 1661 Barrer (increased by 71.7%) and CO2/CH4 selectivity of 28.0 (increased by 44.5%), which was beyond the upper-bound of polymeric membranes. Meanwhile, the hydrogen bond interaction between amino groups on APTMS and carboxyl groups on 6FDA-DAM rendered the resulting DD3R-APTMS MMMs highly enhanced plasticization resistance over 40 bar when equimolar CO2/CH4 mixture as the feed. This work demonstrates a facile approach to simultaneously enhance separation performance and mitigate the plasticization effect.
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•High-purity DD3R zeolite are prepared by tuning ADA amount in synthesis solution.•Well-defined zeolitic pores improve CO2 permeability and CO2/CH4 selectivity.•Hydrogen interaction enhances separation performance and plasticization resistance.
The reach of tribology has expanded in diverse fields and tribology related research activities have seen immense growth during the last decade. This review takes stock of the recent advances in ...research pertaining to different aspects of tribology within the last 2 to 3 years. Different aspects of tribology that have been reviewed including lubrication, wear and surface engineering, biotribology, high temperature tribology, and computational tribology. This review attempts to highlight recent research and also presents future outlook pertaining to these aspects. It may however be noted that there are limitations of this review. One of the most important of these is that tribology being a highly multidisciplinary field, the research results are widely spread across various disciplines and there can be omissions because of this. Secondly, the topics dealt with in the field of tribology include only some of the salient topics (such as lubrication, wear, surface engineering, biotribology, high temperature tribology, and computational tribology) but there are many more aspects of tribology that have not been covered in this review. Despite these limitations it is hoped that such a review will bring the most recent salient research in focus and will be beneficial for the growing community of tribology researchers.
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•Sodium ion batteries (SIBs) are suitable alternative candidate due to abundant sodium metal, cheaper Al as current collector at the negative electrode and Na salts, both for SIBs, ...reduce the cost and therefore, SIBs are suitable candidate for portable energy storage device to a large grid support.•Microcracking and surface degradation of unstable cathode materials during cycling for SIB storage devices have suppressed through doping, reducing particle size, coating and other strategies.•In this review, advantages of surface coating of high conducting carbons, less active oxides and ion conducting materials on different cathodes for SIBs which protect their structure from harmful components, increase conductivity, their capacity as well as longevity have been discussed.
Owing to scarce and expensive lithium based energy storage system, sodium ion batteries have gained attention as a potential alternative, leveraging their low cost components including abundant sodium as anode over competing energy storage technologies. However, structural instability, low electronic and ionic conductivity, severe polarization and low operating potential have significantly limited their practical application. The highly oxidative nature, low tap density and temperature instability of prussian blue, poor electronic conductivity of polyanions and iron-based fluoride based cathode materials have severe capacity fading and need to be optimized for better electrochemical performance. To overcome these challenges, surface engineering of cathode materials through nanostructured organic and inorganic coating have been explored as a means to improve their performance which provide uniform state of charge distribution and strength to cathode, which facilitates fast transport of electrons and ions and also prevents the transition metals dissolution and undesirable side reactions at the interface of cathode and electrolyte. These nanostructured coatings, made of compounds such as oxides, polyanions, conducting polymers and carbon materials have been widely exploited on various cathodes by using solution-phase mixing, Atomic layer deposition (ALD), Physical vapor deposition (PVD) techniques, etc. This review concludes a systematic comparison of different types of nanostructured coating on cathodes and their impact on electrochemical performance with the aim of exploring the potential for practical application of sodium ion batteries.
The use of calcium silicate coatings has extensively increased due to properties such as biocompatibility and proper bioactivity response. The present study was aimed to investigate the bioactivity ...of wollastonite-hydroxyapatite (WS-HA) bio-nanocomposite for the treatment of orthopedic implant coatings by adding magnetic nanoparticles (MNPs) and single-walled carbon nanotubes (SWCNTs) to the matrix. The bio-nanocomposite was coated on Mg substrate for 40 min at 40 V using electrophoretic deposition (EPD), following which the heat treatment was performed at 550–650 °C for 1 h. The coatings were incubated in simulated body fluid (SBF) and phosphate buffer saline (PBS) for 28 days to detect and confirm apatite-like layer formation Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was used to evaluate the concentration of calcium and silicon ions.
Schematic of the process for fabrication of ceramic-magnetic and ceramic-single walled carbon nanotube bio-nanocomposite coated with EPD technique on AZ91 substrate. Display omitted
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