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Research on high‐efficiency and cost‐efficient catalysts for oxygen reduction reaction (ORR) is still a vital but challenging issue for commercializing metal–air batteries. Herein, a single‐molecule/atom hybrid catalyst is developed to boost the ORR, in which iron phthalocyanine molecules containing molecular Fe─N4 moieties couple with atomic Co─N4 sites on the surface of polyhedral carbon. Density functional theory calculations reveal that face‐to‐face laminated construction of Fe─N4 and Co─N4 in the hybrid catalyst can effectively modulate the electronic structure of active iron atoms and reduce the energy barrier of the rate‐determining step for ORR. As a result, this hybrid catalyst demonstrates excellent ORR performance, featuring a half‐wave potential of 0.904 V, a peak power density of 238.3 mW cm−2 for zinc–air battery, and outstanding electrocatalytic stability. This work offers a distinctive and robust molecular/atomic engineering approach to creating efficient electrocatalysts, advancing the fields of metal–air batteries. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMDs) have attracted significant interest as gas‐sensing materials due to their unique crystal structure and surface. However, there are still issues when it comes to expanding the types of sensing gases for the TMD gas sensors. To extend gas‐sensing selectivity for the TMD gas sensors in this study, a monolayer (ML) 2D metal–organic framework (MOF) is introduced on top of the PtSe2 gas sensor, thereby tuning the major sensing analyte of PtSe2 from NO2 to H2S. Density functional theory calculations elucidate that the metal species of ML MOFs are attributed to the tuned selectivity of the analytes, based on the difference in binding energies. It is also demonstrated that ML MOF maintained the high responsivity of the pristine PtSe2 even at a low concentration of gas (200 ppb). This is further confirmed through the molecular dynamics simulations, which reveal that the ML feature of the ML MOF is highly essential to preserve the intrinsic ultra‐low limit detection properties of pristine PtSe2. [ABSTRACT FROM AUTHOR]

Activation of metal oxides by light is a robust yet facile approach to manipulating their surface chemistry for favorable reactions with target molecules in heterogeneous catalysis and gas sensors. However, a limited understanding of interface chemistry and the involved mechanism impedes the development of a rational design of oxide interfaces for light‐activated gas sensing. Herein, the TiOx‐assisted photosensitization of In2O3 toward NO2 sensing is investigated as a case study to elucidate the detailed mechanism of light‐activated surface chemistry at the metal/gas interface. The resultant heterogeneous oxides exhibit outstanding NO2 sensing performance under light irradiation thanks to abundant photoexcited electrons and holes that serve as adsorption and desorption sites, respectively, to accelerate both surface reactions. Furthermore, the facile transfer of electrons and holes across the TiOx‐In2O3 interface contributes to improving the reversibility of sensing kinetics. Through this study, the mechanistic understanding is established of how the surface chemistry of metal oxide surfaces can be tuned by light activation providing an effective route to the design fabrication of high‐performance gas sensors. [ABSTRACT FROM AUTHOR]

Due to the unique properties which are considerably different from macro‐scale or bulk materials, 1D) nanostructures have received great interests. In particular, they have greatly contributed to building next‐generation batteries by providing beneficial features such as short ion/electron pathways, structural versatility (i.e., formation of 3D current collectors, free‐standing electrodes, and separators), and excellent stress relaxation. Owing to these definite advantages, 1D nanostructure is often followed by discovery of new electrode materials. This review provides a systematic overview of the state‐of‐the‐art research progresses on 1D nanostructures, which are extensively used for rechargeable batteries. Specifically, a brief introduction of some important 1D nanostructuring methods is started and then, in situ structural characterizations using 1D nanostructures are summarized, which allow a great step forward in atomic‐scale monitoring of reaction kinetics and observing dynamic structural evolution of electrode materials. 1D nanstructuring in solid‐state electrolytes and stabilization of metal anodes are also highlighted which are not only substantially important in current research trends for future batteries but also rarely discussed in previous reviews. At the end, critical perspective and future research direction of 1D nanoengineering for future batteries are suggested. [ABSTRACT FROM AUTHOR]

In the article "Molecular Fe-N4 Moieties Coupled with Atomic Co-N4 Sites Toward Improved Oxygen Reduction Performance," researchers Shichao Ding, Il-Doo Kim, Jin-Cheng Li, and their team have developed a new single-atom catalyst that enhances the catalytic activity for the oxygen reduction reaction in zinc-air batteries. The catalyst combines Fe-N4 moieties with Co-N4 single-atom sites, resulting in improved performance for flexible all-solid-state zinc-air batteries. The study utilizes density functional theory and iron phthalocyanine to design and test the catalyst. [Extracted from the article]

Thermochromic sensors provide an intuitive and real‐time solution for monitoring the local temperature with naked eyes. Conventional thermochromic sensors often utilize either solution‐type or dense film‐type platforms, which are suboptimal morphologies for exposing a large number of dye molecules to the surface, leading to low sensitivity and sluggish responding speeds. Herein, this article introduces rational synthetic routes to fabricate highly sensitive nanofiber (NF) sensor membranes loaded with thermochromic dyes (C3H6N6·CH2O)x‐loaded nanofibers (NFs) sensor membranes by alignment‐controllable electrospinning techniques (x–y perpendicular and rotary). The NF‐based porous sensor membranes exhibit two‐ to fivefold improved thermochromic sensitivity (ΔRGB) compared to those of dense film‐type sensors at 31.6–42.7 °C. This is attributed to the uniform distribution of dyes throughout the porous NF structure (≈95.7%), which exhibits excellent light transmittance that is 10–30‐fold higher than that of film‐type sensors. Based on the available shape‐conforming synthetic strategies, this article further demonstrates wearable thermochromic sensors in the forms of mask‐, patch‐, and bracelet‐type devices, which can accurately monitor body temperature in real time. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts (SACs) supported on inorganic materials have attracted much attention in numerous research fields for their high catalytic performance. However, such SACs have been limited by the low metal loading, especially on different types of inorganic supports. Herein, a general approach is presented for preparing SACs on metallic, metal oxide, and perovskite nanosheet (NS) supports to reach a high metal loading of up to 3.94 wt%, by utilizing N‐doped graphene as a sacrificial template that spatially confines the single atoms (SAs). Specifically, the target support material precursors are adsorbed onto the SAs‐stabilized sacrificial template, followed by subsequent heat treatment to transfer the SAs to the support material and to remove the graphene layer. Pt SAs on oxide support exhibits little to no aggregation throughout >10 000 min of annealing at 275 °C, demonstrating high thermal stability, as also supported by ex situ post‐anneal electron microscopy and X‐ray absorption fine structure studies. As a proof‐of‐concept, Pt SACs on SnO2 NSs exhibit high catalytic activity toward chemiresistive sensing of acetone gas (response = 95.4 at 10 ppm, 7.6‐fold enhancement compared with pristine SnO2 NSs) and unprecedented stability under highly humid conditions (27.4% response deterioration at 95% relative humidity). [ABSTRACT FROM AUTHOR]

Single‐atom catalysts (SACs) supported on inorganic materials have attracted much attention in numerous research fields for their high catalytic performance. However, such SACs have been limited by the low metal loading, especially on different types of inorganic supports. Herein, a general approach is presented for preparing SACs on metallic, metal oxide, and perovskite nanosheet (NS) supports to reach a high metal loading of up to 3.94 wt%, by utilizing N‐doped graphene as a sacrificial template that spatially confines the single atoms (SAs). Specifically, the target support material precursors are adsorbed onto the SAs‐stabilized sacrificial template, followed by subsequent heat treatment to transfer the SAs to the support material and to remove the graphene layer. Pt SAs on oxide support exhibits little to no aggregation throughout >10 000 min of annealing at 275 °C, demonstrating high thermal stability, as also supported by ex situ post‐anneal electron microscopy and X‐ray absorption fine structure studies. As a proof‐of‐concept, Pt SACs on SnO2 NSs exhibit high catalytic activity toward chemiresistive sensing of acetone gas (response = 95.4 at 10 ppm, 7.6‐fold enhancement compared with pristine SnO2 NSs) and unprecedented stability under highly humid conditions (27.4% response deterioration at 95% relative humidity). [ABSTRACT FROM AUTHOR]

Designing energy storage devices from thick carbon electrodes with high areal/volumetric energy density via a simple and green way is very attractive but still challenging. Cellulose, as an excellent precursor for thick carbon electrodes with abundant sources and low cost, is usually activated by a chemical activator and pyrolysis route to achieve high electrochemical performance. However, there are still some problems to be addressed, such as the harsh activation conditions, easy collapse of porous structures, and the high cost. Herein, a 3D self‐supporting thick carbon electrode derived from wood‐based cellulose is proposed for high areal and volumetric energy density of supercapacitor from a mild, simple, and green enzymolysis treatment. Benefiting from the high specific surface area (1418 m2 g−1) and abundant active sites on the surface of wood‐derived hierarchically porous structures and enzymolysis‐induced micropores and mesopores, the assembled symmetry supercapacitor from the thick carbon electrode can realize the high areal/volumetric energy density of 0.21 mWh cm−2/0.99 mWh cm−3 with excellent stability of 86.58% after 15 000 long‐term cycles at 20 mA cm−2. Significantly, the simple and universal strategy to design material with high specific surface area, provides a new research idea for realizing multi‐functional application. [ABSTRACT FROM AUTHOR]

This review reports on the most updated technological aspects of Li–air battery cathode materials. It provides the reader with recent developments, alongside critical views. The requirements for air‐cathodes, as well as the classification and characterization of carbon‐based and carbon‐free air cathodes, are listed. The effects of two major substituent groups of materials, namely carbon and advanced materials (metals, metal‐oxides, metal‐carbides, and metal‐nitrides) aimed at replacing carbon, are discussed in terms of their chemical and electrochemical stability. The report covers aspects of surface chemistry and structure influence on the electrolyte and discharge products stability. The review also reports on the efforts to suppress side reactions and deterioration of the polymeric binders (if a composite electrode is being considered). This is recognized as a means to enhance Li–air battery performance. The report concludes with an outlook and perspective, providing the readers with some insight on other factors and their impact on the long road toward a viable air‐cathode suitable for Li–air battery operations. [ABSTRACT FROM AUTHOR]

Abstract: Edges of 2D transition metal dichalcogenides (TMDs) are well known as highly reactive sites, thus researchers have attempted to maximize the edge site density of 2D TMDs. In this work, metal‐organic framework (MOF) templates are introduced to synthesize few‐layered WS2 nanoplates (a lateral dimension of ≈10 nm) confined in Co, N‐doped hollow carbon nanocages (WS2_Co‐N‐HCNCs), for highly sensitive NO2 gas sensors. WS2 precursors are assembled in the surface cavity of Co‐based zeolite imidazole framework (ZIF‐67) and subsequent pyrolysis produced WS2_Co‐N‐HCNCs. During the pyrolysis, the carbonized ZIF‐67 are doped by Co and N elements, and the growth of WS2 is effectively suppressed, creating few‐layered WS2 nanoplates functionalized Co‐N‐HCNCs. The WS2_Co‐N‐HCNCs exhibit outstanding NO2 sensing characteristics at room temperature, in terms of response (48.2% to 5 ppm), selectivity, response and recovery speed, and detection limit (100 ppb). These results are attributed to the enhanced adsorption and desorption kinetics of NO2 on abundant WS2 edges, confined in the gas permeable HCNCs. This work opens up an efficient way for the facile synthesis of edge abundant few‐layered TMDs combined with porous carbon matrix via MOF templating route, for applications relying on highly active sites. [ABSTRACT FROM AUTHOR]

Gas Sensors In article number 2214008, Il‐Doo Kim and co‐workers investigated photosensitization of the TiO2‐In2O3 sensing layer to enhance the NO2 detection capabilities of oxides. The heterogeneous interface engineered between two dissimilar oxides improved the accumulation of photogenerated charge carriers, which accelerated the adsorption and desorption of NO2 molecules. The study elaborates on the light‐mediated modulation of the oxide surface chemistry and establishes a rational design of cost‐effective light‐activated gas sensors. [ABSTRACT FROM AUTHOR]

Gas sensors, heterojunctions, indium oxides, interfacial engineering, photocatalysts, semiconducting oxides Keywords: gas sensors; heterojunctions; indium oxides; interfacial engineering; photocatalysts; semiconducting oxides EN gas sensors heterojunctions indium oxides interfacial engineering photocatalysts semiconducting oxides 1 1 1 04/27/23 20230425 NES 230425 B Gas Sensors b In article number 2214008, Il-Doo Kim and co-workers investigated photosensitization of the TiO SB 2 sb -In SB 2 sb O SB 3 sb sensing layer to enhance the NO SB 2 sb detection capabilities of oxides. Imparting Metal Oxides with High Sensitivity Toward Light-Activated NO2 Detection Via Tailored Interfacial Chemistry (Adv. Funct. [Extracted from the article]

Nanostructuring has significantly contributed to alleviating the huge volume expansion problem of the Ge anodes. However, the practical use of nanostructured Ge anodes has been hindered due to several problems including a low tap density, poor scalability, and severe side reactions. Therefore, micrometer-sized Ge is desirable for practical use of Ge-based anode materials. Here, micronized Ge3N4 with a high tap density of 1.1 mg cm−2 has been successfully developed via a scalable wet oxidation and a subsequent nitridation process of commercially available micrometer-sized Ge as the starting material. The micronized Ge3N4 shows much-suppressed volume expansion compared to micrometer-sized Ge. After the carbon coating process, a thin carbon layer (≈3 nm) is uniformly coated on the micronized Ge3N4, which significantly improves electrical conductivity. As a result, micronized Ge3N4@C shows high reversible capacity of 924 mAh g−1 (2.1 mAh cm−2) with high mass loading of 3.5 mg cm−2 and retains 91% of initial capacity after 300 cycles at a rate of 0.5 C. Additionally, the effectiveness of Ge3N4@C as practical anodes is comprehensively demonstrated for the full cell, showing stable cycle retention and especially excellent rate capability, retaining 47% of its initial capacity at 0.2 C for 12 min discharge/charge condition. [ABSTRACT FROM AUTHOR]

2D Ru oxide nanosheets (NSs) with optically punched nanoholes are synthesized and integrated on a flexible heating substrate, i.e., silver nanowire (Ag NW)-embedded colorless polyimide (cPI) film, for application in wearable chemical sensors. Multiple discrete pores on the sub-5-nm scale are formed on the basal planes of Ru oxide NSs by irradiation of intense pulsed light. The chemical sensing characteristic of the porous Ru oxide NSs toward nitrogen dioxide (NO2) is investigated under controlled temperatures by applying DC voltage to the Ag NW-embedded cPI film. The improved NO2 responding and recovery kinetics are achieved using the porous Ru oxide NSs with sensitivity of 1.124% at 20 ppm at a film temperature of 80.3 °C. A wireless patch-type sensor module is developed to demonstrate wearable sensing of NO2 using the Ru oxide NSs on Ag NW-embedded cPI heating film. This work paved the new way for application of atomically thin and porous Ru oxide NSs in chemical sensors, which can detect hazardous species in real time. [ABSTRACT FROM AUTHOR]

1D metal-oxide nanotube (NT) structures have attracted considerable attention for applications in chemical sensors due to their high surface area and unique chemical and physical properties. Moreover, bimodal pores, i.e., meso- and macro-sized pores, which are formed on the shell of NTs, can further facilitate gas penetration into the sensing layers, leading to much improved sensing properties. However, thin-walled NTs with bimodal pore distribution have been rarely fabricated due to the limitations of synthetic methods. Here, Ostwald ripening-driven electrospinning combined with sacrificial templating route using polystyrene (PS) colloid and bioinspired protein is firstly proposed for producing both bi-modal pores and catalyst-loaded thin-walled SnO2 NTs. Homogeneous catalyst loading on porous SnO2 NTs is achieved by the protein cage that contains catalysts and PS colloids and protein shells are thermally decomposed during calcination of electrospun fibers, resulting in the creation of dual-sized pores on NTs. Pt catalyst decorated porous SnO2 NTs (Pt-PS_SnO2 NTs) show exceptionally high acetone gas response, superior selectivity against other interfering gases, and very low limit of detection (10 ppb) to simulated diabetic acetone molecules. More importantly, sensor arrays assembled with developed porous SnO2 NTs enable the direct distinction between the simulated diabetic breath and normal breath from healthy people. [ABSTRACT FROM AUTHOR]

Porous Nanofiber Membranes In article number 2200463, Il‐Doo Kim and co‐workers develop highly sensitive thermochromic sensors using nanofiber (NF) membranes with tunable alignments of the NFs via a fine‐tuned electric field during the electrospinning process. The porous NFs membrane‐based sensors show highly sensitive thermochromic sensing performance at 31.6–42.7 °C. The developed NFs sensors membranes could be further integrated with masks, patches, and bracelets for wearable applications. [ABSTRACT FROM AUTHOR]

The porous NFs membrane-based sensors show highly sensitive thermochromic sensing performance at 31.6-42.7 °C. The developed NFs sensors membranes could be further integrated with masks, patches, and bracelets for wearable applications. Electrospinning, nanofiber alignment, thermochromic sensors, wearable devices, yarn. [Extracted from the article]

Germanium (Ge) possesses a great potential as a high-capacity anode material for lithium ion batteries but suffers from its poor capacity retention and rate capability due to significant volume expansion by lithiation. Here, a facile synthetic route is introduced for producing nanometer-sized Ge crystallites interconnected by carbon (GEC) via thermal decomposition of a Ge-citrate complex followed by a calcination process in an inert atmosphere. The GEC electrode shows outstanding electrochemical performance, i.e., an almost 98.8% capacity retention of 1232 mAh g−1, even after 1000 cycles at the rate of C/2. Importantly, a high discharge capacity of 880 mAh g−1 is maintained at the very high rate of 10 C. The excellent anode performance of GEC stems from both effective buffering of carbon anchored to the Ge nanocrystals and the high open porosity of the GEC aggregated powder with an average pore diameter of 32 nm. Furthermore, the interfacial layer formed between Ge and carbon plays an essential role in prolonging the cycle life. The GEC electrode can be successfully employed as an anode for next generation lithium ion batteries. [ABSTRACT FROM AUTHOR]

A new strategy for developing dye-sensitised solar cells (DSSCs) by combining thin porous zinc tin oxide (Zn2SnO4) fiber-based photoelectrodes with purely organic sensitizers is presented. The preparation of highly porous Zn2SnO4 electrodes, which show high specific surface area up to 124 m2/g using electrospinning techniques, is reported. The synthesis of a new organic donor-conjugate-acceptor (D-π-A) structured orange organic dye with molar extinction coefficient of 44 600 M−1 cm−1 is also presented. This dye and two other reference dyes, one organic and a ruthenium complex, are employed for the fabrication of Zn2SnO4 fiber-based DSSCs. Remarkably, organic dye-sensitized DSSCs displayed significantly improved performance compared to the ruthenium complex sensitized DSSCs. The devices based on a 3 μm-thick Zn2SnO4 electrode using the new sensitizer in conjunction with a liquid electrolyte show promising photovoltaic conversion up to 3.7% under standard AM 1.5G sunlight (100 mW cm−2). This result ranks among the highest reported for devices using ternary metal oxide electrodes. [ABSTRACT FROM AUTHOR]

Hierarchical SnO2 fibers assembled from wrinkled thin tubes are synthesized by controlling the microphase separation between tin precursors and polymers, by varying flow rates during electrospinning and a subsequent heat treatment. The inner and outer SnO2 tubes have a number of elongated open pores ranging from 10 nm to 500 nm in length along the fiber direction, enabling fast transport of gas molecules to the entire thin-walled sensing layers. These features admit exhaled gases such as acetone and toluene, which are markers used for the diagnosis of diabetes and lung cancer. The open tubular structures facilitated the uniform coating of catalytic Pt nanoparticles onto the inner SnO2 layers. Highly porous SnO2 fibers synthesized at a high flow rate show five-fold higher acetone responses than densely packed SnO2 fibers synthesized at a low flow rate. Interestingly, thin-wall assembled SnO2 fibers functionalized by Pt particles exhibit a dramatically shortened gas response time compared to that of un-doped SnO2 fibers, even at low acetone concentrations. Moreover, Pt-decorated SnO2 fibers significantly enhance toluene response. These results demonstrate the novel and practical feasibility of thin-wall assembled metal oxide based breath sensors for the accurate diagnosis of diabetes and potential detection of lung cancer. [ABSTRACT FROM AUTHOR]

2D Oxide Sensors: Heterogeneous, Porous 2D Oxide Sheets via Rapid Galvanic Replacement: Toward Superior HCHO Sensing Application (Adv. Funct. In article number 1903012, Hee Jung Park, Il-Doo Kim, and co-workers develop porous and heterogeneous SnO SB 2 sb /CoO SB I x i sb nanosheets by combining exfoliation with galvanic replacement reaction. Due to the high porosity, thin-thickness (<10 nm), and numerous heterogeneous junctions, the heterogeneous SnO SB 2 sb /CoO SB I x i sb nanosheets show super-sensitive HCHO sensing characteristics with a rapid response (<10 sec). [Extracted from the article]

2D heterogeneous oxide nanosheets (NSs) have attracted much attention in various scientific fields owing to their exceptional physicochemical properties. However, the fabrication of 2D oxide NSs with abundant p–n interfaces and large amounts of mesopores is extremely challenging. Here, a facile synthesis of highly porous 2D heterogeneous oxide NSs (e.g., SnO2/CoOx) is suggested through a 2D oxide exfoliation approach combined with a fast galvanic replacement reaction (GRR). The ultrathin (<5 nm) layered CoOx NSs are simply prepared by ion‐exchange exfoliation and a subsequent GRR process that induces a rapid phase transition from p‐type CoOx to n‐type SnO2 metal oxides (<10 min). The controlled GRR process enables the creation of heterogeneous SnO2/CoOx NSs consisting of small SnO2 grain sizes (<10 nm), high porosity, numerous heterojunctions, and sub‐10 nm thickness, which are highly advantageous characteristics for chemiresistive sensors. Due to the advantage of these features, the porous SnO2/CoOx NSs exhibit an unparalleled HCHO‐sensing performance (Rair/Rgas > 35 @ 5 ppm with a response speed of 9.34 s) with exceptional selectivity compared to that of the state‐of‐the‐art metal oxide‐based HCHO gas sensors. [ABSTRACT FROM AUTHOR]

Metal oxide nanosheets having high mesoporosity, grain size distribution of 5–10 nm, and ultrathin thickness have attracted much attention due to their intriguing properties such as high surface‐to‐volume ratio and superior chemical activities. However, 2D nanostructures tend to restack, inducing a decrease in accessible surface area and a number of pores. To solve this problem, herein, a unique synthetic method of crumpled metal oxide nanosheets using spray pyrolysis of metal ion–coated graphene oxide, followed by heat treatment, is reported. This method is applicable not only to single‐component metal oxides but also to heterogeneous multicomponent metal oxides in which composition can be controlled. Crumpled SnO2, ZnO, and Co3O4 as well as SnO2/ZnO and SnO2/Co3O4 nanosheets with heterogeneous interfaces are successfully synthesized and used as superior gas sensing layers. Because of the abundant reaction sites, well‐developed porosity for high gas accessibility, the formation of heterojunctions, the crumpled SnO2/ZnO and SnO2/Co3O4 nanosheets exhibit outstanding sensing performance (Rair/Rgas = 20.25 toward 5 ppm formaldehyde, and Rair/Rgas = 14.13 toward 5 ppm acetone, respectively). This study can contribute to the realization of a family of heterogeneous crumpled metal oxide nanosheets that can be applied to various research fields. [ABSTRACT FROM AUTHOR]

Interfacial engineering of organic–inorganic halide perovskites in conjunction with different functional materials is anticipated to offer novel heterojunction structures with unique functionalities. Unfortunately, complex material compositions and structures of the organic–inorganic hybrid materials make it difficult to tailor a desirable intermolecular interaction at the interface. Spontaneous and highly specific nucleation of perovskite crystals, that is, methylammonium lead iodide perovskite (CH3NH3PbI3, MAPbI3) at nitrogen‐doped carbon nanotube (NCNT) surfaces for the self‐assembly of MAPbI3/NCNT hybrids is reported. It is demonstrated that the lone‐pair electrons of pyridinic nitrogen‐dopant sites at NCNTs mediate specific interactions with the cationic component in the perovskite structure and serve as the nucleation sites via coordinate bonding formation, as supported by X‐ray photoelectron spectroscopy and density functional theory calculation. The potential suitability of MAPbI3/NCNT hybrids is presented for highly sensitive and selective NO2 sensing layer. This work suggests a reliable self‐assembly route to the molecular level hybridization of organic–inorganic halide perovskites by employing the substitutional dopant sites at graphene‐based nanomaterials. [ABSTRACT FROM AUTHOR]

The physical and chemical degradations of a state‐of‐the‐art proton exchange membrane (PEM) composed of a perfluorinated sulfonic acid (PFSA) ionomer and polytetrafluoroethylene (PTFE) reinforcement are induced through the repeated expansion/shrinkage of the ionomer and free radical attacks. Such degradations essentially originate from the loose structure of the materials and the low interactive binding force among the PEM constituents. In this study, the need for simplified design principles of adhesives led to the use of mussel‐inspired polydopamine (PD) as an interfacial modifier for the fabrication of highly durable PEM. Indeed, a self‐polymerized dopamine layer acts as an interfacial glue, and enables efficient impregnation of a hydrophilic PFSA ionomer into porous hydrophobic PTFE with high packing density, resulting in strong adhesion between the PTFE and the PFSA polymers in the membrane. In addition, the redox property of the PD end groups spontaneously reduces the partial Ce salts in the ionomer solution and anchors them to the PD@PTFE substrate as defective cerium oxide (CeOx) nanoparticles, reducing the dissolution and subsequent migration under cell operations. Finally, a CePD@PTFE membrane shows outstanding durability in fuel cells under an accelerated humidity cycling test with a reduction in the degree of physical and chemical failures. Mussel‐inspired polydopamine and Ce salts are introduced to porous polytetrafluoroethylene (PTFE) substrates for highly durable composite membranes. The multifunctional features of polydopamine, i.e., (i) interfacial glues between perfluorinated sulfonic acid and PTFE layers; and (ii) immobilization of Ce based radical scavengers give rise to outstanding cell performance with long‐term operation of proton exchange membrane fuel cells under humidity cycles. [ABSTRACT FROM AUTHOR]

In article number 1804508, Sang Ouk Kim and co‐workers present a reliable and effective nanopatterning strategy for 2D transition metal dichalcogenides via block copolymer (BCP) lithography. By exploiting various BCP templates, diverse nanostructures, including nanomeshes, nanodots, and nanowire arrays, are demonstrated with wafer‐scale scalability. Edge‐exposed MoS2 nanomeshes exhibit superior sensitivity and reversibility for NO2 gas sensing. [ABSTRACT FROM AUTHOR]

Nanoscale structure engineering is in high demand for various applications of 2D transition metal dichalcogenides (TMDs). An edge‐exposed 2D polycrystalline MoS2 nanomesh thin film is demonstrated via block copolymer (BCP) nanopatterning. Molybdenum nanomesh structure is formed by direct metal deposition of hexagonal cylinder BCP nanotemplate and the following lift‐off process. Subsequent sulfurization of the molybdenum nanomesh creates MoS2 nanomesh thin films without any degradative etching step. The approach is applicable to not only other metal sulfides and oxides but also other nanoscale structures of TMD thin films including nanodot and nanowire array by means of various BCP nanotemplate shapes. As the edge site of MoS2 is highly active for NO2 sensing, the edge‐exposed MoS2 nanomesh demonstrates sevenfold enhancement of sensitivity for NO2 molecules compared to uniform thin film as well as superior reversibility even under 80% relative humidity environment. This structure engineering method could greatly strengthen the potential application of 2D TMD materials with the optimal customized nanoscale structures. Nanopatterning of transition metal dichalcogenides (TMD) is presented. By exploiting block copolymer nanotemplate, desired metal nanopattern, including nanomesh, nanodot, and nanowire arrays, can be readily obtained with large area. The post sulfurization process gives rise to nanopattered TMD. The edge‐exposed MoS2 nanomesh exhibits a sevenfold enhancement of sensitivity for NO2 sensing and superior reversibility compared to the uniform thin film. [ABSTRACT FROM AUTHOR]

A NO2 sensor based on optically sintered 2D Ru oxide nanosheets applied to a flexible heating substrate composed of a colorless polyimide film with embedded Ag nanowires is described by Hee Jung Park, Il‐Doo Kim, and co‐workers in article number 1606026. A sensitivity of 1.124% at 20 ppm and a wearable wireless sensor is demonstrated. [ABSTRACT FROM AUTHOR]

Thin‐wall assembled SnO2 tubes with a number elongated pores are synthesized via electrospinning, controlled by the variation of flow rates. On page 2357, Il‐Doo Kim and co‐workers report that these highly porous SnO2 tubes show a five‐fold higher acetone response compared with dense SnO2 fiber in a humid atmosphere that is similar to the oral cavity. The accurate detection of acetone gas in exhaled breath can provide useful information for real‐time diagnosis of diabetes. [ABSTRACT FROM AUTHOR]