In situ confinement of iron-based active sites within high porosity carbon frameworks with enhanced activity for rechargeable Zn–air battery

Non-noble bifunctional electrocatalysts with robust activity and stability toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are greatly significant but challenging for Zn-air batteries. Here, in situ confinement of FeN_x active sites in high porosity carbon framework (FeN_x/CMCC) derived from chelate of carboxymethylcellulose (CMC) and iron ions were synthesized. Particularly, construction of FeN_x within porous carbon framework accelerates the electron transfer and the sufficient utilization of active centers, and then expedites the reaction kinetics of ORR and OER. As expected, the optimized FeN_x/CMCC exhibits superior ORR activity with a larger half-wave potential of 0.869 V. The rechargeable Zn-air battery delivers a higher power density of 99.6 mW/cm² and a special capacity of 781.9 mA h/g_Zn at 10 mA/cm², together with excellent durability of over 335 h. Remarkably, the as-assembled solid-state battery exhibits a higher open circuit voltage (OCV) of 1.5 V, a special capacity of 709.7 mA h/g_Zn, as well as prolonged cycling stability (90 h). Moreover, the flexible solid-state battery displays negligible loss of electrochemical performance under various bending angles, illustrating its potential application in flexible electronic devices.     

Advances in stable and flexible perovskite solar cells

Roll-to-roll (R2R) production is an innovative approach and is fast becoming a very popular industrial method for high throughput and mass production of solar cells. Replacement of costly indium tin oxide (ITO), which conventionally has served as the transparent electrode would be a great approach for roll to roll production of flexible cost effective solar cells. Indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) are brittle and ultimately limit the device flexibility. Perovskite solar cells (PSCs) have been the centre of photovoltaic research community during the recent years owing to its exceptional performance and economical prices. The best reported PSCs fabricated by employing mesoporous TiO₂ layers require elevated temperatures in the range of 400–500 °C which limits its applications to solely glass substrates. In such a scenario developing flexible PSCs technology can be considered a suitable and exciting arena from the application point of view, them being flexible, lightweight, portable, and easy to integrate over both small, large and curved surfaces.     

Highly Reproducible Flexible Ion-selective Electrodes for the Detection of Sodium and Potassium in Artificial Sweat

It is well known that potentiometric sensors provide a versatile, cost-effective, and efficient platform for wearable applications. Unfortunately, mass production and commercialization of such devices is often constrained by the requirement of a calibration step, which is due to the poor sensor-to-sensor reproducibility and the need of conditioning the electrodes in the analyte before use. Herein, we fabricated calibration-free flexible sensors including ion-selective electrode and reference electrode by integrating single-walled carbon nanotubes (SWCNTs) with poly(3-octylthiophene) (POT) and applying on polyethylene terephthalate (PET) substrate. The developed sodium and potassium ion-selective electrodes (ISEs) display excellent repeatability, selectivity, stability as well as high sensor-to-sensor reproducibility, with a standard deviation of as low as 1.0 mV in artificial sweat microliter samples volume.     

Dynamically Resettable Electrode-Electrolyte Interface through Supramolecular Sol-Gel Transition Electrolyte for Flexible Zinc Batteries

Flexible batteries based on gel electrolytes with high safety are promising power solutions for wearable electronics but suffer from vulnerable electrode-electrolyte interfaces especially upon complex deformations, leading to irreversible capacity loss or even battery collapse. Here, a supramolecular sol-gel transition electrolyte (SGTE) that can dynamically accommodate deformations and repair electrode-electrolyte interfaces through its controllable rewetting at low temperatures is designed. Mediated by the micellization of polypropylene oxide blocks in Pluronic and host-guest interactions between α-cyclodextrin (α-CD) and polyethylene oxide blocks, the high ionic conductivity and compatibility with various salts of SGTE afford resettable electrode-electrolyte interfaces and thus constructions of a series of highly durable, flexible aqueous zinc batteries. The design of this novel gel electrolyte provides new insights for the development of flexible batteries.     

High Performance Dynamic X-ray Flexible Imaging Realized Using a Copper Iodide Cluster-Based MOF Microcrystal Scintillator

X-ray imaging technology has achieved important applications in many fields and has attracted extensive attentions. Dynamic X-ray flexible imaging for the real-time observation of the internal structure of complex materials is the most challenging type of X-ray imaging technology, which requires high-performance X-ray scintillators with high X-ray excited luminescence (XEL) efficiency as well as excellent processibility and stability. Here, a macrocyclic bridging ligand with aggregation-induced emission (AIE) feature was introduced for constructing a copper iodide cluster-based metal–organic framework (MOF) scintillator. This strategy endows the scintillator with high XEL efficiency and excellent chemical stability. Moreover, a regular rod-like microcrystal was prepared through the addition of polyvinyl pyrrolidone during the in situ synthesis process, which further enhanced the XEL and processibility of the scintillator. The microcrystal was used for the preparation of a scintillator screen with excellent flexibility and stability, which can be used for high-performance X-ray imaging in extremely humid environments. Furthermore, dynamic X-ray flexible imaging was realized for the first time. The internal structure of flexible objects was observed in real time with an ultrahigh resolution of 20 LP mm⁻¹.     

A Polarized Gel Electrolyte for Wide-Temperature Flexible Zinc-Air Batteries

The development of flexible zinc-air batteries (FZABs) has attracted broad attention in the field of wearable electronic devices. Gel electrolyte is one of the most important components in FZABs, which is urgent to be optimized to match with Zn anode and adapt to severe climates. In this work, a polarized gel electrolyte of polyacrylamide-sodium citric (PAM-SC) is designed for FZABs, in which the SC molecules contain large amount of polarized −COO⁻ functional groups. The polarized −COO⁻ groups can form an electrical field between gel electrolyte and Zn anode to suppress Zn dendrite growth. Besides, the −COO⁻ groups in PAM-SC can fix H₂O molecules, which prevents water from freezing and evaporating. The polarized PAM-SC hydrogel delivers a high ionic conductivity of 324.68 mS cm⁻¹ and water retention of 96.85 % after being exposed for 96 h. FZABs with the PAM-SC gel electrolyte exhibit long cycling life of 700 cycles at −40 °C, showing the application prospect under extreme conditions.     

High-performance Flexible Symmetric Supercapacitor Based on Heterostructured PANI@MoS2 Nanocomposite Electrode

Three-dimensional (3D) heterostructured molybdenum disulfide (MoS₂) is used as base materials for aniline monomer in situ polymerization on its surface. It is found that the aniline addition has a remarkable effect on the energy storage of the final compounds due to the improvement of the conductivity and structure stability combined with the synergistic effect between the two types of species. The optimal compound of PANI@MoS₂-150 not only shows a high capacitance value of 801.4 F ⋅ g⁻¹ at a current density of 0.5 A ⋅ g⁻¹ but also provides a high retention rate of 77.4 % after 10,000 cycles. The capacitance fading may be due to the increase of the internal resistance analyzed by EIS. Furthermore, a flexible symmetric supercapacitor based on PANI@MoS₂-150 has also been fabricated and the specific capacitance reaches 105 F ⋅ g⁻¹ at a current density of 1 A ⋅ g⁻¹. Impressively, the capacitance retention is larger than 100 % undergoing 10,000 cycles. Besides, the highest energy density of 21 Wh ⋅ kg⁻¹ was obtained. Additionally, the fabricated symmetric supercapacitor demonstrates excellent flexibility.     

Surface-assembled highly flexible Na_3(VOPO_4)_2F nanocube cathode for high-rate binder-free Na-ion batteries

Flexible Na-ion storage cathodes are still very few due to the challenge in achieving both reliable mechanical flexibility and excellent electrochemical performances.Herein,a new type of flexible Na_3(VOPO_4)_2F cathode with nanocubes tightly assembled on carbon cloth is fabricated by a facile solvothe rmal method for the first time.The cathode is able to exhibit superior rate capability and stable cycling performa nce up to 1000 cycles,due to the surface-assembling of crystalline nanocubes on carbon fibers.In addition,it shows good mechanical flexibility,nearly no capacity decay is observed after continuous bending of 500 times.With this novel cathode and a directly-grown Na_2Ti_2O_5 anode,a fully binde r-free Na-ion battery is assembled.It can deliver a high wo rking voltage and increased gravimetric energy/power densities(maximum values:220.2 Wh/kg;5674,7 W/kg),and can power a LED indicator at bending angles fro m 0° to 180°.     

Conformationally Selective Synthesis of Mononitrocalix[4]arene in Cone or Partial Cone

Nitro‐substituted calixarenes in a cone and a partial cone conformation were prepared selectively using distinct synthetic routes. The selective nitration of tris‐ or penta‐substituted phenols of calix[4]arene or calix[6]arene provided mononitrocalix[n ]arenes (n  =  4, 6). Subsequent addition of ethylene glycol (EG) moieties to mononitrocalix[4]arene provided tetraEGylcalix[4]arene in locked partial cone conformation. By an alternative route – initial addition of EG moieties to the non‐derivatized calix[4]arene followed by the uncontrolled nitration – provided mononitro‐ and dinitro‐tetraEGylcalix[4]arenes locked in the cone conformation. These nitrocalix[4]arenes with locked cone or partial cone conformation are useful building blocks for further assembly of supramolecular systems, especially in the area of material sciences.     

柔性电子学中的表界面化学

柔性电子作为新兴的研究热点, 涉及材料、 化学、 物理等多个基础学科的交叉, 以及在生物医用、 可穿戴设备及人工智能等多个领域的应用. 柔性电子设备的制造加工过程中会用到弹性基底、 导电层、 功能层等多种性质各异的材料, 其互相之间的整合受到它们表面性质和界面结合力的限制; 器件的功能、 可靠性、 对环境的敏感性等也受到了器件表界面性质的影响; 因此, 对材料和器件表界面的处理在柔性电子学中具有重要作用. 本文对柔性电子学中常用的表界面化学过程分为3大类进行介绍: 表面电化学过程, 基于特定化合物反应产生的电流制备电化学传感器, 利用电流/电压控制表面负载化合物; 表面修饰, 通过表面改性提高材料的加工性能, 共价修饰分子层或其它材料赋予器件特殊功能性质或保护层; 不同材料之间的界面连接, 通过共价连接或化学反应辅助的物理交联实现不同材料的结合, 提高柔性器件的稳定性, 实现柔性设备的整合. 对各应用进行总结和举例后, 讨论了存在的问题, 并对未来的发展方向及前景进行了展望.