Confinement Strategy Research Articles

Study of Behaviour of Short Concrete Columns Confined with PVC Tube under Uniaxial Load

An experimental investigation has been carried out to evaluate the effectiveness of Polyvinyl chloride (PVC) confinements in short plain circular concrete columns. The experimental part is conducted using different PVC tube diameters (110, 160, 220, and 250 mm) with two types of confinement strategies (fully and confined with the cut ends). The results are validated with unconfined samples (control samples). The test results showed that using external confinement of concrete columns by PVC tubes enhances the ultimate load capacity of the short columns. For fully confined samples, the enhancement ratio ranges between 5% and 8.3%, and from 4.16% to 15% for samples with cut ends. Furthermore, the confining of PVC pipes with the cut ends (CCC) has a more considerable effect on load capacity for all diameters except the ones with 250 mm, where the samples with full confinement (Cc) carried a bigger load than those with cutting ends. Finally, a numerical simulation of samples is carried out by the finite element (FE) model using the ABAQUS software. For all scenarios, the results of the numerical analysis showed considerable similarity to the experimental results, with R2 of 0.95 indicating the high linearity between the actual and simulated compressive strength values. Moreover, the FE induces fewer simulated errors with a relative error (RE) ranging from 0.16% to 6% for all scenarios.

Intrinsic ionic confinement dynamic engineering of ionomers with low dielectric-k, high healing and stretchability for electronic device reconfiguration

Ionomers are gaining much attention in the fields of soft robots, flexible electronics, and artificial intelligence. However, intrinsic dynamics modulation of ionomer molecules to achieve desirable properties is highly required and challenging due to a lack of understanding of the interactions between polymerics and ionic species. In this study, a novel ionic confinement engineering approach was employed, in which the composition of a copolymer, namely, PTAE-Fe, was adjusted to facilitate dynamic ionic crosslinking, which enables high stretchability (>10000 % elongation). The proportion of ionic functional groups in PTAE-Fe significantly enhanced the self-healing efficiency up to 95 %. The ionic confinement strategy also promotes electron momentum locking, resulting in a low dielectric-k property (Dk < 2.5), while a reduction in the heat release rate of 69.1 % makes the ionomer an excellent flame retardant material. In addition, a eutectic gallium-indium (EGaIn)-infused stretchable device and low Dk flexible ink were designed according to the ionic confinement strategy. The as-fabricated ionomer is expected to benefit a wide range of energy and storage technologies.

Incorporating Heteroatom-Doped Graphene in Electrolyte for High-Performance Lithium-Sulfur Batteries

Despite dominating the current commercial energy storage landscape, Li-ion batteries are fast approaching their theoretical limit. Meanwhile, Lithium Sulphur (Li-S) batteries, owing to their ultrahigh theoretical energy density of about 2600 Whkg-1, low-cost, Earth-abundant, and environmentally friendly sulfur (S) cathode, are seen as promising replacements to realize energy densities beyond 500 Whkg-1. Despite these advantages, the large-scale implementation of Li-S technology has been stymied due to several issues, one of the most deleterious of them is the dissolution and shuttling of polysulfide intermediates during cycling resulting in severe self-discharge, lowered S utilization and coulombic efficiency. Over the past decades, substantial amount of research towards mitigating ‘polysulfide shuttling’ shuttling has been focused on cathodic modification strategies such as infiltration of S in porous carbon, metal oxide or conducting polymer scaffold matrix which retard the mobility and loss of active material. However, such simple confinement strategies have been shown to be lacking over long cycling due to the relatively weak intermolecular interactions between the host and polysulfide molecules. An effective solution comes in the form of engineering ‘sulfiphilic’ materials that adsorb polysulfide species. For example, surface modification of cathodes with rGO and functionalized carbon species have shown success in reducing the redox shuttling. However, these approaches require elaborate preparation and hence, are limited in their practical usage.To overcome this, we propose a facile approach to improve cell performance via incorporation of functionalized graphenic species in the Li-S electrolyte. In this work, we have probed the impact of using tailored single-layer, heteroatom-doped graphene as electrolyte additives. We have studied the impact of their morphology and functionalization on the electrochemical performance of the cell. Results show a marked improvement in the discharge capacity and a high capacity retention of 84% over 105 cycles at 0.2 C cycling rate. The GCD cycle analysis showed an improvement in first cycle discharge plateau suggesting improved S utilization which was further substantiated by extensive postmortem analysis and polysulfide adsorption testing. Further, the electrolyte-modified cells showed an impressive three-fold and two-fold improvement in capacity at 1C and 2C cycling rates, respectively.These results demonstrated that tailored heteroatom-doped graphene in the form of electrolyte additive is an effective strategy to improve electrochemical performance via enhanced polysulfide encapsulation, cell conductivity and anode stabilization. Finally, we will present the effect of heteroatom-doped graphenic species on mitigation of polysulfide shuttling and cell performance when they are incorporated in the gel electrolyte system.

(Digital Presentation) Cr-Doped High-Efficiency Broadband Near-Infrared Luminescent Materials

Cr-doped high efficiency broadband near-infrared (NIR) luminescent materials have attracted huge research interests in food analysis, plant growth, night vision and biomedical imaging owing to their invisibility and characteristic absorptions by certain molecules. Transition metal element Cr3+ with [Ar]3d3 configuration serves as an ideal activator for broadband NIR emission due to the broad absorption bands in the blue and orange-red spectral regions, among which the blue band matches well with the commercial blue LED chips. Besides, the NIR emissions of Cr3+-doped phosphors are greatly affected by the crystal field strength of the matrix lattice. In the weak crystal field, the spin-allowed 4T2 → 4A2 transitions give out the preferable wide-band emissions. However, the NIR luminescence of Cr3+ encounters several problems aiming at further developments. The materials with main emission peak beyond 800 nm are lacking. Meanwhile, the quantum efficiency and thermal luminescence stability need improvement to fulfil the application requirements. Also, it remains a challenge to predict the Cr3+ luminescence by crystal-field theory theoretically. To address those problems, we introduce several high-efficiency Cr3+ doped materials with distinct crystal structures, such as SrGa12O19:Cr3+, LaMgGa11O19:Cr3+, LiInGe2O6:Cr3+, and Sr2ScSbO6:Cr3+, together with the structural confinement strategy to improve the NIR performance. The further research topic including the local structure is also discussed.

Double‐Network Confined Supramolecular Phosphorescence Light‐Harvesting Boosting Photocatalysis

AbstractA double‐network phosphorescence light‐harvesting (PLH) supramolecular system is successfully fabricated based on synergistic confinement strategy. First, the bicationic vinyl bromophenyl pyridine derivative (G) is encapsulated by cucurbit[8]uril (CB[8]), inducing weak phosphorescence emission at 510 nm. Subsequently, the G/CB[8] is confined by in situ copolymerization with acrylamide, displaying enhanced phosphorescence emission, then coassembled with hyaluronic acid modified hydroxypropyl‐β‐cyclodextrin (HA‐HP‐β‐CD) to form double‐network hydrogel, further improving phosphorescence lifetime from 442 µs upto 5.17 ms. Benefitting from the confinement of double‐network of supramolecular system, the doped Eosin Y (EY) as acceptor can be photosensitized by the phosphorescence of G/CB[8] leading to delayed fluorescence emission of EY with long lifetime as 36.4 µs. As compared with EY alone, by the synergistic effect of the confined microenvironment and long lifetime photosensitizer, the PLH system is successfully applied in cross‐coupling reaction and exhibits enhanced activity, providing a new strategy for the application of phosphorescence energy transfer boosting photocatalysis.

Self-healing of surface defects on Zn electrode for stable aqueous zinc-ion batteries via manipulating the electrode/electrolyte interphases

The reversibility and stability of aqueous zinc-ion batteries are largely limited by inevitable parasitic reactions at the interface and uncontrollable dendrite growth. Inspired by self-healing smart electronic materials, we propose a confinement strategy with gelatin, an amphiphilic macromolecule, as additive to regulate the deposition behavior of Zn ions and utilize the dendrites to fill the surface defects formed by inevitable interfacial parasitic reactions. Absorbed gelatin molecules impede H2O reaching Zn electrode surface to enhance the anticorrosion behavior and adjust the local pH value, which is a “smart” way to stabilize the electrode/electrolyte interphase. Additionally, the confined effect of absorbed gelatin molecules on Zn2+ and “electrostatic shield” formed from positive charged –CN3H5+ suppress 2D diffusion and accumulation of Zn2+, guiding Zn continuously depositing inside the defect during electrochemical cycling, then self-healing of electrode surface defects is achieved. Under the synergetic effects of these merits, Zn electrode demonstrates almost unchangeable surface after soaking in the electrolyte for 10 days, and stably cycle more than 1100 h at 0.5 mA cm−2 and 1300 h at 3.0 mA cm−2 in symmetric cell. In addition, the full batteries using the base electrolyte with 0.5 and 1.0 g/L gelatin can stably cycle for 3000 cycles.

Competitive Coordination-Pairing between Ru Clusters and Single-Atoms for Efficient Hydrogen Evolution Reaction in Alkaline Seawater.

The coordination environment of Ru centers determines their catalytic performance, however, much less attention is focused on cluster-induced charge transfer in a Ru single-atom system. Herein, by density functional theory (DFT) calculations, a competitive coordination-pairing between Ru clusters (RuRu bond) and single-atoms (RuO bond) is revealed leading to the charge redistribution between Ru and O atoms in ZnFe2 O4 units which share more free electrons to participate in the hydrogen desorption process, optimizing the proton adsorption and hydrogen desorption. Thus, a clicking confinement strategy for building a competitive coordination-pairing between Ru clusters and single-atoms anchored on ZnFe2 Ox nanosheets over carbon via RuO ligand (Ru1, n -ZnFe2 Ox -C) is proposed. Benefiting from the optimized coordination effect and the electronic synergy between Ru clusters and single-atoms, such a catalyst demonstrates the excellent activity and excellent stability in alkaline and seawater media, which has exceptional hydrogen evolution reactionactivity with overpotentials as low as 10.1 and 15.9mV to reach the current density of 10mA cm-2 in alkaline and seawater media, respectively, higher than that of commercial Pt/C catalysts as a benchmark. Furthermore, it owns remarkably outstanding mass activity, approximately 2 and 8 times higher than that of Pt catalysts in alkaline and seawater media, respectively.

Strategy to Construct High Thermal‐Stability Narrow‐Band Green‐Emitting Si‐CDs@MAs Phosphor for Wide‐Color‐Gamut Backlight Displays

AbstractDeveloping innovative narrow‐band green‐emitting phosphors featuring low thermal quenching and eco‐friendliness for white light‐emitting diode (WLED) backlights is a pivotal challenge. Benefitting from narrowband and low toxicity of green‐emitting silanized carbon dots (Si‐CDs), an efficient confinement and protection strategy through embedding Si‐CDs in mesoporous aluminas (MAs) is proposed to construct MAs and Si‐CDs composites (Si‐CDs@MAs) with superior luminescence properties. Si‐CDs@MAs phosphor exhibits green emission at 526 nm with narrow full width at half maximum of 51 nm, zero‐thermal quenching even up to 423 K (104.1%@423 K of the emission peak intensity at 298 K), and the internal quantum efficiency of 64.46%. Compared with broad‐band yellow‐emitting solid‐state Si‐CDs (S‐Si‐CDs), the thermal stability, photostability, and water stability of Si‐CDs@MAs phosphor are remarkably improved due to surface protection. The WLED backlight is fabricated with optimized Si‐CDs@MAs phosphor, which shows high luminous efficacy of 117.43 lm W−1and wide color gamut (107% NTSC). Furthermore, this work provides the design principles of realizing stable narrow‐band solid‐state fluorescence carbon dots, suggesting its great potential for wide‐color‐gamut display application.

Centimeter‐Scale Growth of Unidirectional CsCu2I3 Wire Arrays for High Performance UV Photodetectors

AbstractLead‐free CsCu2I3 has attracted tremendous research interests for photonics and photoelectronics due to their nontoxicity, unique electronic structure, and excellent stability. However, it is still challenging to achieve large‐scale ordered arrays of CsCu2I3 micro/nanowires, which limits their functional applications in integrated optoelectronic devices. Herein, unidirectional CsCu2I3 wire arrays are achieved in centimeter scale through a modified microchannel‐assisted spatial confinement strategy, which can confine the precursor solution into the pre‐fabricated microchannel arrays in large area and control its evaporation. The microstructure characterizations reveal that the orthorhombic CsCu2I3 wires are grown along the c‐axis with high crystallinity. The control experiments and theoretical studies indicate that the initial CsCu2I3 nucleation at the front of the solution in the channels and the stable solute supply maintained by the movement of the coverslip determine the growth of the wires. The photodetectors based on the CsCu2I3 wires show a high responsivity (80 mA W−1 at 365 nm; 1.29 A W−1 at 330 nm) and fast response speed (trise/tdecay = 640 µs/7.1 ms). Furthermore, these CsCu2I3 wire arrays exhibit great potential in future flexible electronic and UV imaging applications. This work opens a new way to grow well‐aligned copper‐based halides nano/microwire arrays for the integrated optoelectronics applications.

Efficient degradation of Health-threatening organic pollutants in water by atomically dispersed Cobalt-Activated peroxymonosulfate

Degrading health-threatening organic pollutants (HTOPs) in water systems through advanced oxidation processes (AOPs) is an effective way to treat environmental wastewater; however, such processes require advanced catalysts. This study combined complexation effects and structural confinement strategies to rapidly prepare Co2+-isolated metal–organic framework polymers and utilized a thermal treatment process to achieve the efficient anchoring of atom-dispersed Co in a boron–carbon-nitrogen matrix (denoted as SACoN/BCN), which can improve the utilization of Co catalytic sites. SACoN/BCN effectively activated peroxymonosulfate (PMS), with the ratio and mineralization rate of sulfamethazine (SMT) removed by degradation within 40 min reached 95.2 % and 70.0 %, respectively. Radical inhibition experiments and electron paramagnetic resonance (EPR) tests showed that 1O2 generated from SACoN/BCN-activated PMS was the key reactive oxygen species that promoted HTOP degradation. Density functional theory calculations revealed that, following the introduction of electron-deficient B heteroatoms, electrons in PMS will be injected into SACoN/BCN, thereby realizing strong adsorption and further activation of PMS. The cytotoxicity of SACoN/BCN is almost negligible because of the chemical bonding (or entrapment) of Co atoms in the inorganic boron–carbon-nitrogen matrix, thereby preventing Co from forming mobile CoII ions in the aqueous system. This research provides information for advanced catalysts for the removal of HTOPs and experimental and theoretical inspiration for the preparation of single-atom catalysts for advanced oxidation processes and the mechanism of PMS activation.

Spatial Confinement Strategy for Micelle-Size-Mediated Modulation of Mesopores in Hierarchical Porous Carbon Nanosheets with an Efficient Capacitive Response.

Commercial supercapacitors using available carbon products have long been criticized for the under-utilization of their prominent specific surface area (SSA). In terms of carbonaceous electrode optimization, excessive improvement in SSA observed in the gaseous atmosphere might have little effect on the final performance because cracked/inaccessible pore alleys considerably block the direct electrolyte ion transport in a practical electrochemical environment. Herein, mesopore-adjustable hierarchically porous carbon nanosheets are fabricated based on a micelle-size-mediated spatial confinement strategy. In this strategy, hydrophobic trimethylbenzene in different volumes of the solvent can mediate the interfacial assembly with a carbon precursor and porogen segment through π-π bonding and van der Waals interaction to yield micelles with good dispersity and the diameter varying from 119 to 30 nm. With an increasing solvent volume, the corresponding diffusion coefficient (3.1-14.3 m2 s-1) of as-obtained smaller micelles increases, which makes adjacent micelles gather rapidly and then grow along the radial direction of oligomer aggregates to eventually form mesopores on hierarchically porous carbon nanosheets (MNC150-4.5). Thanks to the pore-expansion effect of trimethylbenzene, the mesoporous volume can be adjusted from 28.8 to 40.0%. Mesopores on hierarchically porous carbon nanosheets endow MNC150-4.5 with an enhanced electrochemically active surface area of 819.5 m2 g-1, which gives rise to quick electrolyte accessibility and a correspondingly immediate capacitive response of 338 F g-1 at 0.5 A g-1 in a three-electrode system. Electrolyte transport through pathways within MNC150-4.5 ultimately enables the symmetric cell to deliver a high energy output of 50.4 Wh kg-1 at 625 W kg-1 in a 14 m LiOTF electrolyte and 95% capacitance retention after 100,000 cycles, which show its superior electrochemical performance over representative carbon-based supercapacitors with aqueous electrolytes in recent literature.

Single‐Molecule Confinement Induced Intrinsic Multi‐Electron Redox‐Activity to Enhance Supercapacitor Performance

Aggregation of polyoxometalates (POM) is largely responsible for the reduced performance of POM‐based energy‐storage systems. To address this challenge, here, the precise confinement of single Keggin‐type POM molecule in a porous carbon (PC) of unimodal super‐micropore (micro‐PC) is realized. Such precise single‐molecule confinement enables sufficient activity center exposure and maximum electron‐transfer from micro‐PC to POM, which well stabilizes the electron‐accepting molecules and thoroughly activates its inherent multi‐electron redox‐activity. In particular, the redox‐activities and electron‐accepting properties of the confined POM molecule are revealed to be super‐micropore pore size‐dependent by experiment and spectroscopy as well as theoretical calculation. Meanwhile, the molecularly dispersed POM molecules confined steadily in the “cage” of micro‐PC exhibit unprecedented large‐negative‐potential stability and multiple‐peak redox‐activity at an ultra‐low loading of ~11.4 wt%. As a result, the fabricated solid‐state supercapacitor achieves a remarkable areal capacitance, ultrahigh energy and power density of 443 mF cm−2, 0.12 mWh cm−2 and 21.1 mW cm−2, respectively. This work establishes a novel strategy for the precise confinement of single POM molecule, providing a versatile approach to inducing the intrinsic activity of POMs for advanced energy‐storage systems.

Suspended water droplet confined laser shock processing at elevated temperatures

The temperature-assisted laser shock process has application prospects in various manufacturing fields such as forming and surface strengthening. However, the large-scale application of this process is limited by the instability and failure of confinement medium at high temperatures (>300 °C). To address this problem, this paper proposes a novel laser shock strategy based on the Leidenfrost effect, wherein suspended droplets are used as the confinement medium. The dynamic behaviors of the droplets during laser shock process were studied. The focusing enhancement effect of the droplets was comprehensively explored. By combining the dynamic behaviors and focusing enhancement effect of the droplets, a theoretical model of the laser shock pressure under droplet confinement was established. Finally, a typical application of the droplet-confined laser shock process in the fields of forming and strengthening was demonstrated to verify its effectiveness and feasibility at high temperatures. The proposed process provides a flexible, convenient, and green plasma confinement strategy that allows stable operation of laser shock at high temperatures. Moreover, the droplet confinement strategy broadens the application prospects of laser shock, and provides a technical support for enabling enhanced ductility and dynamic strain aging of alloys at high temperatures.

Boosting the deep oxidation of propane over zeolite encapsulated Rh-Mn bimetallic nanoclusters: Elucidating the role of confinement and synergy effects

Metal nanocluster catalysts with superior activity and stability are urgently needed in the deep oxidation of volatile organic compounds (VOCs). In this study, a novel silicalite-1 zeolite confined rhodium-manganese bimetallic nano-cluster (1.6 nm) catalyst (Rh-MnOx@S-1) was designed and prepared by a simple one-pot method using a dual confinement strategy (shell confinement and strong metal-metal oxide interaction) and applied in the deep oxidation of propane. The results revealed that the temperature at 90% conversion (T90) for propane over Rh-MnOx@S-1 was as low as 264 °C, which is evidently higher than the conventional supported (Rh-MnOx/S-1, T90 = 369 °C) and the MnOx-free (Rh@S-1, T90 = 285 °C) catalysts. Moreover, the turnover frequency (TOF) value of Rh-MnOx@S-1 at 220 °C was up to 16 × 10−3 s−1, which is approximately 5–6 times higher than those of comparable catalysts. Most importantly, Rh-MnOx@S-1 also exhibited excellent high temperature thermal stability, water resistance and recyclability, which can be attributed to the confinement effect of the zeolite shell and the synergistic electronic-structure interaction between the Rh and MnOx species. The in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) analysis indicates that the C3H8 deep oxidation mechanism over Rh-MnOx@S-1 catalyst follows the Mars-van Krevelen (MvK) mechanism, i.e., the adsorbed C3H8 species reacted with the activated oxygen species from Rh-MnOx interfaces. The dual confinement strategy developed in this study provides a new way to design high performance catalysts for the removal of VOCs under harsh reaction conditions.

Scalable and Demography-Agnostic Confinement Strategies for COVID-19 Pandemic with Game Theory and Graph Algorithms

In the past, epidemics such as AIDS, measles, SARS, H1N1 influenza, and tuberculosis caused the death of millions of people around the world. In response, intensive research is evolving to design efficient drugs and vaccines. However, studies warn that new pandemics such as Coronavirus (COVID-19), variants, and even deadly pandemics can emerge in the future. The existing epidemic confinement approaches rely on a large amount of available data to determine policies. Such dependencies could cause an irreversible effect before proper strategies are developed. Furthermore, the existing approaches follow a one-size-fits-all control technique, which might not be effective. To overcome this, in this work, we develop a game-theory-inspired approach that considers societal and economic impacts and formulates epidemic control as a non-zero-sum game. Further, the proposed approach considers the demographic information that provides a tailored solution to each demography. We explore different strategies, including masking, social distancing, contact tracing, quarantining, partial-, and full-lockdowns and their combinations, and present demography-aware optimal solutions to confine a pandemic with minimal history information and optimal impact on the economy. To facilitate scalability, we propose a novel graph learning approach, which learns from the previously obtained COVID-19 game outputs and mobility rates of one state (region) depending on the other to produce an optimal solution. Our optimal solution is strategized to restrict the mobility between states based on the impact they are causing on COVID-19 spread. We aim to control the COVID-19 spread by more than 50% and model a dynamic solution that can be applied to different strains of COVID-19. Real-world demographic conditions specific to each state are created, and an optimal strategic solution is obtained to reduce the infection rate in each state by more than 50%.

Polymer nanoreactor mediated controllable synthesis of flexible semiconductor quantum dot nanofiber films

Semiconductor quantum dots (SQDs) find widespread applications, but manufacturing highly dispersed SQDs in films is a challenge. Herein, we report a polymer nanoreactor-mediated confinement strategy for the controllable synthesis of high-density and monodisperse ZrO2 SQDs nanofiber films. In detail, polyvinylpyrrolidone (PVP) is applied to confine zirconium acetate colloids through molecule steric hindrance effect in a water-based sol, which is then assembled into nanofibers by electrospinning. Afterwards, the PVP provides a fencelike spatial confinement in the nanofiber during calcining. With this dual domain confinement, high-loading (84.5 wt%) and monodisperse ZrO2 SQDs (∼4.47 nm) nanofiber film is prepared. The film exhibits superior flexibility and a high surface area of 1245 m2•g−1, as well as tunable light absorption from ultraviolet to visible-light, which breaks through the bottleneck of wide bandgap ZrO2 that can only be excited for photocatalysis under ultraviolet irradiation. This strategy opens new possibilities in large-scale manufacturing of high-quality SQD films for a series of potential applications.

Space-confined fabrication of hydrophobic magnetic carbon nanofibers for lightweight and enhanced microwave absorption

Advanced microwave absorbers (MAs) containing magnetic particles and carbon nanofibers (CNFs) have raised widespread attention in the rapid popularization of electronic communication equipment. However, it is quite challenging to control the growth of magnetic particles in CNFs to improve electromagnetic waves (EMWs) loss and attenuation. Herein, a novel space-confined strategy was adopted to develop Co/CoO/SiO2/CNFs, in which Co/CoO nanoparticles (NPs) with single domain size and dispersed distribution could achieve enhanced magnetic loss and dielectric loss. The introduction of nano-SiO2 in the system could enhance the dielectric confinement effect of the nanofibers (NFs), while an interfacial confinement network could also be constructed to realize the refinement of Co/CoO NPs, enhance the electromagnetic (EM) loss, and ultimately ameliorate the microwave absorption performance of as-obtained NFs. When the additive amount of nano-SiO2 in the spinning solution was 1.0 mg, the as-prepared Co/CoO/SiO2/CNFs reached the optimal reflection loss (RL) of −52.9 dB at 12.64 GHz with a thickness of 2.5 mm, and the effective bandwidth (EBW) reached 5.67 GHz (10.46–16.13 GHz). Furthermore, the excellent hydrophobic properties of the CNFs endow them with potential self-cleaning function. The confinement strategy proposed in this work lays a foundation for the design of low-filling ratio and high-performance CNFs-based microwave absorbers, and presents a general approach for the synthesis of one-dimensional composite materials with controllable structures.

Synergy of staggered stacking confinement and microporous defect fixation for high-density atomic FeII-N4 oxygen reduction active sites

The development of high-performance nonprecious metal catalysts (NPMCs) to supersede Pt-based catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells is highly desirable but remains challenging. In this paper, we present a pyrolysis strategy for spatial confinement and active-site fixation using iron phthalocyanine (FePc), phthalocyanine (Pc) and Zn salts as precursors. In the obtained carbon-based NPMC with a hierarchically porous nanostructure of thin-layered carbon nanosheets, nearly 100% of the total Fe species are FeII-N4 active sites. In contrast, pyrolyzing FePc alone forms Fe-based nanoparticles embedded in amorphous carbon with only 5.9% FeII-N4 active sites. Both experimental characterization and density functional theory calculations reveal that spatial confinement through the staggered π–π stacking of Pc macrocycles effectively prevents the demetallation of Fe atoms and the formation of Fe-based nanoparticles via aggregation. Furthermore, Zn-induced microporous defects allow the fixation of FeII-N4 active sites. The synergistic effect of staggered stacking confinement and microporous defect fixation results in a high density of atomic FeII-N4 active sites that can enhance the ORR. The optimal FeII-N4-C electrocatalyst outperforms a commercial Pt/C catalyst in terms of half-wave potential, methanol tolerance, and long-term stability in alkaline media. This modulation strategy can greatly advance efforts to develop high-performance NPMCs.

Sorption-enhanced glycerol steam reforming over hierarchical hollow Ni-CaO-Ca12Al14O33 bi-functional catalyst derived from hydrotalcite-like compounds

Hydrogen production with in situ CO2 capture by the sorption-enhanced steam reforming (SESR) technology is a promising concept to reduce anthropogenic CO2 emissions. However, its practical applicability is limited by rapid, sintering-induced cyclic performance decay at high reaction rate and decarbonation temperatures. Here, we design a highly stable bi-functional catalyst with a surface spatial confinement strategy. The bi-functional catalyst has a hierarchical hollow microsphere structure, in which the shell is composed of layered metal oxides. The sintering resistance of Ca and Ni species is found to arise from the surface spatial confinement effect in which the aggregation and migration of Ni and CaO particles are suppressed by the layers. High stability for SESRG reaction with only 35% loss of sorption enhancement effect is observed after 20 cycles of repeated SESEG-decarbonation, during which H2 purity is maintained at 99%. The result shed light on the design of the stable bi-functional catalysts in the SESR reaction.

Precisely controlled Pd nanoclusters confined in porous organic cages for size-dependent catalytic hydrogenation

The precise size-controlled formation of palladium (Pd) nanoclusters with size-dependent catalytic activity was achieved through a cage confinement strategy. In this process, three typical porous organic cages (POCs) with gradually decreasing cavity diameters were used as encapsulation carriers. A series of Pd nanoclusters-based catalysts with corresponding Pd cluster sizes of 0.73, 0.68, and 0.43 nm, respectively, was effectively fabricated by confining the Pd nanoclusters in size-adjustable cavities. The obtained Pd@POCs nanocatalysts exhibited excellent crystallinity, high stability, fascinating morphological characteristics, and superior catalytic hydrogenation performance. Especially, the size-dependent catalytic performance toward hydrogenation of 4-nitrophenol and semi-hydrogenation of alkyne compounds was demonstrated by experimental results and theoretical calculations. The prepared Pd(1.71%)@FT-RCC3 catalyst with the smallest Pd cluster size of about 0.43 nm showed the best catalytic performance. This study promotes a better understanding of size-dependent catalysis and provides a new strategy for the fabrication of customized nanocatalysts.