Hierarchical Porous Structure Research Articles

Layered CoS@NC in situ loaded onto Ti3C2Tx MXene as an efficient lithium-ion battery anode.

Due to its large capacity and relatively high conductivity, cobalt sulfide has been considered an excellent electrode material for lithium-ion batteries, but its extreme volume change during charging and discharging and lower conductivity than graphite limits its development. In this work, composite nanosheets of MXene and N-doped carbon-confined cobalt sulfide nanosheets (CoS@NC/MXene) were synthesized by growing the Co metal-organic framework of ZIF-67 onto MXene sheets, followed by sulfidation treatment. Different from normal ZIF-67 generally prepared in methanol, this work fabricates ZIF-67 in aqueous solution, which induces ZIF-67 to undergo some degree of hydrolysis and form more dispersed Co layered hydroxides mounted onto MXene. Also, the MXene incorporation imparts better water stability to ZIF-67(Co) and helps maintain its morphology during the sulfidation. CoS@NC/MXene has a conductive network supported by MXene and enhanced by NC, as well as a 3D hierarchical porous structure offered by the rational combination of its components. These favorable characteristics allow CoS@NC/MXene to deliver a capacity of 691 mA h g-1 at 200 mA g-1 in the 100th cycle and retain the specific capacity of 382 mA h g-1 at a higher current density of 8000 mA g-1.

Controllable synthesis of flower-like hierarchical porous TiO2 at room temperature and its affinity application.

Flower-like particles have attracted much attention due to their efficient surface accessible sites and unique hierarchical porous structure. However, their synthesis is usually challenging and requires complex procedures. Herein, we present a simple method for rapid preparation of flower-like hierarchical porous TiO2 (FHP-TiO2) at room temperature for the first time. This method can accurately control the size of FHP-TiO2 from 150 nm to 400 nm by combining co-assembly and Stober reaction. The formation mechanism and influencing factors of FHP-TiO2 were systematically investigated, and its excellent metal oxide affinity was confirmed by theoretical calculations. Due to its hierarchical porous structure, large surface area and high specificity performance, FHP-TiO2 served as an appealing restricted-access adsorbent for specific and efficient enrichment of molecules with phosphate groups in a complex sample matrix, thereby realizing the quantitative analysis of these important biomolecules by coupling with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Moreover, compared with other morphologies (rough surface, and hollow dendritic and mesoporous structure) of TiO2 and flower-like SiO2, FHP-TiO2 showed the best affinity binding ability. This research not only presents a novel approach for tunable room-temperature synthesis of FHP-TiO2 with different sizes, but also expands the application of FHP-TiO2 as an appealing sample-enricher for food safety monitoring and early disease diagnosis.

Environmentally-friendly preparation of natural hollow carbon spheres derived from a biomass puffball for in situ upgrading of lignin-derived vanillin

Biomass appears to be a potential candidate for the preparation of porous carbon materials with wide applications for catalytic fields due to its low price, green sustainability and natural hierarchical porous structure.

A hierarchical carbon foam-hosted Co2P nanoparticles monolithic electrode for ampere-level and super-durable electrocatalytic hydrogen production.

In this work, we develop a hierarchical carbon foam-based monolithic electrode (Co2P@HCF) from Co2+-adsorbed polyvinyl alcohol (PVA) sponge via the successive carbonization and phosphorization. Owing to the 3D hierarchical porous structure, excellent electrolyte wettability, good mechanical strength, and intimate embedding of highly dispersed Co2P nanoparticles, the Co2P@HCF electrode delivers a high current density of 1.0 A cm-2 for the hydrogen evolution reaction (HER) at ultralow overpotentials of 189.6 and 218.6 mV in 0.5 M H2SO4 and 1.0 M KOH solutions, respectively, with remarkable durability for 100 h.

Fluorinated carbon nitride with a hierarchical porous structure ameliorating PEO for high-voltage, high-rate solid lithium metal batteries

Hierarchical porous fluorinated carbon nitride (FCN) fillers induced the formation of a LiF- and Li3N-rich composite SEI layer and effectively suppressed the lithium dendrite growth in high-voltage, high-rate ASSLBs.

Self-assembled hierarchical porous carbon nanotube sponge bioanode for energy harvesting and gaseous toluene removal

Microbial fuel cells (MFCs) have emerged as a promising technology with potential for volatile organic compounds (VOCs) treatment and energy recovery. However, the low efficiency of electron transfer between microorganisms and electrodes has limited their degradation ability and power output. To address this issue, we designed a macroscopic hierarchical porous super-aligned carbon nanotube (SACNT) sponge bioanode. The hierarchical structure of the SACNT anode exhibited an appropriate distribution of macro/mesopores. The large pores facilitated biofilm formation and mass transfer, enhancing direct electron transfer between bacteria and SACNTs. The abundant mesopores augmented adsorption and electrochemical reaction sites, thereby enhancing flavin-mediated indirect electron transfer. This hierarchical pore structure induced the formation of biofilms mainly composed of electroactive bacteria and toluene-degrading bacteria, promoting toluene removal and power generation. The MFC demonstrated an exceptional power density of 726.18 mW m−2, surpassing existing toluene-fueled MFCs, while achieving the toluene elimination capacity of 61.29 g m−3 h−1.

Microstructural Changes of Synthetic Calcium Silicate Hydrate According to Ca/Si Ratios via Small Angle X-ray Scattering

The evolution of hierarchical porous structure according to Ca/Si ratios of calcium silicate hydrate (C-S-H), which determines the physicochemical properties of cement pastes, is still ambiguous. In this study, the changes in the hierarchical porous structure of synthetic C-S-H pastes with Ca/Si ratios of 0.6, 0.8, and 1.0 were analyzed via small angle X-ray scattering measurements using synchrotron X-ray. The microstructural changes of C-S-H within the length scale of 3-1000 Å were elucidated using the fractal model and the Guinier approximation that were presented as suitable for the cement hydrates in previous studies.

Tailoring hierarchical pore structures in carbon scaffolds for hydrogen storage of nanoconfined magnesium

Various carbon scaffolds have been developed for the nanoconfinement of Mg/MgH2 to achieve the synergistic effects of nanosizing-induced kinetic improvement, Mg-scaffold interaction-induced catalytic enhancement, and mechanical stress-driven thermodynamic stability tuning for advanced hydrogen storage. Yet, systematic studies linking the chemo-structural features of the carbon scaffolds and the hydrogen storage properties of Mg/MgH2 nanoparticles within the scaffolds remain largely unexplored. Here, we investigate the pore-dependent Mg nanoconfinement and its hydrogen storage behavior using hollow carbon nanospheres (HCNs) as scaffolds, dictated by their distinct pore properties. Contrary to the conventional wisdom of nanoconfinement, the Mg nanoparticles confined by the HCN with large mesopores exhibit faster hydrogen sorption kinetics and improved thermodynamic characteristics than those with small mesopores. The detailed analyses reveal that the interplay between reversible mechanical stress upon hydrogenation and nanosizing-induced facile kinetics leads to the observed experimental results. Ab initio computations further show that compressive stress retards bulk diffusion while at the same time enhances the surface hydrogen desorption, suggesting the need for stress optimization within the composite. Our study provides a design guideline for Mg strain engineering and the subsequent carbon scaffold structures for hydrogen storage, possibly leading to advanced hydrogen storage of confined Mg.

Bioinspired radiative cooling coating with high emittance and robust self‐cleaning for sustainably efficient heat dissipation

AbstractTo overcome the overheating phenomena of electronic devices and energy components, developing advanced energy‐free cooling coatings with promising radiative property seem an effective and energy‐saving way. However, the further application of these coatings is greatly limited by their sustainability because of their fragile and easy contamination. Herein, it is reported that a bioinspired radiative cooling coating (BRCC) displayed sustainably efficient heat dissipation by the combination of high emittance and robust self‐cleaning property. With the hierarchical porous structure constructed by multiwalled carbon nanotubes (MWCNTs), modified SiO2 and fluorosilicone (FSi) resin, the involvement of the BRCC improves the cooling performance by increasing ≈25% total heat transfer coefficient. During the abrasion and soiling tests, the BRCC‐coated Al alloy heat sink always displays stable radiative cooling performance. Moreover, the simulation and experimental results both revealed that reducing surface coverage of BRCC (≈80.9%) can still keep highly cooling efficiency, leading to a cost‐effective avenue. Therefore, this study may guide the design and fabrication of advanced radiative cooling coating.

Hierarchical porous SAPO-34 decorated with Mo and W oxides for concurrent transesterification-esterifications for efficient biodiesel production from acidic soybean oil

Hierarchical porous materials have gained much attention as promising heterogeneous catalyst supports due to their high efficiency of mass transfer and high exposure of active centers. In this research, the hierarchical porous SAPO-34 support with microporous, mesoporous, and macroporous hierarchical structure was initially prepared by in-situ alkali etching. Then, Mo and W oxides were incorporated into this hierarchical porous support by using the impregnation method to prepare Mo15W15/HSAPO-34/70 catalyst. This developed catalyst was applied to concurrently catalyze the oil transesterification and free fatty acid (FFA) esterification to biodiesel as the low-value oils severed as feedstocks. The textural and physicochemical properties of the nanocatalysts were evaluated by XRD, XPS, SEM, EDS, TEM, UV–vis, NH3-TPD, Py-FTIR, and nitrogen porosimetry measurement. This catalyst had hierarchical porous structure to ameliorate the large oil molecular transfer, and featured dual Brønsted-Lewis acid sites to synergistically boost the catalytic efficiency for the biodiesel production. Over this catalyst, the oil conversion of 90.1 % and full FFA conversion were achieved under optimized operation conditions, therefore imparting to one-pot conversion to biodiesel with low-value oils as feedstocks. In addition, this catalyst not only exhibited superior tolerance to moisture and FFAs, but also retained high activities after five reuse cycles, thus revealing its tremendous potential of being used in durable and efficient biodiesel production. The present work opens a new avenue for synthesizing a robust solid acid catalyst to achieve a one-pot biodiesel production from low-value oils.

Conversion of Dimethyl Ether to Triptane-Rich Liquid Hydrocarbons on Pd-LaHY with a Hierarchical Porous Structure

Conversion of Dimethyl Ether to Triptane-Rich Liquid Hydrocarbons on Pd-LaHY with a Hierarchical Porous Structure

Self‐Assembled 3D N/P/S‐Tridoped Carbon Nanoflower with Highly Branched Carbon Nanotubes as Efficient Bifunctional Oxygen Electrocatalyst Toward High‐Performance Rechargeable Zn‐Air Batteries

AbstractHeteroatom doping and 3D nanostructures with large specific surface area and hierarchical porous structure can synergically improve oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this study, the 3D N/P/S‐tridoped nanoflower with highly branched carbon nanotubes bifunctional catalyst (Co/SP‐NC) is prepared by a simple self‐assembly pyrolysis method. The powerful driving force of coordination interaction of ammonium ion can promote the self‐assembly of 2D ZnCo‐ZIF nanosheets into 3D ZnCo/S‐ZIF nanoflowers at room temperature stirring. The 3D ZnCo/S‐ZIF nanoflower surface is driven by sodium hypophosphite to form highly branched carbon nanotubes during the pyrolysis process. Moreover, Density functional theory (DFT) calculations also confirm that the simultaneous introduction of N/P/S can promote the redistribution of electron density at the catalyst interface. The proper P‐doping not only enhances the electronic conductivity of the substrate, but also facilitates the charge transfer in the OER/ORR process. Therefore, Co/SP‐NC cathode assembled zinc‐air batteries (ZABs) have a higher power density (187 mW cm−2), a larger specific capacity (801 mAh gZn−1) and excellent cycle stability compared to Pt/C‐RuO2 assembled ZABs. This work will pave the way to regulate the components interactions by designing 3D hierarchical porous structures.

Scalable synthesis of N, O co-doped hierarchical porous carbon for high energy density supercapacitors

Rational design of hierarchical porous architecture with abundant pseudocapacitive sites is highly desirable for carbon electrode materials. However, the lengthy production process and high economic input limit its broader application. Herein, we successfully prepared N, O co-doped hierarchical porous carbon (NOHC) through hydrothermal carbonization (HTC) of chitin biomass with the assist of NH4Cl and subsequent carbonization with NaNH2. The optimal NOHC600 exhibits a remarkable hierarchical porous structure and an ultrahigh specific surface area (SSA) of 2555 m2 g−1. Furthermore, it showcases a significant content of N, O co-doping, thereby providing abundant defects and additional active sites for ion adsorption. The aforementioned characteristics ensure outstanding capacitance performance of NOHC600. In the three-electrode system, NOHC600 exhibits a remarkable specific capacitance of up to 455 F g−1 at a current density of 0.5 A g-1. The symmetric supercapacitors (SCs) based on NOHC600 achieve an impressive energy density of 30.4 Wh kg−1 at a power density of 180 W kg−1. Moreover, the all-solid-state NOHC600 microsupercapacitors (MSCs) demonstrate an exceptional areal capacitance of 78.2 mF cm−2 and an areal energy density of up to 10.8 μWh cm−2. Accordingly, this facile and scalable strategy shows a great potential for producing high-heteroatom-doped porous carbon materials from chitin biomass, which can be applied in practical energy-related applications.

Novel hydrophobic hierarchical porous carbon from sewage sludge for the efficient capture of gaseous iodine

Finding an inexpensive and efficient porous adsorbent to capture the gaseous radioiodine generated during spent fuel reprocessing has been challenging. Herein, we present a design philosophy for waste control to develop porous carbon for gaseous iodine capture from sewage sludge waste. Among them, the novel in situ etching of polytetrafluoroethylene was employed to improve pore accessibility. The hazards of the conventional preparation of sludge-derived carbon using highly corrosive NaOH and HF solutions were overcome. Polytetrafluoroethylene etched porous carbon with large specific surface area (1103 m2/g), interconnected hierarchical porous structure, and excellent hydrophobicity (water contact angle 126.52°), providing efficient adsorption of gaseous iodine in hot (30–150 °C) and humid (50–96% relative humidity [RH]) environments. The iodine adsorption of hierarchical porous carbon was tested under static and dynamic conditions, and high records have been achieved. Notably, due to the structural advantage of hydrophobicity, a considerable dynamic adsorption capacity (1746.77 mg/g) was also maintained in a mixed iodine gas stream containing water vapor in a humid (50% RH) hot (75 °C) condition. This study is the first to use an in situ etching strategy for polytetrafluoroethylene, which opens a new avenue for converting sludge waste into low-cost porous carbon and provides an attractive option for capturing iodine in hot and humid environments.

O, N‐Codoped, Self‐Activated, Holey Carbon Sheets for Low‐Cost And High‐Loading Zinc‐Ion Supercapacitors

AbstractLow‐cost and high‐loading cathodes are crucial for practical application of zinc‐ion supercapacitors (ZICs) but achieving optimal performance in high‐loading electrodes faces challenges due to sluggish ion transport, increased resistance, and unstable structure. Guided by theoretical calculations, high‐loading carbon cathodes based on holey activated carbon sheets (HACS) are fabricated from a carefully chosen molecule. A simple pyrolysis‐leaching treatment transformed the molecule into HACS with large surface area, hierarchical porous structure, and electroactive oxygen/nitrogen dopants. When combined with an aqueous binder, the optimized HACS‐based high‐loading electrode (16.1 mg cm−2) exhibits high‐capacitance (454 F g−1 ) and fast‐rate (1 A g−1) characteristics under lean electrolyte (6.2 µL mg−1). More impressively, HACS is dry‐pressed into free‐standing thick electrodes up to 35.4 mg cm−2 and corresponding practical ZIC under limited Zn and low N/P ratio demonstrates ultrahigh areal capacitance (9 F cm−2) and energy density (3.47 mWh cm−2). The outstanding performance can be attributed to fast ion transport enabled by through‐plane pores of HACS, as well as abundant double‐layer and redox‐active surfaces from favorable heteroatom‐doped porous nanosheets. With its cost‐effectiveness, elemental abundance, and structural tunability, this molecular carbon strategy offers a platform for making self‐activated carbon electrodes at the molecular level towards practical supercapacitors.

π-Conjugated molecule mediated self-doped hierarchical porous carbons via self-stacking interaction for high-energy and ultra-stable zinc-ion hybrid capacitors

Understanding the self-stacking interactions in precursors can facilitate the preparation of high-performance carbon materials and promote the commercial application of zinc ion hybrid capacitors (ZIHCs). Here, a π-conjugated molecule mediated pyrolysis strategy is presented to prepare carbon materials. Taking intermolecular force simulation (reduced density gradient plots) as a guide, the relationship between the self-stacking interactions in π-conjugated molecules and the structural parameters of carbon materials can be extrapolated. The resultant self-doped hierarchical porous carbons (NHPCs) derived from 1, 8, 4, 5-naphthalenetetracarboxdiimide with suitable self-stacking interactions empower the highest specific surface areas (2038 m2/g) and surface opening macropores. The NHPCs-based ZIHCs deliver a high capacity of 220 mAh/g, a high energy density of 149.5 Wh kg−1 and a super-stable cycle lifespan with 93.2 % capacity retention after 200, 000 cycles. The excellent electrochemical performance roots in the superior hierarchical porous structure with surface opening macropores, which guarantees the structural stability of carbon cathodes upon repeated rounds. Meanwhile, the heteroatom doping further relieves the kinetics concern of Zn2+ uptake/removal to enhance O-Zn-N binding particularly at high discharge currents. Besides, the proton-assisted Zn2+ dual-ion storage mechanism plays an essential role in the energy storage process. This work demonstrates a facile synthesis method and advances the fundamental understanding of its dual-ion storage mechanism.

Three-dimensional hydrangea-like layered double hydroxide anchoring hollow metal organic-framework for efficient adsorption of 2, 4-dichlorophenoxyacetic acid

In this work, a facile approach to create a layered double hydroxide@hollow zeolitic imidazolate framework-8 nanocomposites (LDH@HZIF-8) was performed for the removal of 2, 4-dichlorophenoxyacetic acid (2,4-D) in food samples. This novel material inherits the advantages of pristine metal-organic frameworks. Additionally, it possesses a hierarchical pore structure, a hollow cavity, a large specific surface area (624.09 m2 g−1), and improved dispersity of ZIF-8. The potential of LDH@HZIF-8 as an adsorbent for removing 2,4-D from food samples was investigated. Our findings revealed a significant maximum adsorption capacity of 178.6 mg g−1 at 25 °C, along with fast adsorption kinetics within 20 min. The adsorption process was well described by the pseudo-second-order kinetics and Langmuir model. Furthermore, thermodynamic data indicated that the adsorption process was exothermic in nature. This novel composite effectively addresses the issues associated with sluggish mass transfer of target molecules/ions and a shortage of active sites. Moreover, LDH@HZIF-8 offers spacious cavities and channels that are capable of accommodating the desired substances.

Efficient thermal insulation through all-biomass silk fibroin composite aerogel 3D-reinforced by natural down-fiber

Biomass-based aerogels offer numerous individual benefits in thermal insulation applications. However, their generally weak mechanical properties impair the further development of aerogels. Herein, natural down-fiber (DF) reinforced silk fibroin (SF) all-biomass aerogel was rationally designed. The developed 3D-reinforcement structure, in which DF was physically interspersed in SF in multiple directions and hydrogen bonds formed between DF and SF, resulted in significantly enhanced compression stress of 146.3 kPa (3.44 times greater than that of SF aerogel, which attained 42.57 kPa) and impressive compression resilience. Meanwhile, the DF@SF aerogel displayed a hierarchical porous structure (97.64 % porosity) with micron-sized holes and nano-sized pores, as well as low thermal conductivity of 0.034 W m−1 K−1, which would effectively inhibit air circulation and limit heat transfer for improved thermal insulation. Moreover, the addition of DF reduced the average hole diameter, which further prevented heat convection and minimized heat radiation inside the aerogel. As a result, the DF@SF aerogel demonstrated excellent thermal insulation performance with a wide range of working temperatures from −40 to 160 °C and stability for recyclable usage. Therefore, this all-biomass DF@SF aerogel could offer an alternative form of high-performance thermal insulation. This strategy will also inspire more research into the construction of 3D-reinforced functional aerogels and their applications in thermal insulation, sound insulation, biomedicine, and other related areas.

N-Doped Carbon Nanowire-Modified Macroporous Carbon Foam Microbial Fuel Cell Anode: Enrichment of Exoelectrogens and Enhancement of Extracellular Electron Transfer.

Microbial fuel cell (MFC) performance is affected by the metabolic activity of bacteria and the extracellular electron transfer (EET) process. The deficiency of nanostructures on macroporous anode obstructs the enrichment of exoelectrogens and the EET. Herein, a N-doped carbon nanowire-modified macroporous carbon foam was prepared and served as an anode in MFCs. The anode has a hierarchical porous structure, which can solve the problem of biofilm blockage, ensure mass transport, favor exoelectrogen enrichment, and enhance the metabolic activity of bacteria. The microscopic morphology, spectroscopy, and electrochemical characterization of the anode confirm that carbon nanowires can penetrate biofilm, decrease charge resistance, and enhance long-distance electron transfer efficiency. In addition, pyrrolic N can effectively reduce the binding energy and electron transfer distance of bacterial outer membrane hemin. With this hierarchical anode, a maximum power density of 5.32 W/m3 was obtained, about 2.5-fold that of bare carbon cloth. The one-dimensional nanomaterial-modified macroporous anodes in this study are a promising strategy to improve the exoelectrogen enrichment and EET for MFCs.

Unlocking Bifunctional Electrocatalytic Performance of Co-MOF-Derived Catalysts for ORR and OER

As the world is rapidly moving towards renewable energy technologies, the demand for efficient and cost-effective bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is increasing. Metal-organic framework (MOF)-based catalysts possess tunable and hierarchical porous structures with high surface area, making them superior to noble metal catalysts for energy storage technologies due to their high catalytic activity and stability.In this study, we report a novel Co-N-C bifunctional oxygen electrocatalyst synthesized by carbonizing single metal Co-MOF precursor TAL-2. The optimized Co-N-C material demonstrated superior ORR/OER bifunctional catalytic activity compared to the commercial Pt/C and RuO2. The outcomes of this study highlight the considerable potential of utilizing a single metal Co-N-C catalyst as a facile precursor for the development of highly efficient electrocatalyst materials.