Alloying is regarded as one of the most promising strategies for boosting performance of catalysts for hydrogen evolution reaction (HER) due to the adjustable electronic structure and intermediate adsorption. However, there is no theory (including d-band center theory) can accurately guide the preparation and design of alloy catalysts, and thus resulting all the reported alloy catalysts are obtained by time-consuming and laborious experimental exploration. Herein, we proposed a mean d-band center (εas) as a new accurate descriptor for alloy activity prediction. Theoretical simulation and experiment results revealed that this descriptor exhibits a strong scaling relation with H adsorption energy. Besides, the obtained Cu–Ag alloy displays an optimal overpotential of 223 mV at 10 mA/cm2 in 0.5 mol/L H2SO4, which is more than 300 mV lower than those of pristine Cu (530 mV) and Ag (569 mV) powder. Our work provides a new idea toward designing highly efficient HER catalysts and broadens the applicability of d-band theory to activity prediction of alloys.
Copper (Cu) has been regarded as a highly efficient electrocatalyst for the conversion of CO2 into a multicarbon product. However, the catalytic mechanism and the active sites of Cu catalysts under operating conditions still remain elusive. Yang's team applied systematic operando characterization techniques to provide a quantitative analysis of the valence states and the chemical environment of Cu nanocatalysts under electrochemical reaction conditions, which clearly reveal the evolution of Cu nanocatalysts before and after the entire electrochemical CO2 reduction.
As one of the major causes of antimicrobial resistance, β-lactamase develops rapidly among bacteria. Detection of β-lactamase in an efficient and low-cost point-of-care testing (POCT) way is urgently needed. However, due to the volatile environmental factors, the quantitative measurement of current POCT is often inaccurate. Herein, we demonstrate an artificial intelligence (AI)-assisted mobile health system that consists of a paper-based β-lactamase fluorogenic probe analytical device and a smartphone-based AI cloud. An ultrafast broad-spectrum fluorogenic probe (B1) that could respond to β-lactamase within 20 s was first synthesized, and the detection limit was determined to be 0.13 nmol/L. Meanwhile, a three-dimensional microfluidic paper-based analytical device was fabricated for integration of B1. Also, a smartphone-based AI cloud was developed to correct errors automatically and output results intelligently. This smart system could calibrate the temperature and pH in the β-lactamase level detection in complex samples and mice infected with various bacteria, which shows the problem-solving ability in interdisciplinary research, and demonstrates potential clinical benefits.
Aqueous zinc-ion batteries (ZIBs) have attracted extensive interest for the next-generation batteries, which, however, are facing great challenges due to the poor reversibility of zinc (Zn) anodes and side reactions of water decomposition. Herein, we demonstrated a strategy that the solvation sheath of Zn ions could be facilely regulated by supramolecular coordination chemistry by adding small amounts of cyclodextrins (CDs) and, hence, inhibited the side reactions and side products, widened the electrochemical window, facilitated the homogenous deposition of Zn ions, refined the Zn grains, and enhanced the stability of Zn anodes. Importantly, we demonstrated that compared with α- and β-CD, the γ-CD showed the best regulation effect of the solvation sheath of Zn ions either at the same molar ratio or at the same mass concentration, which could be ascribed to their difference in supramolecular coordination chemistry and the strongest interaction of γ-CD with Zn ions. As a result, with γ-CD, the Zn//Zn symmetric cells showed ultrahigh stability with a cycling lifespan of over 2400 h at a current density of 1 mA/cm2. These results highlight the regulation of solvation sheath by supramolecular coordination chemistry for highly stable Zn anodes and pave a new way to realize high-performance ZIBs.
Covalent organic framework (COF) materials have aroused tremendous interest in photocatalytic applications due to their tunable pore structure and photoelectric properties. The regular nanopore of COF itself presents a strongly confinement effect, which provides a unique regulatory effect for photons, electrons, protons, and other quantum-scale reaction groups. However, due to the weak surface electron coupling and transfer ability between the reactive groups and basic elements of its structural units, the activity of pure COFs photocatalyst is still not satisfactory. Therefore, the confinement modification strategy of confining low-dimension entities within COFs has been proposed, thus realizing new active sites construction and band structure regulation has been intensively studied, but yet to be summarized systematically. In this paper, the semi-conductivity of COFs is discussed dialectically based on photocatalytic thermodynamics, and the influence of internal linkage motifs and stacking behaviors on the band structure is collected. Then, the basic understanding of confinement characteristics and their influence on photocatalytic performance in dynamics is further explained according to the spatial dimension classification of low-dimension entities. And the application and mechanism of these COF-based confined catalysts in energy conversion reactions are discussed in detail. Lastly, the current challenges and development prospects of COF-based confined hetero-photocatalysts are discussed.
Polyimides externally deployed in spacecraft or satellites extensively have various aerospace hazards, including atomic oxygen (AO) erosion, irradiation degradation, and electrostatic charge/discharge (ESC/ESD). To cope with these challenges, we fabricate a ZnO/CuNi-polyimide composite film with augmented permanence. Using spectroscopy and microscopy techniques, we have shown that the combination of chelation and cross-linking in the interfacial architecture leads to enhanced interfacial compatibility and mechanical robustness. Besides, due to the positive AO diffusion barrier ability of the wurtzite ZnO, our composite film shows remarkable AO resistance and a very small Ey value of 6.88 × 10−26 cm3/atom, which is merely 2.29% of that of pristine polyimide. Moreover, the well-defined nanocrystalline state with minimal lattice swelling (0.3%–0.7%) of the Fe+-irradiated ZnO/CuNi-polyimide at a damaging dose of 353.4 dpa demonstrates its excellent irradiation resistance. Finally, the ZnO/CuNi-polyimide also shows sufficient electrostatic dissipation capacity to cope with the ESC/ESD events. Our fabrication approach for composite films based on multi-technology integration shows potential for aerospace applications and deployment.
Conductive polymer hydrogels have greatly improved the compatibility of electronic devices with biological tissues for human–machine interfacing. Hydrogels that possess low Young's modulus, low interfacial impedance, and high tensile properties facilitate high-quality signal transmission across dynamic biointerfaces. Direct incorporation of elastomers with conductive polymers may result in undesirable mechanical and/or electrical performance. Here, a covalent cross-linking network and an entanglement-driven network with conductive poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) have been combined. The triple-network conductive hydrogel shows high stretchability (with fracture strain up to 900%), low impedance (down to 91.2 Ω·cm2), and reversible adhesion. Importantly, ultra-low modulus (down to 6.3 kPa) and strain-insensitive electrical/electrochemical performance were achieved, which provides a guarantee for low current stimulation. The material design will contribute to the progression of soft and conformal bioelectronic devices, and pave the way to future implantable electronics.
Research and development of novel fluorine-free materials to replace fluorinated aqueous film-forming foam (AFFF) are crucial for improving pool fire suppression performance and protecting the environment. In this study, we report the thermo-responsive fluorine-free foam stabilized by triblock PEO–PPO–PEO copolymers (EO)100(PO)65(EO)100 for pool fire suppression. Small-angle X-ray scattering (SAXS) and reflected light interferometric techniques are conducted to study the molecular self-assembly in bulk and film thinning behavior, and the foaming kinetics of copolymer solution and thermophysical properties of the liquid foam are studied by dynamic surface tension and oscillatory rheology analysis. At room temperature, the amphipathic structure of PEO–PPO–PEO makes it possible to absorb at the air–liquid interface forming large-scale liquid foams containing the mobile films with a detergent state. Upon heating to the surface cooling temperature of burning oil, the mobile films can be actively switched into mechanically strong films with rigid surfaces. The in situ switching of the two interfacial states leads to the significant enhancement of the foam stability, especially under the dual defoaming effects of heat and oil. What's more, it is observed that the confinement of organized copolymer micelles in the Plateau borders and micellar self-layering in film confinement induce drainage delay of foam and film's stepwise thinning phenomenon, further increasing film thickness and enhancing the thermal stability of the foam. In standard fire-fighting tests, it is proved that the burnback performance exhibited by thermo-responsive copolymer foams is three times better than that for classical fluorine-free foams and almost 1.5 times higher than that for commercial AFFF.
Hybrid perovskites have attracted enormous attention in the next generation resistive switching (RS) memristor for the artificial synapses, owing to their ambipolar charge transport, long diffusion length, and tunable visible bandgap. However, the variable switch, limited reproducibility, and poor endurance are the obstacles to the practical application of the perovskite memristors. Herein, we reported a multilevel RS nonvolatile memory based on a 3D trigonal HC(NH2)2PbI3 (α-FAPbI3) perovskite layer modified by 1-cyanobutyl-3-methylimidazolium chloride ([CNBmim]Cl) and sandwiched between ITO and Au electrodes (Au/[CNBmim]Cl/α-FAPbI3/SnO2/ITO). In contrast to the bare memristor with failure switching from low resistance state (LRS) to high resistance state (HRS), the memristor device based on the α-FAPbI3 modified with [CNBmim]Cl (Target device) shows the retention time over 104 s with On/Off ratio (>102) and endurance up to 550 cycles. The stable RS cycle benefits from the accelerated electrons de-trapping from the reduced defects and fast charge separation in the interface of α-FAPbI3/electrode, leading to the rupture of conductive filaments and transition of LRS to HRS. As a two-terminal analog synaptic device, the target device can realize random handwritten digit recognition with an impressive accuracy of 89.3% on the condition of low learning phases (500 training cycles).
The remarkable successes of graphene have sparked increasing interest in elemental two-dimensional (2D) materials, also referred to as Xenes. Due to their chemical simplicity and appealing physiochemical properties, Xenes have shown particular potential for numerous (opto) electronic, iontronic, and energy applications. Among them, layered α-phase tellurene has demonstrated the most promise, thanks to the recent successes in the chemical synthesis of highly crystalline 2D tellurene. However, the general electronic and electrochemical properties of tellurene in electrolyte systems remain ambiguous, hindering their further development. In this work, we studied the electrostatic gating, electrocatalysis, and electrochemical stability of tellurene in electrolyte systems. Our results show that tellurene obtained from both hydrothermal and chemical vapor deposition methods, two mainstream synthetic approaches for Xenes, demonstrates thickness-dependent ambipolar transport with high hole mobility and stability in both aqueous electrolytes and ionic liquids. More importantly, the electrochemical properties of tellurene are investigated via the emerging on-chip electrochemistry. Pristine tellurene demonstrates hydrogen evolution reaction with low Tafel slopes and remarkable electrochemical stability in acidic electrolytes over a large potential window. Our study provides a comprehensive understanding of the iontronic and electrochemical properties of tellurene, paving the way for the broad adoption of Xenes in sensors, synaptic devices, and electrocatalysis.
Harvesting indoor light to power electronic devices for the Internet of Things has become an application scenario for emerging photovoltaics, especially utilizing organic photovoltaics (OPVs). Combined liquid- and solid-state processing, such as printing and lamination used in industry for developing indoor OPVs, also provides a new opportunity to investigate the device structure, which is otherwise hardly possible based on the conventional approach due to solvent orthogonality. This study investigates the impact of fullerene-based acceptor interlayer on the performance of conjugated polymer–fullerene-based laminated OPVs for indoor applications. We observe open-circuit voltage (VOC) loss across the interface despite this arrangement being presumed to be ideal for optimal device performance. Incorporating insulating organic components such as polyethyleneimine (PEI) or polystyrene (PS) into fullerene interlayers decreases the work function of the cathode, leading to better energy level alignment with the active layer (AL) and reducing the VOC loss across the interface. Neutron reflectivity studies further uncover two different mechanisms behind the VOC increase upon the incorporation of these insulating organic components. The self-organized PEI layer could hinder the transfer of holes from the AL to the acceptor interlayer, while the gradient distribution of the PS-incorporated fullerene interlayer eliminates the thermalization losses. This work highlights the importance of structural dynamics near the extraction interfaces in OPVs and provides experimental demonstrations of interface investigation between solution-processed cathodic fullerene layer and bulk heterojunction AL.
Transition metal carbides, including both MXene and non-MXene metal carbides, have enjoyed a soaring reputation in recent years. Benefitting from their intriguing physical and chemical characteristics, they shine in multifarious research fields and currently, they have emerged as promising nanomaterials for photocatalysis in energy and environmental science. Herein, based on the recent theoretical research and experimental studies, a systematic and comprehensive review of the expeditious advances of metal carbides and their nano-architectures in the flourishing arena of photocatalysis is presented. The fundamental mechanism involved in photocatalysis with metal carbides serving as semiconductors or cocatalysts is thoroughly discussed. Besides, we highlight the main synthetic strategies of MXene and non-MXene metal carbides and unravel the structural properties of the as-obtained metal carbides via different fabrication routes to establish and elucidate their intriguing role in ameliorating photocatalytic activity. Moreover, the state-of-the-art advancements of metal carbides in diverse photocatalytic applications, including hydrogen evolution reaction, oxygen evolution reaction, overall water splitting, and carbon dioxide reduction reaction, are summarized. In particular, insights into the structure–activity relationship of metal carbide in photocatalysis are elucidated. Finally, this review concludes with the ongoing challenges and perspectives on the future directions of metal carbides in the realm of photocatalysis.
Conductive-bridge random access memory (CBRAM) emerges as a promising candidate for next-generation memory and storage device. However, CBRAMs are prone to degenerate and fail during electrochemical metallization processes. To address this issue, herein we propose a self-repairability strategy for CBRAMs. Amorphous NbSe2 was designed as the resistive switching layer, with Cu and Au as the top and bottom electrodes, respectively. The NbSe2 CBRAMs demonstrate exceptional cycle-to-cycle and device-to-device uniformity, with forming-free and compliance current-free resistive switching characteristics, low-operation voltage, and competitive endurance and retention performance. Most importantly, the self-repairable behavior is discovered for the first time in CBRAM. The device after failure can recover its performance to the initially normal state by operating with a slightly large reset voltage. The existence of Cu conductive filament and excellent controllability of Cu migration in the NbSe2 switching layer has been revealed by a designed broken-down point approach, which is responsible for the self-repairable behavior of NbSe2 CBRAMs. Our self-repairable and high-uniform amorphous NbSe2 CBRAM may open the door to the development of memory and storage devices in the future.