Hollow multishelled structure (HoMS), a promising and complex multifunctional structural system, features at least two shells that are separated by internal voids. The unique structure endows it with numerous advantages including low density, high loading capacity, large specific surface area, facilitated mass transport, and multiple spatial confinement effect. In the past twenty years, benefiting from the booming development of synthesis methods, various HoMS materials have been prepared and show promising applications in diverse areas. HoMS has gradually developed into one of the frontiers of materials and chemistry science, attracting extensive attention from many scientists. In this review, the synthesis chemistry of HoMS and its diverse compositions and structures are systematically introduced, the unique properties of “temporal-spatial ordering” and “dynamic smart behavior” of HoMS are highlighted, and the applications of HoMS in energy storage, catalysis, electromagnetic wave absorption, drug delivery and sensor are fully shown. We hope to reveal the intrinsic relationship between the precise synthesis of HoMS and its tunable composition and structural features. We hope the exploration of frontier scientific concepts and phenomena in HoMS research can provide inspiration for its future direction, and promote the flourishing progress of HoMS.
Multi-fountional hollow structures have emerged as promising platforms for intelligent drug delivery due to their unique properties, such as high loading capacities and programmed drug release. In particular, hollow multishell structures (HoMSs) with multilevel shell and space can regulate the molecular-level interaction between drugs and materials, so as to achieve the temporal-spatial order and sequential release of drugs. The anisotropic hollow structures can control the drug diffusion process by inducing the macroscopic interface flow through autonomous movement, realizing the targeted drug transport and release. In this paper, a key focus will be HoMSs with their temporal-ordered architectures and anisotropic hollow carriers with directional movement. Their synthesis mechanisms, structure-property relationships, smartly programmed drug delivery and biomedical applications will be discussed, providing insights into designing next-generation intelligent drug carriers.
Hollow multi-shelled structures (HoMS) have made significant strides across a wide spectrum of scientific investigations since the inception of the sequential templating approach (STA) in 2009, revealing distinctive temporal-spatial ordering properties. The recent establishment of a mathematical model for STA has not only demystified the formation of concentration waves within the STA process but also extended its relevance to gentler solution-based systems, thereby broadening the HoMS landscape. Herein, focusing on photoelectric applications, this review first summarizes the unique temporal-spatial ordering features of HoMS. Subsequentially, the greatly enhanced properties of light capture and absorption, exciton separation, and transfer are deeply discussed. Finally, we conclude with a perspective on the potential challenges and burgeoning opportunities that lie ahead in the advancement of HoMS development.
Due to its highest theoretical capacity and its lowest redox potential, lithium (Li) metal has been considered as the ultimate anode choice for high-energy-density rechargeable batteries. However, its commercialization is severely hindered by its poor cyclic stability and safety issues. Diverse material structure design concepts have been raised to address these failure models, wherein, hollow structure has shown great power in solving the challenges. Especially, a hollow multishelled structure (HoMS) featured with two or more shells has been proved to be more efficient to improve Li metal anode than their single-shelled counterparts. Herein, this up-to-date review summarizes the recent progress of the application of HoMS in Li metal anode, including their adoption as Li metal host, artificial solid electrolyte interphase film, electrolyte additive, solid state electrolyte, etc. HoMS offers unique advantages, such as suppressing Li dendrite growth, stabilizing electrode-electrolyte interface, and improving overall battery performance. Future research directions are outlined, emphasizing the need for multifunctional integrated smart HoMS design and large-scale fabrication of HoMS through low-cost accurate method to further advance the commercialization of Li metal batteries.
Electrochemical water splitting using renewable energy sources has been recognized as a sustainable way to produce hydrogen energy due to the characteristics of low-carbon and no pollution. However, the slow hydrogen/oxygen evolution reactions (HER/OER) seriously hinder the practical application of large-scale water splitting. In this paper, the 0D Ni/Co-based hollow material is discussed in detail because of adjustable morphology, low mass density and abundant active sites, which provides an effective solution for improving the HER/OER reaction kinetics. The synthesis methods of hollow materials, such as hard template, soft template and self-template are introduced. Afterward, catalysts with different structural designs of hollow structures are reviewed, including hollow single-shelled structure, hollow core-shelled structure, hollow double-shelled structure and hollow multi-shelled structure (HoMS) catalysts. Wherein, the research progress of the 0D Ni/Co-based HoMS electrocatalysts in recent years and their prominent performances in water splitting are highlighted. Finally, the challenges and development prospects of designing Ni/Co-based HoMS catalysts in water splitting in the future are discussed.
The surface microstructure can be influenced by surface environment, weak adsorption, and bonding interactions, leading to the changes of surface electronic states and the configuration of active sites, which affects the mass-energy transfer pathway. The interaction between multiple species on the surface of light-absorbing materials directly impacts the performance of photothermal catalytic process. Based on this, we present the latest perspectives on photothermal CO2 capture and conversion, which focus on (1) the mechanism of functional group-assisted photothermal process, (2) the effects of functional group species, configurations, spatial positions, and surface interactions on photothermal catalytic reactions, and (3) the interaction between substrates and functional groups. Finally, an insightful perspective is drawn in the last section.
Single-atom catalysts (SACs) have garnered extensive attention in the field of catalysis due to their exceptional inherent reaction activity, optimal utilization of metal atoms, etc. Controlled synthesis plays a crucial role in elucidating the structure-activity relationship of SACs. This paper reviews various synthetic strategies for SACs, encompassing defect engineering, metal-organic frameworks (MOFs) pyrolysis, and ion exchange. With specific examples, the significance of constructing catalysts at the atomic level is discussed, aiming to comprehensively understand the synthetic strategies of SACs. Finally, it addresses the challenges and prospects associated with controlled synthesis techniques for SACs as well as their future applications.
CeO2 with excellent oxygen storage-exchange capacity and NiO with excellent surface activity were used to construct a heterogeneous NiO-CeO2−δ hollow multi-shelled structure (HoMS) by spray drying. It turned out that as the proportion of CeO2 increases, the overpotential and Tafel slope of NiO-CeO2−δ HoMSs first decreased and then increased. This is mainly because the construction of the NiO-CeO2−δ HoMSs not only increases the specific surface area, but also introduces oxygen vacancy defects, thus improving the interface charge transfer capability of the materials and further improving the oxygen evolution reaction (OER) performance. However, the increase of the calcination temperature will induce the decay of the OER performance of NiO-CeO2−δ HoMSs, which is mainly due to the decrease of the specific surface area, the reduction of oxygen vacancy defects, and the weakening of interface charge transfer capability. Furthermore, a series of heterogeneous composite HoMSs, such as Ni/Co, Mo/Ni, Al/Ni and Fe/Ni oxides was successfully constructed by spray drying, which enriched the diversity of HoMSs.
Photocatalytic CO2 reduction driven by solar light is a green approach that can decrease the greenhouse effect induced by high CO2 concentration in the atmosphere and generate carbon-based chemicals/fuels as well. In this paper, non-metal co-catalysts ZnO/ZnS type-II hetero-junction nanoparticles with a rough surface were prepared through a hydrothermal process. When used as a photocatalyst for CO2 reduction, the optimal one showed good cycle stability and a higher yield rate of 27.8 µmol·g−1·h−1 for CO2 conversion into CO. The outstanding catalytic activity originated from i) the rich interfaces between ZnO and ZnS in the nanoscale could significantly reduce the delivery path of carriers and improve the utilization efficiency of photo-excited electron/hole pairs and ii) enriched surface oxygen defects could supply much more reaction active sites for CO2 adsorption.
Hydrogen energy stands out as one of the most promising alternative energy sources due to its cleanliness and renewability. Electrocatalytic water splitting offers a sustainable pathway for hydrogen production. However, the kinetic rate of the hydrogen evolution reaction (HER) is sluggish, emphasizing the critical need for stable and highly active electrocatalysts to facilitate HER and enhance reaction efficiency. Transition metal-based catalysts have garnered attention for their favorable catalytic activity in electrochemical hydrogen evolution in alkaline electrolytes. In this investigation, flower-like nanorods of MoS2 were directly synthesized in situ on a nickel foam substrate, followed by the formation of MoP/MoS2-nickel foam (NF) heterostructures through high-temperature phosphating in a tube furnace environment. The findings reveal that MoP/MoS2-NF-450 exhibits outstanding electrocatalytic performance in an alkaline milieu, demonstrating a low overpotential (90 mV) and remarkable durability at a current density of 10 mA/cm2. Comprehensive analysis indicates that the introduction of phosphorus (P) atoms enhances the synergistic effect with MoS2, while the distinctive flower-like nanorod structure of MoS2 exposes more active sites. Moreover, the interface between the MoP/MoS2 heterostructure and NF facilitates electron transfer during hydrogen evolution, thereby enhancing electrocatalytic performance. The design and synthesis of such catalysts offer a valuable approach for the development of high-performance hydrogen evolution electrocatalysts.
The abuse of tetracycline antibiotics has caused great harm to human health and ecosystems. Developing inexpensive, convenient and sensitive methods for the detection of tetracycline antibiotics is highly desirable. Herein, based on the H4ddp ligand [H4ddp=3-(3,5-dicarboxyphenyl)pyridine-2,6-dicarboxylic acid], two novel zinc-based metal-organic frameworks (MOFs) {[Zn3(ddp)2(H2O)4]·3H2O} n (Zn1-ddp) and {[Zn3(ddp)2(H2O)4]·3H2O} n (Zn2-ddp) were successfully designed by delicate structural regulation. Both Zn1-ddp and Zn2-ddp exhibited excellent water and chemical stability and showed excellent fluorescence quenching performance for tetracycline antibiotics. Notably, the more advanced framework structure and better fluorescent performance make Zn1-ddp more sensitive than Zn2-ddp in fluorescent detection with a detection limit of 0.29 µmol/L for tetracycline (TC), 0.09 µmol/L for doxycycline (DOX), 0.10 µmol/L for minocycline (MIN) and metacycline (MEL), 0.19 µmol/L for chlortetracycline (CTC), and 0.67 µmol/L for oxytetracycline (OTC) among tetracycline antibiotics. The fluorescence quenching mechanism of Zn1-ddp and Zn2-ddp for tetracycline antibiotics detection was deeply investigated. The reasons for the superior detection performance of Zn1-ddp over Zn2-ddp were also analyzed in depth through Fourier transform infrared spectrophotometry (FTIR), X-ray photoelectron spectroscopy (XPS) analysis and framework structure analysis. The developed method opens up a new perspective for antibiotics detection based on zinc-based MOFs.
Free-standing membranes show extraordinary promise in energy storage applications, however are usually limited by low capacity and poor rate capabilities. Herein, we assembled a series of free-standing MnO2/GO composite membranes with ZIF67 particles embedded between two-dimensional (2D) layers. The particle size of ZIF67 can be adjusted to achieve tunable interlayer spacing. The lithium storage performance of the as-obtained membranes with different interlayer spaces was systematically studied. The MnO2/GO composite membrane embedded with ZIF67 particles with an average diameter of 30 nm (denoted as MnO2/nZIF67/GO) delivers a good long cycling performance, and it retains a capacity of 340.7 mA·h·g−1 after 400 cycles at 0.05 A/g. The MnO2/GO composite membrane embedded with ZIF67 particles with an average diameter of 500 nm (denoted as MnO2/mZIF67/GO) exhibits good rate performance. Regardless of the size of the ZIF67 particles, the performance of the membrane containing ZIF67 is significantly better than that of the membrane without ZIF67, indicating that the ZIF67 particles can enhance the lithium storage performance of the assembled membranes. This work provides a method to fabricate a free-standing membrane for lithium storage with tunable electrochemical performance.
Inspired by the natural photosynthesis systems, the integrated harnessing and conversion of CO2 present a promising solution for addressing the ever-rising global atmospheric concentration of CO2. Hollow multi-shelled structured (HoMS) photocatalysts, featuring alternating shells and cavities, have recently gained recognition as efficient nano-reactors for capturing CO2 molecules and facilitating effective photoreduction within these hierarchical structures, leveraging the preeminent enrichment effect. In this work, to augment the photocatalytic efficacy of HoMS in CO2 treatment, highly dispersed Cu xO nanoparticles (NPs) were incorporated on the CeO2 shells through a polymer-assisted impregnation method to create more active sites and strengthen the interaction between the hetero-shells and CO2 molecules. The photoreduction of the CO2-to-CO rate under a diluted CO2 (15%, volume fraction) atmosphere is improved by the introduction of Cu xO NPs, with the highest CO yielding rate reaching 120 µmol·h−1·g−1 without any sacrificial reagents. Further comparison experiments and theoretical calculations reveal that the Cu xO NPs promote the adsorption of CO2 molecules in HoMS, accelerate the charge transfer efficiency, and stabilize the surface oxygen vacancies (Ovs) during the photoreduction CO2 conversion process. We hope these easy-to-prepare HoMS nanoreactors can contribute to the effective enrichment and valorization of CO2 in industrial exhaust gases.
Acetone is a tracer for monitoring air quality and a potential breath maker for diabetes. It remains a great challenge for current portable sensors to sensitively and selectively detect acetone at low-ppb (part per billion) level. Herein, we present an ordered mesoporous nickel oxide (NiO) with both large mesopores and ultrathin crystalline frameworks for the detection of low-ppb acetone. The ordered mesoporous NiO replicas with predominant large mesopores of 11 nm, high specific surface areas of 121–128 m2/g and ultrathin crystalline frameworks of 5 nm were synthesized by the nanocasting method and the crystalline properties of NiO frameworks were adjusted by changing the annealing temperature from 300 °C to 750 °C, which resulted in different contents of oxygen deficient on the surface of ultrathin frameworks. The gas-sensing properties for all the NiO samples were investigated and the ordered large-pore mesoporous NiO (NiO-600) with maximum oxygen deficient obtained at 600 °C exhibited the highest response (R gas/R air−1=2.9) toward acetone (1 ppm, ppm: part per million), which is 3.4 and 30 times larger than those for common mesoporous NiO obtained at 300 °C and bulk NiO. Notably, a low detection limit (2 ppb), good selectivity and cycling stability were also observed in NiO-600.
Precipitation and impregnation procedures unevenly distribute metals on zeolite, limiting chemical transformation in Lewis-acid, Brönsted-acid and metal-catalyzed tandem reactions. Although, heterogeneous multitask transition metals oxides@zeolites are promising catalysts for sustainable processes; nevertheless, synthesis is fascinating and complex. Herein, the construction of purposely designed multitask materials segregated in selective shells reveals the remarkable spatial organization of metals-zeolite, resulting in them being suitable for a wide range of tandem reactions. The synthesis of multi-site catalysts begins with a universal wet chemistry approach that yields nickel oxide (NiO) crystals. Then, the NiO crystals are stabilized using cationic dodecyltrimethylammonium bromide, followed by achieving cross-linking carbon growth by emulsion polymerization of glucose in hydrothermal treatment to yield uniformed NiO@carbon spheres (NiO@CSs). Next, sequential adsorption of cobalt cations and colloidal ZSM-5 (1% in H2O, mass fraction), followed by calcination in air, yielded NiO@cobalt oxide@zeolite denoted as NiO@Co3O4@ZEO hollow spheres. The hollowing mechanism and materials segregation within shells are revealed by scanning and transmission electron microscopy, thermogravimetric analysis, and X-ray diffraction. The finding advances the rational synthesis of heterogenous core-shell hollow structures for various gas phase catalytic tandem reactions to yield valuable chemicals.
Nano 3C-SiC@multilayer graphene oxide (NS@MGO) heterostructure was in situ prepared by carbothermal reduction of pyrolyzed precursor composed of highly dispersed cured phenolic resin and silicon dioxide derived from tetraethyl orthosilicate. The heterojunction interface, number of layers of MGO, and defect content in graphene are the three most important factors for promoting photocatalytic activity. Direct contact between 3C-SiC nanograins and MGO layers facilitates the photogenerated electrons to migrate across the heterojunction interface and avoid the formation of SiO2 nanolayers on the surface of SiC nanograins. The number of MGO layers is supposed to be less than ten instead of over-thick MGO. The concentrations of oxygenated components, considered the defect contents, decrease with the increase of sintering temperature for NS@MGO 0.175-T-150, and relative carbon content in the multilayer graphene increases. According to the heterostructures, properties, and photocatalytic reaction performance of the NS@MGO materials, the highest photocatalytic kinetic rate constant of 0.00891/min for NS@MGO 0.175-1500-150 shows that the significant enhancement in photocatalytic degradation activity under visible light (>420 nm) irradiation is ascribed to the advantageous synergistic effects between the nano 3C-SiC particles and the direct contact multilayer graphene oxide with appropriate layers and sufficient oxygen content of 3.51% (atomic fraction) in MGO.
Interfacial solar desalination is an emerging technology for freshwater production, but the finding of novel solar evaporators is still challenging. In the present research, graphitic carbon foam (CF) was synthesized from the upcycling of waste plastic polyethylene terephthalate (PET) waste bottles functionalized with carrollite CuCo2S4 as a photothermal layer. Analytical characterization [X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS)] confirms the functionalization of carrollite CuCo2S4 on graphitic carbon foam. The UV-Vis spectroscopy analysis showed an enhanced optical absorption in the UV-Vis-near IR region (>96%) for functionalized CuCo2S4-CF foam compared to carbon foam (67%). The interfacial solar desalination experiment presented a significantly enhanced evaporation rate of 2.4 kg·m−2·h−1 for CuCo2S4-CF compared to that of CF (1.60 kg·m−2·h−1) and that of CuCo2S4 (1.60 kg·m−2·h−1). The obtained results proved that the newly synthesized CuCo2S4-CF from the upcycled plastic into new material for the photothermal desalination process can enhance the practice of a circular economy to produce fresh water.
The halide migration effect in mixed-halide lead-based perovskite is a serious problem hindering the development of its display technology. In this study, we have successfully addressed this issue by reporting formadinium (FA) doped mixed-halide perovskite nanocrystals (NCs) with ultra-deep-blue emission of 450 nm, narrow bandwidth of 16 nm, and a high photoluminescence quantum yield (PLQY) of 66%. The perovskite nanocrystal light-emitting diodes (NC-LEDs) using this nanocrystal as an active layer achieved a maximum external quantum efficiency (EQE) of 0.32%, 30-fold improved compared to that of pristine and stable electroluminescence (EL) spectra at 450 nm under a 4.9–8.0 V bias. These findings demonstrate the potential of our approach in developing stable and efficient deep blue perovskite NC-LEDs.