Mesoporous Arrays Research Articles

Green synthesis of mesoporous graphene oxide/silica nanocomposites from rich husk ash: Characterization and adsorption performance

Abstract Rice husk is an agricultural waste. Rice husk ash (RHA) is the main residue when rice husk is burned to produce biomass energy. The conversion of RHA into high-value-added products is a sustainable method and can help develop a circular economy. In this study, a graphene oxide/SBA-15 composite was synthesized from RHA. Experimental investigations revealed that the various oxygen-containing functional groups of the graphene oxide/SBA-15 composite resulted in considerably enhanced adsorption capacity. Furthermore, the composite possessed a pore volume of 0.978 cm 3/g, pore size of 10.5 nm, and surface area of 625 m2/g. The pore structure of the composite was mainly a hexagonal array of mesopores, which did not change with the addition of GO. TEM images revealed that the SBA-15 surface was homogeneously covered with GO flakes. Raman spectroscopy demonstrated that composite contained disordered carbon with a high degree of oxidation. The effects of adsorption conditions – adsorbent dosage, initial dye concentration, adsorption temperature, and solution pH – on the Rhodamine B adsorption of the graphene oxide/SBA-15 composite were investigated. The composite exhibited the highest adsorption capacity of 151.28 mg/g at 80 ∘ C. The adsorption was endothermic with enthalpy of 11.83 kJ/mol. The isotherm adsorption experiment revealed that the Langmuir model was the best fit for the adsorption results. Kinetic investigations revealed that the adsorption process followed the pseudo-second-order model. The adsorption rate was mainly controlled by the intraparticle diffusion step. Commercially available SBA-15 materials are expensive. This study provides an economically viable method of treating RHA that improves its potential for applications involving removal of dyes from wastewater.

New Class of Trimetallic Oxide Hierarchical Mesoporous Array on Woven Fabric: Electrode for high-Performance and Stable battery type Ultracapacitor

Imperative urgency to substitute outdated combustion engines with safer, faster and efficient energy storage devices and conversion systems has inspired researchers to realize new energy storage materials with high performance. In this work, a facile hydrothermal technique with subsequent calcination procedure has been adopted to prepare Cu-Ni-Co (CNCo) based trimetallic oxide nanowires over carbon cloth (CC). Hierarchical mesoporous CNCo arrays on conducting scaffold delivers excellent supercapacitive performance with specific capacitance as high as 2535 Fg-1 at current density of 1 Ag-1 and excellent rate capability of 94% at 5 Ag-1 even after 5000 cycles. To judge the figure of merit of CNCo electrode, results are compared with the synthesized one-dimensional binary and monoxides nanoform over same platform namely nickel cobalt oxide (NCo) and cobalt oxide (Co). Utility of CNCo as robust and potential electrode material is further assessed by fabricating CNCo based symmetric supercapacitor. Specific energy of 39 Wh/kg at specific power of 0.45 KW/kg and extraordinary cyclic stability (capacitance retention more than 100% after 10000 cycles) register from the fabricated device. Coordination of metal ions strengthens the synergistic effect which affects the rate of redox charge transfer and thereby improves the cyclic stability and rate capability.

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

Correction for ‘Ruthenium oxide coated ordered mesoporous carbon nanofiber arrays: a highly bifunctional oxygen electrocatalyst for rechargeable Zn–air batteries’ by Ziyang Guo et al., J. Mater. Chem. A, 2016, 4, 6282–6289, DOI: 10.1039/C6TA02030E.

Amino-grafted mesoporous MCM-41 and SBA-15 recyclable adsorbents: Desert-rose-petals-like SBA-15 type as the most efficient to remove azo textile dyes and their mixture from water

Amino-grafted Mobil Composition of Matter N. 41 (MCM-41/NH2) and Santa Barbara Amorphous (SBA-15/NH2) type mesoporous adsorbents were successfully used and compared in this work to remove azo dyes (and their mixture) from highly colored solutions. This paper reports a very fast removal and recycle (in 5 min) of great amounts of textile dyes (about the 100%) by materials characterized by high adsorption/desorption capacities. A qmax ≈ 250 mg/g for each adsorption cycle, that should be potentially increase to ≈ 1250 mg/g, under appropriate experimental conditions, was found for the proposed adsorbents. The UV–Vis absorption spectra of dyes were used to support this finding, determining the rate of adsorption. Several parameters affecting the adsorption process were investigated: the contact time, dyes solution pH values and amount of the adsorbent materials, ranging from 0.4 mg to 12 mg, and dyes (5 × 10−5 M and 1 × 10−5 M). Further, the Nitrogen adsorption/desorption isotherms, SAXS patterns, TG analyses, Zeta-potential measurements and microscopic imaging techniques, such as SEM and TEM, were used to detail the nature of interaction between dyes and adsorbents, and to investigate the morphology and the mesoporous array of the amino grafted MCM-41 and SBA-15.

Honeycombed-like nanosheet array composite NiCo2O4/rGO for efficient methanol electrooxidation and supercapacitors

A series of novel honeycombed-like composites NiCo2O4/rGO-T (rGO: reduced graphene oxide, T: 200, 250 and 300 °C) were obtained by a pre-adjusted pH value aq. phase coprecipitation strategy assisted by citric acid, followed annealing in N2 flow. The NiCo2O4/rGO-250 shows the most uniformly highly-ordered honeycombed-like nanosheet array morphology consisting of ultrathin mesoporous nanosheets (~110 nm × 12 nm) interdigitated vertically grown on the rGO surface in both sides with the highest crystallinity, higher surface area (145 m2 g−1), bimodal pore size distribution (3.4 and 12.5 nm) along with the highly open macroporous networks. The NiCo2O4/rGO-250 electrode exhibits the highest current density for methanol oxidation reaction of 90 A g−1 at 0.6 V, as well as high cycling stability (94% after 500 cycles, returned to 98% with fresh electrolyte), which is the best one so far among reported catalysts with similar compositions. Simultaneously, NiCo2O4/rGO-250 electrode exhibits considerable specific capacitance of 1380 F g−1 at 1 A g−1, high rate performance (10 A g−1, 967 F g−1), and good cycling stability which remains 90% at 5 A g−1 after 1000 charge–discharge cycles for supercapacitor. The excellent electrochemical performance of the NiCo2O4/rGO-250 electrode can be attributed to the highly-ordered honeycombed-like mesoporous nanosheet array along with the greatly increased specific surface area exposing more active sites, the highly open macroporous networks formed by adjacent ultrathin NiCo2O4 nanosheets providing more ion/electron diffusion paths and effective contact area of electrolyte, and the strong NiCo2O4– rGO synergy endowing excellent conductivity and structural robustness, thus greatly facilitate the transfer of electrons and ions in electrode and at the electrolyte/electrode interface.

Mesoporous ZnCo2O4 nanowire arrays with oxygen vacancies and N-dopants for significant improvement of non-enzymatic glucose detection

An efficient electrode for use in a sensitive, nonenzymatic catalyst for electro-oxidation of glucose is urgently needed to reduce the cost of regular diabetic monitoring. Finding a way to improve sensitivity while reserving the catalytic activity for glucose monitoring presents a big challenge. Replacing oxygen defects with nitrogen atoms in a nanostructured transition metal oxide can expose more catalytic active sites with improved electrical conductivity. Herein, a simple and scalable technique has been demonstrated to fabricate N-doped mesoporous ZnCo2O4 nanowire arrays (N-doped ZnCo2O4 electrode) through NH3-plasma treatment toward high-performance nonenzymatic glucose sensors. As a result, an N-doped ZnCo2O4 electrode exhibits ultra-sensitivity of 14,000 μA·mM−1 cm−2, a detection limit of 0.54 μM (S/N = 3), and a short response time of about 7.9 s. The impressive electrocatalytic performance originates from the filling of oxygen vacancies with nitrogen atoms in the mesoporous ZnCo2O4 nanowire arrays, which helps to accelerate the kinetics by increasing the pre-oxidation state of Co3+ and improving the electrical conductivity. Therefore, this study provides new insights into investigating the rational design of nanostructured transition metal oxides/hydroxides with tunable active sites and electrical conductivities for high-performance non-enzymatic glucose sensors.

Mitigation of silica-rich wastes: An alternative to the synthesis eco-friendly silica-based mesoporous materials

The synthesis of nano-architectured mesoporous materials is of great importance for the sciences of multifunctional materials, since the textural and structural features of mesoporous silicas allows its application in the most different areas of technological knowledge. In view of growing interest of the scientific community in the use of silica-based mesoporous materials, as well as the environmental concern of obtaining advanced materials through increasingly cleaner, low-cost, and eco-friendly processes, this review aims to give an overview in the literature of main alternative silica sources that have been used to synthetize the silica-based mesoporous arrays. Also, we present what are the main applications of these mesoparticles. We can highlight that the main mesoporous materials studied in the literature are those of the M41S, SBA- n , FDU- n , and KIT- n families, which presented well-structured silica-based mesoporous materials with different pore geometries and architectures. Thus, allowing the application of these architectured materials in different scientific areas. The synthesis of silicon-based mesoporous materials has been increasingly sought from the use of low-cost and eco-friendly silica sources from the reuse of industrial wastes, in an attempt to minimize the possible impacts on the environment and human health of inadequate disposal of these wastes. Based on our literature review, the main alternative silica sources that are being used for the synthesis of silica-based mesoporous materials are rice hush ash, wheat husk ash, palm oil fuel ash, Miscanthus ash, e-waste, coal ash, reed ash, sedge ash, Carex riparia, sugarcane ash, bamboo leaf ash, natural clay, ore tailing, and others. Sustainable and renewable silica sources used in the preparation of the eco-friendly silica-based mesoporous materials and their environmental applications. • Sustainable silica sources are used in the preparation of mesoporous materials. • Silica-based mesoporous arrays have multifunctional properties. • Eco-friendly mesoporous arrays are highly efficient for use in environmental sciences. • Nanostructured mesoporous materials have different pore geometries and architectures. • The use of low-cost and eco-friendly silica sources is of environmental importance.

N and S Co-doped Ordered Mesoporous Carbon: An Efficient Electrocatalyst for Oxygen Reduction Reaction in Microbial Fuel Cells

Background: Porous carbon materials are promising candidate supports for various applications. In a number of these applications, doping of the carbon framework with heteroatoms provides a facile route to readily tune the carbon properties. The oxygen reduction reaction (ORR), where the reaction can be catalyzed without precious metals is one of the common applications for the heteroatom-doped carbons. Therefore, heteroatom doped catalysts might have a promising potential as a cathode in Microbial fuel cells (MFCs). MFCs have a good potential to produce electricity from biological oxidization of wastes at the anode and chemical reduction at the cathode. To the best of our knowledge, no studies have been yet reported on utilizing Sulfur trioxide pyridine (STP) and CMK-3 for the preparation of (N and S) doped ordered porous carbon materials. The presence of highly ordered mesostructured and the synergistic effect of N and S atoms with specific structures enhance the oxygen adsorption due to improving the electrocatalytic activity. So the optimal catalyst, with significant stability and excellent tolerance of methanol crossover can be a promising candidate for even other storage and conversion devices. Methods: The physico-chemical properties of the prepared samples were determined by Small Angle X-ray Diffraction (SAXRD), N2 sorption-desorption, Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FESEM) and X-ray Photoelectron Spectroscopy (XPS). The prepared samples were further applied for oxygen reduction reaction (ORR) and the optimal cathode was tested with the Microbial Fuel Cell (MFC) system. Furthermore, according to structural analysis, The HRTEM, and SAXRD results confirmed the formation of well-ordered hexagonal (p6mm) arrays of mesopores in the direction of (100). The EDS and XPS approved that N and S were successfully doped into the CMK-3 carbon framework. Results: Among all the studied CMK-3 based catalysts, the catalyst prepared by STP precursor and pyrolysis at 900°C exhibited the highest ORR activity with the onset potential of 1.02 V vs. RHE and 4 electron transfer number per oxygen molecule in 0.1 M KOH. The high catalyst durability and fuel-crossover tolerance led to stable performance of the optimal cathode after 5000 s operation, while the Pt/C cathode-based was considerably degraded. Finally, the MFC system with the optimal cathode displayed 43.9 mW·m-2 peak power density showing even reasonable performance in comparison to a Pt/C 20 wt.%.cathode. Conclusions: The results revealed that the synergistic effect of nitrogen and sulfur co-doped on the carbon substrate structure leads to improvement in catalytic activity. Also, it was clearly observed that the porous structure and order level of the carbon substrate could considerably change the ORR performance.

Coupling PEDOT on Mesoporous Vanadium Nitride Arrays for Advanced Flexible All-Solid-State Supercapacitors.

Tailored construction of advanced flexible supercapacitors (SCs) is of great importance to the development of high-performance wearable modern electronics. Herein, a facile combined wet chemical method to fabricate novel mesoporous vanadium nitride (VN) composite arrays coupled with poly(3,4-ethylenedioxythiophene) (PEDOT) as flexible electrodes for all-solid-state SCs is reported. The mesoporous VN nanosheets arrays prepared by the hydrothermal-nitridation method are composed of cross-linked nanoparticles of 10-50nm. To enhance electrochemical stability, the VN is further coupled with electrodeposited PEDOT shell to form high-quality VN/PEDOT flexible arrays. Benefiting from high intrinsic reactivity and enhanced structural stability, the designed VN/PEDOT flexible arrays exhibit a high specific capacitance of 226.2 F g-1 at 1 A g-1 and an excellent cycle stability with 91.5% capacity retention after 5000 cycles at 10 A g-1 . In addition, high energy/power density (48.36Wh kg-1 at 2 A g-1 and 4kW kg-1 at 5 A g-1 ) and notable cycling life (91.6% retention over 10 000 cycles) are also achieved in the assembled asymmetric flexible supercapacitor cell with commercial nickel-cobalt-aluminum ternary oxides cathode and VN/PEDOT anode. This research opens up a way for construction of advanced hybrid organic-inorganic electrodes for flexible energy storage.

Controllably Engineering Mesoporous Surface and Dimensionality of SnO2 toward High‐Performance CO2 Electroreduction

AbstractCurrently, the precise control of the architecture and surface of functional materials for high‐performance still remains a great challenge. Here, a feasible approach is presented to synchronously manipulate mesoporous surface and dimensionality of SnO2 catalysts into hierarchically mesoporous nanosheets and nanospheres within one simple reaction system. By adjustment of the hydrophobic chain length of different fluorinated surfactants, 0D SnO2 nanospheres with average size of 165 nm, and 2D SnO2 ulthrathin nanosheets with thickness of 22.5 nm with the distinct dimensionalities are separately obtained (one stone, two birds), both of which are well decorated with ordered mesopore arrays on their surfaces (pore size of 16 nm). The following calcination gave rise to the formation of hierarchically mesopores (5 and 16 nm, respectively) with high crystallization and improved surface area (96.8 m2 g−1). The resultant mesoporous SnO2 nanosheets as catalyst for CO2 electroreduction reaction (CO2 RR) exhibit excellent selectivity, with a high Faraday efficiency (FE) of HCOOH reaching up to 90.0% at −1.3 V and C1 FE of 97.4% at −1.2 V versus reversible hydrogen electrode, as well as long‐term stability, which is among the best performance compared to reported SnO2 materials, thanks to the collective contributions of the unique architecture and mesoporous structure.

Activity descriptor identification for hydrogen evolution reaction on well-dispersed few layer MoS2(O) nanosheets over the mesoporous carbonic arrays

Abstract Advanced nonprecious group metal coupled with various forms of carbon for electrocatalytic water splitting holds tremendous promise for renewable energy. Despite recent progress, lack of fundamental understanding concerning the synergetic interaction between active sites in catalysts and the underlying host material (carbon) would be inadequate to offer explicit vision in designing hydrogen evolution reaction (HER) catalysts and beyond. Here we report a highly intrinsic active and stable MoS2(O) electrocatalyst supported on mesoporous carbonic arrays (OMCA) via a facile method for HER. The MoS2(O)/OMCA hybrid allows few layer MoS2(O) nanosheets to be highly dispersed on the surface of OMCA, which provides an increasing number of exposed active sites. Coupling with OMCA not only facilitates electron transfer between the edge sites and the substrate, but also modulates electronic structure of metal Mo d orbital by tuning electron donating/withdrawing capability, thus enabling energetically favorable hydrogen binding on MoS2(O). This work elucidates the mechanistic origin of HER activity, and establishes a volcano relationship in depicting the change of hydrogen evolution turnover number as a function of donating capability of carbon support.

Ordered Mesoporous Ni-P Amorphous Alloy Nanowire Arrays: High-Efficiency Catalyst for Production of Polyol from Sugar.

Mesoporous metals have shown significant potential for use in catalysis; however, controllably synthesizing highly ordered mesoporous amorphous alloys is a serious challenge. In this paper, a synthesis strategy was developed for generating ordered amorphous alloy nanowire arrays from mesoporous Ni-P by combining mesoporous silica templating with electroless plating. Mesoporous silica is externally grafted with -CH3 and internally covered with -NH2 acting as an efficient template, ensuring the formation of Ni-P nanowires inside the pore channels and endowing the final product with an ordered mesoporous array structure. The resulting ordered mesoporous Ni-P amorphous alloy nanowire arrays were subjected to a liquid-phase sugar hydrogenation to polyols and exhibited a highly superior catalytic performance (97% glucose conversion and 94% maltose conversion) within 4 h at 4 MPa hydrogen pressure and 373 K relative to those reference catalysts, including conventionally prepared Ni-P amorphous alloy nanoparticles (87% glucose conversion and 86% maltose conversion), ordered mesoporous Ni nanowire arrays (90% glucose conversion and 87% maltose conversion), and the commercial Raney Ni catalyst (76% glucose conversion and 66% maltose conversion). According to a comparative study, the enhanced catalytic efficiencies can be ascribed to the integration of amorphous alloy properties and mesoporous material characteristics. The composition- and morphology-controllable synthesis presented here might supply a general synthetic methodology for rationally designing ordered mesoporous amorphous alloys for a broader range of applications.

Three-dimensional Ni2P–MoP2 mesoporous nanorods array as self-standing electrocatalyst for highly efficient hydrogen evolution

Electrochemical hydrogen evolution reaction (HER) via the splitting of water has required electrocatalysts with cost-effectiveness, environmentally friendliness, high catalytic activity, and superior stability to meet the hydrogen economy in future. In this context, we report the successful synthesis of self-standing mesoporous Ni2P–MoP2 nanorod arrays on nickel foam (Ni2P–MoP2 NRs/3D-NF) through an effective phosphidization of the corresponding NiMoO4 NRs/3D-NF. The as-synthesis Ni2P–MoP2 NRs/3D-NF, as an efficient HER electrocatalyst, exhibits small overpotential of 82.2 and 124.7 mV to reach current density of 10 and 50 mA cm−2, a low Tafel slope of 52.9 mV dec−1 and it retains its catalytic performance for at least 20 h in alkaline condition. Our work also offers a new strategy in designing and using transition metal phosphide-based 3D nanoarrays catalysts with enhanced catalytic efficiency for mass production of hydrogen fuels.

Removing the barrier to water dissociation on single-atom Pt sites decorated with a CoP mesoporous nanosheet array to achieve improved hydrogen evolution

Single-atom Pt immobilized in the lattice of CoP mesoporous nanosheets (MNSs) grown on carbon fiber cloth (CFC) (Ptat–CoP MNSs/CFC) was synthesized for the HER in alkaline solution and seawater. The improved HER is mainly attributed to water dissociation that becomes spontaneous on Ptat–CoP MNSs/CFC.

An Ordered Mesoporous Carbon Nanofiber Array for the Sensitive Electrochemical Detection of Malachite Green

AbstractThe recycling of environmental wastes to produce value‐added materials is an attractive prospect for both economic and social development. Herein, we use natural crab shell as the templates to synthesize ordered mesoporous carbon nanofiber arrays (OMCNs) based on a combined hard‐templating and surfactant self‐assembly approach. The Brunauer‐Emmett‐Teller surface area of the OMCNs is calculated to be 1200 m2 g−1, which is accompanied by good conductivity and a mesoporous structure. The as‐prepared OMCNs exhibit a remarkable electrochemical performance for the detection of malachite green (MG). Differential pulse voltammetry (DPV) reveals that the MG sensor has a wide linear range from 0.1 μM to 22.1 μM with a low detection limit of 0.05 μM. The MG sensor also shows a good stability and excellent anti‐interference, which are investigated by cyclic voltammetry. Furthermore, such an electrochemical sensor is successfully applied for the determination of MG in fishery water samples.

An efficient 3D ordered mesoporous Cu sphere array electrocatalyst for carbon dioxide electrochemical reduction

The electrochemical reduction of CO2 is a promising solution for sustainable energy research and carbon emissions. However, this solution has been challenged by the lack of active and selective catalysts. Here, we report a two-step synthesis of 3D ordered mesoporous Cu sphere arrays, which is fabricated by a dual template method using a poly methyl methacrylate (PMMA) inverse opal and the nonionic surfactant Brij 58 to template the mesostructure within the regular voids of a colloidal crystal. Therefore, the well-ordered 3D interconnected bi-continuous mesopores structure has advantages of abundant exposed catalytically active sites, efficient mass transport, and high electrical conductivity, which result in excellent electrocatalytic CO2RR performance. The prepared 3D ordered mesoporous Cu sphere array (3D-OMCuSA) exhibits a low onset potential of -0.4 V at a 1 mA cm−2 electrode current density, a low Tafel slope of 109.6 mV per decade and a long-term durability in 0.1 M potassium bicarbonate. These distinct features of 3D-OMCuSA render it a promising method for the further development of advanced electrocatalytic materials for CO2 reduction.

Performance of the MCM-41-NH2 Functionalized Mesoporous Material Synthetized from the Rice Husk Ash on the Removal of the Polycyclic Aromatic Hydrocarbons

In this work, the authors propose of the synthesis of a new adsorbent functionalized mesoporous material (MCM-41-NH2 (RHA)) from the Brazilian rice husk for the removal of the polycyclic aromatic hydrocarbons (PAHs). The new MCM-41-NH2 (RHA) was characterized using FTIR, TGA, SAXS, and N2 adsorption-desorption analyses, on the other hand, the removal experiments were performed to determine the adsorption parameters, such as the initial concentration, MCM-41-NH2 (RHA) amount, pH, time, and temperature. The hydrothermal/post-grafting methods were sustainable for the synthesis of the MCM-41-NH2 (RHA) functionalized mesoporous material, the same presented the main characteristic absorption bands of the mesoporous arrays, hexagonal mesostructure, type IV isotherms with H1 hysteresis, high surface area, and good thermal stability. Assessment of the adsorption of the MCM-41-NH2 (RHA) showed that the amount of the PAHs mixture adsorbed increased with the increase of the initial concentration, MCM-41-NH2 (RHA) amount, and contact time, as well as, the pH = 5.6 was the best for the removal of the PAHs mixture. However, the temperature variation did not significantly alter the efficiency of the MCM-41-NH2 (RHA). The removal percentage of the PAHs were 81.20, 94.25, 94.87, and 98.14% for the naphthalene (Nap), benzo[a]pyrene (B[a]P), benzo[k]fluoranthene (B[k]F), and benzo[b]fluoranthene (B[b]F), respectively, with the equilibrium time of approximately 200 min for the all PAHs. In addition, the adsorption equilibrium followed the nonlinear pseudo-second-order and the Langmuir models, which describe satisfactory adsorption of the PAHs mixture on the MCM-41-NH2 (RHA) functionalized mesoporous material.

In-situ growth of mesoporous In2O3 nanorod arrays on a porous ceramic substrate for ppb-level NO2 detection at room temperature

Mesoporous In2O3 nanorod arrays were synthesized directly on a porous ceramic substrate via a one-step hydrothermal method. The morphology and structure of the obtained In2O3 nanorod arrays were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results revealed that In2O3 nanorod arrays with cubic phase were densely distributed on the porous ceramic substrate, showing the diameter of 120–200 nm and length of 0.5–1 μm. Especially, the nanorod was assembled by aggregated In2O3 nanoparticles with the diameters of 10–30 nm, and its large specific surface ensured the highly gas sensing performance for ppb-level NO2 detection. The response value of the mesoporous In2O3 nanorod arrays to 800 ppb NO2 was 14.9 at room temperature of 25 °C with a short response time of 14 s, and the ultraviolet light was loaded in the recovery process to shorten the recovery time to about 32 s. The growth and gas sensing mechanisms of the mesoporous In2O3 nanorod arrays were discussed. It demonstrates that this work provides a low-cost route for the fabrication of room-temperature NO2 gas sensor with high performance through in-situ growth of the sensing materials on a porous ceramic substrate.

Ultrathin carbon coated mesoporous Ni-NiFe2O4 nanosheet arrays for efficient overall water splitting

Developing low-cost, highly efficient electrocatalysts for water splitting is a crucial and challengeable task to produce clean hydrogen fuel. Here, for the first time, we reported a novel ultrathin carbon layer coated mesoporous Ni-NiFe2O4 (Ni-NiFe2O4@C) nanosheet arrays catalyst by hydrothermal growth of NiFe-precursor on carbon cloth followed by a thermal decomposition process. The resultant Ni-NiFe2O4@C catalyst displays excellent electrocatalytic performances toward both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline electrolyte, which requires overpotential of 212 mV for OER and 217 mV for HER to reach 10 mA cm−2 with Tafel slope of 51 and 96 mV dec−1, respectively. Moreover, the two-electrode electrolyzer made of Ni-NiFe2O4@C electrodes requires a cell voltage of 1.57 V to deliver a current density of 10 mA cm−2 with long-term stability, which is superior to that of RuO2//Pt/C electrolyzer. This work offers new insight into the design and development of transition metal-based oxides catalysts for overall water splitting.

General Interfacial Self-Assembly Engineering for Patterning Two-Dimensional Polymers with Cylindrical Mesopores on Graphene.

Free-standing 2D porous nanomaterials have attracted considerable interest as ideal candidates of 2D film electrodes for planar energy storage devices. Nevertheless, the construction of well-defined mesopore arrays parallel to the lateral surface, which facilitate fast in-plane ionic diffusion, is a challenge. Now, a universal interface self-assembly strategy is used for patterning 2D porous polymers, for example, polypyrrole, polyaniline, and polydopamine, with cylindrical mesopores on graphene nanosheets. The resultant 2D sandwich-structured nanohybrids are employed as the interdigital microelectrodes for the assembly of planar micro-supercapacitors (MSCs), which deliver outstanding volumetric capacitance of 102 F cm-3 and energy density of 2.3 mWh cm-3 , outperforming most reported MSCs. The MSCs display remarkable flexibility and superior integration for boosting output voltage and capacitance.