http://onlinelibrary.wiley.com/rss/journal/10.1002/(ISSN)1521-4095

Owing to quantum size effect and high redox activity, quantum dots (QDs) play very essential roles toward electrochemical energy storage. However, it is very difficult to obtain different-type and uniformly dispersed high-active QDs in a stable conductive microenvironment, because QDs prepared by traditional methods are mostly dissolved in solution or loaded on the surface of other semiconductors. Herein, dual-type semiconductor QDs (Co9S8 and CdS) are skillfully constructed within the interlayer of ultrathin layered double hydroxides (LDH). In particular, the expandable interlayer provides a very suitable confined space for the growth and uniform dispersion of QDs, where Co9S8 originates from in-situ transformation of cobalt atoms in laminate and CdS is generated from interlayer pre-embedding Cd2+. Meanwhile, XAFS and GGA+U calculations are employed to explore and prove the mechanism of QDs formation and energy storage characteristics as compared to surface loading QDs. Significantly, the hybrid supercapacitors achieve high energy density of 329.2 μWh cm−2, capacitance retention of 99.1% and coulomb efficiency of 96.9% after 22,000 cycles, which is superior to the reported QDs-based supercapacitors. These findings provide unique insights for designing and developing stable, ordered, and highly active QDs.

This article is protected by copyright. All rights reserved

As electric vehicles, portable electronic devices and tools have increasingly high requirements for battery energy density and power density, constantly improving battery performance has become a research focus. Accurate measurement of the structure-activity relationship of active materials is the key to advancing the research of high-performance batteries. However, the conventional performance tests of active materials are based on the electrochemical measurement of porous composite electrodes containing active materials, polymer binders, and conductive carbon additives, which cannot establish an accurate structure-activity relationship with the physical characterization of microregions. In this review, in order to promote the accurate measurement and understanding of the structure-activity relationship of materials, the electrochemical measurement and physical characterization of energy storage materials at single-particle scale are reviewed. The potential problems and possible improvement schemes of the single particle electrochemical measurement and physical characterization are proposed. Their potential applications in single particle electrochemical simulation and machine learning are prospected. This review aims to promote the further application of single particle electrochemical measurement and physical characterization in energy storage materials, hoping to achieve three-dimensional unified evaluation of physical characterization, electrochemical measurement, and theoretical simulation at the single particle scale to provide new inspiration for the development of high-performance batteries.

This article is protected by copyright. All rights reserved

Electronic stethoscope used to detect cardiac sounds that contains essential clinical information is a primary tool for diagnosis of various cardiac disorders. However, the linear electro-mechanical constitutive relation makes conventional piezoelectric sensors rather ineffective to detect low-intensity, low-frequency heart acoustic signal without the assistance of complex filtering and amplification circuits. Herein, we find that triboelectric sensor features superior advantages over piezoelectric one for micro-quantity sensing originated from the fast saturated constitutive characteristic. As a result, the triboelectric sensor shows ultrahigh sensitivity (1215 mV/Pa) than the piezoelectric counterpart (21 mV/Pa) in the sound pressure range of 50 – 80 dB under the same testing condition. By designing a trumpet-shaped auscultatory cavity with a power function cross-section to achieve acoustic energy converging and impedance matching, triboelectric stethoscope delivers 36 dB signal-to-noise ratio for human test (2.3 times of that for piezoelectric one). Further combining with machine learning, five cardiac states can be diagnosed at 97% accuracy. In general, the triboelectric sensor is distinctly unique in basic mechanism, provides a novel design concept for sensing micromechanical quantities, and presents significant potential for application in cardiac sounds sensing and disease diagnosis.

This article is protected by copyright. All rights reserved

The energy storage density of Li-ion batteries could be improved by replacing graphite anodes with high-capacity Si-based materials, though instabilities have limited their implementation. Performance degradation mechanisms that occur in Si-anodes can be divided into cycling stability (capacity retention after repeated battery cycles) and calendar aging (shelf life). While the cycling stability and improvement strategies have been researched intensively, there is little known about the underlying mechanisms that cause calendar aging. In this work multiple electron microscope techniques were used to explore the mechanism that governs the calendar aging from sub-nanometer-to-electrode scale. Plasma focused ion beam tomography were used to create 3D reconstructions of calendar aged electrodes and revealed the growth of a LiF-rich layer at the interface between the copper current collector and silicon material, which can lead to delamination and increased interfacial impendence. The LiF layer appeared to derive from the fluoro-ethylene-carbonate electrolyte additive, which is commonly used to improve cycling stability in Si-based systems. The results reveal that additives necessary to improve cycling stability can cause performance degradation over the long-term during calendar aging. The results show that high performing, stable system require careful design to simultaneously mitigate both cycling and calendar aging instabilities.

This article is protected by copyright. All rights reserved

The discovery of superconducting states in diverse topological materials generated a burgeoning interest to explore a topological superconductor and to realize a fault-tolerant topological quantum computation. A variety of routes to realize topological superconductors have been proposed and many types of topological materials have been developed. However, a pristine topological material with a natural superconducting state is relatively rare as compared to topological materials with artificially induced superconductivity. Here, we report that the planar honeycomb structured three-dimensional (3D) topological Dirac semimetal (TDS) SrCuBi, which is the Zintl phase, shows a natural surface superconductivity at 2.1 K under ambient pressure. It is clearly identified from theoretical calculations that a topologically non-trivial state exists on the (100) surface. Further, its superconducting transition temperature (T c) increases by applying pressure, exhibiting a maximal T c of 4.8 K under 6.2 GPa. We believe that this discovery opens up a new possibility of exploring exotic Majorana fermions at the surface of 3D TDS superconductors.

This article is protected by copyright. All rights reserved

Nerve guidance conduits (NGCs) have been considered as promising treatment strategy and frontier trend for peripheral nerve regeneration; while their therapeutic outcomes are limited by the lack of controllable drug delivery and available physicochemical cues. Herein, we propose novel aligned piezoelectric nanofibers derived hydrogel NGCs with ultrasound (US)-triggered electrical stimulation (ES) and controllable drug release for repairing peripheral nerve injury. The inner layer of the NGCs was the barium titanate piezoelectric nanoparticles (BTNPs)-doped polyvinylidene fluoride-trifluoroethylene [BTNPs/P(VDF-TrFE)] electrospinning nanofibers with improved piezoelectricity and aligned orientation. The outer side of the NGCs was the thermoresponsive poly(N-isopropylacrylamide) (pNIPAM) hybrid hydrogel with bioactive drug encapsulation. Such NGCs could not only induce neuronal oriented extension and promote neurite outgrowth with US-triggered wireless ES, but also realize the controllable nerve growth factor (NGF) release with the hydrogel shrinkage under US-triggered heating. Thus, the NGC could positively accelerate the functional recovery and nerve axonal regeneration of rat models with long sciatic nerve defects. We believe that the proposed US-responsive aligned piezoelectric nanofibers derived hydrogel NGCs will find important applications in clinic neural tissue engineering.

This article is protected by copyright. All rights reserved

Constructing an anti-counterfeiting material with non-interference dual optical modes is an effective way to improve information security. However, it remains challenging to achieve multistage secure information encryption due to the limited stimulus responsiveness and color tunability of the current dual-mode materials. Herein, a dual-mode hydrogel with both independently tunable structural and fluorescent colors towards multistage information encryption is reported. In this hydrogel system, the rigid lamellar structure of poly(dodecylglyceryl itaconate) (pDGI) formed by shear flow-induced self-assembly provides the restricted domains wherein monomers undergo polymerization to form a hydrogel network, producing structural color. The introduction of fluorescent monomer 6-acrylamidopicolinate (6APA) as a complexation site provides the possibility of fluorescent color formation. The hydrogel's angle-dependent structural color can be controlled by adjusting the crosslinking density and water content. Additionally, the fluorescence color can be modulated by adjusting the ratio of lanthanide ions. Information of dual-mode can be displayed separately in different channels and synergistically overlayed to read the ultimate message. Thus, a multistage information encryption system based on this hydrogel is devised through the programmed decryption process. This strategy holds tremendous potential as a platform for encrypting and safeguarding valuable and authentic information in the field of anti-counterfeiting.

This article is protected by copyright. All rights reserved

Two-dimensional (2D) polarization materials have emerged as promising candidates for meeting the demands of device miniaturization, attributed to their unique electronic configurations and transport characteristics. Although the existing inherent and sliding mechanisms have been increasingly investigated in recent years, strategies for inducing 2D polarization with innovative mechanisms remain rare. In this study, we introduce a novel 2D Janus state by modulating the puckered structure. Combining scanning probe microscopy, transmission electron microscopy, and density functional theory calculations, we realized force-triggered out-of-plane and in-plane dipoles with distorted smaller warping in GeSe. The Janus state is preserved after removing the external mechanical perturbation, which could be switched by modulating the sliding direction. Our work offers a versatile method to break the space inversion symmetry in a 2D system to trigger polarization in the atomic scale, which may open an innovative insight into configuring novel 2D polarization materials.

This article is protected by copyright. All rights reserved

Two-dimensional (2D) Janus Transition Metal Dichalcogenides (TMDs) have attracted much interest due to their exciting quantum properties arising from their unique two-faced structure, broken-mirror symmetry, and consequent colossal polarisation field within the monolayer. While efforts have been made to achieve high-quality Janus monolayers, the existing methods rely on highly energetic processes that introduce unwanted grain-boundary and point defects with still unexplored effects on the material's structural and excitonic properties Through High-resolution scanning transmission electron microscopy (HRSTEM), density functional theory (DFT), and optical spectroscopy measurements; this work introduces the most encountered and energetically stable point defects. It establishes their impact on the material's optical properties. HRSTEM studies show that the most energetically stable point defects are single (VS  and VSe ) and double chalcogen vacancy (VS −VSe ), interstitial defects (Mi), and metal impurities (MW) and establish their structural characteristics. DFT further establishes their formation energies and related localized bands within the forbidden band. Cryogenic excitonic studies on h-BN-encapsulated Janus monolayers offer a clear correlation between these structural defects and observed emission features, which closely align with the results of the theory. The overall results introduce the defect genome of Janus TMDs as an essential guideline for assessing their structural quality and device properties.

This article is protected by copyright. All rights reserved

Sn-based perovskite solar cells normally show low open circuit voltage due to serious carrier recombination in the devices, which can be attributed to the oxidation and the resultant high p-type doping of the perovskite active layers. Considering the grand challenge to completely prohibit the oxidation of Sn-based perovskites, a feasible way to improve the device performance is to counter-dope the oxidized Sn-based perovskites by replacing Sn2+ with trivalent cations in the crystal lattice, which however has been rarely reported. Here, we present the introduction of Sb3+, which can effectively counter-dope the oxidized perovskite layer and improve the carrier lifetime. Meanwhile, Sb3+ can passivate deep-level defects and improve carrier mobility of the perovskite layer, which are all favourable for the photovoltaic performance of the devices. Consequently, the target devices yield a relative enhancement of the power conversion efficiency (PCE) of 31.4% as well as excellent shelf-storage stability. This work provides a novel strategy to improve the performance of Sn-based perovskite solar cells, which can be developed as a universal way to compensate for the oxidation of Sn-based perovskites in optoelectronic devices.

This article is protected by copyright. All rights reserved

Atom-site catalysts, especially for graphitic carbon nitride-based catalysts, represents one of the most promising candidates in catalysis membrane for water decontamination. However, unravelling the intricate relationships between synthesis-structure-properties remains a great challenge. This study addressed the impacts of coordination environment and structure units of metal central sites based on Mantel test, correlation analysis and evolution of metal central sites. An optimized unconventional oxygen doping cooperated with Co-N-Fe dual-sites (OCN Co/Fe) exhibited synergistic mechanism for efficient peroxymonosulfate activation, which benefited from a significant increase in charge density at the active sites and the regulation in the natural population of orbitals, leading to selective generation of SO4 •−. Building upon these findings, the OCN-Co/Fe/PVDF composite membrane demonstrated a 33 min−1 ciprofloxacin (CIP) rejection efficiency and maintained over 96% CIP removal efficiency (over 24 h) with an average permeance of 130.95 L m−2 h−1. Our work offers a fundamental guide for elucidating the definitive origin of catalytic performance in advance oxidation process (AOPs) to facilitate the rational design of separation catalysis membrane with improved performance and enhanced stability.

This article is protected by copyright. All rights reserved

Binary antimony selenide (Sb2Se3) is a promising inorganic light-harvesting material with high stability, non-toxicity and wide light harvesting capability. In this photovoltaic material, it has been recognized that deep energy level defects with large carrier capture cross section, such as VSe (selenium vacancy), lead to serious open-circuit voltage (V OC) deficit and in turn limit the achievable power conversion efficiency (PCE) of Sb2Se3 solar cells. Understanding the nature of deep-level defects and establishing effective method to eliminate the defects are vital to improving V OC. In this study, we propose a novel directed defect passivation strategy to suppress the formation of VSe and maintaining the composition and morphology of Sb2Se3 film. In particularly, through systematic study on the evolution of defect properties, we reveal the pathway of defect passivation reaction. Owing to the inhibition of defect-assisted recombination, the V OC increases, resulting in an improvement of PCE from 7.69% to 8.90%, where is the highest efficiency of Sb2Se3 solar cells prepared by thermal evaporation method with superstrate device configuration. This study proposes a new understanding of the nature of deep-level defects and enlightens the fabrication of high quality Sb2Se3 thin film for solar cell applications.

This article is protected by copyright. All rights reserved

Seawater electrolysis is a potentially cost-effective approach to green hydrogen production, but it currently faces substantial challenges for its high energy consumption and the interference of chlorine evolution reaction (ClER). Replacing the energy-demanding oxygen evolution reaction (OER) with the methanol oxidation reaction (MOR) represents a promising alternative, as the MOR occurs at a significantly low anodic potential, which cannot only reduces the voltage needed for electrolysis but also completely circumvents the ClER. To this end, developing high-performance MOR catalysts is a key. Herein, we report a novel quaternary Pt1.8Pd0.2CuGa/C intermetallic nanoparticles (i-NPs) catalyst, which shows a high mass activity (11.13 A mgPGM −1), a large specific activity (18.13 mA cmPGM −2), and outstanding stability toward alkaline MOR. Advanced in-situ surface-enhanced Raman spectroscopy (SERS), online differential mass spectrometry (DEMS) and density functional theory (DFT) calculations reveal that the introduction of atomically distributed Pd in Pt2CuGa intermetallic markedly promotes the oxidation of key reaction intermediates by enriching electron concentration around Pt sites, resulting in weak adsorption of carbon-containing intermediates and favorable adsorption of the synergistic OH− groups near Pd sites. Using Pt1.8Pd0.2CuGa/C i-NPs as anodic catalysts, we demonstrate MOR-assisted seawater electrolysis that continuously operates under 1.23 V for 240 h in simulated seawater and 120 h in natural seawater without notable degradation, showing great potential for energy-saving and cost-competitive hydrogen production from seawater.

This article is protected by copyright. All rights reserved

Photocatalytic synthesis of hydrogen peroxide (H2O2) from O2 and H2O under near-infrared light is a sustainable renewable energy production strategy, but challenging reaction. The bottleneck of this reaction lies in the regulation of O2 reduction path by photocatalyst. Herein, we construct the center of the one-step two-electron reduction (OSR) pathway of O2 for H2O2 evolution via the formation of the hydroxyl-bonded Co single-atom sites on boroncarbonitride surface (BCN-OH2/Co1). Our experimental and theoretical prediction results confirm that the hydroxyl group on the surface and the electronic band structure of BCN-OH2/Co1 are the key factor in regulating the O2 reduction pathway. In addition, the hydroxyl-bonded Co single-atom sites can further enrich O2 molecules with more electrons, which can avoid the one-electron reduction of O2 to •O2 −, thus promoting the direct two-electron activation hydrogenation of O2. Consequently, BCN-OH2/Co1 exhibited a high H2O2 evolution apparent quantum efficiency of 0.8% at 850 nm, better than most of the previously reported photocatalysts. This study reveals an important reaction pathway for the generation of H2O2, emphasizing that precise control of the active site structure of the photocatalyst is essential for achieving efficient conversion of solar-to-chemical.

This article is protected by copyright. All rights reserved

Flexible supercapacitors are potential to power next-generation flexible electronics. However, the mechanical and electrochemical stability of flexible supercapacitors under different flexible conditions is limited by the weak bonding between adjacent layers, posing a significant hindrance to their practical applicability. Herein, based on the uninterrupted 3D network during the growth of bacterial cellulose (BC), w e have cultivated a flexible all-in-one supercapacitor through a continuous biosynthesis process. This strategy ensures the continuity of the 3D network of BC throughout the material, thereby forming a continuous electrode-separator-electrode structure. Benefitting from this bioinspired structure, the all-in-one supercapacitor not only achieves a high areal capacitance (3.79 F cm−2) of electrodes but also demonstrates the integration of high tensile strength (2.15 MPa), high shear strength (more than 54.6 kPa), and high bending resistance, indicating a novel pathway towards high-performance flexible power sources.

This article is protected by copyright. All rights reserved

Single-crystal metal foils with high-index facets are currently being investigated owing to their potential application in the epitaxial growth of high-quality van der Waals (vdW) film materials, electrochemical catalysis, gas sensing and other fields. However, the controllable synthesis of large single-crystal metal foils with high-index facets remains a great challenge because high-index facets with high surface energy are not preferentially formed thermodynamically and kinetically. Herein, single-crystal nickel foils with a series of high-index facets are efficiently prepared by applying prestrain energy engineering technique, with the largest single-crystal foil exceeding 5×8 cm2 in size. In terms of thermodynamics, the internal mechanism of prestrain regulation on the formation of high-index facets is proposed. Molecular dynamics simulation is utilized to replicate and explain the phenomenon of multiple crystallographic orientations resulting from prestrain regulation. Additionally, large-sized and high-quality graphite films are successfully fabricated on single-crystal Ni(012) foils. Compared to the polycrystalline nickel, the graphite/single-crystal Ni(012) foil composites show more than five-fold increase in thermal conductivity, thereby showing great potential applications in thermal management. This study hence presents a novel approach for the preparation of single-crystal nickel foils with high-index facets, which is beneficial for the epitaxial growth of certain two-dimensional materials.

This article is protected by copyright. All rights reserved

Considerable attention has been drawn to the use of volatile two-terminal devices relying on the Mott transition for the stochastic generation of probabilistic bits (p-bits) in emerging probabilistic computing. To improve randomness and endurance of bit streams provided by these devices, delicate control of the transient evolution of switchable domains is required to enhance stochastic p-bit generation. Herein, we demonstrate that the randomness of p-bit streams generated via the consecutive pulse inputs of pump-probe protocols can be increased by the deliberate incorporation of metal nanoparticles (NPs), which influence the transient dynamics of the nanoscale metallic phase in VO2 Mott switches. Among the vertically stacked Pt-NP-containing VO2 threshold switches, those with higher Pt NP density show a considerably wider range of p-bit operation (e.g., up to ∼300% increase in ΔV probe upon going from (Pt NP/VO2)0 to (Pt NP/VO2)11) and can therefore be operated under the conditions of high speed (400 kbit/s), low power consumption (14 nJ/bit), and high stability (>105,200 bits) for p-bit generation. Thus, our study presents a novel strategy that exploits nanoscale phase control to maximize the generation of nondeterministic information sources for energy-efficient probabilistic computing hardware.

This article is protected by copyright. All rights reserved

Based on experimental and computational evidence, phthalocyanine (Pc) compounds in the form of quaternary bound metal-nitrogen (N) atoms are the most effective catalysts for oxygen reduction reaction (ORR). However, the heat treatment process used in their synthesis may compromise the ideal structure, causing the agglomeration of transition metals. To overcome this issue, we developed a novel method for synthesizing iron (Fe) single-atom catalysts with ideal structures supported by thermally exfoliated graphene oxide (GO). This was achieved through a short heat-treatment of only 2.5 min involving FePc and N,N-dimethylformamide in the presence of GO. According to the synthesis mechanism revealed by this study, carbon monoxide acts as a strong linker between the single Fe atoms and graphene. It facilitates the formation of a structure containing oxygen species between FeN4 and graphene, which provides high activity and stability for the ORR. These catalysts possess an enormous number of active sites and exhibit enhanced activity towards the alkaline ORR. They have demonstrated excellent performance when applied to real electrochemical devices, such as zinc-air batteries and anion exchange membrane fuel cells. We expect that the instantaneous heat treatment method developed in our study will aid in the development of high-performing single-atom catalysts.

This article is protected by copyright. All rights reserved

In contrast to biological cell membranes, it is still a major challenge for synthetic membranes to efficiently separate ions and small molecules, due to their similar sizes in the sub-nanometer range. Inspired by biological ion channels with their unique channel wall chemistry that facilitates ion sieving by ion-channel interactions, we report here the first free-standing, ultrathin (10–17 nm) nanomembranes composed entirely of polydopamine (PDA) as ion and molecular sieves. These nanomembranes are obtained via an easily scalable electropolymerization strategy and provide nanochannels with various amine and phenolic hydroxyl groups that offer a favorable chemical environment for ion-channel electrostatic and hydrogen bond interactions. They exhibit remarkable selectivity for monovalent ions over multivalent ions and larger species with K+/Mg2+ of ≈4.2, K+/[Fe(CN)6]3− of ≈10.3, and K+/Rhodamine B of ≈273.0 in a pressure-driven process, as well as cyclic reversible pH-responsive gating properties. Infrared spectra reveal hydrogen bond formation between hydrated multivalent ions and PDA, which prevents the transport of multivalent ions and facilitates high selectivity. We propose chemically rich, free-standing, and pH-responsive PDA nanomembranes with specific interaction sites as customizable high-performance sieves for a wide range of challenging separation requirements.

This article is protected by copyright. All rights reserved

Intracranial implants for diagnosis and treatment of brain diseases have been developed over the past few decades. However, the platform of conventional implantable devices still relies on invasive probes and bulky sensors in conjunction with large-area craniotomy and provides only limited biometric information. Here, we report an implantable multi-modal sensor array that can be injected through a small hole in the skull and inherently spread out for conformal contact with the cortical surface. The injectable sensor array, composed of graphene multi-channel electrodes for neural recording and electrical stimulation and MoS2-based sensors for monitoring intracranial temperature and pressure, was designed based on a mesh structure whose elastic restoring force enables the contracted device to spread out. We demonstrated that the sensor array injected into a rabbit's head can detect epileptic discharges on the surface of the cortex and mitigate it by electrical stimulation while monitoring both intracranial temperature and pressure. This method provides good potential for implanting a variety of functional devices via minimally invasive surgery.

This article is protected by copyright. All rights reserved