Regulating Ir-O Covalency to Boost Acidic Oxygen Evolution Reaction.

The unsatisfactory oxygen evolution reaction (OER) activity of IrO2 has intensively raised the cost and energy consumption of hydrogen generation from proton exchange membrane water electrolyzers. Here, the acidic OER activity of the rutile IrO2 is significantly enhanced by the incorporation of trivalent metals (e.g., Gd, Nd, and Pr) to increase the Ir-O covalency, while the high-valence (pentavalent or higher) metal incorporation decreases the Ir-O covalency resulting in worse OER activity. Experimental and theoretical analyses indicate that enhanced Ir-O covalency activates lattice oxygen and triggers lattice oxygen-mediated mechanism to enhance OER kinetics, which is verified by the finding of a linear relationship between the natural logarithm of intrinsic activity and Ir-O covalency described by charge transfer energy. By regulating the Ir-O covalency, the obtained Gd-IrO2-δ merely needs 260 mV of overpotential to reach 10 mA cm-2 and shows impressive stability during a 200-h test in 0.5 м H2SO4. This work provides an effective strategy for significantly enhancing the OER activity of the widely used IrO2 electrocatalysts through the rational regulation of Ir-O covalency.

A Dielectric MXene-Induced Self-Built Electric Field in Polymer Electrolyte Triggering Fast Lithium-Ion Transport and High-Voltage Cycling Stability.

Quasi-solid polymer electrolyte (QPE) lithium (Li)-metal battery holds significant promise in the application of high-energy-density batteries, yet it suffers from low ionic conductivity and poor oxidation stability. Herein, a novel self-built electric field (SBEF) strategy is proposed to enhance Li+ transportation and accelerate the degradation dynamics of carbon-fluorine bond cleavage in LiTFSI by optimizing the termination of MXene. Among them, the SBEF induced by dielectric Nb4C3F2 MXene effectively constructs highly conductive LiF-enriched SEI and CEI stable interfaces, moreover, enhances the electrochemical performance of the QPE. The related Li-ion transfer mechanism and dual-reinforced stable interface are thoroughly investigated using ab initio molecular dynamics, COMSOL, XPS depth profiling, and ToF-SIMS. This comprehensive approach results in a high conductivity of 1.34 mS cm-1, leading to a small polarization of approximately 25 mV for Li//Li symmetric cell after 6000 h. Furthermore, it enables a prolonged cycle life at a high voltage of up to 4.6 V. Overall, this work not only broadens the application of MXene for QPE but also inspires the great potential of the self-built electric field in QPE-based high-voltage batteries.

Stabilization of 2D Imine-Linked Covalent Organic Frameworks: From Linkage Chemistry to Interlayer Interaction.

Imine-linked covalent organic frameworks (imine-COFs) represent the most sought-after class of COFs due to their broad monomer scope and ease of synthesis. Owing to the reversible nature of imine linkages, however, the chemical stability of most imine-COFs is still far from adequate. In this context, emerging strategies, ranging from linkage chemistry to interlayer interaction, have been employed to construct stable imine-COFs for their applications in electronics, sensing, and energy storage devices. This Concept article summarizes the latest advances aimed at tuning the structural stability of imine-COFs. Furthermore, this Concept provides a prospective for the precise design of stable imine-COFs based on the characteristics of structure, physical properties, and chemical functions, as well as the mechanism of structure locking and stabilization during crystal growth.

Enabling Scalable Polymer Electrolyte with Synergetic Ion Conductive Channels via a Two Stage Rheology Tuning UV Polymerization Strategy.

Lithium metal batteries with polyethylene oxide (PEO) electrolytes are considered as one of the ideal candidates for next generation power sources. However, the low ambient operation capability and conventional solvent-based fabrication process of PEO limit their large-scale application. In this work, a comb-like quasi-solid polymer electrolyte (QPE) reinforced with polyethylene glycol terephthalate nonwoven is fabricated. Combining the density functional theory calculation analysis and polymer structure design, optimized and synergized ion conductive channels are established by copolymerization of tetrahydrofurfuryl acrylate and introduction of plasticizer tetramethyl urea. Additionally, a unique two-stage solventless UV polymerization strategy is utilized for rheology tuning and electrolyte fabrication. Compared with the conventional one-step UV process, this strategy is ideally suited for the roll-to-roll continuous coating fabrication process with environmental friendliness. The fabricated QPE exhibits high ionic conductivity of 0.40 mS cm-1 and Li+ transference number (t = 0.77) at room temperature. LiFePO4 //Li batteries are assembled to evaluate battery performance, which deliver excellent discharge capacity (144.9 mAh g-1 at 0.5 C) and cycling stability (with the retention rate 94.5% at 0.5 C after 200 cycles) at room temperature. The results demonstrate that it has high potential for solid-state lithium metal batteries.

Tuning the Interlayer Interactions of 2D Covalent Organic Frameworks Enables an Ultrastable Platform for Anhydrous Proton Transport.

The development of effective, stable anhydrous proton-conductive materials is vital but challenging. Covalent organic frameworks (COFs) are promising platforms for ion and molecule conduction owing to their pre-designable structures and tailor-made functionalities. However, their poor chemical stability is due to weak interlayer interactions and intrinsic reversibility of linkages. Herein, we present a strategy for enhancing the interlayer interactions of two-dimensional COFs via importing planar, rigid triazine units into the center of C3 -symmetric monomers. The developed triazine-core-based COF (denoted as TPT-COF) possesses a well-defined crystalline structure, ordered nanochannels, and prominent porosity. The proton conductivity was ≈10 times those of non-triazinyl COFs, even reaching up to 1.27×10-2  S cm-1 at 160 °C. Furthermore, the TPT-COF exhibited structural ultrastability, making it an effective proton transport platform with remarkable conductivity and long-term durability.

Li ions traffic controller on thin lithium metal anode: Regulating deposition, optimizing and protecting solid electrolyte interphase.

The performance of thin lithium metal anodes is affected due to issues that weaken the electrode-electrolyte interphase. In this work, a coating layer serving as a Li+ traffic controller based on hexadecyl trimethyl ammonium bis(trifluoromethanesulphonyl)imide ([CTA][TFSI]) and poly (vinylidene difluoride co-hexafluoropropylene) (P(VDF-HFP)) is used to stabilize the thin lithium metal interface. The CTA+ ions in the coating layer can effectively regulate the distribution of Li+ concentration to promote uniform deposition of lithium. The anion of [CTA][TFSI] can optimize solid electrolyte interphase (SEI) with inorganic-rich components, which improve the ionic conductivity and reaction kinetics. Furthermore, the flexible polymer skeleton can fortify the fragile SEI, facilitating the consistent operation of the battery. Due to these improvements, a thin Li metal anode (4 mAh cm-2) with a coating layer in a Li||Li symmetric cell demonstrates a lifespan of 600 h at 1 mA cm-2 and 1 mAh cm-2. Notably, full cells with an ultra-low negative electrode/positive electrode = 1 (N/P = 1) demonstrate a stable performance over 200 cycles and 90 cycles at 0.5C and 1C (1C = 170 mA g-1), respectively.

Separator Engineering Based on Cl-Terminated MXene Ink: Enhancing Li+ Diffusion Kinetics with a Highly Stable Double-Halide Solid Electrolyte Interphase.

Separator engineering is a promising route to designing advanced lithium (Li) metal anodes for high-performance Li metal batteries (LMBs). Conventional separators are incapable of regulating the Li+ diffusion across the solid electrolyte interphase (SEI), leading to severe dendritic deposition. To address this issue, a polypropylene (PP) separator modified by spray coating the Cl-terminated titanium carbonitride MXene ink is designed (PP@Ti3CNCl2). The lithiophilic MXene provides excellent electrolyte wettability and low Li+ diffusion barriers, finally enhancing the Li+ diffusion kinetics of excessively stable SEI. The X-ray photoelectron spectroscopy depth profiling as well as cryo-transmission electron microscopy reveals that a gradient SEI hierarchy with evenly distributed LiF and LiCl is spontaneously formed during the electrochemical process. As a consequence, PP@Ti3CNCl2 delivers a high Coulombic efficiency (99.15%) coupled with a prolonged lifespan of over 5500 h in half cells and 3100 cycles at 2 C in full cells. This work offers an effective strategy for constructing dendrite-free and Li+ permeable interfaces toward high-energy-density LMBs.

Bifunctional scaffolds of hydroxyapatite/poly(dopamine)/carboxymethyl chitosan with osteogenesis and anti-osteosarcoma effect.

The bifunctional tissue engineering scaffold with anti-tumor and bone repair properties is promising for the therapy of bone tumor where large bone defects often occur. In this study, hydroxyapatite (HA), poly(dopamine) (PDA), and carboxymethyl chitosan (CMCS) composite scaffolds were prepared by the 3D-printing technology. PDA significantly improved the rheological properties of the slurry for molding, mechanical properties, surface relative potential, and water absorption of composite scaffolds. The osteogenic properties of HA/PDA/CMCS composite scaffolds were evaluated by the cell experiment in vitro. The photothermal properties and anti-tumor effects of the scaffolds in vivo were assessed by the tumor model in nude mice. HA/PDA/CMCS composite scaffolds could promote more osteogenic differentiation of mouse bone marrow stromal cells (mBMSCs) than scaffolds without PDA in vitro and the effect was not hindered by the photothermal process. The PDA-modified composite scaffold had excellent photothermal properties. Cell experiments showed that scaffolds with PDA under irradiation could suppress the tumor effectively. In vivo anti-tumor effects in nude mice indicated that the HA/PDA/CMCS composite scaffold promoted cell apoptosis/necrosis by the direct photothermal effect. Vascular injury was developed subsequently, which lead to the suppression of tumor cell proliferation due to hypoxia-ischemia. HA/PDA/CMCS composite scaffolds with multiple effects have great potential application in bone tumor therapy.

Biomimetic three-layered membranes comprising (poly)-ε-caprolactone, collagen and mineralized collagen for guided bone regeneration.

The distinct structural properties and osteogenic capacity are important aspects to be taken into account when developing guided bone regeneration membranes. Herein, inspired by the structure and function of natural periosteum, we designed and fabricated using electrospinning a fibrous membrane comprising (poly)--ε-caprolactone (PCL), collagen-I (Col) and mineralized Col (MC). The three-layer membranes, having PCL as the outer layer, PCL/Col as the middle layer and PCL/Col/MC in different ratios (5/2.5/2.5 (PCM-1); 3.3/3.3/3.3 (PCM-2); 4/4/4 (PCM-3) (%, w/w/w)) as the inner layer, were produced. The physiochemical properties of the different layers were investigated and a good integration between the layers was observed. The three-layered membranes showed tensile properties in the range of those of natural periosteum. Moreover, the membranes exhibited excellent water absorption capability without changes of the thickness. In vitro experiments showed that the inner layer of the membranes supported attachment, proliferation, ingrowth and osteogenic differentiation of human bone marrow-derived stromal cells. In particular cells cultured on PCM-2 exhibited a significantly higher expression of osteogenesis-related proteins. The three-layered membranes successfully supported new bone formation inside a critical-size cranial defect in rats, with PCM-3 being the most efficient. The membranes developed here are promising candidates for guided bone regeneration applications.

Highly efficient capture of circulating tumor cells with low background signals by using pyramidal microcavity array.

This report demonstrates that a microfluidic device with integrated silicon filter exhibits outstanding capture efficiency and superior enrichment purity when employed to separate tumor cells from whole blood samples. We fabricate the silicon filter with pyramidal microcavity array (MCA) by microfabrication. We design the structure of the cavity to efficiently enrich tumor cells, while allowing hematologic cells to deform and pass through. The capture efficiency of MCF-7, SW620 and Hela cells spiked in 1 mL of whole blood are approximately 80%. Unwanted white blood cells (WBCs) trapped on the MCA are below 0.003%. In addition, this microfluidic device successfully identifies circulating tumor cells (CTCs) in 5 of 6 patients' blood samples, with a range of 5-86 CTCs per mL. These results reveal that the disposable microfluidic device can effectively enrich tumor cells with different sizes and various morphologies, while maintaining high capture efficiency and purity. Therefore, this label-free technique can serve as a versatile platform to facilitate CTCs analysis in diverse biochemical applications.