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A bimetallic oxide Cu2O@MnO2 shows superior dynamic HCHO removal efficiency and pathogen inactivation ability, which is attributed to the electron-rich region at the phase-interface inducing the capture and activation of O2 on the material surface.

When the power conversion efficiency (PCE) of perovskite solar cells (PSCs) rapidly approaches that of commercial solar cells, the stability becomes the most important obstacle for the commercialization of PSCs. Aside from the widely studied slow PCE degradation, the PSCs also show a unique rapid PCE degradation. Although the degradation due to oxygen and humidity can be avoided by encapsulation, that due to bias voltage, light and heat could not be effective suppressed and will lead to considerable degradation. Usually, the rapid PCE degradation is believed to be from ion migration. However, a systematic investigation is yet to be carried out. This work quantitatively and systematically investigated the relationships between external fields (bias voltage, light or heat), ion migration and device performance. By comparing the performance of reference PSCs after 90 min degradation under these fields, we conclude that (1) the electric field affects the spatial distribution of mobile ions; (2) the light field changes the mobile ion densities and drives the ion migration; (3) the heat field results in perovskite decomposition as well as changing the mobile ion densities. In addition to the analysis of the reference device, we experimentally proved that the improved device stability upon introducing phenethylammonium iodide (PEAI) or poly-methyl methacrylate (PMMA) layers originates from the inhibition of mobile ion density and migration.

Hybrid lead halide perovskites have made great strides in next-generation photovoltaic and optoelectronic devices. Random lasers based on perovskite materials have been intensively investigated, but the miniaturization of perovskite random lasers has not been achieved up to now. Here, we report the fabrication of perovskite random lasers based on perovskite films deposited on the optical fiber facets using a dip-coating method. Under optical pumping conditions, random lasing was observed with minimum threshold energy of 32.3 μJ/cm2 at ~550 nm; also, the lasing threshold decreased with increasing diameter of the optical fiber. The results show that the random lasing emission originates from the scattering between the perovskite crystal grains, and the decreased threshold is attributed to the increased active area of the perovskite film. The directionality of perovskite random lasers indicates that the divergence angle of the laser beam is less than 60°. We also demonstrate that the perovskite random laser on the fiber facet can prevent speckle formation and improve image quality. These results may promote the applications of random lasers in compact sources and integrated optoelectronic devices.

The poor stability of perovskite solar cells is a crucial obstacle for its commercial applications. Here, we investigate the thermal stability of the mixed cation organic–inorganic lead halide perovskites (FAPbI3)1−xMAPb(Br3−yCly)x films and devices in air atmosphere. The results show that with the increase of heat treatment from 25 to 250 °C, the MA-perovskite decomposed into PbI2 firstly and the efficiency of corresponding solar cells reduced linearly. For the perovskite film, the increased heat treatment temperature can bring the redshift of the absorption edge leading to the decrease of band gap from 1.569 to 1.508 eV and increase of defect density from 3.87 × 1017 cm−3 to 9.03 × 1017 cm−3. However, a proper heat treatment time (10 min) at certain temperature (85 °C) can passivate defects effectively and improve the efficiency to 16.50%, realizing a 15% relative improvement of average efficiency. This work reveals a detailed thermal decomposition behavior of perovskite material and solar cells, which may provide insights into the stability of perovskite solar cells.

Catalytically active metals atomically dispersed on supports presents the ultimate atom utilization efficiency and cost‐effective pathway for electrocatalyst design. Optimizing the coordination nature of metal atoms represents the advanced strategy for enhancing the catalytic activity and the selectivity of single‐atom catalysts (SACs). Here, we designed a transition‐metal based sulfide‐Ni3S2 with abundant exposed Ni vacancies created by the interaction between chloride ions and the functional groups on the surface of Ni3S2 for the anchoring of atomically dispersed Pt (PtSA‐Ni3S2). The theoretical calculation reveals that unique Pt‐Ni3S2 support interaction increases the d orbital electron occupation at the Fermi level and leads to a shift‐down of the d ‐band center, which energetically enhances H2O adsorption and provides the optimum H binding sites. Introducing Pt into Ni position in Ni3S2 system can efficiently enhance electronic field distribution and construct a metallic‐state feature on the Pt sites by the orbital hybridization between S‐3p and Pt‐5d for improved reaction kinetics. Finally, the fabricated PtSA‐Ni3S2 SAC is supported by Ag nanowires network to construct a seamless conductive three‐dimensional (3D) nanostructure (PtSA‐Ni3S2@Ag NWs), and the developed catalyst shows an extremely great mass activity of 7.6 A mg−1 with 27‐time higher than the commercial Pt/C HER catalyst., A transition‐metal sulfide‐Ni3S2, with abundant exposed Ni vacancies in the outside layers, to anchor and modulate atomically dispersed Pt as the durable catalyst (PtSA‐Ni3S2) for efficiently electrocatalytic hydrogen evolution.

High-activity catalysts in alkaline media are compelling for durable hydrogen evolution reaction (HER). Single-atom catalysts (SACs) provide an effective approach to reduce the amount of precious metals meanwhile maintain their catalytic activity. However, the sluggish activity of SACs for water dissociation in alkaline media has extremely hampered advances in highly efficient hydrogen production. Herein, we developed a platinum SAC immobilized NiO/Ni heterostructure (PtSA-NiO/Ni) as an alkaline HER catalyst. It was found that Pt SACs coupled with NiO/Ni heterostructure enable the tunable binding abilities of hydroxyl ions (OH*) and hydrogen (H*), which efficiently tailors the water dissociation energy for accelerating alkaline HER. In particular, the dual active sites consisting of metallic Ni sites and O vacancies modified NiO sites near the interfaces of NiO/Ni in PtSA-NiO/Ni have preferred adsorption affinity for H* and OH* groups, respectively, which efficiently lowers the energy barrier of water dissociation of Volmer step. Moreover, anchoring Pt single atoms at the interfaces of NiO/Ni heterostructure induces more free electrons on Pt sites due to the elevated occupation of the Pt 5d orbital at the Fermi level and reaches a near-zero H binding energy (ΔGH*, 0.07 eV), which further promotes the H* conversion and H2 evolution. Further enhancement of alkaline HER performance was achieved by constructing PtSA-NiO/Ni nanosheets on the Ag nanowires to form a hierarchical three-dimensional (3D) morphology that provides abundant active sites and accessible channels for charge transfer and mass transport. Consequently, the fabricated PtSA-NiO/Ni catalyst displays extremely high alkaline HER performances with a quite high mass activity of 20.6 A mg-1 for Pt at the overpotential of 100 mV, which is 41 times greater than that of the commercial Pt/C catalyst, significantly outperforming the reported catalysts.

Organic–inorganic perovskite single crystals are promising in the field of optoelectronics due to their excellent optoelectronic properties. However, the ion transport of perovskite precursor is poor in confined spaces, which results in difficulty in the preparation of perovskite single-crystal films. Herein, MAPbBr3 films consisting of square grains were fabricated by the surface-confined process using the organic molecule PEAI (phenethylammonium iodide). Under the effect of oversaturation gradient, PEA+ is combined with the surface of perovskite grain from top to side, which constrains the lateral growth of grains and induces a downward growth of perovskite, leading to the formation of square grains. With the improvement of concentration PEAI, the perovskite film exhibits a decreased side length of grains (from 0.98 to 12.96 μm) and increased grain number and coverage, as well as crystallinity. The perovskite single crystalline grain films with PEAI showed double photoluminescence (PL) emission peaks due to the existence of iodine-rich perovskite. This work may provide a practical way to fabricate high-quality perovskite films for perovskite photoelectronic devices.

We developed a high-efficiency rotating triboelectric nanogenerator (R-TENG)-enhanced multilayered antibacterial polyimide (PI) nanofiber air filters for removing ultrafine particulate matter (PM) from ambient atmosphere. Compared to single-layered PI nanofiber filters, the multilayered nanofiber filter can completely remove all of the particles with diameters larger than 0.54 μm and shows enhanced removal efficiency for smaller PM particles. After connecting with aR-TENG, the removal efficiency of the filer for ultrafine particles is further enhanced. The highest removal efficiency for ultrafine particulate matter is 94.1% at the diameter of 53.3 nm and the average removal efficiency reached 89.9%. Despite an increase in the layer number, the thickness of each individual layer of the film decreased, and hence, the total pressure drop of the filter decreased instead of increasing. Moreover, the nanofiber film exhibited high antibacterial activity because of the addition of a small amount of silver nanoparticles. This technology with zero ozone release and low pressure drop is appropriate for cleaning air, haze treatment, and bacterial control.

A square-grid triboelectric nanogenerator (SG-TENG) is demonstrated for harvesting vibrational energy and sensing impulsive forces. Each square of the three-dimensional (3D)-printed square grid is filled with an aluminum (Al) ball. The grid structure allows the SG-TENG to harvest vibrational energy over a broad bandwidth and operate at different vibrational angles. The most striking feature of the SG-TENG is its ability of being scaled and integrated. After connecting two SG-TENGs in parallel, the open-circuit voltage and short-circuit current are significantly increased over the full vibrational frequency range. Being integrated with a table tennis racket, the SG-TENG can harvest the vibrational energy from hitting a ping pong ball using the racket, where a direct hit by the racket generates an average output voltage of 10.9 ± 0.6 V and an average output current of 0.09 ± 0.02 μA. Moreover, the SG-TENG integrated into a focus mitt can be used in various combat sports, such as boxing and taekwondo, to monitor the frequency and magnitude of the punches or kicks from boxers and other practitioners. The collected data allow athletes to monitor their status and improve their performance skills. This work demonstrates the enormous potential of the SG-TENG in energy harvesting and sensing applications.

The triboelectric nanogenerator (TENG) has emerged as a new and effective mechanical energy harvesting technology. In this work, a theoretical model for a rotary-sliding disk TENG with grating structure was constructed, including the dielectric-to-dielectric and conductor-to-dielectric cases. The finite element method (FEM) was utilized to characterize the fundamental physics of the rotarysliding disk TENG working in both contact and non-contact modes. The basic properties of disk TENG were found to be controlled by the structural parameters such as tribo-surface spacing, grating number, and geometric size. From the FEM calculations, an approximate V–Q–α relationship was built through the interpolation method, and then the TENG dynamic output characteristics with arbitrary load resistance were numerically calculated. Finally, the dependencies of output power and matched resistance on the structural parameters and rotation rate were revealed. The present work provides an in-depth understanding of the working principle of the rotary-sliding disk TENG and serves as important guidance for optimizing TENG output performance in specific applications.

Nowadays, indoor air pollution of low-concentration formaldehyde (HCHO) is threatening seriously human health. In this work, a carbon cloth supported MnOx composite (MnOx-CC) with coaxial cable structure was synthesized as catalysts by electric-enhanced hydrothermal synthesis. The MnOx-CC catalysts showed a flower-liked MnOx nanospheres structure with interconnected nanosheets. During the static testing, the HCHO concentration can be reduced from 7 ppm to 0.074 ppm at 25 ℃, which is below the international guideline values (0.08 ppm). Under the WHSV of ~120,000 mL/(gMnOxh), the removal efficiency was as high as ~97% and the catalyst can keep working for 24 h without an significant drop at room temperature. A novel mechanism – synergistic catalytic effect mechanism of MnOx was proposed to illuminate the catalyst performance. It reveals that the mutual conversion process among different valences of MnO2, Mn2O3 and MnO is critical to the generation of active oxygen and decomposition of intermediates, and they jointly promote the effective degradation of HCHO. This work may provide a new strategy to synthesizing the catalysts for HCHO removal with high efficiency and present an insight for catalytic process of MnOx.

Coordination polymers constructed from metal ions and organic ligands have attracted considerable attention owing to their diverse structural topologies and potential applications. Ligands containing carboxylate groups are among the most extensively studied because of their versatile coordination modes. Reactions of benzene-1,4-dicarboxylic acid (H2BDC) and pyridine (py) with ZnIIor CoIIyielded two new coordination polymers, namely, poly[(μ4-benzene-1,4-dicarboxylato-κ4O:O′:O′′:O′′′)(pyridine-κN)zinc(II)], [Zn(C8H4O2)(C5H5N)]n, (I), andcatena-poly[aqua(μ3-benzene-1,4-dicarboxylato-κ3O:O′:O′′)bis(pyridine-κN)cobalt(II)], [Co(C8H4O2)(C5H5N)2(H2O)]n, (II). In compound (I), the ZnIIcation is five-coordinated by four carboxylate O atoms from four BDC2−ligands and one pyridine N atom in a distorted square-pyramidal coordination geometry. Four carboxylate groups bridge two ZnIIions to form centrosymmetric paddle-wheel-like Zn2(μ2-COO)4units, which are linked by the benzene rings of the BDC2−ligands to generate a two-dimensional layered structure. The two-dimensional layer is extended into a three-dimensional supramolecular structure with the help of π–π stacking interactions between the aromatic rings. Compound (II) has a one-dimensional double-chain structure based on Co2(μ2-COO)2units. The CoIIcations are bridged by BDC2−ligands and are octahedrally coordinated by three carboxylate O atoms from three BDC2−ligands, one water O atom and two pyridine N atoms. Interchain O—H...O hydrogen-bonding interactions link these chains to form a three-dimensional supramolecular architecture.

In recent years, triboelectric nanogenerators have attracted much attention because of their unique potential in self-powered nanosensors and nanosystems. In this paper, we report a cylindrical spiral triboelectric nanogenerator (S-TENG), which not only can produce high electric output to power display devices, but also can be used as a self-powered displacement sensor integrated on a measurement ruler. At a sliding speed of 2.5 m/s, S-TENG can generate a short-circuit current (I SC) of 30 µA and an open-circuit voltage (V OC) of 40 V. As the power source, we fabricate a transparent and flexible hand-driven S-TENG. Furthermore, we demonstrate a self-powered S-TENG-based measuring tapeline that can accurately measure and display the pulled-out distance without the need for an extra battery. The results obtained indicate that TENG-based devices have good potential for application in self-powered measurement systems.

A novel self-powered acceleration sensor based on triboelectric nanogenerator is proposed, which consists of an outer transparent shell and an inner mass-spring-damper mechanical system. The PTFE films on the mass surfaces can slide between two aluminum electrodes on an inner wall owing to the acceleration in the axis direction. On the basis of the coupling of triboelectric and electrostatic effects, the potential difference between the two aluminum electrodes is generated in proportion to the mass displacement, which can be used to characterize the acceleration in the axis direction with a detection range from about 13.0 to 40.0 m/s(2) at a sensitivity of 0.289 V·s(2)/m. With the integration of acceleration sensors in three axes, a self-powered 3D acceleration sensor is developed for vector acceleration measurement in any direction. The self-powered 3D acceleration sensor has excellent performance in the stability test, and the output voltages have a little decrease of ∼6% after 4000 cycles. Moreover, the self-powered acceleration sensor can be used to measure high collision acceleration, which has potential practicability in automobile security systems.

UV is a high-energy electromagnetic radiation that has been widely used in industrial production and the scientific research domain. In this work, a deep UV light emission was obtained using triboelectrification induced plasma discharge without any extra power supply. By a mechanical friction between polymer and quartz glass, the triboelectric charges cause a changing electric field, which may bring plasma discharge of low pressure gas (Ar-Hg) and give out 253.7 nm irradiation. The UV light caused by continuous friction can excite a trichromatic phosphor and afford a bright white light emission. A UV sterilization experiment shows that ∼98% of Escherichia coli can be killed in 30 min by UV irradiation, which reveals that a self-powered sterilization apparatus with good sterilization effect was fabricated. This work provides a novel design to fabricate a self-powered UV light emitting device using low-frequency mechanical friction and realizes the coupling of triboelectrification and plasma luminescence, which may further expand the application of UV light in special circumstances.

Harvesting mechanical energy from our surroundings to acquire a steady and high power output has attracted intensive interest due to the fast development of portable electronics. In this work, the disk-structured triboelectric nanogenerator (TENG) was prepared based on the mature printed circuit board (PCB) technology and the composite structure for effectively improving the utilization in space. A narrow grating of 1° was designed to produce high output. Operated at a rotation rate of 1,000 rpm, the TENG produces a high output power density of 267 mW/cm2 (total power output of 25.7 W) at a matched load of 0.93 MΩ. After introducing a transformer, the output power can be managed so that it can be directly used to charge a battery for a smart phone. With the PCB production technology, fabrication of high performance TENG at low cost and large-scale becomes feasible.

To date, quite a few wearable electronics have entered the market, which are changing the life pattern of consumers. However, the limited lifetime and energy storage capacity have made rechargeable batteries the bottleneck in wearable technology, especially with the increase of number of wearable devices and their large distribution. To solve this problem, we demonstrate a woven-structured triboelectric nanogenerator (W-TENG) using commodity nylon fabric, polyester fabric, and conductive silver fiber fabric. With the advantage of being flexible, washable, breathable, wearable, and able to be triggered by a freestanding triboelectric layer, this W-TENG can move freely without any constraint and is suitable for wearable electronics. To demonstrate the potential applications of the W-TENG, the W-TENG is integrated into shoes, coats, and trousers to harvest different kinds of mechanical energy from human motion. This work presents a new approach in applying triboelectric nanogenerator to wearable devices.

The triboelectric nanogenerator (TENG), based on the well-known triboelectric effect and electrostatic induction effect, has been proven to be a simple, cost effective approach for self-powered systems to convert ambient mechanical energy into electricity. We report a flexible and transparent paper-based triboelectric nanogenerator (PTENG) consisting of an indium tin oxide (ITO) film and a polyethylene terephthalate (PET) film as the triboelectric surfaces, which not only acts as an energy supply but also as a self-powered active sensor. It can harvest kinetic energy when the sheets of paper come into contact, bend or slide relative to one another by a combination of vertical contact-separation mode and lateral sliding mode. In addition, we also integrate grating-structured PTENGs into a book as a self-powered anti-theft sensor. The mechanical agitation during handling the book pages can be effectively converted into an electrical output to either drive a commercial electronic device or trigger a warning buzzer. Furthermore, different grating-structures on each page produce different numbers of output peaks by sliding relative to one another, which can accurately act as a page mark and record the number of pages turned. This work is a significant step forward in self-powered paper-based devices.

Reactions of cadmium(II) salts with 3-amino-5-methylthio-1H-1,2,4-triazole (Hamstz) afforded two cadmium(II) coordination polymers, [Cd2(amstz)2Cl2]n (1) and [Cd2(amstz)2(NO3)2]n (2). Compounds 1 and 2 feature 2-D layered structures based on the dinuclear [Cd2(amstz)2] subunits. The cadmium coordination polyhedra are tetrahedral and tetragonal pyramidal in 1 and 2, respectively, due to the presence of different coordinated anions, Cl− and NO3−. Compounds 1 and 2 exhibit photoluminescence emission with maxima at 620 and 621 nm upon excitation at 470 and 472 nm, respectively, which can be attributed to the ligand-to-metal charge transfer emssion.

Triboelectric nanogenerators (TENGs) have emerged as a highly effective and easily scalable technology for harvesting mechanical energy. Recently, standards and figure-of-merits have been defined to quantify the performance of TENGs. In this work, the figure-of-merits of rolling-friction-based TENGs are investigated through a theoretical model based on the rolling freestanding mode, including the conductor-to-dielectric and dielectric-to-dielectric cases. By combining finite-element simulations and semi-analytical derivations, the basic properties and resistive load output characteristics of rolling TENGs are calculated for various structural parameters, such as the electrode gap or rod diameter. The average output power is optimized by maximizing the structural figure-of-merit, which depends on the structural parameters. The results gained in this work could provide useful guidance for optimizing the performance of rolling-friction-based TENGs toward practical self-powered systems.

A GaN/Si nanoheterostructure array was prepared by growing GaN nanostructures on silicon nanoporous pillar array (Si-NPA). Based on as-grown and annealed GaN/Si-NPA, two light-emitting diodes (LEDs) were fabricated. It was found that after the annealing treatment, both the turn-on voltage and the leakage current density of the nanoheterostructure varied greatly, together with the electroluminescence (EL) changed from a yellow band to a near infrared band. The EL variation was attributed to the radiative transition being transformed from a defect-related recombination in GaN to an interfacial recombination of GaN/Si-NPA. Ours might have provided an effective approach for fabricating GaN/Si-based LEDs with different emission wavelengths.