Mesoporous Arrays Research Articles

Self-Standing 3D Thin Film Cathodes for Micobatteries

While the microelectronic industry is advancing at a rapid pace with smaller and smaller devices, the implementation of microelectro-mechanical systems (MEMS) on the market strongly depends on the availability of on-board power sources. However, traditional rechargeable batteries based on liquid electrolyte are not applicable due to the restrictions for on-chip design, size and inherent risk of leakage, which give rise to the development of all-solid-state thin film lithium-ion microbattery technology. As more energy is required in microelectronic devices, two-dimensional (2D) thin film microbatteries are no longer the ideal battery design because the limited footprint area results in a compromise between energy density and power density for the build-in power source. A move to all-solid-state three-dimensional (3D) architectures has been proposed as a promising approach to tackle this challenge and achieve both high energy and power densities within the footprint area [1]. 3D microbatteries generally require the fabrication of 3D nanoarchitectured electrodes with large capacity at high charge/discharge rates and long-term cycling capability. Without using binders or conductive additives, the direct fabrication of nanoarchitectures for the electrode materials on conductive substrates represents a new class of electrodes: 3D self-supported electrodes. Except as the key component for constructing 3D microbatteries, the 3D self-supported electrodes using flexible substrates (such as metal foil and carbon cloth) can be ideal electrodes for flexible lithium-ion batteries. Active research efforts have been devoted to the synthesis and characterization of various 3D self-supported electrodes on different conductive substrates. However, most of the previous works focused on the preparation of 3D self-supported nanoarchitectures for anode materials such as Si, Co3O4, and TiO2 [2], while very limited work has been reported on the 3D self-supported nanoarchitectures for cathode materials. The difficulty lies in the fact that the synthesis of cathode materials such as LiCoO2 and LiMn2O4 involves high temperature treatment, which is difficult for retaining the nanostructures after heat treatment. In this work, we present a new "hydrothermal lithiation" method to construct 3D LiCoO2 and LiMn2O4 nanoarrays on metal substrates [3,4]. Mesoporous low-temperature LiCoO2 nanowire arrays can be directly prepared by a two-step hydrothermal method and they can be easily converted into chain-like high-temperature LiCoO2 nanowire arrays through further calcination. The layered LiCoO2 nanowire arrays exhibit both high gravimetric capacity and areal capacity, while maintaining good cycling stability and rate capability. Similar method was used to prepare vertically aligned porous LiMn2O4 nanowall arrays, comprising highly crystallized spinel nanoparticles, on various conductive substrates without high temperature treatment. The "hydrothermal lithiation" can effectively convert Mn3O4 spinel nanowall arrays into LiMn2O4 spinel nanowall arrays without severe morphology change. The binder-free three-dimensional porous LiMn2O4 nanowall arrays exhibit high specific reversible capacity up to 131 mAh g-1 (or 0.29 mAh cm-2) as well as outstanding cycling stability and rate capability, making them promising as cathodes for both three-dimensional thin film lithium-ion microbatteries. The 3D cathode design and the effective low-temperature synthesis route will lead to new opportunities to develop high-performance microbatteries and flexible lithium-ion batteries.

Hierarchical Heterostructures of NiCo2O4@XMoO4 (X = Ni, Co) as an Electrode Material for High-Performance Supercapacitors.

Hierarchical heterostructures of NiCo2O4@XMoO4 (X = Ni, Co) were developed as an electrode material for supercapacitor with improved pseudocapacitive performance. Within these hierarchical heterostructures, the mesoporous NiCo2O4 nanosheet arrays directly grown on the Ni foam can not only act as an excellent pseudocapacitive material but also serve as a hierarchical scaffold for growing NiMoO4 or CoMoO4 electroactive materials (nanosheets). The electrode made of NiCo2O4@NiMoO4 presented a highest areal capacitance of 3.74 F/cm2 at 2 mA/cm2, which was much higher than the electrodes made of NiCo2O4@CoMoO4 (2.452 F/cm2) and NiCo2O4 (0.456 F/cm2), respectively. Meanwhile, the NiCo2O4@NiMoO4 electrode exhibited good rate capability. It suggested the potential of the hierarchical heterostructures of NiCo2O4@CoMoO4 as an electrode material in supercapacitors.

Mesoporous Ni[sbnd]Co based nanowire arrays supported on three-dimensional N-doped carbon foams as non-noble catalysts for efficient oxygen reduction reaction

Homologous NiCo based mesoporous nanowire arrays, involving nickel cobalt oxide (NiCo2O4) and nickel cobalt sulfide (NiCo2S4), are successfully grown on three-dimensional (3D) nitrogen-doped carbon foam (NDCF) via a facile hydrothermal reaction followed by annealing and sulfurization treatment, respectively. The NiCo2O4 nanowires in the obtained NiCo2O4/NDCF composites are composed of numerous small nanoparticles with the presence of mesopores, while the NiCo2S4 nanowires of NiCo2S4/NDCF composites exhibit unique hollow structures with mesoporous walls. When served as non-noble catalysts for oxygen reduction reaction (ORR), the homologous NiCo2O4/NDCF and NiCo2S4/NDCF composites exhibit a comparable catalytic activity with a four-electron pathway, superior selectively and methanol tolerance over commercial Pt/C catalyst. Especially, the NiCo2S4/NDCF composites possess much higher stability than the Pt/C catalyst in alkaline electrolyte, thus holding great promise in practical application. The impressive performance may originate from the hollow nanowire morphology and the unique mesoporous structure which provide a high surface density of catalytic active sites exposed to oxygen molecules and facilitate the efficient transport of reactant species. Meanwhile, the introduced NDCF with enhanced catalytic activity from the incorporation of the N element generates synergistic effect with NiCo2O4 and NiCo2S4, and enhances their conductivities, therefore playing a significant role in improving their catalytic performance.

Removal of Cr(VI) from aqueous solution using Fe-modified activated carbon prepared from luffa sponge: kinetic, thermodynamic, and isotherm studies

In this study, the removal of Cr(VI) from aqueous solution using Fe-modified activated carbon (AC-Fe) was investigated. AC-Fe before and after Cr(VI) adsorption was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller surface area. The effects of various parameters were investigated by batch experiments, such as contact time, temperature, pH, adsorbent dose, and initial Cr(VI). The results showed that the modification method greatly improves the adsorption property. The surface area of the activated carbon was relatively high (834.006 m2), and the Fe-AC structure was found to be a well-developed array of microvoids and mesopores. FTIR revealed that the abundance of O–H, N–H, C–O, metal-oxygen, and metal-hydroxyl functional groups on the surface of the Fe-AC may play an important role for the adsorption of Cr(VI). The optimum pH was 1 with maximum removal efficiency of 98.71%. The batch equilibrium data fitted well to the Langmuir isotherm (R2 = 0.9960) at 308 K, which indicated monolayer adsorption. Kinetic data were best fitted with the pseudo-second-order kinetic model, which was considered as the rate-limiting factor. The negative ΔG values confirmed the spontaneity of the adsorption process. Positive ΔH and ΔS values indicated endothermic and irreversible adsorption.

Hierarchical Ni3S2 nanosheets coated on mesoporous NiCo2O4 nanoneedle arrays as high-performance electrode for supercapacitor

A novel hierarchical structure of Ni3S2 nanosheets coated on mesoporous NiCo2O4 nanoneedles arrays was designed and investigated. Due to the positive synergistic effect of the two materials resulting from the three-dimensional coated structure, the as-prepared NiCo2O4/Ni3S2 heterostructure hybrid exhibited excellent electrochemical performance with areal capacitance of 4569.1mFcm−2 at current density of 1mAcm−2 as well as remarkable cycling stability of 89.2% capacitance retention after 1000 cycles. The impressive results here may pave the way to development of high-performance electrode materials for supercapacitors.

Adsorption of Methyl Blue on Mesoporous Materials Using Rice Husk Ash as Silica Source.

It is recognized that recycling and reuse of waste can result in significant savings in materials and energy. In this research, the adsorption of methyl blue (MB) using waste rice husk ash (Rha) and mesoporous silica materials made from Rha (R-MCM) were analyzed. Mesoporous silica materials were synthesized using cetyltrimethyl ammonium bromide (CTAB) as a cationic surfactant and Rha as the silica source. The prepared samples were characterized by Brunnaur-Emmet-Teller (BET) adsorption isotherm analyzer and transmission electron microscope (TEM) analysis. The results showed the surface area of R-MCM materials was 1347 m2g-1 and the pore volume was 0.906 cm3g-1. TEM analysis showed that the mesoporous materials generally exhibited ordered hexagonal arrays of mesopores with a uniform pore size. The effects on adsorption performance under different initial dye concentrations, different pH values and different dosages of adsorbent were also studied. Both Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. The results show that the maximum removal efficiency of MB more than 99%.

One-step fabrication of cytocompatible micro/nano-textured surface with TiO2 mesoporous arrays on titanium by high current anodization

High current anodization (HCA) is a novel strategy to fabricate micro/nano-textured surface with TiO2 mesoporous arrays (MNT-TMAs) on biomedical titanium (Ti) and its alloys. However, our previous study shows that the structure prepared in AgNO3 electrolyte has severe cytotoxicity because of the incorporation of Ag into the surface. The present work tries to prepare MNT-TMAs on Ti surfaces in Cu(NO3)2 electrolyte to eliminate the side effect of Ag. Our results show that the unique structure can be generated in a wide range of Cu(NO3)2 concentrations (1.0 to 12.0g/l). The increase of Cu(NO3)2 concentration has little influence on its micromorphology but decreases the diameter of mesopores. Good interfacial strength is observed. The resultant surface possesses good cytocompatibility because of the absence of toxic Cu in the coatings. Addition of Na3PO4 into the electrolyte has little influence on its microstructure, but can further improve the cytocompatibility due to the incorporation of P into the surface. Good cytocompatibility and interfacial strength render the technique promising in surface modification of implant materials.

Hierarchical Porous Nickel Cobaltate Nanoneedle Arrays as Flexible Carbon-Protected Cathodes for High-Performance Lithium-Oxygen Batteries.

Rechargeable lithium-oxygen (Li-O2) batteries are consequently considered to be an attractive energy storage technology because of the high theoretical energy densities. Here, an effective binder-free cathode with high capacity for Li-O2 batteries, needle-like mesoporous NiCo2O4 nanowire arrays uniformly coated on the flexible carbon textile have been in situ fabricated via a facile hydrothermal process followed by low temperature calcination. Because of the material and structural features, the needle-like NiCo2O4 nanowire arrays (NCONWAs) served as a binder-free cathode exhibits high specific capacity (4221 mAh g(-1)), excellent rate capability, and outstanding cycling stability (200 cycles). This cathode based on nonprecious mesoporous metal oxides nanowire arrays has large open spaces and high surface area, providing numerous catalytically active sites and effective transmission pathways for lithium ion and oxygen, and promises the abundant Li2O2 storage. The fast electron transport by directly anchoring on the substrate ensures fast electrochemical reaction process involved with the every nanowire. Furthermore, a bendable Li-O2 battery assembled by using the flexible NCONWAs as the cathode, can be able to light an LED and shows good rate capability and cyclic stability.

High loading Pt nanoparticles on ordered mesoporous carbon sphere arrays for highly active methanol electro-oxidation

Abstract Three-dimensionally (3D) ordered mesoporous carbon sphere arrays (OMCS) are explored to support high loading (60 wt%) Pt nanoparticles as electrocatalysts for the methanol oxidation reaction (MOR). The OMCS has a unique hierarchical nanostructure with ordered large mesopores and macropores that can facilitate high dispersion of the Pt nanoparticles and fast mass transport during the reactions. The prepared Pt/OMCS exhibits uniformly dispersed Pt nanoparticles with an average size of ∼2.0 nm on the mesoporous walls of the carbon spheres. The Pt/OMCS catalyst shows significantly enhanced specific electrochemically active surface area (ECSA) (73.5 m 2 g −1 ) and electrocatalytic activity (0.69 mA cm −2 ) for the MOR compared with the commercial 60 wt% Pt/C catalyst.

Ordered Mesoporous Nickel Sphere Arrays for Highly Efficient Electrocatalytic Water Oxidation

We report the preparation and use of the three-dimensionally ordered mesoporous Ni sphere arrays (3D-OMNiSA) as a highly effective OER catalyst in alkaline electrolyte. The 3D-OMNiSA is fabricated through lyotropic liquid crystal templating within a polymer inverse opal. The prepared 3D-OMNiSA catalyst exhibits a low overpotential of 254 mV at 10 mA cm–2 and a small Tafel slope of 39 mV decade–1, better than the commercial precious RuO2 catalyst. The mass activity (166.5 A g–1) and turnover frequency (0.0281 s–1) of 3D-OMNiSA are about 4.3 and 2.2 times that of RuO2, respectively. Additionally, this 3D-OMNiSA catalyst shows a high durability under harsh water oxidation cycling test. The outstanding OER performance of the 3D-OMNiSA could be attributed to the large surface area, efficient mass and charge transport, and high structural stability arising from the unique 3D hierarchical porous structure of the 3D-OMNiSA consisting of ordered close-packed mesoporous spheres.

Hierarchical NiCoO2 mesoporous microspheres as anode for lithium ion batteries with superior rate capability

Nanostructured materials with small particle size and large surface area exhibit excellent rate capability, however, their cyclic performances are normally limited by the intemperate side reaction with electrolyte, which is resulted from the large contact surface area of nanosized active particles with electrolyte. To avoid this issue, a relatively denser NiCoO2 (NCO) hierarchical microspheres built by mesoporous thorn array are developed by pyrolyzing the agave-stricta-like NiCo(OH)2CO3 thorn microspheres under nitrogen gas in this work. The analysed experimental results suggest that the hierarchical mesoporous nanostructure constructed by interconnected nanoparticles with a proper size (neither too small nor to large) shows a favorable BET specific surface area to well balance the rate and cyclic performance of transition metal oxide anodes. Compared to reported similar works, the as-prepared hierarchical NCO mesoporous microspheres deliver superior rate capability and greatly promoted cyclic stability, i.e. 844.6, 627.9 and 396.6mAhg−1 at 80, 1600 and 4000mAg−1, respectively.

A high performance three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection.

We describe here a high performance oxygen-rich three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection. We demonstrate that its linear detection upper limit is 30 mM, more than 15 times higher than that can be obtained on the normal enzyme-electrode. Notably, the three-phase enzyme electrode output is insensitive to the significant oxygen level fluctuation in analyte solution.

Integrated copper-nickel oxide mesoporous nanowire arrays for high energy density aqueous asymmetric supercapacitors.

An integrated (Cu,Ni)O mesoporous nanowire array was fabricated by a simple hydrothermal method with subsequent annealing, which with optimized Cu : Ni ratio = 1 : 1 delivers a high specific capacitance of 1710 F g-1. The further assembled aqueous asymmetric supercapacitor (Cu,Ni)O(+)//activated carbon(-) demonstrates high energy/power densities and long cycle life.

Ruthenium oxide coated ordered mesoporous carbon nanofiber arrays: a highly bifunctional oxygen electrocatalyst for rechargeable Zn–air batteries

Zn–air batteries with a RuO2-coated MCNA catalyst display relatively low overpotentials, long cycle life and superior rate capability.

Low-temperature solution synthesis of a ZnO nanorod array with a mesoporous surface mediated by cadmium ions

A ZnO nanorod (NR) array grown on a substrate by a wet chemical method usually exhibits a single crystalline nature and smooth surface which cannot adsorb a large amount of dye molecules. Thus, surface modification is necessary for a ZnO NR array in its photocatalysis application. In this work, a mesoporous structure has been introduced into the surface of a ZnO NR array via a facile chemical bath method mediated by cadmium (Cd) ions at 80 °C and subsequent calcination. During the growth process of the ZnO NR array, Cd ions can react with NH3 molecules and OH− ions in the growth solution to form Cd complexes and prefer to adsorb on the neutral {10-10} surface of ZnO NRs rather than on the positive (0001) facets due to face-selective electrostatic interactions. This will probably cause the formation of Zn(C2H3O2)2(C2H8N2) which can be decomposed into ZnO nanoparticles after calcination, leading to the production of mesopores on the {10-10} surface of ZnO NRs. Also, the pore density and aspect ratio of the ZnO NR array with mesoporous surface are controlled by adjusting the Cd ion concentration and reaction temperature. The mesoporous ZnO NR array exhibits enhanced photocatalytic properties for the degradation of a methylene blue (MB) aqueous solution compared with the pristine ZnO NR array. Therefore, our finding indicates that this method may be employed to synthesize porous nanostructures on devices.

Design and construction of a film of mesoporous single-crystal rutile TiO2 rod arrays for photoelectrochemical water oxidation

A film of mesoporous single-crystal rutile TiO2 rod arrays supported on a transparent conductive glass substrate was synthesized with the assistance of a template layer of closely packed silica nanospheres. This film was used as a photoanode and showed significant improvement for photoelectrochemical water oxidation compared with a reference film of nonporous single-crystal rutile TiO2 rod arrays.

Hierarchical Mesoporous Zinc-Nickel-Cobalt Ternary Oxide Nanowire Arrays on Nickel Foam as High-Performance Electrodes for Supercapacitors.

Nickel foam supported hierarchical mesoporous Zn-Ni-Co ternary oxide (ZNCO) nanowire arrays are synthesized by a simple two-step approach including a hydrothermal method and subsequent calcination process and directly utilized for supercapacitive investigation for the first time. The nickel foam supported hierarchical mesoporous ZNCO nanowire arrays possess an ultrahigh specific capacitance value of 2481.8 F g(-1) at 1 A g(-1) and excellent rate capability of about 91.9% capacitance retention at 5 A g(-1). More importantly, an asymmetric supercapacitor with a high energy density (35.6 Wh kg(-1)) and remarkable cycle stability performance (94% capacitance retention over 3000 cycles) is assembled successfully by employing the ZNCO electrode as positive electrode and activated carbon as negative electrode. The remarkable electrochemical behaviors demonstrate that the nickel foam supported hierarchical mesoporous ZNCO nanowire array electrodes are highly desirable for application as advanced supercapacitor electrodes.

Self‐Supported Cobalt Phosphide Mesoporous Nanorod Arrays: A Flexible and Bifunctional Electrode for Highly Active Electrocatalytic Water Reduction and Oxidation

Water splitting for the production of hydrogen and oxygen is an appealing solution to advance many sustainable and renewable energy conversion and storage systems, while the key fact depends on the innovative exploration regarding the design of efficient electrocatalysts. Reported herein is the growth of CoP mesoporous nanorod arrays on conductive Ni foam through an electrodeposition strategy. The resulting material of well‐defined mesoporosity and a high specific surface area (148 m2 g−1) can be directly employed as a bifunctional and flexible working electrode for both hydrogen and oxygen evolution reactions, showing superior activities as compared with noble metal benchmarks and state‐of‐the‐art transition‐metal‐based catalysts. This is intimately related to the unique nanorod array electrode configuration, leading to excellent electric interconnection and improved mass transport. A further step is taken toward an alkaline electrolyzer that can achieve a current density of 10 mA cm−2 at a voltage around 1.62 V over a long‐term operation, better than the combination of Pt and IrO2. This development is suggested to be readily extended to obtain other electrocatalysis systems for scale‐up water‐splitting technology.

Direct synthesis, characterization and catalytic performance of Al–Fe-SBA-15 materials in selective catalytic reduction of NO with NH3

A series of Al–Fe-SBA-15 catalysts were synthesized by microwave methods with various iron and aluminum contents. The samples were characterized by XRD, SEM, TEM, BET, NH3-TPD, FT-IR. Results indicated that all the samples that exhibited well-ordered hexagonal arrays of mesopores, disk-like and petal-like morphologies were observed for different catalysts. NH3-TPD indicated that the introduction of Al results in the generation of Brönsted acid originated from Al–OH. Brönsted acid played important roles in the selective catalytic reduction of NO by NH3, NOx conversion over Al–Fe-SBA-15 samples increased rapidly as temperature increased and achieved 95% at about 360°C.

Three-Dimensional NiCo2O4@Polypyrrole Coaxial Nanowire Arrays on Carbon Textiles for High-Performance Flexible Asymmetric Solid-State Supercapacitor.

In this article, we report a novel electrode of NiCo2O4 nanowire arrays (NWAs) on carbon textiles with a polypyrrole (PPy) nanosphere shell layer to enhance the pseudocapacitive performance. The merits of highly conductive PPy and short ion transport channels in ordered NiCo2O4 mesoporous nanowire arrays together with the synergistic effect between NiCo2O4 and PPy result in a high specific capacitance of 2244 F g(-1), excellent rate capability, and cycling stability in NiCo2O4/PPy electrode. Moreover, a lightweight and flexible asymmetric supercapacitor (ASC) device is successfully assembled using the hybrid NiCo2O4@PPy NWAs and activated carbon (AC) as electrodes, achieving high energy density (58.8 W h kg(-1) at 365 W kg(-1)), outstanding power density (10.2 kW kg(-1) at 28.4 W h kg(-1)) and excellent cycling stability (∼89.2% retention after 5000 cycles), as well as high flexibility. The three-dimensional coaxial architecture design opens up new opportunities to fabricate a high-performance flexible supercapacitor for future portable and wearable electronic devices.