Hollow Heterostructures Research Articles

Cu2O@Cu-composed hollow spheres capable of Generating Rich reactive oxygen species for efficient photodynamic antibacterial application

Cuprous oxide (Cu2O), which has an appropriate band gap, is widely used as a marine antifouling biocide. This makes it increasingly valuable for photocatalytic antibacterial applications. Using crystal engineering technology to create Cu2O with tailored Cu2O/Cu interfaces and crystal planes can effectively enhance its performance but presents challenges. Herein, we report a simple wet chemical method for the controlled preparation of Cu2O@Cu hollow heterostructure. Experimental results demonstrate that the prepared composites exhibited highly efficient and broad-spectrum photocatalytic antibacterial effects against both Gram-negative and Gram-positive bacteria, achieving 100% antibacterial efficiency under 10 min of irradiation, much more effective than the bulk Cu2O. Characterization results show that a hollow spherical structure consisted of fine Cu2O@Cu nanoparticles in their wall, and the generated interfaces facilitated the migration and separation of photogenerated charge carriers and promoted the formation of hydroxyl radicals with stronger oxidizing abilities. Meanwhile, the Cu outside layer of each Cu2O@Cu particle not only acted as a shield to protect Cu2O from corrosion but also served as an electron acceptor to efficiently transfer photogenerated electrons, thereby demonstrating highly effective and stable antibacterial performance. This study not only offers a valuable reference for developing highly efficient and universal photocatalytic materials but also provides insight into the chemical reaction in the photocatalytic antibacterial process.

NH4Cl-Assisted Electrosynthesis of P-Doped Co(OH)2 Nanosheet on Cu2S Hollow Nanotube Arrays for Glycerol Electrooxidation.

The glycerol oxidation reaction (GOR) for producing high-value-added organic compounds is of great research interest due to its potential in alleviating the energy crisis. Herein, a facile NH4Cl-assisted electrodeposition strategy is reported to fabricate 3D nano-forest array-like hollow nanostructures. The hierarchical heterojunction by combining phosphorus doping Co(OH)2 nanosheets with Cu2S nanotube arrays (P-Co(OH)2@Cu2S NTs/CF) is developed to realize the optimization on GOR. The optimized P-Co(OH)2@Cu2S NTs/CF catalyst exhibits an exceptional activity with a formate Faradaic efficiency (FE) of 97.40% at a potential of 1.30V (vs RHE). The experimental results indicate that this unique hollow nano-forest structure, grown on a conductive support, can expose more active sites and facilitate electron transfer, thereby demonstrating excellent GOR performance. This work provides new opportunities for the design of electrocatalysts of high-activity and low-cost hollow heterostructure electrocatalysts for glycerol electrooxidation.

Amorphous CoFePOx hollow nanocubes decorated with g-C3N4 quantum dots to achieve efficient electrocatalytic performance in the oxygen evolution reaction.

Simultaneously enriching active sites and enhancing intrinsic activity in a simple way is of great importance for the design of highly active electrocatalysts for the oxygen evolution reaction (OER), but it still faces challenges. Herein, g-C3N4 quantum dot decorated amorphous hollow CoFe bimetallic phosphate nanocubes (a-CoFePOx@CNQD) are prepared as an efficient OER electrocatalyst by a simple in situ etching-phosphating process. Research shows that their unique hollow architecture and amorphous structure can help provide generous exposed active sites for OER, and the incorporation of g-C3N4 quantum dots can effectively adjust the electronic structure to improve the intrinsic activity. Therefore, a-CoFePOx@CNQD exhibits excellent OER performance with a low overpotential (239 mV) at 10 mA cm-2 and a small Tafel slope (58.4 mV dec-1), surpassing the commercial RuO2. Furthermore, a-CoFePOx@CNQD as an electrode catalyst for a water electrolyzer and zinc-air battery also shows higher performance and stability than RuO2 + Pt/C catalysts. This study provides a feasible strategy for preparing efficient and stable amorphous hollow heterostructure OER electrocatalysts.

Chemically bonded nonmetallic LSPR S-scheme hollow heterostructure for boosting photocatalytic performance

The light absorption, mass transfer, and charges separation are essential to the efficiency of photocatalytic reaction, but constructing photocatalyst with the three excellent properties is still challenging. Herein, the interfacial Mo-S bonds and oxygen vacancy synchronously decorated MoO3-x/Zn3In2S6 (MoO3-x/ZIS) heterostructure was rationally designed and synthesized. The oxygen-defective MoO3-x nanotubes showed hollow structure and local surface plasmonic resonance (LSPR) effect, which improved mass transfer and solar light absorption. Besides, the built-in electric field and interfacial Mo-S bond provided endogenetic impetus and channels for rapid photoexcited charge carriers transfer and separation. The photocatalytic hydrogen (H2) evolution and hydrogen peroxide (H2O2) production on optimal MoO3-x/ZIS composite were 17.34 and 4.47 mmol g−1 h−1, respectively. The apparent quantum efficiency of MoO3-x/ZIS for H2 evolution at 400 nm was about 13.92 %, which was 8.09 times higher than that of ZIS. Moreover, the MoO3-x/ZIS also displayed excellent activities on the selective 5-hydroxymethylfurfural dehydrogenation. The in-situ X-ray photoelectron spectroscopy, electron paramagnetic resonance, in-situ selective photodeposition, and density functional theory calculation confirmed the S-scheme charge transfer pathway between MoO3-x and ZIS. This study provides an effective avenue for designing multifunctional photocatalysts based on the synergistic effects of chemically bonded S-scheme heterostructure and nonmetallic LSPR effect.

Triphasic heterostructured Zn–Sn–S hollow nanoboxes encapsulated by N, S-codoped carbon as anodes for high-performance sodium-ion batteries

Metal sulfides have been expected huge practical potential for sodium-ion batteries (SIBs), which are mainly owing to their admirable merits of natural abundance, low price, and high theoretical capacity. However, the inferior electrical conductivity and enormous volume variation originating from sodiation/desodiaziton reactions usually result in unsatisfied rate and cycling properties. In this work, a coprecipitation with a following sulfurization method has been rationally designed to prepare the triphasic heterostructured hollow Zn–Sn–S nanoboxes encapsulated by N, S-codoped carbon (ZSS@NCS) as anodes for SIBs. The coexistence of triphasic ZSS heterostructures that consist of ZnS, SnS2, and Sn2S3 effectively facilitates the fast Na + diffusion. The N, S-codoped carbon (NSC) derived from the polydopamine is coated outside of the ZSS heterostructures, which provides infinite affinity between ZSS and NSC that efficiently accelerates the electron transport and maintains the structural stability via the confinement effect. The synergistic effects of the heterostructured ZSS and NSC endow the ZSS@NSC anode with favorable sodium storage properties including decent discharge capacity (683.8 mAh g−1 at 0.1 A g−1), satisfying rate (232.6 mAh g−1 at 10.0 A g−1) and cycling properties (402.2 mAh g−1 over 150 cycles).

In situ construction of metal organic framework derived FeNiCoSe@NiV-LDH polymetallic heterostructures for high energy density hybrid supercapacitor electrode materials

Metal-organic framework (MOF) derivatives as supercapacitor electrodes are limited by their poor conductivity and capacitance properties. Therefore, it is crucial to improve the performance by constructing a rational structure. Here, MIL-88A is converted into a unique hollow heterostructure FeNiCoSe@NiV layered double hydroxide (FeNiCoSe@NiV-LDH, simplified as FNCS@NVL) by a simple ion-exchange combined with co-precipitation technique. The Ni-Co ratio is modulated by an intermediate optimization strategy. Owing to the multi-metal sites and the unique structure, the designed FNCS@NVL shows excellent electrochemical properties as expected. It exhibits excellent specific capacity (1964.4 F·g−1 at 1 A·g−1) and capacitance retention (82.1 % at 10,000 cycles) at three-electrode setup. In addition, the hybrid supercapacitor (HSC) assembled by FNCS@NVL as the positive electrode and activated carbon as the negative electrode also exhibits a high energy density of 71.9 W h·kg−1 at a power density of 800.01 W·kg−1. These results demonstrate that the designed FNCS@NVL complex is an excellent energy storage material and further validate the great potential of polymetallic materials in energy storage. It provides a unique idea for constructing supercapacitors with high energy density and power density.

Hollow heterojunction with dual-vacancy engineering to boost photocatalytic performance for photoreduction of CO2 coupled with selective oxidation of benzyl alcohol to benzaldehyde

CO2 photoreduction into chemical fuels is hopeful and sustainable for a carbon–neutral future. Herein, a bifunctional dual-vacancy-modified hollow heterojunction photocatalyst is ingeniously designed for CO2 photoreduction to CO coupling with selective oxidation of benzyl alcohol to benzaldehyde. Synergistic catalysis effect resulted from hollow heterostructures, TiO2 with O vacancies (TiO2-x) and Zn0.3-xCd0.7S with Zn vacancies (ZCS) leads to excellent photoreduction and photoxidation performances. The optimized sample (TiO2-x/ZCS hollow sphere) exhibits highest photocatalytic activity of all the obtained samples. The yields of CO and benzaldehyde are 105 and 323.5 μmol g–1h−1, respectively. The construction of Z-scheme heterojunction realizes the spatial separation of redox reaction sites, and the dual-vacancy distributed on the heterojunction enhance the interfacial reactivity. Additionally, density functional theory calculation and in-situ technology reveal that Zn vacancy in ZCS and O vacancy in TiO2-x function as active sites for the binding and activation of *COOH and *PhCH2O-, respectively, thereby stabilizing the crucial step in the formation of intermediates such as CO and benzaldehyde. This work enhances the utilization of photogenerated carrier, and affords a new opportunity to design hollow heterojunction with dual-vacancy engineering to boost photocatalytic performance for coupling reaction system.

Preparation and electrocatalytic oxygen evolution of bimetallic phosphates (NiFe)2P/NF

Abstract The energy and environmental crisis pose a great challenge to human development in the 21st century. The design and development of clean and renewable energy and the solution for environmental pollution have become a hotspot in the current research. Based on the preparation of transition metal phosphates, transition metals were used as raw materials, Prussian blue-like NiFe(CN)6 as a precursor, which was in situ grown on nickel foam (NF) substrate. After low temperature phosphating treatment, a bimetallic phosphide electrocatalyst (NiFe)2P/NF was prepared on NF substrate. Using 1 mol·L−1 KOH solution as a basic electrolyte, based on the electrochemical workstation of a three-electrode system, the electrochemical catalytic oxygen evolution performance of the material was tested and evaluated. Experiments show that (NiFe)2P/NF catalyst has excellent oxygen evolution performance. In an alkaline medium, the overpotential required to obtain the catalytic current density of 10 mA·cm−2 is only 220 mV, and the Tafel slope is 67 mV·dec−1. This is largely due to: (1) (NiFe)2p/NF nanocatalysts were well dispersed on NF substrates, which increased the number of active sites exposed; (2) the hollow heterostructure of bimetallic phosphates promotes the electron interaction between (NiFe)2P and NF, increased the rate of charge transfer, and the electrical conductivity of the material is improved; and (3) theoretical calculations show that (NiFe)2P/NF hollow heterostructure can effectively reduce the dissociation barrier of water, promote the dissociation of water; furthermore, the kinetic reaction rate of electrocatalytic oxygen evolution is accelerated. Meanwhile, the catalyst still has high activity and high stability in 30 wt% concentrated alkali solution. Therefore, the construction of (NiFe)2P/NF electrocatalysts enriches the application of non-noble metal nanomaterials in the field of oxygen production from electrolytic water.

Core-Shell CoS2@MoS2 with Hollow Heterostructure as an Efficient Electrocatalyst for Boosting Oxygen Evolution Reaction.

It is imperative to develop an efficient catalyst to reduce the energy barrier of electrochemical water decomposition. In this study, a well-designed electrocatalyst featuring a core-shell structure was synthesized with cobalt sulfides as the core and molybdenum disulfide nanosheets as the shell. The core-shell structure can prevent the agglomeration of MoS2, expose more active sites, and facilitate electrolyte ion diffusion. A CoS2/MoS2 heterostructure is formed between CoS2 and MoS2 through the chemical interaction, and the surface chemistry is adjusted. Due to the morphological merits and the formation of the CoS2/MoS2 heterostructure, CoS2@MoS2 exhibits excellent electrocatalytic performance during the oxygen evolution reaction (OER) process in an alkaline electrolyte. To reach the current density of 10 mA cm-2, only 254 mV of overpotential is required for CoS2@MoS2, which is smaller than that of pristine CoS2 and MoS2. Meanwhile, the small Tafel slope (86.9 mV dec-1) and low charge transfer resistance (47 Ω) imply the fast dynamic mechanism of CoS2@MoS2. As further confirmed by cyclic voltammetry curves for 1000 cycles and the CA test for 10 h, CoS2@MoS2 shows exceptional catalytic stability. This work gives a guideline for constructing the core-shell heterostructure as an efficient catalyst for oxygen evolution reaction.

In Situ-Generated Hollow CoFe-LDH/Co-MOF Heterostructure Nanorod Arrays for Oxygen Evolution Reaction.

Assembling a heterostructure is an effective strategy for enhancing the electrocatalytic activity of hybrid materials. Herein, CoFe-layered double hydroxide and Co-metal-organic framework (CoFe-LDH/Co-MOF) hollow heterostructure nanorod arrays are synthesized. First, [Co(DIPL)(H3BTC)(H2O)2]n [named as Co-MOF, DIPL = 2,6-di(pyrid-4-yl)-4-phenylpyridine, H3BTC = 1,3,5-benzenetricarboxylic acid] crystalline materials with a uniform hollow structure were prepared on the nickel foam. The CoFe-LDH/Co-MOF composite perfectly inherits the original hollow nanorod array morphology after the subsequent electrodeposition process. Optimized CoFe-LDH/Co-MOF hollow heterostructure nanorod arrays display excellent performance in oxygen evolution reaction (OER) with ultralow overpotentials of 215 mV to deliver current densities of 10 mA cm-2 and maintain the electrocatalytic activity for a duration as long as 220 h, ranking it one of the non-noble metal-based electrocatalysts for OER. Density functional theory calculations validate the reduction in free energy for the rate-determining step by the synergistic effect of Co-MOF and CoFe-LDH, with the increased charge density and noticeable electron transfer at the Co-O site, which highlights the capability of Co-MOF to finely adjust the electronic structure and facilitate the creation of active sites. This work establishes an experimental and theoretical basis for promoting efficient water splitting through the design of heterostructures in catalysts.

CoO/MoO3@Nitrogen-Doped carbon hollow heterostructures for efficient polysulfide immobilization and enhanced ion transport in Lithium-Sulfur batteries

Lithium-sulfur batteries (LSBs) have emerged as a promising energy storage system, but their practical application is hindered by the polysulfide shuttle effect and sluggish redox kinetics. To address these challenges, we have developed CoO/MoO3@nitrogen-doped carbon (CoO/MoO3@NC) hollow heterostructures based on porous ZIF-67 as separators in LSBs. CoO has a strong anchoring effect on polysulfides. The heterostructure formed after the introduction of MoO3 increases the adsorption of polysulfides. The carbon coating outside the heterostructure improves the ion transmission efficiency of the battery, leading to enhanced electrochemical performance. The modified LSB demonstrates a low-capacity decay rate of 0.092% over 500 cycles at 0.5C, with a high discharge capacity of 613 mAh g−1 at 1C. This work presents a novel approach for the preparation of hollow heterostructure materials, aiming for high-performance LSBs.

CoTe2/NiTe2 heterojunction embedded in N-doped hollow carbon nanoboxes as high-efficient ORR/OER catalyst for rechargeable zinc-air battery

Interface engineering has been recognized as one of the most promising strategies for tuning the catalytic properties of catalysts. However, building well-defined nanointerfaces for efficient oxygen reduction/evolution reactions (ORR/OER) remains a challenge. Herein, a hollow heterostructure composed of highly-dispersed CoTe2 inside the mesoporous walls of nitrogen-doped carbon nanoboxes and uniformly-dispersed NiTe2 outside the mesoporous walls (H-CoTe2/NiTe2@NCBs) is designed via a ZIF67-involved etching-anchoring-tellurization strategy. Promising half-wave potential of 0.86 V and overpotential of 320 mV at 10 mA cm−2 are obtained by H-CoTe2/NiTe2@NCBs. The excellent ORR/OER activity of H-CoTe2/NiTe2@NCBs is ascribed to the synergistic coupling based on nanointerfaces between CoTe2 and NiTe2. Density functional theory calculations confirm that the nanointerface-based electronic coupling between CoTe2 and NiTe2 facilitates the charge transfer between two components and generates abundant catalytically active sites at the heterointerface, thereby significantly promoting the ORR/OER activities. This work provides the design principles for transitional bimetallic tellurides as bifunctional electrocatalysts.

Photoelectrothermocatalytic reduction of CO2 to glycol via CdIn2S4-N/C hollow heterostructure mimicking plant cell

A series of novel semiconductor composites of CdIn2S4-N/C, in which CdIn2S4 is grown on hollow nitrogen-doped carbon spheres to mimic plant cells, were designed and applied to photoelectrothermocatalytic reduction of CO2. Our results reveal that the unique hollow structure and photothermal properties of N/C contribute to excellent performance of catalyst in CO2 reduction. Specifically, the optimal catalyst of CdIn2S4-N/C-2–800 demonstrates an outstanding catalytic activity with a formation rate of 168.5 µM h−1 cm−2 for carbon-based products and an electron selectivity for C2 products of 66.9 %. DFT calculations demonstrate that pyridine N and pyrrole N can reduce the energy barrier during CO2 reduction. Two important species of *=C=O and OC-COH* were detected by operando IR spectra and suggested to be key intermediates to C2 products via a carbene (*=C=O) coupling mechanism. CdIn2S4-N/C provides thermoelectrons and active sites like in the membrane of plant to enhance the probability of C-C coupling.

Rational Design of Three Dimensional Hollow Heterojunctions for Efficient Photocatalytic Hydrogen Evolution Applications.

The efficiency of photocatalytic hydrogen evolution is currently limited by poor light adsorption, rapid recombination of photogenerated carriers, and ineffective surface reaction rate. Although heterojunctions with innovative morphologies and structures can strengthen built-in electric fields and maximize the separation of photogenerated charges. However, how to rational design of novel multidimensional structures to simultaneously improve the above three bottleneck problems is still a research imperative. Herein, a unique Cu2O─S@graphene oxide (GO)@Zn0.67Cd0.33S Three dimensional (3D) hollow heterostructure is designed and synthesized, which greatly extends the carrier lifetime and effectively promotes the separation of photogenerated charges. The H2 production rate reached 48.5mmolg-1h-1 under visible light after loading Ni2+ on the heterojunction surface, which is 97 times higher than that of pure Zn0.67Cd0.33S nanospheres. Furthermore, the H2 production rate can reach 77.3mmolg-1h-1 without cooling, verifying the effectiveness of the photothermal effect. Meanwhile, in situ characterization and density flooding theory calculations reveal the efficient charge transfer at the p-n 3D hollow heterojunction interface. This study not only reveals the detailed mechanism of photocatalytic hydrogen evolution in depth but also rationalizes the construction of superior 3D hollow heterojunctions, thus providing a universal strategy for the materials-by-design of high-performance heterojunctions.

Porous In2O3 Hollow Tube Infused with g-C3N4 for CO2 Photocatalytic Reduction.

Converting CO2 into energy-rich fuels by using solar energy is a sustainable solution that promotes a carbon-neutral economy and mitigates our reliance on fossil fuels. However, affordable and efficient CO2 conversion remains an ongoing challenge. Here, we introduce polymeric g-C3N4 into the pores of a hollow In2O3 microtube. This architecture results in a compact and staggered arrangement between g-C3N4 and In2O3 components with an increased contact interface for improved charge separation. The hollow interior further contributes to strengthening light absorption. The resulting g-C3N4-In2O3 hollow tubes exhibit superior activity (274 μmol·g-1·h-1) toward CO2 to CO conversion in comparison with those of pure In2O3 and g-C3N4 (5.5 and 93.6 μmol·g-1·h-1, respectively), underlining the role of integrating g-C3N4 and In2O3 in this advanced system. This work offers a strategy for the advanced design and preparation of hollow heterostructures for optimizing CO2 adsorption and conversion by integrating inorganic and organic semiconductors.

Multipath charge transfer in Cu-BTC@CuS@CeO2 double p-n heterojunction hollow octahedrons for enhanced photocatalytic amine oxidation

Hollow heterostructured catalysts have been widely investigated and applied in photocatalytic organic reactions. However, achieving hybrid catalysts with optimized hollow structure and controllable components is still a challenge. Herein, Cu-BTC@CuS@CeO2 ternary heterostructure hollow octahedrons were designed and prepared using a copper-based metal–organic framework (Cu-BTC) as both copper source and template. A thin CeO2 nanolayer was first formed and covered on the prepared Cu-BTC octahedron surface through a hydrothermal process. In the meanwhile, the Cu-BTC octahedrons were controllably etched in this hydrothermal process, leading to the formation of Cu-BTC@CeO2 hollow octahedron. The following sulfidation reaction produced Cu-BTC@CuS@CeO2 double p-n heterojunction hollow octahedrons. Benefiting from the novel hollow octahedron double p-n heterojunctions, excellent visible-near infrared light absorption, and fast charge transfer and separation, the obtained Cu-BTC@CuS@CeO2 hollow octahedron hybrid catalyst exhibited a significantly higher photocatalytic activity toward the oxidative coupling of amines to imines at room temperature under visible-near infrared light irradiation compared to the control single component catalysts (Cu-BTC, CeO2, and CuS) and binary hybrid catalysts (Cu-BTC@CeO2, Cu-BTC@CuS, and CuS@CeO2). The enhanced charge transfer at the double p-n heterojunction was discussed. Meanwhile, the photocatalytic oxidation products and reaction mechanism were investigated by surface-enhanced Raman spectroscopy, gas chromatography-mass spectrometry, and pyridine adsorption FT-IR spectroscopy. This work presents a promising strategy for the design of multi-component hollow heterostructure catalysts.

Synthesis of a Ni(OH)2@Cu2Se hetero-nanocage by ion exchange for advanced glucose sensing in serum and beverages.

Cu2Se nanosheets were coated on the surface of Ni(OH)2 nanocages (NCs) by ion exchange driven by selenium incorporation. The resulting Ni(OH)2@Cu2Se hollow heterostructures (Ni(OH)2@Cu2Se HHSs) showed high electrical conductivity and electrocatalytic activities derived from the synergistic effects of Ni/Cu phases. These structures enhanced glucose adsorption abilities, confirmed by density function theory (DFT) calculations, and the robustness of the integrated nano-electrocatalyst. Remarkably, Ni(OH)2@Cu2Se HHSs modified electrodes excited excellent glucose sensing behavior with a wide linear range (0.001-7.5mM), a sensitivity up to 2420.4ΜamM-1 cm2, a low limit of detection (LOD, 0.15μM), and fast response (less 2s). Furthermore, Ni(OH)2@Cu2Se HHSs competently analyzed glucose in serum and beverages with good recoveries ranging from 94.4 to 103.6%. Integrating copper selenide and Ni-based materials as 3D hollow heterostructures expands the selection of electrocatalysts for sensitive glucose detection in food and biological samples.

Hollow Starlike Ag/CoMo-LDH Heterojunction with a Tunable d-Band Center for Boosting Oxygen Evolution Reaction Electrocatalysis.

It is a challenging task to utilize efficient electrocatalytic metal hydroxide-based materials for the oxygen evolution reaction (OER) in order to produce clean hydrogen energy through water splitting, primarily due to the restricted availability of active sites and the undesirably high adsorption energies of oxygenated species. To address these challenges simultaneously, we intentionally engineer a hollow star-shaped Ag/CoMo-LDH heterostructure as a highly efficient electrocatalytic system. This design incorporates a considerable number of heterointerfaces between evenly dispersed Ag nanoparticles and CoMo-LDH nanosheets. The heterojunction materials have been prepared using self-assembly, in situ transformation, and spontaneous redox processes. The nanosheet-integrated hollow architecture can prevent active entities from agglomeration and facilitate mass transportation, enabling the constant exposure of active sites. Specifically, the powerful electronic interaction within the heterojunction can successfully regulate the Co3+/Co2+ ratio and the d-band center, resulting in rational optimization of the adsorption and desorption of the intermediates on the site. Benefiting from its well-defined multifunctional structures, the Ag0.4/CoMo-LDH with optimal Ag loading exhibits impressive OER activity, the overpotential being 290 mV to reach a 10 mA cm-2 current density. The present study sheds some new insights into the electron structure modulation of hollow heterostructures toward rationally designing electrocatalytic materials for the OER.

Gradient Hierarchical Hollow Heterostructures of Ti3C2Tx@rGO@MoS2 for Efficient Microwave Absorption.

Heterostructure engineering has emerged as a promising approach for creating high-performance microwave absorption materials in various applications such as advanced communications, portable devices, and military fields. However, achieving strong electromagnetic wave attenuation, good impedance matching, and low density in a single heterostructure remains a significant challenge. Herein, a unique structural design strategy that employs a hollow structure coupled with gradient hierarchical heterostructures to achieve high-performance microwave absorption is proposed. MoS2 nanosheets are uniformly grown onto the double-layered Ti3C2Tx MXene@rGO hollow microspheres through self-assembly and sacrificial template techniques. Notably, the gradient hierarchical heterostructures, comprising a MoS2 impedance matching layer, a reduced graphene oxide (rGO) lossy layer, and a Ti3C2Tx MXene reflective layer, have demonstrated significant improvements in impedance matching and attenuation capabilities. Additionally, the incorporation of a hollow structure can further improve microwave absorption while reducing the overall composite density. The distinctive gradient hollow heterostructures enable Ti3C2Tx@rGO@MoS2 hollow microspheres with exceptional microwave absorption properties. The reflection loss value reaches as strong as -54.2 dB at a thin thickness of 1.8 mm, and the effective absorption bandwidth covers the whole Ku-band, up to 6.04 GHz. This work provides an exquisite perspective on heterostructure engineering design for developing next-generation microwave absorbers.

Tightly contacted heterojunction of ZnS/ZIS/In2S3: In situ construction from ZIF-8@MIL-68(In) and visible-light induced photocatalytic hydrogen generation

The construction of a tightly contacted heterojunction consisting of multi-components is proven to be one of the effective strategies to promote the photogenerated charges separation and to develop high-efficient photocatalysts in hydrogen evolution. Herein, a ternary hollow heterostructure of ZnS/ZIS/In2S3 has been fabricated by using a binary MOF@MOF (ZIF-8@MIL-68(In)) as the precursor, and an in-situ sulfurization of ZIF-8@MIL-68(In) is controlled to optimize the photocatalytic performances. The resulting samples are signed as Z@M-t, where the t is pointed to the sulfurization time being varied from 4 h to 48 h. It’s shown that the hierarchical and hollow architecture is formed for Z@M-t, and with the reinforced light harvest ability in both UV and visible light regions. In the subsequent visible-light-induced photocatalytic hydrogen generation, the optimized Z@M-24 manifests significantly improved hydrogen evolution rate of 607.34 μmol g-1 h−1, which values are evidently higher than that by the single MOF and binary ZIF-8@MIL-68(In) heterostructure. The electrochemical analyses and the electron paramagnetic resonance (EPR) spectrum were analyzed to clarify the charge transfer routes and the enhanced photocatalytic mechanism, in which the contribution of each metal sulfide is also discussed. Finally, the good photocatalytic stability and reusability of Z@M-24 heterostructure are also represented, which define the structure superior brought by the effective heterojunction based on the in-situ sulfurization strategy of binary ZIF-8@MIL-68(In), and determine their prospect applications in the efficient H2 production under visible light irradiation.