Structural Engineering Strategy Research Articles

Structural Engineering of Metal‐Organic Frameworks for Efficient CO2 Reduction Reaction

AbstractMetal‐organic framework (MOF) materials have attracted much attention due to their diverse topological structures, excellent adsorption capacity, and unique physicochemical properties, which hold great promise in catalytic CO2 reduction reaction (CO2RR). However, the original MOFs materials have disadvantages such as poor electrical conductivity, high diffusion barrier and limited accessible catalytic sites, which seriously limit their application in CO2RR. Therefore, many structural engineering strategies have been used to improve the CO2RR performance of the MOFs materials. In this review, we mainly review the four main structure engineering strategies, i. e. crystal engineering, 2D engineering, heterostructure engineering and MOF derivatives engineering, in enhancing the catalytic CO2RR performance of the MOFs. We hope that this review will not only provide insights for the rational design of efficient MOFs materials for the CO2RR, but also stimulate more research work in this field.

Spider-silk-inspired strong and tough hydrogel fibers with anti-freezing and water retention properties

Ideal hydrogel fibers with high toughness and environmental tolerance are indispensable for their long-term application in flexible electronics as actuating and sensing elements. However, current hydrogel fibers exhibit poor mechanical properties and environmental instability due to their intrinsically weak molecular (chain) interactions. Inspired by the multilevel adjustment of spider silk network structure by ions, bionic hydrogel fibers with elaborated ionic crosslinking and crystalline domains are constructed. Bionic hydrogel fibers show a toughness of 162.25 ± 21.99 megajoules per cubic meter, comparable to that of spider silks. The demonstrated bionic structural engineering strategy can be generalized to other polymers and inorganic salts for fabricating hydrogel fibers with broadly tunable mechanical properties. In addition, the introduction of inorganic salt/glycerol/water ternary solvent during constructing bionic structures endows hydrogel fibers with anti-freezing, water retention, and self-regeneration properties. This work provides ideas to fabricate hydrogel fibers with high mechanical properties and stability for flexible electronics.

Order-disorder structural engineering of vanadium oxide anode: Balancing ionic and electronic dynamic for fast-charging aqueous Li-ion battery

Fast-charging aqueous lithium-ion batteries (ALIBs) are considered as promising energy storage devices because of their non-flammability and environmentally friendly characteristics. However, how to balance the ionic and electronic dynamics for fast charging reactions remains a significant challenge under the current research status. Here, the order-disorder structural engineering strategy is adopted to resolve this issue, considering the difference between ion and electron transportation in the crystalline and amorphous phases, respectively. Vanadium oxide anodes were developed with optimized ionic and electronic dynamics by using an organic-inorganic hybrid material as a precursor along with refined regulation on the calcination temperature and time. This facile and large-scale extendable approach harnesses the benefits of the order-disorder structure to optimize Li+ storage efficiency and facilitate the high reversibility of Li-ion during fast charging. Consequently, the order-disorder V2O5-based full cell with LiMn2O4 as a cathode exhibits high specific capacity (262.71 mAh g−1, 89.35 % of the theoretical capacity of V2O5), high energy density (166.04 Wh kg−1), fast Li-ion diffusion coefficient (7.34×10−5 cm2 s−1) and fast-charging performance (only 6 min achieves 82.84 % of initial state-of-charge capacity). This work explores the ionic and electronic dynamic of ordered-disorder structure and offers new insights into the development of fast-charging metal ion batteries.

Isomerization Engineering of Oxygen-Enriched Carbon Quantum Dots for Efficient Electrochemical Hydrogen Peroxide Production.

Hydrogen peroxide (H2O2) has emerged as a kind of multi-functional green oxidants with extensive industrial utility. Oxidized carbon materials exhibit promises as electrocatalysts in the two-electron (2e-) oxygen reduction reaction (ORR) for H2O2 production. However, the precise identification and fabrication of active sites that selectively yield H2O2 present a serious challenge. Herein, a structural engineering strategy is employed to synthesize oxygen-doped carbon quantum dots (o-CQD) for the 2e- ORR. The surface electronic structure of the o-CQDs is systematically modulated by varying isomerization precursors, thereby demonstrating excellent electrocatalyst performance. Notably, o-CQD-3 emerges as the most promising candidate, showcasing a remarkable H2O2 selectivity of 96.2% (n = 2.07) at 0.68V versus RHE, coupled with a low Tafel diagram of 66.95mV dec-1. In the flow cell configuration, o-CQD-3 achieves a H2O2 productivity of 338.7mmol gcatalyst -1 h-1, maintaining consistent production stability over an impressive 120-hour duration. Utilizing in situ technology and density functional theory calculations, it is unveil that edge sites of o-CQD-3 are facilely functionalized by C-O-C groups under alkaline ORR conditions. This isomerization engineering approach advances the forefront of sustainable catalysis and provides a profound insight into the carbon-based catalyst design for environmental-friendly chemical synthesis processes.

Constructing NiO/Co3O4/KNbO3 heterostructure with NiO and Co3O4 particles coupled on KNO3 cubes for high-performance urea-assisted alkaline oxygen evolution reaction

In this study, a novel NiO/Co3O4/KNbO3 heterostructured electrocatalyst with NiO and Co3O4 particles coupled on KNO3 cubes was constructed using simple sol–gel and calcination processes. The formation of multiple interfaces between NiO, Co3O4, and KNbO3 in the heterostructure contributed to a synergistic effect, adjusted the electronic structure, and generated abundant active sites at the interfaces. As a result, the NiO/Co3O4/KNbO3 electrocatalyst exhibited remarkable urea electrolysis performance, including a low potential of 1.67 V at 100 mA cm-2 and a small Tafel slope of 29 mV dec-1. Furthermore, the change in the overpotential was negligible even after a rigorous stability test of 3000 cycles, highlighting its exceptional durability and reliability. This study provides a novel structural engineering strategy for achieving efficient hydrogen production and purification from urea-containing wastewater.

Multifunctional tri-layer aramid nanofiber composite separators for high-energy-density lithium-sulfur batteries

Lithium-sulfur (Li-S) battery has attracted much attention due to their high theoretical energy density. However, severe shuttling effect, sluggish reaction kinetics and uncontrolled dendrite formation of Li anode greatly deter their practical applications. Different to conventional separator engineering strategies that are always focused on surface coating of functional interlayer on commercial polyolefin separators, herein, we proposed a structural engineering tactic by rationally tuning the porous structure and composition of the p-aramid nanofiber (ANF) composite separator to address simultaneously the above problems. A two-step film-casting process combined with a phase inversion approach was developed to fabricate a multifunctional tri-layer ANF composite separator. This innovative separator was especially engineered to comprise a conductive and catalytic NiFe2O4 modified multi-walled carbon nanotubes/ANF layer for rapid and efficient conversion of lithium polysulfides, a microporous ANF layer for fast ion transport, and a dense nanoporous ANF layer for lithium dendrite inhibition. This tri-layer ANF-based separator possessed high porosity, excellent thermal stability, and superb electrolyte wettability. Batteries with the tri-layer ANF- based separator exhibited outstanding cyclic stability with high capacity of >3 mAh cm−2 at high sulfur loading (4 mg cm−2) and high current density (4 mA cm−2). This work opens up new opportunities for design of functional separators based on high performance polymers using the structural engineering strategy.

Cationic Engineering Strategy to Achieve Controllable Room‐Temperature‐Phosphorescence in Hybrid Zinc Halides

AbstractDespite rapid progress and wide applications of room temperature phosphorescence (RTP) materials, it is still a great challenge to optimize the RTP activity through rational structural design at a molecular level. Herein, a successful cationic engineering strategy is demonstrated to modulate the crystal flexibility achieving controllable RTP in a new pair of metal halides [APML]ZnCl4 ([APML] = N‐(3‐Aminopropyl)morpholine) and [AEML]ZnCl4 ([AEML] = N‐(2‐Aminoethyl)morpholine). Both halides display blue fluorescence under 365 nm UV. Comparing with longer [APML]+, shorter [AEML]+ significantly enhances crystal rigidity and restrains non‐radiative scattering, boosting photoluminescence quantum yield (PLQY) from 18.89% to 22.41%. Synchronously, enhanced crystal rigidity significantly promotes the inter‐system crossing from singlet to triplet excited states. As a consequence, [AEML]ZnCl4 displays long‐lived green RTP property with millisecond scale lifetime in contrast to the blank RTP activity of [APML]ZnCl4. Comprehensive investigations demonstrate that the energy transfer between inorganic and organic components greatly changes the redistribution of singlet and triplet excited states, resulting in distinct phosphorescence activity. The different short‐lived blue fluorescence and long‐lived green phosphorescence provide a color‐time‐dual‐resolved luminescent tag with advanced applications in anti‐counterfeiting, etc. This work highlights a new structural engineering strategy to achieve controllable RTP affording a guide to rationally design RTP materials.

Robust micro-nano hybrid aerogel derived from waste resources for thermal management and high-efficiency adsorption

Ultra-low density nanoaerogels as the lightest solid material have aroused extensive attention. However, lacking crack extension resistance limited their further development and application. Here, aramid and cellulose wastes were recycled to prepare high value-added nanofibers, which were further self-assembled to construct multilfunctional hybrid aerogels. In-situ growth of zeolitic imidazolate frameworks-8 (ZIF-8) on the cellulose nanofiber (CNF) created a robust skeleton. Flexible aramid nanofibers (ANF), as burgeoning building blocks were employed to inlay into the microscopic skeleton structure for establishing micro-nano double networks. Benefiting from the existence of multiscale networks, the maximum value in the compressive stress of S0, S1, S2 and S3 increased from 2.74 to 4.63, 5.19 and 6.61 MPa, respectively.Meanwhile, ANF-ZIF-8-CNF hybrid aerogels exhibited low thermal conductivity of 3.58–3.97 × 10-2 W/(m⋅K). The significant increase in the specific surface area (481.46 m2/g) endowed hybrid aerogels with high adsorption abilities for nitrogen (280.83 cm3/g), prussian blue (34.12 mg⋅g−1), rhodamine B (37.30 mg⋅g−1), DMF (25.13 g⋅g−1) and DMSO (15.48 g⋅g−1), respectively. This multiscale structural engineering strategy opens an avenue toward to upcycle waste resources into the next-generation high-performance nanoaerogels, showing huge application potential in thermal management, air purification and sewage treatment.

Allying interfacial engineering of 2D carbon nanosheet‐, graphene‐, and graphdiyne‐based heterostructured electrocatalysts toward hydrogen evolution and overall water splitting

AbstractElectrochemical hydrogen evolution reaction (HER) and overall water splitting (OWS) for renewable energy generation have recently become a highly promising and sustainable strategy to tackle energy crisis and global warming arising from our overreliance on fossil fuels. Previously, tremendous research breakthroughs have been made in 2D carbon‐based heterostructured electrocatalysts in this field. Such heterostructures are distinguished by their remarkable electrical conductivity, exposed active sites, and mechanical stability. Herein, with fundamental mechanisms of electrocatalytic OWS summarized, our review critically emphasized on state‐of‐the‐art 2D carbon nanosheet‐, graphene‐, and graphdiyne‐based heterostructured electrocatalysts in HER and OWS since 2018. Particularly, the three emerging carbonaceous substrates tend to be incorporated with metal carbides, phosphides, dichalcogenides, nitrides, oxides, nanoparticles, single atom catalysts, or layered double hydroxides. Meanwhile, fascinating structural engineering and facile synthesis strategies were also unraveled to establish the structure–activity relationship, which will enlighten future electrocatalyst developments toward ameliorated HER and OWS activities. Additionally, computational results from density functional theory simulations were highlighted as well to better comprehend the synergistic effects within the heterostructures. Finally, current stages and future recommendations of this brand‐new electrocatalyst type were concluded and discussed for advanced catalyst designs and future practical applications.

Efficient Polytelluride Anchoring for Ultralong-Life Potassium Storage: Combined Physical Barrier and Chemisorption in Nanogrid-in-Nanofiber

HighlightsThe hierarchical nanogrid-in-nanofiber-structured dual-type carbon-confined CoTe2 nanodots (CoTe2@NC@NSPCNFs) were synthesized via facile templates and an electrospinning approach.Hierarchical nanogrid-in-nanofiber structure effectively suppresses the volume change of CoTe2 and the shuttle of potassium polytelluride (K-pTex) through robust physical restraint and strong chemisorption.CoTe2@NC@NSPCNFs hybrid achieves ultralong lifespan potassium-storage performance over 3500 cycles, and the deep mechanisms underlying the evolution, dissolution, and shuttle of K-pTex have been clearly revealed.

Biomimetic Bouligand chiral fibers array enables strong and superelastic ceramic aerogels

Ceramic aerogels are often used when thermal insulation materials are desired; however, they are still plagued by poor mechanical stability under thermal shock. Here, inspired by the dactyl clubs of mantis shrimp found in nature, which form by directed assembly into hierarchical, chiral and Bouligand (twisted plywood) structure exhibiting superior mechanical properties, we present a compositional and structural engineering strategy to develop strong, superelastic and fatigue resistance ceramic aerogels with chiral fibers array resembling Bouligand architecture. Benefiting from the stress dissipation, crack torsion and mechanical reinforcement of micro-/nano-scale Bouligand array, the tensile strength of these aerogels (170.38 MPa) is between one and two orders of magnitude greater than that of state-of-the-art nanofibrous aerogels. In addition, the developed aerogels feature low density and thermal conductivity, good compressive properties with rapid recovery from 80 % strain, and thermal stability up to 1200 °C, making them ideal for thermal insulation applications.

Insight into the intrinsic activity of various transition metal sulfides for efficient hydrogen evolution reaction.

The electrocatalytic hydrogen evolution reaction (HER) is an efficient approach to convert sustainable energy sources into clean energy carriers, H2. Although various transition metal sulfides (TMSs) have been reported as promising alternatives to precious metal-based catalysts, the top catalyst among TMSs remains unclear as there is a dearth of high-quality studies that provide a 'fair' comparison of the performance of these TMSs synthesized and tested under the same conditions. In this work, layered transition metal sulfides (MS2: MoS2, WS2, VS2) and non-layered transition metal sulfides (MxSy: FeS2, CoSx, NiS) were obtained by a straightforward hydrothermal method, and thus a comprehensive platform was established for the comparison of the intrinsic activity of these materials in the HER. Experimental results demonstrate that layered MS2 exhibits better performance than non-layered MxSy in acidic electrolytes, while CoSx and NiS can catalyze hydrogen evolution more effectively under alkaline conditions due to structural reconfiguration. MoS2 shows the best HER performance in both acidic and alkaline electrolytes, particularly in 1 M KOH solution. This work provides guidance for the optimal design of transition metal electrocatalysts, and structural engineering strategies can be used to further enhance their catalytic activity.

Functional design of stimuli-responsive poly(phthalaldehyde)-based adhesives: depolymerization kinetics and mechanical strength management through plasticizer addition

Through a strategic polymer engineering design, this paper shows that self-immolative poly(phthalaldehyde) (PPA) can be employed as a responsive debonding-on-demand adhesive for the detection of fluorides and acids in liquid and solid states.

Reactant enrichment in yolk-shell structured Pd/TiN nanoreactors for boosting electrocatalytic hydrodechlorination performance

Enhancing the enrichment behavior of low-concentration chlorinated organic pollutants remains a significant challenge in electrocatalytic hydrodechlorination (EHDC) technology. Metal-loaded hollow nanoarchitecture has emerged as a promising nanoreactor to improve reaction enrichment behavior because of its tailorable microenvironments and electronic properties. Herein, a structural engineering strategy is developed to synthesize yolk-shell structured TiN spheres supported Pd nanoreactors (Pd/YS-TiN) with confined mesoscopic spaces. Characterization by multiple techniques reveals that the yolk-shell structure of YS-TiN, with high specific surface area (139.0 m2/g) and appropriately mesoporosity (6.9 nm), exposes numerous Pd nanoparticles (∼4.0 nm) on outer/inner surface of the shell and yolk-core solid sphere, ensuring an efficient utilization of active sites for enhancing the 2,4-DCP detoxification. Consequently, the structurally optimized Pd/YS-TiN nanoreactor consistently displays maximum reaction kinetics, dechlorination degree, faradaic current density, H* utilization and product selectivity, surpassing hollow TiN-supported Pd and Pd/C catalysts. The super EHDC performance of 91.8 % 2,4-DCP conversion, a specific activity of 1.68 min−1 molPd−1, and a mass activity of 6.06 min−1 gPd−1 is obtained at −0.85 V and 180 min, outperforming most reported catalysts. Combining experimental and density functional theory results, the exceptional reaction enrichment behavior of Pd/YS-TiN originates from (1) alleviating the overstrong adsorption of product phenol through strong metal-support interactions and (2) enhancing mass transport efficiency facilitated by the local concentration gradient and mesoporous shell. This study elucidates how metal-support interactions and mass transport synergistically enhance reaction enrichment behavior, showcasing potential benefits in environmental remediation applications.

Construction of Co1-xS Nanoparticles Embedding in N-Doped Amorphous Carbon@Graphene with Enhanced Li-Ion Storage.

Cobalt sulfide is deemed a promising anode material, owing to its high theoretical capacity (630mAhg-1). Due to its low conductivity, fast energy decay, and the huge volume change during the lithiation process limits its practical application. In this work, a simple and large-scale method are developed to prepare Co1-xS nanoparticles embedding in N-doped carbon/graphene (CSCG). At a current density of 0.2C, the reversible discharge capacity of CSCG maintains 937mAhg-1 after 200 cycles. The discharge capacity of CSCG maintains at 596mAhg-1 after 500 cycles at the high current density of 2.0C. The excellent performance of CSCG is due to its unique structural features. The addition of rGO buffered volume changes while preventing Co1-xS from crushing/aggregating during the cycle, resulting in multiplier charge-discharge and long cycle life. The N-doped carbon provides a simple and easy way to achieve excellent performance in practical applications. Combined with density functional theory calculation, the presence of Co-vacancies(Co1-x) increases more active site. Moreover, N-doping carbon is beneficial to the improve adsorption energy. This work presents a simple and effective structural engineering strategy and also provides a new idea to improve the performance of Li-ion batteries.

Photocatalytic aqueous environmental remediation via two-dimensional carbon nitride nanosheets

Graphitic carbon nitride (GCN) has garnered considerable attention across diverse fields, particularly in photocatalysis for energy and environmental applications, due to its unique physicochemical properties. Among the various structural engineering strategies applied to GCN, two-dimensional (2D) nanosheet design stands out as a fascinating direction due to the 2D geometric advantages. This review explicitly explores the various synthetic (classified as bottom-up and top-down) and physicochemical structural modification methods of GCN-NS matrix and their based composites, as well as their application in photocatalytic remediation of aqueous pollutants. The features of these synthetic strategies in the formation of 2D GCN-NS are first compared. Different modification strategies of GCN-NS, such as surface modification, crystal structure design, doping and heterojunction construction, are summarized. Furthermore, the structure-activity relationship of GCN-NS in various photocatalytic water treatments regarding light absorption, carrier transport and catalytic reaction paths is discussed. Lastly, the developed perspectives are described, including the challenge of GCN-NS-based materials. We expect this review to provide guidelines and inspirations for preparing, modifying, and utilizing two-dimensional GCN materials in the photocatalytic field.

Homogenous conduction: Stable multifunctional gel polymer electrolyte for lithium-sulfur batteries

The low sulfur utilization rate and polysulfide shuttle are the main reasons that hinder the practical process of lithium-sulfur batteries. Here, an effective structural engineering strategy of multifunctional gel polymer electrolyte (GPE) by electrospinning was proposed. The HCNF@HPAN-GPE for lithium-sulfur batteries contained halloysite-base carbon nanofibers (HCNF) offered abundant active sites as sulfur fixation layer and halloysite-base polyacrylonitrile (HPAN) provided ion transport channel as ion transport layer. Both layers were abundant in the halloysite nanotubes as “transduction segment” and established the synergistic interface conduction. The HCNF@HPAN-GPE exhibited an ionic conductivity of 8.01 × 10−3 S cm−1. Therefore, the HCNF@HPAN-GPE displayed excellent interface compatibility and stabilized lithium deposition/ stripping over 800 h. Meanwhile, it demonstrated an initial discharge specific capacity of 1461.2 mA h g−1 at 0.1 C and an ultra-low-capacity attenuation of 0.056 % per cycle of 800 cycles at 1 C. In sum, this study may provide a novel strategy for the effective design of GPE toward the high performance lithium-sulfur batteries.

A Review of Structure Engineering of Strain-Tolerant Architectures for Stretchable Electronics.

Stretchable electronics possess significant advantages over their conventional rigid counterparts and boost game-changing applications such as bioelectronics, flexible displays, wearable health monitors, etc. It is, nevertheless, a formidable task to impart stretchability to brittle electronic materials such as silicon. This review provides a concise but critical discussion of the prevailing structural engineering strategies for achieving strain-tolerant electronic devices. Not only the more commonly discussed lateral designs of structures such as island-bridge, wavy structures, fractals, and kirigami, but also the less discussed vertical architectures such as strain isolation and elastoplastic principle are reviewed. Future opportunities are envisaged at the end of the paper.

Structural Engineering-Enabled Joule Heating Effect Cooperated with Capillary Effect Toward Fast Spreading of Droplets for High-Flux Separation of Viscous Emulsion.

Viscous emulsions with poor fluidity and high adhesion are extremely difficult to separate. Herein, high-flux separation of viscous emulsions is realized by developing structural engineered collagen fibers (CFs)-based composite membrane that featured 3D conductive hierarchical fiber structure with the spaced carbon nanofibers (CNFs) and activated carbon (AC) serving as conductive network and competitive adsorption-based demulsifying sites, respectively. The as-designed membrane structure boosts fast spreading of emulsion droplets on membrane surface aided by the synergistic effect of joule heat in situ generated by the spaced CNFs and the capillary effect derived from CFs, which guarantees the full contact of viscous emulsions with the spaced AC for achieving ultra-efficient demulsifying. The permeation of resultant oily filtrate is accelerated by the capillary effect of hierarchically fibrous structured CFs to exhibit fast transport kinetics, therefore accomplishing high-flux separation. The structural engineered membrane achieves high-performance separation toward different viscous emulsions (55.4-123.7 mPa·s) with separation efficiency >99.9% and flux high up to 259 L m-2 h-1 . The investigations provide a novel structural engineering strategy for realizing high-performance separation of viscous emulsions.

A morphology control engineered strategy of Ti3C2Tx/sulfated cellulose nanofibril composite film towards high-performance flexible supercapacitor electrode

2D Ti3C2Tx MXene is an ideal material for fabricating supercapacitor electrodes due to its excellent physical-chemical properties. However, the inherent self-stacking, narrow interlayer spacing, and low general mechanical strength limit its application in flexible supercapacitors. Herein, facile structural engineering strategies by drying (vacuum drying, freeze drying, and spin drying) were proposed to fabricate 3D high-performance Ti3C2Tx/sulfated cellulose nanofibril (SCNF) self-supporting film supercapacitor electrodes. Compared with other composite films, the freeze-dried Ti3C2Tx/SCNF composite film exhibited a looser interlayer structure with more space which was conducive to charge storage and ion transport in the electrolyte. Therefore, the freeze-dried Ti3C2Tx/SCNF composite film exhibited a higher specific capacitance (220 F/g) compared to the vacuum-dried Ti3C2Tx/SCNF composite film (191 F/g) and the spin-dried Ti3C2Tx/SCNF composite film (211 F/g). After 5000 cycles, the capacitance retention rate of the freeze-dried Ti3C2Tx/SCNF film electrode was close to 100 %, showing excellent cycle performance. Meanwhile, the tensile strength of freeze-dried Ti3C2Tx/SCNF composite film (13.7 MPa) was much greater than that of the pure film (7.4 MPa). This work demonstrated a facile strategy for control of Ti3C2Tx/SCNF composite film interlayer structure by drying for fabricating well-designed structured flexible and free-standing supercapacitor electrodes.