Self-Thermal Management in Filtered Selenium-Terminated MXene Films for Flexible Safe Batteries.

Li-ion batteries with superior interior thermal management are crucial to prevent thermal runaway and ensure safe, long-lasting operation at high temperatures or during rapid discharging and charging. Typically, such thermal management is achieved by focusing on the separator and electrolyte. Here, the study introduces a Se-terminated MXene free-standing electrode with exceptional electrical conductivity and low infrared emissivity, synergistically combining high-rate capacity with reduced heat radiation for safe, large, and fast Li+ storage. This is achieved through a one-step organic Lewis acid-assisted gas-phase reaction and vacuum filtration. The Se-terminated Nb2Se2C outperformed conventional disordered O/OH/F-terminated materials, enhancing Li+-storage capacity by ≈1.5 times in the fifth cycle (221 mAh·g-1 at 1 A·g-1) and improving mid-infrared adsorption with low thermal radiation. These benefits result from its superior electrical conductivity, excellent structural stability, and high permittivity in the infrared region. Calculations further reveal that increased permittivity and conductivity along the z-direction can reduce heat radiation from electrodes. This work highlights the potential of surface groups-terminated layered material-based free-standing flexible electrodes with self-thermal management ability for safe, fast energy storage.

Injectable Fluorescent Neural Interfaces for Cell-Specific Stimulating and Imaging.

Building on current explorations in chronic optical neural interfaces, it is essential to address the risk of photothermal damage in traditional optogenetics. By focusing on calcium fluorescence for imaging rather than stimulation, injectable fluorescent neural interfaces significantly minimize photothermal damage and improve the accuracy of neuronal imaging. Key advancements including the use of injectable microelectronics for targeted electrical stimulation and their integration with cell-specific genetically encoded calcium indicators have been discussed. These injectable electronics that allow for post-treatment retrieval offer a minimally invasive solution, enhancing both usability and reliability. Furthermore, the integration of genetically encoded fluorescent calcium indicators with injectable bioelectronics enables precise neuronal recording and imaging of individual neurons. This shift not only minimizes risks such as photothermal conversion but also boosts safety, specificity, and effectiveness of neural imaging. Embracing these advancements represents a significant leap forward in biomedical engineering and neuroscience, paving the way for advanced brain-machine interfaces.

Illuminating the Brain: Advances and Perspectives in Optoelectronics for Neural Activity Monitoring and Modulation.

Optogenetic modulation of brain neural activity that combines optical and electrical modes in a unitary neural system has recently gained robust momentum. Controlling illumination spatial coverage, designing light-activated modulators, and developing wireless light delivery and data transmission are crucial for maximizing the use of optical neuromodulation. To this end, biocompatible electrodes with enhanced optoelectrical performance, device integration for multiplexed addressing, wireless transmission, and multimodal operation in soft systems have been developed. This review provides an outlook for uniformly illuminating large brain areas while spatiotemporally imaging the neural responses upon optoelectrical stimulation with little artifacts. Representative concepts and important breakthroughs, such as head-mounted illumination, multiple implanted optical fibers, and micro-light-delivery devices, are discussed. Examples of techniques that incorporate electrophysiological monitoring and optoelectrical stimulation are presented. Challenges and perspectives are posed for further research efforts toward high-density optoelectrical neural interface modulation, with the potential for nonpharmacological neurological disease treatments and wireless optoelectrical stimulation.

Boosting Cycling Stability of Polymer Sodium Battery by "Rigid-Flexible" Coupled Interfacial Stress Modulation.

The discontinuous interfacial contact of solid-state polymer metal batteries is due to the stress changes in the electrode structure during cycling, resulting in poor ion transport. Herein, a rigid-flexible coupled interface stress modulation strategy is developed to solve the above issues, which is to design a rigid cathode with enhanced solid-solution behavior to guide the uniform distribution of ions and electric field. Meanwhile, the polymer components are optimized to build an organic-inorganic blended flexible interfacial film to relieve the change of interfacial stress and ensure rapid ion transmission. The fabricated battery comprising a Co-modulated P2-type layered cathode (Na0.67Mn2/3Co1/3O2) and a high ion conductive polymer could deliver good cycling stability without distinct capacity fading (72.8 mAh g-1 over 350 cycles at 1 C), outperforming those without Co modulation or interfacial film construction. This work demonstrates a promising rigid-flexible coupled interfacial stress modulation strategy for polymer-metal batteries with excellent cycling stability.

Charge self-regulation in 1T'''-MoS2 structure with rich S vacancies for enhanced hydrogen evolution activity.

Active electronic states in transition metal dichalcogenides are able to prompt hydrogen evolution by improving hydrogen absorption. However, the development of thermodynamically stable hexagonal 2H-MoS2 as hydrogen evolution catalyst is likely to be shadowed by its limited active electronic state. Herein, the charge self-regulation effect mediated by tuning Mo-Mo bonds and S vacancies is revealed in metastable trigonal MoS2 (1T'''-MoS2) structure, which is favarable for the generation of active electronic states to boost the hydrogen evolution reaction activity. The optimal 1T'''-MoS2 sample exhibits a low overpotential of 158 mV at 10 mA cm-2 and a Tafel slope of 74.5 mV dec-1 in acidic conditions, which are far exceeding the 2H-MoS2 counterpart (369 mV and 137 mV dec-1). Theoretical modeling indicates that the boosted performance is attributed to the formation of massive active electronic states induced by the charge self-regulation effect of Mo-Mo bonds in defective 1T'''-MoS2 with rich S vacancies.

Bimetal Modulation Stabilizing a Metallic Heterostructure for Efficient Overall Water Splitting at Large Current Density.

Large current-driven alkaline water splitting for large-scale hydrogen production generally suffers from the sluggish charge transfer kinetics. Commercial noble-metal catalysts are unstable in large-current operation, while most non-noble metal catalysts can only achieve high activity at low current densities <200 mA cm-2 , far lower than industrially-required current densities (>500 mA cm-2 ). Herein, a sulfide-based metallic heterostructure is designed to meet the industrial demand by regulating the electronic structure of phase transition coupling with interfacial defects from Mo and Ni incorporation. The modulation of metallic Mo2 S3 and in situ epitaxial growth of bifunctional Ni-based catalyst to construct metallic heterostructure can facilitate the charge transfer for fast Volmer H and Heyrovsky H2 generation. The Mo2 S3 @NiMo3 S4 electrolyzer requires an ultralow voltage of 1.672 V at a large current density of 1000 mA cm-2 , with ≈100% retention over 100 h, outperforming the commercial RuO2 ||Pt/C, owing to the synergistic effect of the phase and interface electronic modulation. This work sheds light on the design of metallic heterostructure with an optimized interfacial electronic structure and abundant active sites for industrial water splitting.

Pt modulation of NbSe2 for enhanced activity and stability: a new Pt3Nb2Se8 compound for highly-efficient alkaline hydrogen evolution.

Transition metal dichalcogenides (TMDs) have attracted great attention as electrocatalysts for the hydrogen evolution reaction (HER) due to their tunable crystal structures and active sites. However, compared with group VI TMDs (such as MoS2 and WS2), the group V TMDs exhibit poor intrinsic catalytic activity towards the HER because the outermost d orbitals of group V metals have only one electron. Herein, we design a new compound Pt3Nb2Se8 by Pt modulation of NbSe2 with enhanced catalytic activity and structural stability for robust HER in an alkaline medium. The introduction of Pt atoms can not only be used as efficient active sites, but also to transfer electrons to Se to synthetically boost the catalytic activity. The Pt3Nb2Se8 exhibits an overpotential of 44 mV at 10 mA cm-2 and a Tafel slope of 38.4 mV dec-1, superior to those of intrinsic NbSe2 and PtSe2, and even exceeding those of commercial Pt/C. This work aims to provide an approach to design group V-based TMDs with enhanced catalytic activity and stability by electronic regulation, as highly efficient electrocatalysts for the HER.

Tailoring Ultrafast and High-Capacity Sodium Storage via Binding-Energy-Driven Atomic Scissors.

Controllably tailoring alloying anode materials to achieve fast charging and enhanced structural stability is crucial for sodium-ion batteries with high rate and high capacity performance, yet remains a significant challenge owing to the huge volume change and sluggish sodiation kinetics. Here, a chemical tailoring tool is proposed and developed by atomically dispersing high-capacity Ge metal into the rigid and conductive sulfide framework for controllable reconstruction of GeS bonds to synergistically realize high capacity and high rate performance for sodium storage. The integrated GeTiS3 material with stable Ti-S framework and weak GeS bonding delivers high specific capacities of 678 mA h g-1 at 0.3 C over 100 cycles and 209 mA h g-1 at 32 C over 10 000 cycles, outperforming most of the reported alloying type anode materials for sodium storage. Interestingly, in situ Raman, X-ray diffraction (XRD), and ex situ transmission electron microscopy (TEM) characterizations reveal the formation of well-dispersed Nax Ge confined in the rigid Ti-S matrix with suppressed volume change after discharge. The synergistically coupled alloying-conversion and surface-dominated redox reactions with enhanced capacitive contribution and high reaction reversibility by a binding-energy-driven atomic scissors method would break new ground on designing a high-rate and high-capacity sodium-ion batteries.

A π-Conjugated Polyimide-Based High-Performance Aqueous Potassium-Ion Asymmetric Supercapacitor.

Aqueous asymmetric supercapacitor has captured widespread attention as a sustainable high-power energy resource. Organic electrode materials are appealing owing to their sustainability and high redox reactivity, but suffer from structural instability and low power density. Here the π-conjugated polyimide-based organic electrodes with different lengths of alkyl chains are explored to achieve high rate capability and long lifespan in an aqueous K+ -ion electrolyte. The fabricated asymmetric supercapacitor exhibits high capacities of 107 mAh g-1 at 2 A g-1 and 67 mAh g-1 at 90 A g-1 . A specific capacity of 65 mAh g-1 over 70% of the initial performance is obtained after 65 000 cycles. Molecular engineering of long alkyl chains in polyimide can reduce the degree of π-conjugation and spatially block the π-conjugated imide bond with limited redox activity but improved stability against chemical degradation. Further electrochemical quartz crystal microbalance, ex-situ Fourier transformed infrared spectroscopy, and X-ray photoelectron spectroscopy characterizations reveal the pseudocapacitance behavior originating from the π-conjugated polyimide-based redox reaction with potassium ions and hydrated potassium ions. A promising polyimide-based polymer with extended π-conjugated system for high-performance asymmetric supercapacitor is showcased.

Band structure engineering of W replacement in ReSe2 nanosheets for enhancing hydrogen evolution.

Layered transition metal dichalcogenide rhenium selenide (ReSe2) has attracted great attention as an electrocatalyst for the hydrogen evolution reaction (HER) due to its excellent stability and sufficient active sites. However, ReSe2 has intrinsically poor conductivity, which leads to the insufficient utilization of electrocatalytic active sites. Herein, we designed the regulation of the electronic band structure by W replacement in ReSe2 nanosheets to greatly improve the conductivity. The Re0.7W0.3Se2 exhibits an overpotential of 141 mV at 10 mA cm-2 and a Tafel slope of 65.3 mV dec-1, superior to that of the original ReSe2 and WSe2. This work aims to provide a feasible strategy to promote the HER activity of ReSe2.

Solid Base Assisted Dual-Promoted Heterogeneous Conversion of PVC to Metal-Free Porous Carbon Catalyst.

Polyvinyl chloride (PVC) is widely used in daily life, but its waste has become a serious environmental problem. A solid base assisted low-temperature solvothermal dehalogenation was developed in this work to sustainably and efficiently transform PVC into high-value dimethylamine hydrochloride (DMACl) chemical and N,O co-doped carbon monolith with hierarchically porous structure. The synergistic promotion of solid-base catalyst and solvent decomposition with the removal of HCl can shift forward the chemical equilibrium to promote the dechlorination of PVC and increase the carbon yield. Meanwhile, the solid-base catalyst can also act as a pore-forming additive to fabricate the carbon monolith with hierarchical pores. Induced by the high specific surface area, hierarchical pores and N,O co-doped structure, the generated carbon monolith exhibits superior electrocatalytic performance towards H2 evolution. These discoveries shed light on the design of synergistically coupled solvent and solid catalyst to promote the heterogeneous conversion of waste chlorinated plastics into high-value chemicals for a sustainable future.

MA Cation-Induced Diffusional Growth of Low-Bandgap FA-Cs Perovskites Driven by Natural Gradient Annealing.

Low-bandgap formamidinium-cesium (FA-Cs) perovskites of FA1-x Cs x PbI3 (x < 0.1) are promising candidates for efficient and robust perovskite solar cells, but their black-phase crystallization is very sensitive to annealing temperature. Unfortunately, the low heat conductivity of the glass substrate builds up a temperature gradient within from bottom to top and makes the initial annealing temperature of the perovskite film lower than the black-phase crystallization point (~150°C). Herein, we take advantage of such temperature gradient for the diffusional growth of high-quality FA-Cs perovskites by introducing a thermally unstable MA+ cation, which would firstly form α-phase FA-MA-Cs mixed perovskites with low formation energy at the hot bottom of the perovskite films in the early annealing stage. The natural gradient annealing temperature and the thermally unstable MA+ cation then lead to the bottom-to-top diffusional growth of highly orientated α-phase FA-Cs perovskite, which exhibits 10-fold of enhanced crystallinity and reduced trap density (~3.85 × 1015 cm-3). Eventually, such FA-Cs perovskite films were fabricated into stable solar cell devices with champion efficiency up to 23.11%, among the highest efficiency of MA-free perovskite solar cells.

Bioinspired Graphene Oxide Membranes with pH-Responsive Nanochannels for High-Performance Nanofiltration.

Tunable gating graphene oxide (GO) membranes with high water permeance and precise molecular separation remain highly desired in smart nanofiltration devices. Herein, bioinspired by the filtration function of the renal glomerulus, we report a smart and high-performance graphene oxide membrane constructed via introducing positively charged polyethylenimine-grafted GO (GO-PEI) to negatively charged GO nanosheets. It was found that the additional GO-PEI component changed the surface charge, improved the hydrophilicity, and enlarged the nanochannels. The glomerulus-inspired graphene oxide membrane (G-GOM) shows a water permeance up to 88.57 L m-2 h-1 bar-1, corresponding to a 4 times enhancement compared with that of a conventional GO membrane due to the enlarged confined nanochannels. Meanwhile, owing to the electrostatic interaction, it can selectively remove positively charged methylene blue at pH 12 and negatively charged methyl orange at pH 2, with a removal rate of over 96%. The high and cyclic water permeance and highly selective organic removal performance can be attributed to the synergic effect of controlled nanochannel size and tunable electrostatic interaction in responding to the environmental pH. This strategy provides insight into designing pH-responsive gating membranes with tunable selectivity, representing a great advancement in smart nanofiltration with a wide range of applications.

Engineering bandgap of CsPbI3 over 1.7 eV with enhanced stability and transport properties.

Potential multijunction application of CsPbI3 perovskite with silicon solar cells to reach efficiencies beyond the Shockley-Queisser limit motivates tremendous efforts to improve its phase stability and further enlarge its band gap between 1.7 and 1.8 eV. Current strategies to increase band gap via conventional mixed halide engineering are accompanied by detrimental phase segregation under illumination. Here, ethylammonium (EA) in a relatively small fraction (x < 0.15) is first investigated to fit into three-dimensional CsPbI3 framework to form pure-phase hybrid perovskites with enlarged band gap over 1.7 eV. The increase of band gap is closely associated with the distortion of Pb-I octahedra and the variation of the average Pb-I-Pb angle. Meanwhile, the introduction of EA can retard the crystallization of perovskite and tune the perovskite structure with enhanced phase stability and transport properties.

Understanding the Ion-Sorption Dynamics in Functionalized Porous Carbons for Enhanced Capacitive Energy Storage.

Heteroatom-functionalized porous carbon has long been regarded as a promising electrode material to construct high-performance capacitive energy storage devices. However, the development of this field is seriously limited due to the lack of an in-depth understanding of the ion-sorption dynamics. Herein, the component and structure controllable N, O, and Cl codoped bimodal (micro-to-meso) porous carbons were prepared and further used as the investigated object for exploring the intrinsic ion-sorption dynamics, which is the root of the enhanced electrochemical response in capacitive energy storage devices. Voltammetry response analysis is employed to quantify the charge storage contributions from both electrostatic adsorption effect (electrical double-layer capacitance) and highly reversible redox process (pseudocapacitance). The existence of electronic capacitance enables a positive correlation between surface capacitance and the ratio of micropores. Besides, an electron-dependent correlation between the electroactive functional groups and redox reaction induced capacitance is also explored. This work will advance the capacitive energy storage field by presenting a clear understanding of the ion-sorption dynamics in the functionalized porous carbons.

Multistaged discharge constructing heterostructure with enhanced solid-solution behavior for long-life lithium-oxygen batteries.

Inferior charge transport in insulating and bulk discharge products is one of the main factors resulting in poor cycling stability of lithium-oxygen batteries with high overpotential and large capacity decay. Here we report a two-step oxygen reduction approach by pre-depositing a potassium carbonate layer on the cathode surface in a potassium-oxygen battery to direct the growth of defective film-like discharge products in the successive cycling of lithium-oxygen batteries. The formation of defective film with improved charge transport and large contact area with a catalyst plays a critical role in the facile decomposition of discharge products and the sustained stability of the battery. Multistaged discharge constructing lithium peroxide-based heterostructure with band discontinuities and a relatively low lithium diffusion barrier may be responsible for the growth of defective film-like discharge products. This strategy offers a promising route for future development of cathode catalysts that can be used to extend the cycling life of lithium-oxygen batteries.

Isolated Diatomic Ni-Fe Metal-Nitrogen Sites for Synergistic Electroreduction of CO2.

Polynary single-atom structures can combine the advantages of homogeneous and heterogeneous catalysts while providing synergistic functions based on different molecules and their interfaces. However, the fabrication and identification of such an active-site prototype remain elusive. Here we report isolated diatomic Ni-Fe sites anchored on nitrogenated carbon as an efficient electrocatalyst for CO2 reduction. The catalyst exhibits high selectivity with CO Faradaic efficiency above 90 % over a wide potential range from -0.5 to -0.9 V (98 % at -0.7 V), and robust durability, retaining 99 % of its initial selectivity after 30 hours of electrolysis. Density functional theory studies reveal that the neighboring Ni-Fe centers not only function in synergy to decrease the reaction barrier for the formation of COOH* and desorption of CO, but also undergo distinct structural evolution into a CO-adsorbed moiety upon CO2 uptake.

Top-down fabrication of hierarchical nanocubes on nanosheets composite for high-rate lithium storage.

A top-down method was developed to synthesize hierarchical composites consisting of NiCo2O4 nanocubes and graphene nanosheets through the electrostatic interaction of negatively charged graphene oxide nanosheets and positively charged NiCo2O4 spheres. Employed as anode materials for lithium-ion batteries, the hierarchical composites exhibit remarkably high electrochemical performance, including large reversible capacity, superior rate capability, and excellent cycling performance. Large reversible capacities of 1024 and 648 mA h g-1 are maintained at a current density of 500 and 3000 mA g-1, respectively, for over 200 cycles. The excellent electrochemical performance of the composite is attributed to the synergistic effect of the hierarchical structure, the well dispersed NiCo2O4 nanocubes and the uniform graphene coating. This work provides an effective and promising strategy for the rational structural design of the metal oxide electrode material.

Cascade Amplifiers of Intracellular Reactive Oxygen Species Based on Mitochondria-Targeted Core-Shell ZnO-TPP@D/H Nanorods for Breast Cancer Therapy.

Tumor cells are vulnerable to reactive oxygen species (ROS). However, it is still a challenge to induce ROS efficiently in tumor cells. In this study, cascade amplifiers of intracellular ROS based on charge-reversible mitochondria-targeted ZnO-TPP@D/H nanorods (NRs) were first developed for breast cancer therapy. The core-shell ZnO-TPP@D/H NR with a particle size of 179.60 ± 5.67 nm was composed of a core of a ZnO NR, an inner shell of triphenyl phosphonium (TPP), and an outer shell of heparin. Doxorubicin (DOX) was loaded on ZnO-TPP@D/H NRs with high drug loading efficiency of 22.00 ± 0.18%. The zeta potential of ZnO-TPP@D/H NRs varied from 24.00 ± 0.83 to -34.06 ± 0.87 mV after heparin coating, protecting ZnO-TPP@D/H NRs from nonspecific adsorption in circulation. Mitochondrial targeting was achieved after the degradation of heparin. Cellular uptake assays showed that ZnO-TPP@D/H NRs could accumulate in mitochondria. ROS generation assays showed that ZnO-TPP@D/H NRs could triple the intracellular ROS in 4T1 cells (highly metastatic breast cancer cells) than free DOX. Western blot demonstrated that ZnO-TPP@D/H NRs dramatically induced cell apoptosis in 4T1 cells. In vivo experiments suggested the antitumor potential of ZnO-TPP@D/H NRs.

Free-Standing Air Cathodes Based on 3D Hierarchically Porous Carbon Membranes: Kinetic Overpotential of Continuous Macropores in Li-O2 Batteries.

Free-standing macroporous air electrodes with enhanced interfacial contact, rapid mass transport, and tailored deposition space for large amounts of Li2 O2 are essential for improving the rate performance of Li-O2 batteries. An ordered mesoporous carbon membrane with continuous macroporous channels was prepared by inversely topological transformation from ZnO nanorod array. Utilized as a free-standing air cathode for Li-O2 battery, the hierarchically porous carbon membrane shows superior rate performance. However, the increased cross-sectional area of the continuous macropores on the cathode surface leads to a kinetic overpotential with large voltage hysteresis and linear voltage variation against Butler-Volmer behavior. The kinetics were investigated based on the rate-determining step of second electron transfer accompanied by migration of Li+ in solid or quasi-solid intermediates. These discoveries shed light on the design of the air cathode for Li-O2 batteries with high-rate performance.