Bending States Research Articles

Centimeter‐Scale and Honeycomb‐Like Bismuth Sulfide Film Composed of Triangular Structural Units for Flexible Photodetector

AbstractFilms with honeycomb‐like structures have became ideal network structures for the development of flexible photodetectors due to their superior mechanical stability and merits in large active surface area, high carrier transport efficiency and well light absorption capacity. In this work, a honeycomb‐like Bi2S3 film with centimeter‐scale (2 cm × 2 cm) is synthesized on an ultrathin flexible fluorophlogopite mica substrate, which consists of a well‐stabilized arrangement of triangular unit structures forming an interconnected network structure. Based on the as‐grown honeycomb‐like Bi2S3 film, a flexible photodetector with a broadband response from ultraviolet to infrared is constructed, which displays the highest responsivity (Rλ) of 611.2 mA W−1 and specific detectivity (D*) of 4.77 × 1010 Jones. And at 850 nm light illumination, there is nearly no deterioration in Rλ and D* of the Bi2S3 flexible photodetector after successive multiple bends, benefiting from the excellent structural stability of the triangular honeycomb network structure. Notably, the device maintains excellent detection performance after 1 week of prolonged bending in air without any encapsulation, and its photocurrent can still reach 90.39% of the initial photocurrent. In addition, the device also exhibits favorable durability, cycle stability, as well as high‐definition imaging ability in bending state and after bending recovery.

A multilevel resistive switching memristor based on flexible organic–inorganic hybrid film with recognition function

Abstract Brain-inspired neuromorphic computing systems fueled the emergence of memristor-based artificial synapses, however, conventional silicon-based devices restricted their usage in the wearable field because of their difficulty in bending. To tackle the above challenge, a vertically structured flexible memristor with aluminum-based hydroquinone organic–inorganic hybrid film and Al2O3 as the functional layer, ITO and Pt as the bottom and top electrodes, and PET as the substrate has been developed utilizing molecular/atomic layer deposition to achieve a tradeoff between the resistive transition properties and the flexibility of memristors. The obtained devices combine stable resistive switching behavior and flexibility, showing high switching ratio of 103, better retention (up to 105 s) and endurance properties (up to 104 cycles), and robustness at radius of curvature of 4.5 mm after 104 bending cycles. Furthermore, the presence of multilevel resistive states in these devices ensures that the memristor can emulate synaptic properties such as paired-pulse facilitation, transition from short-term plasticity to long-term plasticity, long-term potentiation and depression, and spike-time-dependent plasticity. The resistive switching mechanism and the role of the bending state on the electrical performance of the device are explored. The fully connected artificial neural network based on the memristor can achieve a recognition accuracy of 90.2% for handwritten digits after training and learning. Flexible memristor will bring feasible advances to the integration of neuromorphic computing and wearable functionality.

Microfluidic Wearable Electrochemical Sensor Based on MOF-Derived Hexagonal Rod-Shaped Porous Carbon for Sweat Metabolite and Electrolyte Analysis.

Wearable sensors enable the noninvasive continuous analysis of biofluid, which is of great importance for healthcare monitoring. In this work, a wearable sensor was seamlessly integrated with a microfluidic chip which was prepared by a three-dimensional printing technology for noninvasive and multiplexed analysis of metabolite and electrolytes in human sweat. The microfluidic chip could enable rapid sampling of sweat, which avoids the sweat evaporation and contamination. Using a Zn metal-organic framework as a sacrificial template, the hexagonal rod-shaped porous carbon nanorod (PCN) with high porosity, a large specific surface area, and excellent conductivity was synthesized and exhibited the robust electrocatalytic ability of uric acid (UA) oxidation. Therefore, the PCN-based sensor showed high sensitivity and good selectivity of UA with a wide linear range of 10-200 μM and a low detection limit of 4.13 μM. Meanwhile, the potentiometry-based ion-selective electrode was constructed for detection of pH and K+, respectively, with good sensitivity, selectivity, reproducibility, and stability. In addition, the testing under different bending states demonstrated that mechanical deformation had little effect on the electrochemical performance of the wearable sensors. Furthermore, we evaluated the utility of the wearable sensor for multiplexed real-time analysis of UA, pH, and K+ in sweat during aerobic exercise, and the effect of the amount of consumed purine-rich foods on uric acid metabolite levels in sweat and urine was further investigated. The relationship between urine UA and sweat UA was obtained. Overall, this wearable sensor enables multiple electrolyte and metabolite analysis in different noninvasive biofluids, suggesting its potential application in personalized disease prevention.

Flexible and transparent leaf-vein electrodes fabricated by liquid film rupture self-assembly AgNWs for application of heaters and pressure sensors

The leaf veins with hierarchically interconnected network structures have great potential as self-assembly templates for transparent and flexible electrodes. In this paper, a liquid membrane ruptured assisted AgNWs self-assembly method was adopted to obtain conductive veins, which show a low sheet resistance of 3.6Ω/□ and a high transparency of 79 % at a minimal materials waste. The figure of merit of conductive veins was as high as 433Ω-1 and can be further increased by increasing the number of soaking because the light transmittance is nearly immune to the AgNWs layer number. The veins maintained a good electrical conductivity even after bending 10,000 times at a 2 mm radius of curvature and exhibited a good corrosion resistance under harsh conditions. Heaters based on the conductive veins are shown as application examples. A high temperature of 104 °C was achieved at a low voltage of 2 V, which is enough to heat cold water. They still have good heating properties even in the bending state or tensile state. Furthermore, pressure sensors based on the conductive veins were fabricated as examples of wearable devices. The sensor exhibits a high sensitivity of 3.8 kPa−1 in the low-pressure range (0–15 kPa) and 17.4 kPa−1 in the high pressure range (15–50.96 kPa). It can monitor human actions such as finger bending, finger taping, throat swallowing and wrist pulse in real-time, which has promising potential for motion monitoring and information encryption applications.

Intramolecular Vibrational Energy Redistribution in the Reaction H3+ + CO → H2 + HCO.

An ab initio direct molecular dynamics (MD) calculation at the RS2/aug-cc-pVQZ level, followed by vibration mapping, has been applied to the H3+ + CO → H2 + HCO+ reaction to elucidate the intramolecular vibrational energy redistribution (IVR) processes during the reaction. Direct MD calculations were carried out for 20 K (a typical temperature for interstellar dark clouds) and 330 K (a typical translational temperature for ions in a glow discharge). Under the Cs symmetry constraint, the approach of H3+ turned out to be the H-C stretching mode of the [H···CO]+ part, which invoked the C-O stretching and then the H-C-O bending modes. Under no symmetry constraint, a strong bending mode was first invoked, and the intensities of the subsequent H-C and C-O stretching modes were kept relatively small. The detailed analyses of the IVR during the reaction, in terms of vibration mixing, gave a clue to understanding experimentally observed anomalies in the bending modes, such as population inversion at some bending states. In the MD simulation at 20 K, less than two-thirds of the reaction energy was converted to the vibrational energy of the resultant HCO+ part and one-third to the translational and rotational energies of the leaving H2 molecule. These direct MD simulations, when combined with the experimental spectroscopy data, shed light on a clear understanding of the reaction mechanism, including the IVR during the reaction.

High‐Performance Flexible Gas Sensor Using Natural Rubber/MXene Composite for Selective and Stable VOC Detection

AbstractFlexible gas sensors are gaining interest for real‐time volatile gas monitoring. A natural rubber (NR)/MXene nanocomposite sensor is developed. Among the six selected target volatile gases, the composite sensor exhibited a strong response value (82% toward 100 ppm NH3) with the fastest response/recovery time (12.3 s/15.5 s) to NH3. The sensitivity showed a clear dependence of gases, suggesting a good selectivity to varying gases. Ti3C2Tx MXene gas sensors exhibited a very low limit of detection of 50–100 ppb for volatile organic compounds (VOCs) at room temperature. In addition, the NR/MXene sensor allows detection of the mixture of ammonia (NH3), dimethyl sulfoxide (DMSO), and acetone (C3H6O) and it shows good response depending on the total concentration of VOC gases. Furthermore, the flexible nanocomposite sensor exhibits stable sensing performance at different bending states (0‐120°) and shows 20‐day atmospheric stability. This sensor's ability extends to alcohol breath analysis, useful for drunk driving detection. This work paves the way to the possibility of using robust MXene‐based toward practical realization of electronic devices.

Controlled Fabrication of Wafer-Scale, Flexible Ag-TiO2 Nanoparticle-Film Hybrid Surface-Enhanced Raman Scattering Substrates for Sub-Micrometer Plastics Detection.

As an important trace molecular detection technique, surface-enhanced Raman scattering (SERS) has been extensively investigated, while the realization of simple, low-cost, and controllable fabrication of wafer-scale, flexible SERS-active substrates remains challenging. Here, we report a facile, low-cost strategy for fabricating wafer-scale SERS substrates based on Ag-TiO2 nanoparticle-film hybrids by combining dip-coating and UV light array photo-deposition. The results show that a centimeter-scale Ag nanoparticle (AgNP) film (~20 cm × 20 cm) could be uniformly photo-deposited on both non-flexible and flexible TiO2 substrates, with a relative standard deviation in particle size of only 5.63%. The large-scale AgNP/TiO2 hybrids working as SERS substrates show high sensitivity and good uniformity at both the micron and wafer levels, as evidenced by scanning electron microscopy and Raman measurements. In situ bending and tensile experiments demonstrate that the as-prepared flexible AgNP/TiO2 SERS substrate is mechanically robust, exhibiting stable SERS activity even in a large bending state as well as after more than 200 tensile cycles. Moreover, the flexible AgNP/TiO2 SERS substrates show excellent performance in detecting sub-micrometer-sized plastics (≤1 μm) and low-concentration organic pollutants on complex surfaces. Overall, this study provides a simple path toward wafer-scale, flexible SERS substrate fabrication, which is a big step for practical applications of the SERS technique.

Flexible, Multifunctional, and Durable MXene/CeO2/Cellulose Nanofibers for Efficient Energy Conversion‐Storage Capacity Toward Self‐Powered Monitoring of Ammonia

AbstractThe appeal of wearable gas sensors for Internet of Things (IoTs) necessitates flexible sensory units along with sustainable source of energy supply. The key factors required for emergence of these devices are choice of electroactive materials, flexibility, skin‐compatibility, and robustness against harsh environment. Considering this, the multifunctional MXene/CeO2 composites reinforced with electrospun cellulose nanofibers are constructed and investigated for energy conversion, energy storage, and gas sensing applications. Among the synthesized composites, MXene/CeO2 (10 wt%) coated onto cellulose nanofibers outperformed triboelectric nanogenerator (TENG) with open‐circuit voltage of 160 V and supercapacitor (SC) specific capacitance of 388.98 F g−1 and sensing response of 212% toward 10 ppm NH3. The fabricated devices show promising outlooks against practical challenges of influence of humid conditions and different bending states. Lastly, the self‐chargeable device is integrated and the practical implications of charging of SC through TENG and its utilization in sensor powering is demonstrated. The above findings are expected to contribute significantly in envisioning development of wearable health monitors, combining the flexibility features and facilitating autonomous measurements of NH3 pollutant and biomarker.

Wearable Inorganic Oxide Chemiresistor Based on Flexible Al2O3-Stabilized ZrO2 Ceramic Sponge Substrate for NO2 Sensing.

Wearable gas sensors, possessing the advantages of high sensitivity, excellent flexibility, high permeability, low weight, and workability at ambient conditions, hold great promise for real-time health monitoring and early warnings of poisonous gases. However, obtaining high-performance wearable gas sensors utilizing the current well-developed inorganic semiconductor oxide sensing materials is still very limited due to their fragile and rigid nature. Herein, a newly designed wearable gas sensor based on an all-inorganic ASZ (Al2O3-stabilized ZrO2)/ZnO/SnO2 nanofibers is introduced for the first time. The flexible ASZ ceramic sponge substrate (with a Young's modulus of 4.15 MPa) and ultrathin ZnO/SnO2 sensing layer endow the wearable gas sensor with promising properties such as super flexibility (with a bending radius of 5 mm), high gas permeability, and low weight. Furthermore, driven by UV light irradiation, this all-inorganic wearable sensor also demonstrates a stable NO2 sensing response under different bending states at room temperature, which enables the gas sensor to be more compatible with wearable sensing applications. This work offers a general method to achieve a high-performance wearable gas sensor based on inorganic materials and provides new insights into their potential in wearable gas-sensing applications.

Intermolecular Bending States and Tunneling Splittings of Water Trimer from Rigorous 9D Quantum Calculations: I. Methodology, Energy Levels, and Low-Frequency Spectrum.

We present the computational methodology that enables the first rigorous nine-dimensional (9D) quantum calculations of the intermolecular bending states of the water trimer, as well as its low-frequency spectrum for direct comparison with experiment. The water monomers, treated as rigid, have their centers of mass (cm's) at the corners of an equilateral triangle, and the intermonomer cm-to-cm distance is set to a value slightly larger than that in the equilibrium geometry of the trimer. The remaining nine strongly coupled large-amplitude bending (angular) degrees of freedom (DOFs) enter the 9D bend Hamiltonian of the three coupled 3D rigid-water hindered rotors. Its 9D eigenstates encompass excited librational vibrations of the trimer, as well as their torsional and bifurcation tunneling splittings, which have been the subject of much interest. The calculations of these eigenstates are extremely demanding, and a sophisticated computational scheme is developed that exploits the molecular symmetry group of the water trimer, G48, in order to make them feasible in a reasonable amount of time. The spectrum of the low-frequency vibrations of the water trimer simulated using the eigenstates of the 9D bend Hamiltonian agrees remarkably well with the experimentally observed far-infrared (FIR) spectrum of the trimer in helium nanodroplets over the entire frequency range of the measurements from 70 to 620 cm-1. This shows that most peaks in the experimental FIR spectrum are associated with the intermolecular bending vibrations of the trimer. Moreover, the ground-state torsional tunneling splittings from the present 9D calculations are in excellent agreement with the spectroscopic data. These results demonstrate the high quality of the ab initio 2 + 3-body PES employed for the DOFs included in the bound-state calculations.

Ultra‐Wide Modulation and Reversible Reconfiguration of a Flexible Organic Crystalline Optical Waveguide Between 645 and 731 nm

Flexible organic crystalline optical waveguides, i.e., delivering input or self‐emit lights through various dynamic organic crystals, have attracted increasing attentions in the past decade. However, the modulation of waveguide outputs relies on chemical design and substituent modification, being time‐consuming and laborious. Here we report an elastic organic crystal that displays long‐distance light transducing capability up to 2.0 cm and ultra‐wide modulation of crystalline optical waveguides between red (645 nm) and near infrared (731 nm) in both the pristine and the elastically bent states based on a pre‐designed self‐absorption effect. The flexible organic crystalline optical waveguides can be precisely and reversibly reconfigured by controlling irradiation point. In addition, deep red amplified spontaneous emissions (ASE) that are able to transduce through a 5.0 mm bent crystal with an ultra‐low optical loss coefficient of 0.092 dB/mm has been attained. To the best of our knowledge, this is the first report of flexible organic ASE waveguides. The present study not only provides a simple yet effective strategy to remarkably modulate flexible organic crystalline optical waveguides but also demonstrates the superiority of laser over normal emission as flexible optical communication elements.

Flexible Tactile Sensors with Gradient Conformal Dome Structures.

The trade-off between high sensitivity and wide detection range remains a challenge for flexible capacitive pressure sensors. Gradient structure can provide continuous deformation and lead to a wide sensing range. However, it simultaneously augments the distance between two electrodes, which diminishes the variation in the relative distance and results in a decreased sensitivity. Herein, a conformal design is introduced into the gradient structure to construct a flexible capacitive pressure sensor. The gradient conformal dome structure is fabricated by a simple reverse dome adsorption process. Taking advantage of the progressive deformation behavior of the gradient dielectric, and the significant improvement of relative distance variation between two electrodes from the conformal design, the sensor achieves a sensitivity of 0.214 kPa-1 in an ultrabroad linear range up to 200 kPa. It maintains high-pressure resolution under the preload of 10 and 100 kPa. Benefiting from the rapid response and excellent repeatability, the sensor can be used for physiological monitor and human motion detection, including arterial pulse, joint bending, and motion state. The gradient conformal design strategy may pave a promising avenue to develop pressure sensors with high sensitivity and wide linear range.

Interplay between strain and charge in Cu(In,Ga)Se2 flexible photovoltaics

Flexible and lightweight Cu(In,Ga)Se2 (CIGS) thin-film solar cells are promising for versatile applications, but there is limited understanding of stress-induced changes. In this study, the charge carrier generation and trapping behavior under mechanical stress was investigated using flexible CIGS thin-film solar cells with various alkali treatments. Surface current at the CIGS surface decreased by convex bending, which occurs less with the incorporation of alkali metals. The formation energy of the carrier generating defects increased in convex bending environments clarifying the degradation of the surface current. Moreover, alkali-related defects had lower formation energy than the intrinsic acceptors, mitigating current degradation in mechanical stress condition. The altered defect energy levels were attributed to the deformation of the crystal structure under bending states. This study provides insights into the mitigating of strain-induced charge degradation for enhancing the performance and robustness of flexible CIGS photovoltaic devices.

Magnetostrictive bi-perceptive flexible sensor for tracking bend and position of human and robot hand

The sensor that simultaneously perceives bending strain and magnetic field has the potential to detect the finger bending state and hand position of the human and robot. Based on unique magneto-mechanical coupling effect of magnetostrictive materials, the proposed a bi-perceptive flexible sensor, consisting of the Co–Fe film and magnetic sensing plane coils, can realize dual information perception of strain/magnetic field through the change of magnetization state. The sensor structure and interface circuit of the sensing system are designed to provide high sensitivity and fast response, based on the input–output characteristics of the simulation model. An asynchronous multi-task deep learning method is proposed, which takes the output of the position task as the partial input of the bending state task to analyze the output information of the sensor quickly and accurately. The sensing system, integrating with the proposed model, can better predict the bending state and approach distance of human or robot hand.

A General Strategy toward Enhanced Electrochemical and Mechanical Performance of Solid‐State Lithium Batteries through Constructing Covalently Bonded Electrode Materials/Electrolyte Interfaces

AbstractSolid‐state lithium batteries (SSLBs) offer inherent safety and high energy density for next‐generation energy storage, but the large interfacial resistance and poor physical connection between electrode materials and the solid electrolyte (SE) severely impede their practical applications. This work reports a general strategy to introduce covalent bonds between electrode materials and SE, not only reducing interfacial resistance but also enhancing electrochemical stability and mechanical robustness of SSLBs. The covalent bonding is accomplished by functionalizing electrode surfaces with C═C groups, enabling in situ copolymerization with telechelic polymers in the SE. This approach is applicable to various cathode/anode materials and SEs. Particularly, the SSLBs comprising LiFePO4 cathode, Li6.75La3Zr1.75Ta0.25O12/(polyethylene oxide (PEO)/lithium bis(trifluoromethylsulfonyl)imide (LiTFSI)/silk composite SE and metallic lithium anode exhibit a specific capacity of 158.4 mAh g−1 and can be cycled at 2 C for 2200 times with >80% retention. Additionally, the SSLBs containing the high nickel‐content LiNi0.96Co0.03Mn0.01O2 cathode can afford a high specific capacity of 201.8 mAh g−1. Comprehensive experimental examination and theoretical simulations confirm that the lowered interfacial resistance and intimately contacted electrode materials/electrolyte interfaces facilitate Li+ transport at different stages of charge. Furthermore, the covalently bonded electrode/electrolyte interfaces also endow SSLBs with outstanding mechanical stability, enabling flexible SSLB pouch cells to operate under various bending states without performance decay.

Multifunctional electrochromic yarns for variable optical and thermal regulation

In this study, tungsten oxide and polyaniline hybrid films were deposited on the surface of stainless steel yarns by electrochemical deposition, and the electrochromic yarns with double electrochromic layer structure were formed. WO3 acts as a protective layer and binder to connect PANI nanorods, thereby improving electrochemical stability and electrochromic performance. The electrochromic yarns present five color changes in the voltage range of −0.4 V-1.1 V, the optical modulation of 59.98 %, the response time of 0.75 s, the coloration efficiency of 74.89 cm2/C, good electrochemical cycling stability (100 cycles without significant degeneration) and washing durability. At the same time, stable electrochromic behavior is still maintained in the bending state. The device based electrochromic yarns also has reversible multi-color variation, fast reaction time, and long-term stability. What's more, the device can be embroidered or woven into the fabric and designed into patterns of different colors. More color combinations can be achieved by adjusting the voltage. Finally, the fabric based on multifunction electrochromic yarns are used to study the thermal shielding performance. It can effectively block thermal radiation. These results indicate that the electrochromic yarn has promising potential for high-performance optical and thermal regulation applications. This research provides a prospective strategy for constructing multifunctional electronic devices in wearable application.

Photo-annealed electrospun TiO2 nanofibers as ion-storage layer for self-rechargeable Zn-based electrochromic energy storage device

Developing a self-rechargeable transparent electrochromic energy storage device (EESD) is highly demanding for advancing electrochromic technology and energy harvesting capabilities. In this study, we introduce a room-temperature photo-annealing method to fabricate electrospun titanium oxide (TiO2) nanofibers, serving as an ion-storage layer (ISL) on the counter electrode. By monitoring the composition and morphology of the precursor before and after ultraviolet/ozone irradiation, we confirm the formation of oxide nanostructures in electrospun TiO2 nanofibers, which enhances ion transport in the fabricated EESDs. The structural and surface properties of the photo-annealed ISL are comprehensively analyzed using various characterization techniques. Enhanced electrochromic performances are evidenced through cyclic voltammetry, spectroelectrochemical measurements, and charge storage assessments. The Zn-based EESDs with ISL (ISL Zn-EESDs) display rapid electrochemical kinetics, high charge-storing capacities, and long lifespans, with open-circuit potential of 1.2 V, optical contrast of 77 %, discharge capacity of 92 mA h/g, coloration efficiency of 58.63 cm2/C, and 99.9 % efficiency retention up to 250 cycles in both flat and bent states. Furthermore, the practical viability of the ISL Zn-EESDs is demonstrated by powering an LED lamp for several minutes. This approach highlights the potential of ISL Zn-EESDs for developing flexible smart windows, opening up a range of promising applications.

Chitin and Cellulose as Constituents of Efficient, Sustainable, and Flexible Zinc-Ion Hybrid Supercapacitors

A zinc-ion hybrid supercapacitor (ZIHS) is a prospective energy storage device featuring cost-effectiveness, operational safety, environmental friendliness, high-power performance, and satisfied energy density.1 The sustainability of this ZIHS technology is even improved by introducing biopolymer constituents into the cell construction.2 Herein, efficient, sustainable, and flexible ZIHSs employing polysaccharide (chitin- or cellulose-based) components are developed.3 Using green ionic liquid solvents, biopolymer-bound, activated carbon-based cathode materials and hydrogel biopolymer electrolytes containing conductive zinc salts are obtained. According to systematical characterization results, the prepared materials possess favorable functional properties. Biopolymer binders provide homogeneity and integrity within the electrode network and high adhesion to the surface of the current collector. Depending on the type of zinc salt, hydrogel biopolymer electrolytes display high ionic conductivity (up to 46 mS cm−1), expanded electrochemical stability window (up to ca. 2.8 V), and zinc dendrites growth suppression. Biopolymer components assembled with zinc foil electrodes operate efficiently in both coin and pouch ZIHS cell configurations, providing satisfactory energy (45–50 Wh kg−1) and high power (10–20 kW kg−1) density combined with excellent cycle stability. Moreover, these ZIHS pouch-type devices exhibit superior durability and flexibility, withstanding mechanical stress up to 150° bending states with at least 90% of capacitance retention. It suggests a prospect for their application in wearable electronics.4 References(1) Wang, Y.; Sun, S.; Wu, X.; Liang, H.; Zhang, W. Status and Opportunities of Zinc Ion Hybrid Capacitors: Focus on Carbon Materials, Current Collectors, and Separators. Nano-Micro Lett. 2023, 15 (1), 78.(2) Kasprzak, D.; Mayorga-Martinez, C. C.; Pumera, M. Sustainable and Flexible Energy Storage Devices : A Review. Energy & Fuels 2023, 37, 74–97.(3) Kasprzak, D.; Liu, J. Chitin and Cellulose as Constituents of Efficient, Sustainable, and Flexible Zinc-Ion Hybrid Supercapacitors. Sustain. Mater. Technol. 2023, 38, e00726.(4) Dubal, D. P.; Chodankar, N. R.; Kim, D. H.; Gomez-Romero, P. Towards Flexible Solid-State Supercapacitors for Smart and Wearable Electronics. Chem. Soc. Rev. 2018, 47 (6), 2065–2129. Figure 1. Graphical abstract of the research on biopolymer-based Zn-ion hybrid supercapacitors. Figure 1

PtCo nanoalloy embedded nitrogen-doped carbon nanotube for rechargeable Zn-air batteries

The large-scale application of metal-air batteries strongly depends on the development of cost-effective, highly efficient, and durable bifunctional oxygen catalysts. In this work, a facile approach for preparing the monodisperse PtCo nanoalloy anchored the nitrogen-doped carbon nanotubes (PtCo/NCNT) for zinc-air batteries is reported. The nitrogen-doped carbon shell prevents PtCo nanoalloy from exfoliation, dissolution, and aggregation and enables the accessibility of electrolytes to the alloy surface and the electron transfer. Besides, the strong interaction between PtCo nanoalloy and nitrogen-doped carbon can efficiently modulate the electronic structure of the formed active sites. When used as a cathode catalyst, the constructed rechargeable zinc-air battery presents higher power density (268 mW cm−2), specific capacity (840 mAh g−1), and excellent stability. More importantly, the PtCo/NCNT catalyst allows the all-solid-state cell to exhibit remarkable flexibility and high round-trip efficiency at various bending states, demonstrating a potential possibility to replace the conventional Pt/C and RuO2 catalysts.

Vibrational relaxation of HOD by collisions with Ar atoms.

Vibrational relaxation of HOD(v12, v3) molecules by collisions with Ar was studied at 298K (v12 denotes coupled bending, v2, and OD stretching, v1, vibrational modes and v3 denotes OH stretching mode). The vibrationally excited HOD molecules were generated by exothermic abstraction reactions of OD radicals with 13 different RH reactants and observed by infrared emission from a fast-flow reactor as a function of Ar pressure and reaction time. State-specific relaxation rate constants were obtained by comparison of the time evolution of the experimental vibrational distributions with numerical kinetic calculations for vibrational populations. The relaxation mechanism was based on the relaxation scheme of H2O studied earlier with the addition of specific channels for HOD(v12, v3). Unlike H2O, energy in stretching and bending vibrations of HOD cannot be separated due to close ν1 and 2ν2 energies, which leads to fast collisional equilibration between these Fermi-resonant levels. For relaxation of the only pure bending state (10), a rate constant of (1.5 ± 0.3) × 10-13cm3molecule-1s-1 was obtained. The relaxation rate of higher v12 states linearly increases with quantum number and very likely includes transfer of population from OD stretch levels, v1, to a lower energy bend level. The average rate constants for the loss of population from (01), (02), and (03) stretching states are (1.1 ± 0.3) × 10-14, (3.2 ± 1.0) × 10-14, and (5.6 ± 1.2) × 10-14cm3molecule-1s-1, respectively.