Hierarchical Mesoporous Structure Research Articles

Highly selective separation of lithium with hierarchical porous lithium-ion sieve microsphere derived from MXene

Lithium recovery from brine is critical for the sustainable development of energy-storage devices. However, the current lithium-ion sieve adsorbents are hampered by the adsorption rate and adsorption capacity. Herein, ultrathin nanosheets-assembled Li4Ti5O12 porous microspheres with hierarchical mesoporous structure are prepared by a hydrothermal method. Their high specific surface area (above 180 m2/g) exposed more adsorption sites and significantly accelerated the adsorption rate (equilibrium in 1 h). Besides, the H4Ti5O12 (HTO) microspheres showed superior Li+ adsorption capacity of 43.20 mg/g and high selectivity for Li+ from high Mg-containing aqueous solutions. The lithium adsorption over HTO is endothermic and can be well defined as pseudo-second-order kinetic model and Langmuir model, indicating the chemical adsorption and monolayer adsorption. The facial regeneration of HTO by HCl shows excellent stability and the Li+ adsorption capacity remains above 93% after 20 cycles. Thus, this HTO microspheres can be regarded as a helpful candidate for lithium recovery.

Enhanced n-butanol sensing performance of SnO2/ZnO nanoflowers fabricated via a facile solvothermal method

High-performance gas sensors have important application prospects in the detection and monitoring of toxic and harmful gases that exist in the environment and workshop. Herein, SnO2/ZnO nanoflowers with core-shell like structure were successfully fabricated by a two-step solvothermal method. Morphology and mineral phase characterizations demonstrate that the nanoflowers, composed of a SnO2 flower core in a diameter of about 50 nm and ZnO nanoparticles embedded in the interstice of SnO2 petals, has a novel mesoporous hierarchical structure with pore size distributed in about 3 nm and 30 nm and a specific surface area of 36.474 m2/g, benefitting to gas-sensing. The results reveal that, compared to pure SnO2 nanoflowers, the optimal SnO2/ZnO (Zn/Sn is 5%) based gas sensor shows 2.7-fold sensing enhancement, fast response (3 s), long-term stability toward n-butanol. It has an outstanding selectivity to n-butanol rather than other gas, its response toward 100 ppm n-butanol at 200 °C is up to 13, 34, 15 and 32 times of that to acetone, xylene, ammonia and carbon monoxide respectively. Hence, SnO2/ZnO nanoflowers can be considered as a practical sensing material for n-butanol detection.

Hierarchical Nanocellulose-Based Gel Polymer Electrolytes for Stable Na Electrodeposition in Sodium Ion Batteries.

Sodium ion batteries (NIBs) based on earth-abundant materials offer efficient, safe, and environmentally sustainable solutions for a decarbonized society. However, to compete with mature energy storage technologies such as lithium ion batteries, further progress is needed, particularly regarding the energy density and operational lifetime. Considering these aspects as well as a circular economy perspective, the authors use biodegradable cellulose nanoparticles for the preparation of a gel polymer electrolyte that offers a high liquid electrolyte uptake of 2985%, an ionic conductivity of 2.32 mS cm-1 , and a Na+ transference number of 0.637. A balanced ratio of mechanically rigid cellulose nanocrystals and flexible cellulose nanofibers results in a mesoporous hierarchical structure that ensures close contact with metallic Na. This architecture offers stable Na plating/stripping at current densities up to ±500µA cm-2 , outperforming conventional fossil-based NIBs containing separator-liquid electrolytes. Paired with an environmentally sustainable and economically attractive Na2 Fe2 (SO4 )3 cathode, the battery reaches an energy density of 240 Wh kg-1 , delivering 69.7 mAh g-1 after 50 cycles at a rate of 1C. In comparison, Celgard in liquid electrolyte delivers only 0.6 mAh g-1 at C/4. Such gel polymer electrolytes may open up new opportunities for sustainable energy storage systems beyond lithium ion batteries.

Mesoporous Tubes Composed of Graphitic Carbon-Doped Co3O4 Nanoparticles for Lithium Storage

The cheap biomass-derived carbon-encapsulated strategy has recently attracted much attention in enhancing the properties of metal oxide-based anodes for lithium-ion batteries (LIBs). Herein, graphitic carbon (GC)-encapsulated Co3O4 material with mesoporous hierarchical structure was prepared by immersion, carbonization, and air calcination with poplar branch as a biotemplate and carbon source. We also investigated the impact of different carbon contents on the nanostructure and electrochemical performance of composites. The microtube wall of Co3O4/GC350 oxidized at 350 °C is assembled by cross-linking Co3O4 nanoparticles and graphitic carbon, making Co3O4/GC350 possess a large specific surface area of 70.4 m2 g–1 and a concentrated mesopore size distribution of 3.75 nm. As an anode for LIBs, Co3O4/GC350 exhibits better lithium storage performance than the product oxidized at 450 °C. At 1 A g–1, it delivers a stable capacity of 665.7 mA h g–1 after long cycling 1200 times and even retains a capacity of 294.1 mA h g–1 at 5 A g–1, indicating that Co3O4/GC350 nanomaterial has good rate performance and long-cycling stability. The excellent electrochemical performance is primarily ascribed to the unique mesoporous nanostructure, large specific surface area, encapsulated GC in Co3O4/GC350, and the synergism of pseudocapacitive behavior arising from oxygen vacancy defects and the mesoporous structure. Therefore, the simple, eco-friendly, and large-scale poplar branch-templated strategy in this work can offer a beneficial experience for synthesizing other transition-metal oxide anodes.

Urchin-like structured magnetic hydroxyapatite for the selective separation of cerium ions from aqueous solutions

In this study, bio-inspired urchin-like structured hydroxyapatite (UHdA) and its magnetic composite (UHdA@Fe3O4) were developed for efficient and easy separation of cerium ions (Ce3+) from aquatic waste streams. UHdA and UHdA@Fe3O4 exhibited superior Ce3+ adsorption capacities of 248.39 and 230.01 mg/g-UHdA respectively, compared to a commercial HdA (141.71 mg/g-HdA) due to their hierarchical mesoporous structure and large specific surface area. The adsorption of Ce3+ to UHdA and UHdA@Fe3O4 were heterogeneous, pseudo-second-order-kinetic, and the rate-limiting step was external mass transfer and intra-particle diffusion. Moreover, thermodynamic studies revealed that the adsorption process was spontaneous and endothermic nature. The high selectivity towards Ce3+ in multi-ionic systems is attributed to the strong affinity between strong Lewis acid (Ce3+) and base (PO43- and OH-) interactions. XRD, FTIR, and XPS analysis demonstrated that the adsorption was mainly attributable to the ion exchange of Ce3+ with Ca2+ and to surface complexation. The desorption of Ce3+ was efficiently accomplished using 0.1 M HNO3. The results suggest that UHdA and UHdA@Fe3O4 could be promising choices for the adsorption and recovery of rare earth elements.

Fabrication of three-dimensional hierarchical porous 2D/0D/2D g-C3N4 modified MXene-derived TiO2@C: Synergy effect of photocatalysis and H2O2 oxidation in NO removal

A novel three-dimensional multi-level porous g-C3N4 modified MXene-derived TiO2@C aerogel (g-C3N4/TiO2@C aerogel) was synthesized for NO removal. Through SEM analysis, 2D g-C3N4 and 2D Ti3C2 nanosheets were constructed into an interconnected macroscopic framework with continuous macropores via ice template. OD TiO2 nanoparticles uniformly covered 2D C nanosheets with irregular mesopores and macropores in in-situ oxidation of Ti3C2 nanosheets by calcination via TEM analysis. g-C3N4/TiO2@C aerogel for photocatalytic activation of hydrogen peroxide (H2O2) had an excellent efficiency of 90.7% for NO removal at parts per million level. This efficiency was 4.9 times and 7.8 times that of g-C3N4/TiO2@C aerogel and H2O2 individually, due to the synergy between photocatalysis and H2O2 oxidation. Meantime, g-C3N4/TiO2@C aerogel exhibited an enhanced performance compared with g-C3N4 nanosheet (55.7%) and TiO2@C aerogel (38.5%). It was attributed to the large specific surface area (93.82 m2/g) with hierarchical mesoporous and macroporous structure and the 2D/OD/2D heterojunction of g-C3N4/TiO2@C aerogel, further enhancing electron-hole separation. The mechanism was hypothesized that g-C3N4/TiO2@C aerogel activated H2O2 to generate hydroxyl radicals (·OH) and superoxide radicals (·O2–) for oxidation of NO.

Hybrid MnO-SiOx@C microspheres with a hierarchical mesoporous structure for advanced lithium-ion battery anodes

A novel porous structure MnO-SiOx @C composite has been designed and prepared as an anode material for lithium-ion batteries through scalable spray pyrolysis and a subsequent annealing process. XRD, SEM, TEM, Raman, and BET measurements indicate that the MnO-SiOx @C composite displays a spherical mesoporous structure with SiOx particles, embedded in the porous MnO structure combined with carbon coated on the surfaces. The enhanced electrochemical performance can be attributed to the mutual segregation of the heterogeneous oxides of MnO and SiOx during delithiation and the buffer composition region at the origin of uniform carbon layers and abundant nanopores. In addition, the new phase Mn2SiO4, which is formed in the MnO-SiOx @C composite after 800 ºC, can act as the joint between MnO and SiOx to restrain the strain force originating from the volume change during the charge and discharge process. As a result, the obtained MnO-SiOx @C composite exhibits significantly enhanced electrochemical performance in terms of high Coulombic efficiency, excellent rate capability and good cyclability.

Magnesiothermic reduction improved route to high-yield synthesis of interconnected porous Si@C networks anode of lithium ions batteries

Silicon (Si) based materials has been envisaged as a promising anode material for the next-generation high energy-density lithium-ion batteries (LIBs) thanks to its ultrahigh specific capacity. The development of reliable Si anode yet faces challenges of how to explore a simple, convenient and controllable synthetic route of Si composite anode with high conductivity and favorable structure. Herein, we report a newly synthetic route by extending the well-known Mg-thermal reduction method for the high-yield fabrication of three-dimensional (3D) porous Si/C nano-architectures (p-Si@C) featuring interconnected conductive networks and hierarchical mesoporous structure, endowing it with favorable properties and structure as anode of lithium-ions batteries (LIBs). Comprehensive characterization via various techniques coupling with density functional theory calculations demonstrates the as-prepared p-Si@C nano-architectures are favorable for forming stable solid-electrolyte interface (SEI), facilitating Li+ transport and electrons transfer, and mitigating the volume expansion effect upon for Li+ storage. As such, the Si@C nano-architectures not only exhibit high reversible capacity of 1078.68 mAh g−1 and impressively high cycling stability over 500 cycles at 1 A g−1 but also keep a quite attractive capacity retention rate of 47.9% even increasing rate to 10 A g−1. The feasibility of its practical application has been demonstrated by a lithium-ion full battery with the commercial lithium iron phosphate (LFP) as cathode, which delivers a stable reversible capacity of 124.4 mA g−1 and boasting high energy density of 381.61 Wh kg−1 at 0.2 C based on total mass of active material of the cathode and anode.

Synthesis of highly porous iron-doped carbonated hydroxyapatite spheres for efficient adsorption of carmine dyes

Highly porous Fe-doped carbonate hydroxyapatite spheres (Fe-CHAs) were synthesized by two-step hydrothermal method and characterized by SEM, XRD and FTIR. The synthesized Fe-CHAs were confirmed as B-type substituted CHAs. Fe-CHAs with desirable hierarchical mesoporous structure exhibited BET surface area of 93.8 m2/g, pore diameter of 37.4 nm, and pore volume of 0.523 cm3/g. Carmine dye was chosen as model organic dye to investigate the adsorption properties of Fe-CHAs. The maximum adsorption capacity of Fe-CHAs was 55.89 mg/g, which was about seven times as much as that of HA powder. Adsorption kinetics carmine dye molecules onto Fe-CHAs followed the second-order kinetic equation and Langmuir model, indicating that adsorption of carmine dye molecules onto Fe-CHAs was mainly monolayer chemical adsorption. Experimental results show that these highly porous Fe-CHAs could be a potential efficient adsorption material for removing organic dyes in industrial wastewater.

P- N heterojunction NiO/ZnO electrode with high electrochemical performance for supercapacitor applications

Due to environmental pollution and the increasing shortage of fossil fuels, sustainable hybrid electrode materials must be developed to improve the performance of semiconductor-based supercapacitors, thus allowing for the realization of alternative energy storage systems. An ordered mesoporous (OM) NiO/ZnO p-n heterojunction electrochemical electrode was prepared by using a soft-template method and facile hydrothermal technique. The p-type NiO was successfully assembled on the ordered mesoporous n-type ZnO matrix, thus forming p-n heterojunction artifacts with hierarchical porous structures. The capacitive performance and mechanism were systemically investigated. The prepared p-n heterojunction OM-NiO/ZnO supercapacitor exhibited excellent capacitive performances with a significantly higher specific capacity of 1394 C g − 1 (1 A g − 1), high rate capability of 560 C g − 1 at 20 A g − 1, stable cycling property (constant at 538 C g − 1 after 2000 cycles at 5 A g − 1), and wide potential window of 0.6 V. These high supercapacitor performances can be mainly attributed to the synergistic effects of the nanoscale ordered mesoporous structure, loose 3D- networks, and p-n heterojunction formed by two phases of ZnO and NiO, which provide abundant active sites and charge transfer pathways for the diffusion of ions and electron transfer, respectively. The results show that this novel approach involving the p-n heterojunction with a hierarchical mesoporous structure allows for the development of energy materials.

Three-Dimensional Hierarchical Porous TiO2 for Enhanced Adsorption and Photocatalytic Degradation of Remazol Dye.

Three-dimensional hierarchical mesoporous structures of titanium dioxide (3D-HPT) were synthesized by self-assembly emulsion polymerization. Polymethyl methacrylate (PMMA) and pluronic 123 (P123) were used as the soft templates and co-templates for assisting the formation of hierarchical 3D porous structures. The TiO2 crystal structure, morphology, and Remazol red dye degradation were investigated. The 3D-HPT and normal three-dimensional titanium dioxide (3D-T) presented the good connection of the nanoparticle-linked honeycomb within the form of anatase. The 3D-HPT structure showed greatly enhanced adsorption of Remazol dye, and facilitated the efficient photocatalytic breakdown of the dye. Surprisingly, 3D-HPT can adsorb approximately 40% of 24 ppm Remazol dye in the dark, which is superior to 3D-T and the commercial anatase at the same condition (approx. 5%). Moreover, 3D-HPT can completely decolorize Remazol dye within just 20 min, which is more than three folds faster than the commercial anatase, making it one of the most active photocatalysts that have been reported for degradation of Remazol dye. The superior photocatalytic performance is attributed to the higher specific surface area, amplified light-harvesting efficiency, and enhanced adsorption capacity into the hierarchical 3D inverse opal structure compared to the commercial anatase TiO2.

Synthesis of Highly Porous Iron-Doped Carbonated Hydroxyapatite Spheres for Efficient Adsorption of Carmine Dyes

Highly porous Fe-doped carbonate hydroxyapatite spheres (Fe-CHAs) were synthesized by two-step hydrothermal method and characterized by SEM, XRD and FTIR. Fe-CHAs with desirable hierarchical mesoporous structure exhibited BET surface area of 93.849 m2/g, pore diameter of 37.387 nm, and pore volume of 0.523 cm3/g. Carmine dye was chosen as model organic dye to investigate the adsorption properties of Fe-CHAs. The adsorption capacity of Fe-CHAs is about seven times as much as that of HA powder. Adsorption kinetics carmine dye molecules onto Fe-CHAs followed the second-order kinetic equation and Langmuir model, indicating that adsorption of carmine dye molecules onto Fe-CHAs is mainly monolayer chemical adsorption. Experimental results show that these highly porous Fe-CHAs could be a potential efficient adsorption material for removing organic dyes in industrial wastewater.

CoO hierarchical mesoporous nanospheres@TiO2@C for high-performance lithium-ion storage

The hierarchical mesoporous structure is an ideal active material structure for lithium-ion batteries and other energy storage devices. In this work, we report a universal chelation-carbonization-oxidation path to synthesize CoO nanocrystalline-assembled hierarchical mesoporous nanospheres with Co-glycerate inorganic-organic hybrid spheres as the precursor, followed by the coating of TiO2 and amorphous carbon. The electrochemical measurements demonstrate, as an anode of lithium-ion batteries, as-prepared CoO@TiO2@C exhibits high reversible capacity, stable cycling performance and good rate capability. It can deliver discharge capacity of 1136 mAh g−1 after 200 cycles at current density of 0.5 A g−1 and average discharge capacity of 493 mAh g−1 even at high current density of 5 A g−1. The excellent lithium storage performance benefits from the multiple structural advantages. The nanocrystalline-assembled hierarchical mesoporous nanosphere endows CoO with high electrochemical activity. The robust TiO2 and amorphous carbon shells improve structure stability and electronic conductivity of CoO hierarchical mesoporous nanospheres.

3D flower-like mesoporous Bi4O5I2/MoS2 Z-scheme heterojunction with optimized photothermal-photocatalytic performance

3D flower-like hierarchical mesoporous Bi4O5I2/MoS2 Z-scheme layered heterojunction photocatalyst was fabricated by oil bath and hydrothermal methods. The heterojunction with narrow band gap of ∼1.95 eV extended the photoresponse to near-infrared region, which showed obvious photothermal effect due to the introduction of MoS2 with broad spectrum response. MoS2 nanosheets were anchored onto the surface of flower-like hierarchical mesoporous Bi4O5I2 nanosheets, thereby forming efficient layered heterojunctions, the solar-driven photocatalytic efficiency in degradation of highly toxic dichlorophenol and reduction of hexavalent chromium was improved to 98.5% and 99.2%, which was ∼4 and 7 times higher than that of the pristine Bi4O5I2, respectively. In addition, the photocatalytic hydrogen production rate reached 496.78 μmol h−1 g−1, which was ∼6 times higher than that of the pristine Bi4O5I2. The excellent photocatalytic performance can be ascribed to the promoted photothermal effect, as well as, the formation of compact Z-scheme layered heterojunctions. The 3D flower-like hierarchical mesoporous structure provided adequate surface active-sites, which was conducive to the mass transfer. Moreover, the high stability of the prepared photocatalyst further promoted its potential practical application. This strategy also provides new insights for fabricating layered Z-scheme heterojunctions photocatalysts with highly photothermal-photocatalytic efficiency.

Self-assembled mesostructured Co0.5Fe2.5O4 nanoparticle superstructures for highly efficient oxygen evolution

Self-assembly of colloidal nanoparticles (NPs) into well-defined superstructures has been recognized as one of the most promising ways to fabricate rationally-designed functional materials for a variety of applications. Introducing hierarchical mesoporosity into NP superstructures will facilitate mass transport while simultaneously enhancing the accessibility of constituent NPs, which is of critical importance for widening their applications in catalysis and energy-related fields. Herein, we develop a colloidal co-assembly strategy to construct mesostructured, carbon-coated Co0.5Fe2.5O4 NP superstructures (M-C@CFOSs), which show great promise as highly efficient electrocatalysts for the oxygen evolution reaction (OER). Specifically, organically-stabilized SiO2 NPs are employed as both building blocks and sacrificial template, which co-assemble with Co0.5Fe2.5O4 NPs to afford binary NP superstructures through a solvent drying process. M-C@CFOSs are obtainable after in situ ligand carbonization followed by the selective removal of SiO2 NPs. The hierarchical mesoporous structure of M-C@CFOSs, combined with the conformal graphitic carbon coating derived from the native organic ligands, significantly improves their electrocatalytic performance as OER electrocatalysts when compared with nonporous Co0.5Fe2.5O4 NP superstructures. This work establishes a new and facile approach for designing NP superstructures with hierarchical mesoporosity, which may find wide applications in energy storage and conversion.

Biomolecules induce the synthesis of hollow hierarchical mesoporous structured hydroxyapatite microflowers: application in macromolecule drug delivery

A novel hollow HAp microflower with hierarchical mesoporous structure was designed through biomolecules induction and explored as macromolecular drug carrier. It is found that biomolecules play a vital role in the formation of hollow morphology and the construction of hierarchical mesoporous structure, which could remarkably improve the specific surface area of microflowers. Moreover, the microflowers display a higher drug loading capacity (263 ± 7.2 mg/g), sustained release behavior and exhibit a better biocompatibility in the cytotoxicity test, suggesting the microflowers can be regarded as a promising candidate in macromolecular drug delivery fields. In addition, it is proved that the excellent drug delivery property is attributed not only to the interaction among carrier, drug and medium environment but also to the pore structure and morphology of carrier. Over all, the work represents a versatile, new route toward the preparation of hollow HAp-based macromolecular drug carrier with hierarchical mesoporous structural features and provides new insight into the optimization of macromolecular drug delivery performance.

Mechanistic Understanding of Catalytic Conversion of Ethanol to 1-Butene over 2D-Pillared MFI Zeolite

Ethanol is an important C2 platform molecule for producing value-added chemicals and distillate hydrocarbon fuels (e.g., jet and diesel). Among these, catalytic upgrading of ethanol to butenes can generate valuable commodity chemicals (e.g., 1-butene) and provide C4 olefin intermediates that can be further upgraded to jet/diesel fuels. Two-dimensional (2D) zeolites offer hierarchical mesoporous structures, leading to improved mass transport and reduced diffusion length, which can help to address the coking challenges faced by ethanol conversion to hydrocarbons over three-dimensional (3D) zeolites. In this study, we investigate the acid-catalyzed conversion of ethanol to 1-butene over the Brønsted acid sites (BAS) in 2D-pillared MFI zeolite (2D-PMFI) using ab initio molecular dynamics (AIMD) simulations, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and calorimetric measurements. A detailed thermodynamic analysis, using quasi-harmonic approximation (QHA), on the Gibbs free-energy pathway of ethanol conversion shows that the consideration of entropy is critical to accurately capture the detailed thermodynamic profiles. Employing the Blue Moon ensemble method, the formation of framework-bound butoxide from ethoxy and ethene is found to be the likely rate-determining step (RDS), proceeding via a stepwise mechanism. The reactivity of 2D-PMFI can be further tuned by manipulating RDS through careful control of the number of BAS and operating temperatures. The calculated vibrational density of states (VDOS) validate the structural models of adsorbed ethanol by comparing with the experimental DRIFTS measurements. Overall, our study provides mechanistic insights into ethanol upgrading over the 2D-PMFI and shows the importance of evaluating entropic effects in such a confined system.

Coral‐like nitrogen doped carbon derived from polyaniline‐silicon nitride hybrid for highly active oxygen reduction electrocatalysis

AbstractIn this work, a coral‐like nitrogen‐doped carbon electrocatalyst has been prepared via self‐assembly oxidative polymerization of aniline monomers onto silicon nitride (Si3N4) nanospheres, followed by carbonization. The prepared catalyst at 900°C (denoted as NC‐900) shows excellent oxygen reduction reaction (ORR) activity by achieving an onset potential (η) of 0.90 V versus reversible hydrogen electrode (RHE) and half wave potential (E1/2) of 0.82 V versus RHE comparable to that of the commercial Pt/C (η = 0.99 V vs. RHE and E1/2 = 0.87 V vs RHE) and even outperforming many carbon‐based electrocatalysts recently reported in the literature. The catalyst NC‐900 also displays better stability and resistance toward methanol crossover effect than Pt/C in alkaline solution. The high ORR performance of NC‐900 catalyst was associated with high content of nitrogen species and hierarchical mesoporous structure that facilitate high electron and mass transport.

Hierarchical mesoporous NiCoP hollow nanocubes as efficient and stable electrodes for high-performance hybrid supercapacitor

As one of the major materials of supercapacitor, Transitional Metal phosphides have been extensively studied for superior electrical conductivity, rich valences and high electrochemical activity, and the reasonably designed architecture of bimetals phosphides is considered to be very effective for adequately making full of its material advantages and breaking through its flaws of the low rate capability and bad cycle lifespan in applications. Therefore, bimetals phosphides NiCoP with hollow mesoporous structure is rationally prepared by template etching and phosphorization treatment procedure. This delivered high specific capacity of 658.5 C g−1 at a specific current of 1 A g−1, ultra-high rate capability of 66% achieved even at a high specific current of 30 A g−1 and 80.7% cycling stability after 5000 cycles at 20 A g−1, beneficent from the hierarchical mesoporous hollow structure. Moreover, a hybrid supercapacitor was assembled by NiCoP and activated carbon, which achieves an ultra-high energy density of 41.3 Wh kg−1 at the power density of 373.3 W kg−1, as well as high power density of 7058.3 W kg−1 at an energy density 26.7 Wh kg−1, Remarkably, the hybrid supercapacitor remains exceptional cycling stability of 90.8% at 10 A g−1 after 10,000 cycles. Overall suggest that hierarchical mesoporous NiCoP hollow nanocubes electrode material shows great potential as a novel battery-type electrode for supercapacitor.

Enhanced photocatalytic activity of ultrahigh-surface-area TiO2@C nanorod aggregates with hierarchical porosities synthesized from natural ilmenite

Cost-effective methods to produce effective TiO2 photocatalytic materials for degrading organic pollutants are in high demand. Herein, we present an approach to enhancing the photocatalytic activity of TiO2@C nanorod-aggregate catalysts with an ultrahigh surface area and hierarchical pore structure synthesized from natural ilmenite using mechanical activation, annealing, HCl leaching, and calcination. The photocatalytic activity of the catalysts was analyzed for degrading methylene blue under UV and visible light irradiation. Leaching in the presence of HCl formed TiO2 nanorods containing micropores with a large specific surface area (876 m2/g). Further calcination led to the formation of hierarchical mesoporous structures by aggregation of the nanorods. TiO2@C calcined at 700 °C (TiO2@C-700), with its high crystallinity and improved pore structure, possessed an excellent adsorption capacity and a reaction rate constant (k) of 0.0631 min-1 under visible light. The enhanced photocatalytic performance of the catalyst despite its rutile phase is attributable to the large surface area offering more active sites and the hierarchical pore structure, which facilitates mass transport and a high crystallinity. In addition, the durability of TiO2@C-700 was evaluated under visible light irradiation for 100 cycles, and the k value and decomposition efficiency at 60 min were retained at 88.8 % and 92.0 % respectively, as compared with the first cycle. Therefore, we believe that the proposed strategy provides an efficient way to overcome the economic aspects that limit the industrial application of porous TiO2-based catalysts.