Multifunctional Layer Research Articles

Energy efficient out-of-oven manufacturing of natural fibre composites with integrated sensing capabilities and improved water barrier properties

Bio-based and eco-friendly materials have gained a great amount of attention, thanks to the increased awareness of sustainable development and global environments. The use of natural fibres in composites can reduce greenhouse gas emissions and the carbon footprint compared to many synthetic fibres. However, some challenges and concerns remain in natural fibre-reinforced plastics, such as the high moisture absorption and high energy consumption during their manufacturing stage. To tackle these challenges, this study developed an energy-efficient out-of-oven manufacturing method based on a conductive biopolymer nanocomposite film to fabricate natural fibre-reinforced composites with integrated multifunctionalities throughout their life cycle. The smart nanocomposite layer works as an autonomous self-regulating heating element to cure the laminates at the desired temperature without the risk of overheating. Extremely high energy efficiency has been achieved with a significantly reduced energy consumption (a 95% reduction compared with traditional oven curing), which has been attained through the direct heat conduction from the surface layer to the laminates. The embedded nanocomposite surface film on the cured laminate subsequently becomes an integrated multifunctional layer, providing integrated real-time deformation and damage sensing capabilities with enhanced water barrier properties to prolong the service life of natural fibre composites.

Enhanced electroenzymatic CO2 reduction by a multifunctional ZIF-8 layer on silica nanoflower with immobilized enzyme

Carbon capture, utilization and storage have become a hot topic in recent years, and enzymatic CO2 reduction benefits from high selectivity, high efficiency and mild conditions making it promising. However, the low solubility of CO2, poor stability of free enzyme and high cost of coenzyme limit the application. Therefore, mesoporous silica nanoflower (SNF) was used to immobilize formate dehydrogenase (FDH) by electrostatic adsorption followed by the coating of a multifunctional zeolitic imidazolate framework (ZIF-8) layer by sequential coating of Zn2+ and 2-methylimidazole (2-MeIm), thus obtaining a novel integrated nanocatalyst ZIF-8@FDH@SNF. Regulated by controlling the ratio of ligands, the ZIF-8 coating layer not only protected the enzyme and prevented leakage, but also increased the local CO2 concentration using the imidazole group of ZIF-8 which improved the CO2 adsorption by 34.5% compared with SNF. And the expensive NADH was regenerated by the coupled electrocatalysis. The optimized integrated nanocatalyst showed excellent stability and reusability. Highly efficient electroenzymatic CO2 reduction was achieved with 1.38 mM formate yield after 3 h, 48.4% higher than that without ZIF-8 layer.

Periodically Alternating Electric Field Layers Induces the Preferential Growth of Zn (002) Plane for Ultralow Overpotential Zinc‐Ion Batteries

AbstractThe sluggish de‐solvation kinetics and uneven Zn2+ transport behavior at the Zn anode are undesirable for commercialization of zinc ion batteries. To address these issues, a periodically alternating electric field is introduced on the Zn anode by constructing a laponite nano‐clay layer with unique electric field separation properties. This layer exhibits negative and positive electric fields together in the same space but in different directions (negative electric field in the normal direction while the positive electric field is in the radial direction); thus, achieving both homogeneous Zn2+ transport and an effective de‐solvation effect. The laponite film (LAP@Zn) as a multifunctional artificial layer can induce Zn2+ nucleation for preferential orientation growth of Zn along the (002) planes, thereby suppressing dendrite growth on the Zn anode. Consequently, the LAP@Zn symmetric cells exhibit an ultralow overpotential (12 mV) and cycle smoothly over 1100 h at 0.5 mA cm−2. Even at an ultrahigh current density of 40 mA cm−2, the cell still operates stably for 500 h. More encouragingly, the effectiveness is also convincing in MnO2‐based full cells with excellent rate performance and cycle stability. The periodically alternating electric field strategy provides an effective path toward high‐performance and dendrite‐free Zn‐based storage systems.

Building Sustainable Saturated Fatty Acid-Zinc Interfacial Layer toward Ultra-Stable Zinc Metal Anodes

The commercialization pace of aqueous zinc batteries (AZBs) is seriously limited due to the uncontrolled dendrite growth and severe corrosion reaction of the zinc anode. Herein, a universal and extendable saturated fatty acid-zinc interfacial layer strategy for modulating the interfacial redox process of zinc toward ultrastable Zn metal anodes is proposed. The in situ complexing of saturated fatty acid-zinc interphases could construct an extremely thin zinc compound layer with continuously constructed zincophilic sites which kinetically regulates Zn nucleation and deposition behaviors. Furthermore, the multifunctional interfacial layer with internal hydrophobic carbon chains as a protective layer is efficient to exclude active water molecules from the surface and efficiently inhibit the surface corrosion of zinc. Consequently, the modified anode shows a long cycle life of over 4000 h at 5 mA cm-2. In addition, the assembled Zn||V2O5 full cells based on modified zinc anodes have excellent rate performance and long cycle stability.

Multifunctional Hybrid Interfacial Layers for High-Performance Inverted Perovskite Solar Cells.

Challenges remain hindering the performance and stability of inverted perovskite solar cells (PSCs), particularly for the nonstable interface between lead halide perovskite and charge extraction metal oxide layer. Herein, a simple yet scalable interfacial strategy to facilitate the assemble of high-performance inverted PSCs and scale-up modules is reported. The hybrid interfacial layer containing self-assembly triphenylamine and conjugated poly(arylamine) simultaneously improves the chemical stability, charge extraction, and energy level alignment of hole-selective interface, meanwhile promoting perovskite crystallization. Consequently, the correspondent inverted PSCs and modules achieve remarkable power conversion efficiencies (PCEs) of 24.5% and 20.7% (aperture area of 19.4 cm2 ), respectively. The PSCs maintain over 80% of its initial efficiency under one-sun equivalent illumination of 1200 h. This strategy is also effective to perovskite with various bandgaps, demonstrating the highest PCE of 19.6% for the 1.76-eV bandgap PSCs. Overall, this work provides a simple yet scalable interfacial strategy for obtaining state-of-the-art inverted PSCs and modules.

Upcycling of phosphogypsum waste for efficient zinc-ion batteries

Zinc metal is a promising anode material for next-generation aqueous batteries, but its practical application is limited by the formation of zinc dendrite. To prevent zinc dendrite growth, various Zn2+-conducting but water-isolating solid-electrolyte interphase (SEI) films have been developed, however, the required high-purity chemical materials are extremely expensive. In this work, phosphogypsum (PG), an industrial byproduct produced from the phosphoric acid industry, is employed as a multifunctional protective layer to navigate uniform zinc deposition. Theoretical and experimental results demonstrate that PG-derived CaSO4·2H2O can act as an artificial SEI layer to provide fast channels for Zn2+ transport. Moreover, CaSO4·2H2O could release calcium ions (Ca2+) due to its relatively high Ksp value, which have a higher binding energy than that of Zn2+ on the Zn surface, thus preferentially adsorbing to the tips of the protuberances to force zinc ions to nucleate at inert region. As a result, the Zn@PG anode achieves a high Coulombic efficiency of 99.5% during 500 cycles and long-time stability over 1000 hours at 1 mA cm−2. Our findings will not only construct a low-cost artificial SEI film for practical metal batteries, but also achieve a high-value utilization of phosphogypsum waste.

Functional ceramic support as an independent catalyst layer for direct liquid fuel solid oxide fuel cells

A porous ceramic support is designed as a multi-functional independent catalyst layer for solid oxide fuel cells (SOFCs) running on liquid hydrocarbon fuel. The layer consists of a highly porous Ce_0.9Ca_0.1O_{2−<i>δ</i>} ceramic backbone and active NiMo catalysts, which could be integrated into the conventional Ni metal containing the anode for internal reforming of the hydrocarbon fuel. Compared to conventional catalyst layers sintered on the anodes, this independent catalyst layer could be simply assembled on top of the anode without additional sintering, thereby avoiding the mismatch of the thermal expansion coefficient between the catalyst layer and the anode and improving stability of a single cell. Moreover, a current collector layer could be inserted between the catalyst and the anode to enhance current collection efficiency and electrochemical performance of the single cell. At 750 ℃, the independent catalyst layer displays high activity towards the catalytic decomposition of methanol, and the single cell could achieve the maximum power density of 400–500 mW·cm⁻² in dry methanol. Furthermore, by employing the independent catalyst layer, the single cell offers additional <i>in-situ</i> catalyst regeneration capability under the methanol operation mode. Feeding 10 mL·min⁻¹ air into an anode channel for 5 min is found to be effective to burn out carbon species in the catalyst layer, which reduces the degradation rate of the cell voltage by orders of magnitude from 2.6 to 0.024 mV·h⁻¹ during the operation of 360 h in dry methanol. The results demonstrate the significance of the independent catalyst layer design for direct internal reforming methanol fuel cells.

Multifunctional Edible Oil-Impregnated Nanoporous Oxide Layer on AISI 304 Stainless Steel.

Slippery liquid-infused porous surface (SLIPS) realized on commercial materials provides various functionalities, such as corrosion resistance, condensation heat transfer, anti-fouling, de/anti-icing, and self-cleaning. In particular, perfluorinated lubricants infused in fluorocarbon-coated porous structures have showed exceptional performances with durability; however, they caused several issues in safety, due to their difficulty in degradation and bio-accumulation. Here, we introduce a new approach to create the multifunctional lubricant-impregnated surface with edible oils and fatty acid, which are also safe to human body and degradable in nature. The edible oil-impregnated anodized nanoporous stainless steel surface shows a significantly low contact angle hysteresis and sliding angle, which is similar with general surface of fluorocarbon lubricant-infused systems. The edible oil impregnated in the hydrophobic nanoporous oxide surface also inhibits the direct contact of external aqueous solution to a solid surface structure. Due to such de-wetting property caused by a lubricating effect of edible oils, the edible oil-impregnated stainless steel surface shows enhanced corrosion resistance, anti-biofouling and condensation heat transfer with reduced ice adhesion.

Functionalization of the Implant Surface Made of NiTi Shape Memory Alloy

To functionalize and improve the biocompatibility of the surface of a medical implant made of NiTi shape memory alloy and used in practice, a clamp, multifunctional layers composed of amorphous TiO2 interlayer, and a hydroxyapatite coating were produced. Electrophoresis, as an efficient method of surface modification, resulted in the formation of a uniform coating under a voltage of 60 V and deposition time of 30 s over the entire volume of the implant. The applied heat treatment (800 °C/2 h) let toa dense, crack-free, well-adhered HAp coating with a thickness of ca. 1.5 μm. and a high crack resistance to deformation associated with the induction of the shape memory effect in the in the deformation range similar to the real implant work after implantation. Moreover, the obtained coating featured a hydrophilic (CA = 59.4 ± 0.3°) and high biocompatibility.

A Multifunctional Interphase Layer Enabling Superior Sodium-Metal Batteries under Ambient Temperature and -40°C.

The sodium (Na)-metal anode with high theoretical capacity and low cost is promising for construction ofhigh-energy-density metal batteries. However, the unsatisfactory interface between Na and the liquid electrolyte induces tardy ion transfer kinetics and dendritic Na growth, especially at ultralow temperature (-40°C). Herein, an artificial heterogeneous interphase consisting of disodium selenide (Na2 Se) and metal vanadium (V) is produced on the surface of Na (Na@Na2 Se/V) via an in situ spontaneous chemical reaction. Such interphase layer possesses high sodiophilicity, excellent ionic conductivity, and high Young's modulus, which can promote Na-ion adsorption and transport, realizing homogenous Na deposition without dendrites. The symmetric Na@Na2 Se/V cell exhibits outstanding cycling life span of over 1790h (0.5mA cm-2 /1 mAh cm-2 ) in carbonate-based electrolyte. More remarkably, ab initio molecular dynamics simulations reveal that the artificial Na2 Se/V hybrid interphase can accelerate the desolvation of solvated Na+ at -40°C. The Na@Na2 Se/V electrode thus exhibits exceptional electrochemical performance in symmetric cell (over 1500h at 0.5mA cm-2 /0.5 mAh cm-2 ) and full cell (over 700 cycles at 0.5 C) at -40°C. This work provides an avenue to design artificial heterogeneous interphase layers for superior high-energy-density metal batteries at ambient and ultralow temperatures.

Perylene Monoimide Phosphorus Salt Interfacial Modified Crystallization for Highly Efficient and Stable Perovskite Solar Cells

Reducing the interfacial defects of perovskite films is key to improving the performance of perovskite solar cells (PSCs). In this study, two kinds of perylene monoimide (PMI) derivative phosphonium bromide salts were designed and used as a multifunctional interface-modified layer in PSCs. These two molecules are inserted between SnO2 and perovskite to produce a bidirectional passivation effect. The interaction with SnO2 reduces the oxygen vacancy on the surface of SnO2 and tunes the energy level of the electron transport layer, making more matches with the perovskite layer. The modified layer can promote the growth of perovskite crystals and reduce the interfacial defects of the perovskite film. Furthermore, the power conversion efficiency (PCE) of PSCs increased from 19.49 to 22.85%, and the open-circuit voltage (VOC) increased from 1.06 to 1.14 V. At the same time, the PCE of the SnO2/PMI-TPP-based device remained 88% of the initial PCE after 240 h of continuous illumination. In addition, these two PMI derivatives with a quasi-planar structure can improve the flexibility of flexible PSCs. This study provided a new strategy for the interfacial modification of PSCs and a new insight into the application of flexible PSCs.

A Review of Transition Metal Compounds as Functional Separators for Lithium‐Sulfur Batteries

AbstractLithium‐sulfur (Li−S) batteries have great potential for the development of next‐generation high‐energy‐density secondary batteries owing to their high theoretical energy density, active material (sulfur) environmental friendliness, and low cost. However, their application is still impeded by the inherent sluggish kinetics and solubility of intermediate products of the sulfur cathode. Interface design is an important direction to address challenges in the development of Li−S batteries. The modification of the separator has been shown to effectively suppress the shuttling effect of physical hindrance or chemical bonding without affecting the utilization of active materials. This review encompasses the application of nanostructured transition metal oxides (TMOs), transition metal sulfides (TMSs), transition metal nitrides (TMNs), transition metal phosphides (TMPs), such as incorporating functional separators beyond the approach for preparing novel cathodes, and discusses their composites in a new multifunctional barrier layer for Li−S batteries. The objective properties of various metal compounds and the effect of the shuttle effect in particular on the electrochemical performance in Li−S batteries are highlighted, and give an outlook on the promising approaches for the construction of reliable Li−S batteries.

In situ defect engineering in a multifunctional layer with strong zincophilicity and high Zn-ion conductivity on Zn anodes

A multifunctional dual protection layer with a high Zn2+ transference number and strong zincophilicity is in situ constructed on Zn anodes.

High performance Zn anodes enabled by a multifunctional biopolymeric protective layer for a dendrite-free aqueous zinc-based battery

We design a multifunctional biopolymeric protective layer composed of chitosan and gelatin. It acts as a desolvation layer to hinder the water-induced side reaction and works as a zinc-ion flux regulator to inhibit the growth of dendrites.

Reactive boride as a multifunctional interface stabilizer for garnet-type solid electrolyte in all-solid-state lithium batteries.

All-solid-state batteries are one of the most important game changers in electrochemical energy storage since they are free from the risk of leakage of hazardous flammable liquid solvents. Among the various types of solid-state electrolytes, Li7-xLa3Zr2-xTaxO12 garnets possess many desirable advantages to be considered a suitable candidate for lithium-ion batteries. However, their practical application has been hindered by premature short-circuits due to lithium dendrite growth, nonnegligible electronic conductivity and interfacial air sensitivity issues. Herein, we propose a multifunctional layer strategy to simultaneously address both the interface and electronic conductivity issues. With the help of a facile chemical process based on reactive cobalt boride, electron leakage was effectively blocked and the electrochemical performance/stability could be well maintained over extended cycles. The cobalt boride-coating layer also possessed an impressive Li metal wetting ability while sustaining a low interfacial resistance. A full cell paired with a commercialized cathode showed satisfactory performance with low overpotentials and a high specific capacity over 150 mA h g-1. Moreover, first-principle calculations further revealed the status of the rearrangement of the electron cloud behind the charge-density difference, and the nature of the low diffusion energy barrier of the reactive cobalt boride protective layer. Our strategy highlights the necessity of designing proper multifunctional layers in the garnet-type solid-state lithium-ion battery system.

A hybrid polymer protective layer with uniform Li+ flux and self-adaption enabling dendrite-free Li metal anodes.

Lithium (Li) metal is considered as an ideal negative electrode material for next-generation secondary batteries; however, the hideous dendrite growth and parasitic reactions hinder the practical applications of Li metal batteries. Herein, a hybrid polymer film composed of polyvinyl alcohol (PVA) and polyacrylic acid (PAA) is adopted as an artificial protective layer to inhibit the dendritic formation and side reactions in Li metal anodes. PVA with large quantities of polar functional groups can induce even distribution of Li ions (Li+). Alternatively, PAA can in situ react with Li metal to form highly elastic and ionic conducting lithium polyacrylic acid (LiPAA), thereby enabling tight contact and flexible self-adaption with Li metal anodes. Therefore, such a rationally designed functional composite layer, with good binding ability and relatively high Li+ conductivity, as well as excellent capability of homogenizing Li+ flow, accordingly enables Li metal anodes to reveal dendrite-free plating/stripping behaviours and minimum volume variation. As a result, the PVA-PAA modified Li metal anode delivered stable cycling for 700 and 250 h, respectively, at current densities of 1 and 3 mA cm-2 under an areal capacity of 1 mA h cm-2, in a carbonate ester-based electrolyte without any additive, exhibiting boosted cycling and rate performances. The Li anode with a functional PVA-PAA hybrid interlayer can maintain the dense and smooth texture without dendrite formation after long cycles. The full cell of Li|LiFeO4 with our modified Li anode and a cathode with a high areal capacity of 2.45 mA h cm-2 delivers, change to achieved a long-term lifespan of 180 cycles at 1.0 C, with a capacity retention of 96.7%. This work demonstrates a simple and effective strategy of designing multi-functional artificial protective layers, targeting dendrite-free Li anodes.

Two-Dimensional Organic-Inorganic Heterostructure as a Multifunctional Protective Layer for High Performance Zinc Metal Anode.

Dendrite growth and side reactions of Zn metal anodes remain unresolved obstacles for practical application of aqueous Zn ion batteries. Herein, a two-dimensional (2D) organic-inorganic heterostructure with controlled thickness was constructed as a protective layer for a Zn metal anode. The reduction of uniformly distributed polyoxometalate in the layer causes a negative charge density gradient, which can accelerate zinc ion transfer, homogenize zinc deposition, and shield sulfates at the electrode interface, while the exposed hydrophobic alkyl chain of the layer can isolate the direct contact of water with the Zn anode. As a result of the synergetic effect, this 2D organic-inorganic heterostructure enables high Zn plating/stripping reversibility, with high average Coulombic efficiencies of 99.97% for 3700 cycles at 2 mA cm-2. Under high Zn utilization conditions, a high areal-capacity full cell with hundreds of cycles was demonstrated.

Application of Electrospun Water-Soluble Synthetic Polymers for Multifunctional Air Filters and Face Masks.

The worsening of air quality is an urgent human health issue of modern society. The outbreak of COVID-19 has made the improvement of air quality even more imperative, both for the general achievement of major health gains and to reduce the critical factors in the transmission of airborne diseases. Thus, the development of solutions for the filtration of airborne pollutants is pivotal. Electrospinning has gained wide attention as an effective fabrication technique for preparing ultrafine fibers which are specifically tailored for air filtration. Nevertheless, the utilization of harmful organic solvents is the major barrier for the large-scale applicability of electrospinning. The use of water-soluble synthetic polymers has attracted increasing attention as a 'green' solution in electrospinning. We reported an overview of the last five years of the scientific literature on the use of water-soluble synthetic polymers for the fabrication of multifunctional air filters layers. Most of recent studies have focused on polyvinyl alcohol (PVA). Various modifications of electrospun polymers have been also described. The use of water-soluble synthetic polymers can contribute to the scalability of electrospinning and pave the way to innovative applications. Further studies will be required to fully harness the potentiality of these 'greener' electrospinning processes.

Balanced Coexistence of Reversible and Irreversible Covalent Bonds in a Conductive Triple Polymeric Network Enables Stretchable Hydrogels with High Toughness and Adhesiveness.

The application of soft hydrogels to stretchable devices has attracted increasing attention in deformable bioelectronics owing to their unique characteristic, "modulus matching between materials and organs". Despite considerable progress, their low toughness, low conductivity, and absence of tissue adhesiveness remain substantial challenges associated with unstable skin-interfacing, where body movements undesirably disturb electrical signal acquisitions. Herein, we report a material design of a highly tough strain-dissipative and skin-adhesive conducting hydrogel fabricated through a facile one-step sol-gel transition and its application to an interactive human-machine interface. The hydrogel comprises a triple polymeric network where irreversible amide linkage of polyacrylamide with alginate and dynamic covalent bonds entailing conjugated polymer chains of poly(3,4-ethylenedioxythiophene)-co-(3-thienylboronic acid) are simultaneously capable of high stretchability (1300% strain), efficient strain dissipation (36,209 J/m2), low electrical resistance (590 Ω), and even robust skin adhesiveness (35.0 ± 5.6 kPa). Based on such decent characteristics, the hydrogel was utilized as a multifunctional layer for successfully performing either electrophysiological cardiac/muscular on-skin sensors or an interactive stretchable human-machine interface.

Rational design and low-cost fabrication of multifunctional separators enabling high sulfur utilization in long-life lithium-sulfur batteries

The lithium-sulfur (Li-S) battery with an ultrahigh theoretical energy density has emerged as a promising rechargeable battery system. However, the practical applications of Li-S batteries are severely plagued by the sluggish reaction kinetics of sulfur species and notorious shuttling of soluble lithium polysulfides (LiPSs) intermediates that result in low sulfur utilization. The introduction of functional layers on separators has been considered as an effective strategy to improve the sulfur utilization in Li-S batteries by achieving effective regulation of LiPSs. Herein, a promising self-assembly strategy is proposed to achieve the low-cost fabrication of hollow and hierarchically porous Fe3O4 nanospheres (p-Fe3O4-NSs) assembled by numerous extremely-small primary nanocrystals as building blocks. The rationally-designed p-Fe3O4-NSs are utilized as a multifunctional layer on the separator with highly efficient trapping and conversion features toward LiPSs. Results demonstrate that the nanostructured p-Fe3O4-NSs provide chemical adsorption toward LiPSs and kinetically promote the mutual transformation between LiPSs and Li2S2/Li2S during cycling, thus inhibiting the LiPSs shuttling and boosting the redox reaction kinetics via a chemisorption-catalytic conversion mechanism. The enhanced wettability of the p-Fe3O4-NSs-based separator with the electrolyte enables fast transportation of lithium ions. Benefitting from these alluring properties, the functionalized separator with p-Fe3O4-NSs endows the battery with an admirable rate performance of 877 mAh g−1 at 2 C, an ultra-durable cycling performance of up to 2176 cycles at 1 C, and a promising areal capacity of 4.55 mAh cm−2 under high-sulfur-loading and lean-electrolyte conditions (4.29 mg cm−2, electrolyte/ratio: 8 µl mg−1). This study will offer fresh insights on the rational design and low-cost fabrication of multifunctional separator to strengthen electrochemical reaction kinetics by regulating LiPSs conversion for developing efficient and long-life Li-S batteries.