Porous Heterostructures Research Articles

New Porous Heterostructures Based on Organo-Modified Graphene Oxide for CO2 Capture.

In this work, we report on a facile and rapid synthetic procedure to create highly porous heterostructures with tailored properties through the silylation of organically modified graphene oxide. Three silica precursors with various structural characteristics (comprising alkyl or phenyl groups) were employed to create high-yield silica networks as pillars between the organo-modified graphene oxide layers. The removal of organic molecules through the thermal decomposition generates porous heterostructures with very high surface areas (≥ 500 m2/g), which are very attractive for potential use in diverse applications such as catalysis, adsorption and as fillers in polymer nanocomposites. The final hybrid products were characterized by X-ray diffraction, Fourier transform infrared and X-ray photoelectron spectroscopies, thermogravimetric analysis, scanning electron microscopy and porosity measurements. As proof of principle, the porous heterostructure with the maximum surface area was chosen for investigating its CO2 adsorption properties.

Exfoliated Graphitic Carbon Nitride Nanosheets/Gold Nanoparticles/Spherical Montmorillonite Ternary Porous Heterostructures for the Degradation of Organic Dyes

Water-soluble organic carcinogenic pollutants have become a serious threat to both health and environment. Here, porous ternary spherical montmorillonite/exfoliated graphitic carbon nitride nanosheets/gold nanoparticles (SMt/g-C3N4/Au NPs) heterostructures were facile and green synthesized through a polydopamine chemistry method. These involved the coating of porous SMt with exfoliated g-C3N4 nanosheets and in situ growth of Au NPs. The prepared heterostructures exhibited a universal catalytic ability toward organic dyes, such as methylene blue (MB), rhodamine 6G, and Congo red, in the presence of sodium borohydride (NaBH4). The catalytic activity would improve under high SMt/g-C3N4/Au NPs concentration, high temperature, and high pH values. For example, the apparent reduction rate constant (kapp) and turnover frequency (TOF) toward MB can reach 5.91 min–1 and 302 h–1, respectively, at 35 °C and pH values of 11. Furthermore, the influences of the pH values on the catalytic performance were investigated, and the reason can be attributed to the strong enhanced adsorption capacity of SMt/g-C3N4/Au NPs heterostructures toward organic dyes under the high pH values for facilitating electron transfer from NaBH4 to organic dyes. Moreover, the SMt/g-C3N4/Au NPs heterostructures were quite stable, being recycled at least 10 times with almost unchanged kapp. The excellent catalytic performance and recyclability recommend our synthesized SMt/g-C3N4/Au NPs heterostructures for a wide range of applications in environment and wastewater treatment.

Construction of hierarchical photocatalysts by growing ZnIn2S4 nanosheets on Prussian blue analogue-derived bimetallic sulfides for solar co-production of H2 and organic chemicals

Abstract Exploring highly efficient bifunctional photocatalysts for simultaneous H2 evolution and organic chemical production in pure water represents a green route for sustainable solar energy storage and conversion. Herein, a facile strategy was explored for preparing a hierarchical porous heterostructure of Fe4Ni5S8@ZnIn2S4 (FNS@ZIS) by the in situ growth of ZIS nanosheets on Prussian blue analogue (PBA)-derived bimetallic FNS sulfides. A series of FNS@ZIS hierarchical structures were facilely prepared by adjusting the loading amount (n%) of FNS (n = 19, 26, and 32 for FNS@ZIS-1-3). These structures can efficiently drive the solar co-production of H2 and organic chemicals. The optimal co-production was achieved with FNS@ZIS-2, affording a H2 evolution rate of 10465 μmol·g−1·h−1, along with high selectivity for the oxidation of benzyl alcohol to benzaldehyde (>99.9%). The performance was 22 and 31 times higher than that of FNS and ZIS, respectively, and even superior to the state-of-the-art results achieved using various sacrificial agents. Further mechanistic study indicated that the unique hierarchical core/shell architecture can facilitate interfacial charge separation, afford bimetallic synergy, abundant active sites and excellent photostability. This work highlights a simple and efficient method for preparing porous multimetallic hierarchical structures for the solar co-production of organic chemicals and H2 fuel.

Pd supported on graphene modified g‐C3N4 hybrid: a highly efficient catalyst for hydrogenation of nitroarenes

Graphitic carbon nitride (g‐C3N4) and graphene (GO) have been greatly utilized as supports in the field of heterogeneous catalysis. In this work, layered C3N4 polymer/graphene hybrid (CNNS/rGO20) with heterostructure was fabricated by a hydrothermal method followed by loading Pd nanoparticles on the hybrid. The palladium was well dispersed uniformly (1.31 nm) owing to the layered and porous heterostructure of CNNS/rGO20. The obtained catalyst was used for the transfer hydrogenation of a series of nitro‐compounds to give the corresponding aromatic amines with outstanding activity by employing formic acid as hydrogen donor under mild conditions. The catalytic activity of the heterogeneous catalyst showed no significant loss after five continuous use.

Facile synthesis and photocatalytic efficacy of UiO-66/CdIn2S4 nanocomposites with flowerlike 3D-microspheres towards aqueous phase decontamination of triclosan and H2 evolution

Construction of porous heterostructure photocatalyst material with improved surface and optoelectrical properties is a practical and effective strategy for mineralization of toxic organic pollutants and water splitting reaction under visible light irradiation. Herein, we have developed a facile hydrothermal route to prepare a series of novel UiO-66/CdIn2S4 heterojunction nanocomposite materials containing finely dispersed UiO-66 spherical nanoparticles (20−40 nm) anchored over high aspect ratio CdIn2S4 nanosheets. Comprehensive characterization of the UiO-66/CdIn2S4 nanocomposites revealed a hierarchical 3D microflower structure with enhanced surface reactive sites, better channelization of charge carriers, high resistance to charge recombination and a favorable band alignment between the two semiconductor components. The optimal photocatalyst (30UiO-66/CdIn2S4) showed improved photocatalytic efficiency towards triclosan degradation with rate constant (0.0094 min−1) twelve times higher than the pure CdIn2S4 (0.0007 min−1). The 30UiO-66/CdIn2S4 photocatalyst also exhibited higher H2 evolution rate (2.95 mmolg−1 h−1) with apparent conversion efficiency of 20.8 %.

Rational design and tunable synthesis of Co3O4 nanoparticle-incorporating into In2O3 one-dimensional ribbon as effective sensing material for gas detection

The development of gas sensor with innovative designs is highly desirable for widespread deployments of sensors in applications of monitoring indoor air quality and industrial safety. Herein, an approach is put forward to substantially improve gas sensing performance via electrospinning of metal ion and cross-linked polymer to porous and hetero indium trioxide (In2O3) ribbon combined with cobaltosic oxide (Co3O4) particles. The structural evaluation was systematically discussed and the content of the Co3O4 was subtly regulated. The gas sensing results indicated that the obtained vacancy oxygen and adsorbed oxygen-abundant In2O3-Co3O4 ribbons exhibited significantly high response towards volatile organic compounds (VOCs) encompassing acetone (52, 280 °C) and formaldehyde (39, 260 °C), which can be ascribed to hierarchical porous hetero-structures, ion mismatch and catalytic property of p-type Co3O4. This facile way sheds light on the rational design of gas sensitive materials via structure and composition engineering, resulting in facilitating the gas molecules adsorption and diffusion.

Interfacial effects in hierarchically porous α-MnO2/Mn3O4 heterostructures promote photocatalytic oxidation activity

Constructing hybrid nanocatalysts with more active surfaces/interfaces is crucial for promoting catalytic activities for oxidative removal of volatile organic compounds (VOCs). Herein, we have successfully designed and synthesized a hierarchically porous α-MnO2/Mn3O4 nanostructure with numerous interfaces using a simple topotactic transformation synthesis strategy. The real time observation of the growth dynamics from δ-MnO2 to α-MnO2/Mn3O4 is achieved by in-situ transmission electron microscopy. The in-situ formed α-MnO2/Mn3O4 hybrid supplies not only numerous intimate interfaces but also a direct Z-scheme junction, greatly promoting the generation of superoxide radicals. It also forms more oxygen vacancies that brings about absorption of more O2 molecules on the surface, thus generating more superoxide radicals in unit time. As a result, the hybrid shows much better catalytic oxidation activity for eliminating VOCs as compared to pure α-MnO2 and Mn3O4. The results demonstrate a feasible way to construct hierarchically porous heterostructures with improved photocatalytic activity for eliminating VOCs.

Ultrafine Co2P anchored on porous CoWO4 nanofiber matrix for hydrogen evolution: Anion-induced compositional/morphological transformation and interfacial electron transfer

Even though transition metal phosphides (TMPs) have been regarded as very promising catalysts for hydrogen evolution reaction (HER), exploring highly reactive TMPs-based catalysts with reliable stability in alkaline media remains an enormous challenge. Herein, using wafer-like Co(CO3)0.5(OH)·0.11H2O as template followed by anion-exchange and further phosphorization process, it is synthesized a three-dimensional (3D) hierarchical porous heterostructure with highly dispersed ultrafine metallic Co2P nanoparticles uniformly anchored on porous conductive CoWO4 nanofiber matrix, which not only promotes the electron transfer, but also avoids the deterioration of phosphide. In addition, the electron densities re-distribution within the heterostructure also contributes to the improved catalytic activity. Furthermore, the doping of W into Co2P gives proper H adsorption free energy ΔGH. Impressively, the Co2P/CoWO4/Ni foam (NF) exhibits an overpotential of 81 mV at −10 mA cm−2 and a Tafel slop of 47 mV dec−1 along with supreme long-term durability at −40 mA cm−2. The present work also demonstrates different dosages of Na2WO4 in the anion-exchange step will lead to different phase compositions and morphologies, giving rise to different HER electrocatalytic performances of the phosphorized samples.

Oxygen Vacancy-Rich In-Doped CoO/CoP Heterostructure as an Effective Air Cathode for Rechargeable Zn-Air Batteries.

An efficient and low-cost electrocatalyst for reversible oxygen electrocatalysis is crucial for improving the performance of rechargeable metal-air batteries. Herein, a novel oxygen vacancy-rich 2D porous In-doped CoO/CoP heterostructure (In-CoO/CoP FNS) is designed and developed by a facile free radicals-induced strategy as an effective bifunctional electrocatalyst for rechargeable Zn-air batteries. The electron spin resonance and X-ray absorption near edge spectroscopy provide clear evidence that abundant oxygen vacancies are formed in the interface of In-CoO/CoP FNS. Owing to abundant oxygen vacancies, porous heterostructure, and multiple components, In-CoO/CoP FNS exhibits excellent oxygen reduction reaction activity with a positive half-wave potential of 0.81 V and superior oxygen evolution reaction activity with a low overpotential of 365 mV at 10 mA cm-2 . Moreover, a home-made Zn-air battery with In-CoO/CoP FNS as an air cathode delivers a large power density of 139.4 mW cm-2 , a high energy density of 938 Wh kgZn -1 , and can be steadily cycled over 130 h at 10 mA cm-2 , demonstrating great application potential in rechargeable metal-air batteries.

Bifunctional NiFe layered double hydroxide@Ni3S2 heterostructure as efficient electrocatalyst for overall water splitting

The tailored construction of non-noble metal bifunctional electrocatalysts for high-efficiency oxygen/hydrogen evolution reactions (OER/HER) is vital for the development of electrochemical energy conversion. Herein, we report a powerful combined wet chemical method to fabricate a novel binder-free NiFe layered double hydroxide@Ni3S2 (NiFe LDH@Ni3S2) heterostructure as an efficient bifunctional electrocatalyst for overall water splitting. The hydrothermal-synthesized NiFe LDH nanosheets are uniformly coated on the Ni3S2 nanosheet skeleton forming 3D porous heterostructure arrays. By virtue of its synergistic advantages, including its binder-free characteristics, increased catalysis sites and structural stability, the as-obtained NiFe LDH@Ni3S2/NF electrode exhibits low overpotentials of 184 and 271 mV at 20 mA cm−2 for HER and OER in 1 M KOH, respectively. Notably, a low operation potential of 1.74 V at a current density of 20 mA cm−2 is achieved for overall water splitting with a stable cycling life. In addition, the intimate composite structure and sensitive interface of NiFe LDH@Ni3S2 are responsible for the good electrocatalytic activity with a low Tafel slope, fast reaction kinetics and high stability. The versatile fabrication protocol and heterostructure interface engineering provide a new way to construct other bifunctional and cost-effective electrocatalysts for electrocatalysis.

Block-Co-polymer-Assisted Synthesis of All Inorganic Highly Porous Heterostructures with Highly Accessible Thermally Stable Functional Centers.

Here, we propose a simple approach for the design of highly porous multicomponent heterostructures by infiltration of block-co-polymer templates with inorganic precursors in swelling solvents followed by gas-phase sequential infiltration synthesis and thermal annealing. This approach can prepare conformal coatings, free-standing membranes, and powders consisting of uniformly sized metal or metal oxide nanoparticles (NPs) well dispersed in a porous oxide matrix. We employed this new, versatile synthetic concept to synthesize catalytically active heterostructures of uniformly dispersed ∼4.3 nm PdO nanoparticles accessible through three-dimensional pore networks of the alumina support. Importantly, such materials reveal high resistance against sintering at 800 °C, even at relatively high loadings of NPs (∼10 wt %). At the same time, such heterostructures enable high mass transport due to highly interconnected nature of the pores. The surface of synthesized nanoparticles in the porous matrix is highly accessible, which enables their good catalytic performance in methane and carbon monoxide oxidation. In addition, we demonstrate that this approach can be utilized to synthesize heterostructures consisting of different types of NPs on a highly porous support. Our results show that swelling-based infiltration provides a promising route toward the robust and scalable synthesis of multicomponent structures.

Facile synthesis and improved Li-storage performance of Fe-doped MoS2/reduced graphene oxide as anode materials

MoS2 nanosheets have been widely explored as LIB anode materials due to higher theoretical capacity and weak interlayer interactions, but limited by their low conductivity and ease of stacking. Herein, we reported a novel Fe doped MoS2/reduced graphene oxide (Fe-MoS2/rGO) composite as LIB anode material and its one-step synthesis method. The results show that the synthesized Fe-MoS2/rGO composite has unique porous heterostructure, where networked Fe-MoS2 nanosheets of several nm thickness grow upon crumpled rGO sheets with high specific area. Due to the Fe doping as well as the mild synthesis conditions, the resulting Fe-MoS2 upon rGO sheets has wide interlayer spacing, abundant lattice defects and lower inner resistance. As a result, the Fe-MoS2/rGO electrode exhibits significant improvement in electrochemical performance relative to the non-doped MoS2/rGO electrode. The reversible capacities of Fe-MoS2/rGO electrode reach 1255 mAh/g (2nd circle) and 946 mAh g−1 (100th circle) with a retention of 75.4%. By comparison, the reversible capacities of MoS2/rGO electrode are only 654.1 mAh g−1 (2nd circle) and 429 mAh g−1 (100th circle) with a low retention of 64.1%.

A versatile strategy towards magnetic/dielectric porous heterostructure with confinement effect for lightweight and broadband electromagnetic wave absorption

Advanced electromagnetic (EM) wave absorbing materials containing both magnetic and dielectric components have attracted considerable attention for the ever-developing electronic and telecommunication devices. It is however, rather challenging to combat the sacrificed magnetic loss due to magnetic dilution by the introduction of the dielectric component. Here a novel confinement strategy has been adopted to develop porous heterogeneous Fe7Co3/ZnO nanosheets where Fe7Co3 nanoparticles with single domain size and dispersed distribution can be achieved for enhanced natural resonance. The nanosheets exhibit unique porous feature with significantly reduced density. Also, tunable dielectric loss achieved via interruption of the Fe7Co3 conductive network functions synergistically with the magnetic loss for enhanced absorption over a wide frequency range (7.92 GHz), covering the complete Ku band and half of the X band. The confinement strategy proposed in this study not only paves the way for designing high-performance EM wave absorber with low density and broad bandwidth, but also provides a versatile method for the synthesis of two-dimensional composites with tunable composition for extended applications in energy storage, catalysis, biomedicine and sensing.

Bio-inspired multilayered graphene-directed assembly of monolithic photo-membrane for full-visible light response and efficient charge separation

Highly efficient and easily recyclable monolithic photocatalysts with elaborate hierarchical heterostructure and functional components are desirable to tap solar energy and produce green hydrogen fuels for the sustainable future. Inspired by the natural leaves, here we have rationally designed and fabricated an efficient artificial leaf photocatalyst, i.e., the first monolithic photomembrane of CdS/ZnO nanocage arrays grown into the interspaces of multilayered reduced graphene oxide (rGO) nanosheets (denoted as CdS/ZnO/rGO). The CdS/ZnO/rGO have elaborate hierarchical porous heterostructure and multifunctional components, such as multilayer rGO nanosheets for visible light absorption/harvesting, rapid charge transport and collection, hollowed CdS/ZnO nanocage arrays for light harvesting and charge utilization, and multiple heterojunction interfaces for efficient charge separation. It can been used not only as a monolithic photocatalyst, but also directly as a freestanding photoanode in the photoelectrochemical (PEC) cell system, exhibits an enhanced performance of photocatalytic (PC) or PEC hydrogen generation under different monochrome light irradiation in full-visible light region. Moreover, the CdS/ZnO/rGO photo-membrane can macroscopically realize the separation of photogenerated hole elimination and hydrogen generation by adjusting co-catalysts loading position. Impressively, it still delivered a PC H2 generation activity (0.79 μmol cm−2 h-1) and a photocurrent response of 250 μA cm-2 even under near-infrared light (λ = 700 nm) irradiation, a striking feature rarely achieved in prior arts.

A facile synthesis of CuAg nanoparticles on highly porous ZnO/carbon black-cellulose acetate sheets for nitroarene and azo dyes reduction/degradation.

A facile and highly porous heterostructure nanocomposite was designed for the support of zero-valent metal nanoparticles. This nanocomposite comprising of ZnO/carbon black (ZnO/CB) embedded in cellulose acetate polymer (CA), named as ZCA sheet, supported the metallic Cu, Ag and bimetallic CuAg nanoparticles (NPs). The ZnO/CB was incorporated to CA polymer host molecule in 3, 4 and 5 wt% and are designated as ZCA-3, ZCA-4 and ZCA-5. The catalytic tunability was evaluated for CuAg/ZCA-5 by adjusting the concentration of Cu and Ag ions in different molar ratio. Therefore, the CuAg/ZCA-5 was further selected for the removal of eight model pollutants comprising of o-nitrophenol (ONP), m-nitrophenol (MNP), p-nitrophenol (PNP), 2,6-dinitrophenol (DNP), methyl orange (MO), congo red (CR), methylene blue (MB) and rhodamine B (RB). The Kapp value for PNP was 1.9 × 10-1 min-1 and 9.0 × 10-2 min-1 for MO. Among the various nitrophenols, the rate of reaction with CuAg/ZCA-5 followed the ordered as PNP ˃ ONP ˃ MNP ˃ DNP, while methyl orange (MO) is degraded faster as compared to other dyes. The morphology, shape, elemental analysis, functional groups and peak crystallinity were scrutinized through FESEM, EDS, ATR-FTIR and XRD respectively.

Facile synthesis of TiO2/In2S3/CdS ternary porous heterostructure arrays with enhanced photoelectrochemical and visible-light photocatalytic properties

TiO2/In2S3/CdS ternary porous heterostructure arrays were synthesized and characterised with the aim of enhancing photoelectrochemical and visible-light photocatalytic properties.

Construction of NiCo2O4@MnO2 nanosheet arrays for high-performance supercapacitor: Highly cross-linked porous heterostructure and worthy electrochemical double-layer capacitance contribution

A highly cross-linked three-dimensional (3D) hierarchical porous NiCo2O4 nanosheet@MnO2 nanosheet arrays (NNAs) on Ni foam is fabricated by a facile and stepwise hydrothermal approach. The NiCo2O4@MnO2 hybrid electrode demonstrates excellent electrochemical properties with high area capacitance of 5.3 F cm-2 at 1 mA cm−2, tremendous rate performance (68.9% with current density increased to 20 mA cm−2), and outstanding cycling stability (90.1% capacitance retention over 5000 cycles at 20 mA cm−2). The intriguing performance is related to unique cross-linked porous heterostructure with open geometry that provides large surface areas and superb channels for the electrolyte penetration and ion diffusion. Besides, by analyzing non-faradaic capacitive current upon repeated potential cycling, this honor attributes to not only sufficient Faraday reactions, but also a worthy electrochemical double-layer capacitance (EDLC) contribution with an electrochemical surface area (ESA) value of 616 mF cm−2 (220 F g−1 with a mass loading of 2.8 mg cm−2), which approximates to that of porous carbon.

Assembly-disassembly switching of self-sorted nanotubules forming dynamic 2-D porous heterostructure.

We report the pH-driven formation of a dynamic 2-D porous heterostructure through assembly-disassembly switching of the stacked macrocycles of nanotubules and their subsequent spreading on the surfaces of a self-sorted sheet assembly in a hierarchical co-assembly. The 2-D ordered porous heterostructure is able to discriminate spherical C60 from flat coronene through shape selective adsorption.

Exceptional visible-light photoelectrocatalytic activity of In2O3/In2S3/CdS ternary stereoscopic porous heterostructure film for the degradation of persistent 4-fluoro-3-methylphenol

Abstact In this work, In2O3/In2S3/CdS ternary stereoscopic porous heterostructure films were successfully fabricated via consecutive in situ ionic exchange reactions to degrade persistent 4-Fluoro-3-methylphenol through photoelectrocatalytic process. The optimized In2O3/In2S3/CdS ternary stereoscopic porous heterostructure film electrode showed much higher photoelectrocatalytic efficiency than the In2O3 and In2O3/In2S3 films. The resulting degradation reaction constant is about 3 and 2 times higher than that on In2O3 and binary In2O3/In2S3 films, respectively. The extraordinary higher degradation and mineralization efficiencies of the In2O3/In2S3/CdS composite film electrode come from the synergy of ternary components in the stereoscopic porous heterostructure. The existence of double type-II band alignment with nanosized interfaces in the ternary heterostructure can significantly improve charge transport and electron-hole separation. The stereoscopic porous architechture can greatly enhance visible light utilization and superhydrophilicity, and meanwhile facilitate the mass transport and accessibility of active sites. Ion chromatography, gas chromatography–mass spectrometry, total organic carbon analysis, active species trapping experiment as well as electron spin resonance techniques were employed to probe the degradation and the mineralization processes of 4-Fluoro-3-methylphenol. A unifying photoeletrocatalytic degradation route and mechanism is provided to explain the degradation and the mineralization processes. The generated more superoxide ions and holes promoted the defluorination process and favored the subsequent benzene ring cleavage and mineralization of low molecular weight fragments (e.g. carboxylic acids). This work provides a route to degrade persistent organic pollutants and realize efficient water contamination purification via efficient visible light photoelectrocatalytic process.

Highly stable 3D porous heterostructures with hierarchically-coordinated octahedral transition metals for enhanced performance supercapacitors

Designing and tailoring the assembly of complex ternary transition metal oxide (TTMO) structures are a key step in the pursuit of high performance pseudo-capacitive materials for the development of next-generation energy storage devices. Here, we present uniquely assembled 3D porous heterostructures with hierarchically-coordinated TTMOs, comprising the multiply interconnected primary nanoporous frameworks of ZnCo2O4/NiMoO4 core-shell structures and the secondary protruding structures of NiMoO4 layered nanosheets. By benefiting from the combination of hierarchically cooperative two TTMOs, the developed 3D ZnCo2O4/NiMoO4 heterostructures with their stable, porous, and conductive features exhibit robust pseudo-capacitive performance with high capacitances of 6.07Fcm–2 and 1480.48Fg–1 at 2mAcm–2 as well as an excellent cycling stability of 90.6% over 15,000 cycles. Moreover, an asymmetric supercapacitor device can deliver a high energy density of 48.6Whkg–1 and a power density of 2820Wkg–1. The superior pseudo-capacitive energy storage characteristics are strongly attributed to the interconnected 3D nanoporous network architectures of the TTMOs along with the secondary layered nanosheets that provide 1) the enlarged surface area with the high conductivity, 2) the facile and multi-access ion paths, and 3) the favorable structural stability. Combined, these results highlight the importance of novel nanostructure design in maximizing the pseudo-capacitive performance and provide a viable way to develop new electrode materials.