Porous Arrays Research Articles

Boosting hydrogen and oxygen evolution of porous CoP nanosheet arrays through electronic modulating with oxygen-anion-incorporation

The exploration of earth-abundant single catalyst with high-efficiency bifunctional catalytic active sites for accelerated hydrogen and oxygen evolution reactions (HER and OER) is highly desirable but challenging. Herein, the synthesis of self-supported directional flake oxygen-incorporated cobalt phosphide arrays (O-CoP) with efficient bifunctional catalytic active sites was achieved by in situ oxidation followed by phosphorization of cobalt metal–organic framework nanosheet arrays (Co-MOF). By controlling the phosphating time, the P/O atomic ratio in the oxygen-incorporated cobalt phosphide could be adjusted, leading to the change of Co3+/Co2+ couples, and thus affecting the electronic environment of the cobalt active site. Benefiting from the tunable electronic structure and unique array architecture, the synthesized catalysts exhibited excellent electrocatalytic water decomposition for both HER and OER. Moreover, in the HER and OER couple system (HER||OER), the optimal O-CoP-40 catalyst delivers a low overpotential of only 1.54 V to obtain the 10 mA cm−2 and stably-running for 36 h. Theoretical calculations demonstrated that the electron-rich P-3p and O-2p orbitals could co-modulate the electronic environment of Co sites, which boosted water dissociation in the HER process and balanced the adsorption/desorption of intermediates in the OER pathway, resulting in a good overall water splitting. This research provides an effective strategy for the construction of efficient bifunctional phosphide electrocatalysts, as well as contributes to the understanding of anion incorporating to regulate the electronic structure of phosphides.

Two-Dimensional V2O5 Inverse Opal: Fabrication and Electrochromic Application.

The open-layered structure of Vanadium pentoxide (V2O5) has triggered significant interest in exploring its energy-related application as lithium (Li) intercalation cathode material. Various methods are extensively studied to improve the Li diffusion using thin films or nanoarchitecture. In this work, high-quality two-dimensional (2D) inverse opal α-V2O5 films were synthesized via a modified ‘dynamic hard template’ infiltration strategy using sacrificial polystyrene spheres (PS, a diameter of 530 nm) photonic crystal as a template. The new material exhibited an excellent porous array with featured structural colors in a large area. The electrochromic behavior was explored by combining bandgap and electrochemical characterization. On the one hand, the intercalation/deintercalation of Li+ played an important role in the bandgap (Eg), and thereafter on the visible range transmittance through changing the film’s stoichiometry and the valence of vanadium ions. On the other hand, the asymmetry of the lattice due to the disordered distribution of Li+ within the V2O5 interlayer and/or the formation of an irreversible phase explained the change in transmittance with voltage.

High‐Performance Freshwater Harvesting System by Coupling Solar Desalination and Fog Collection with Hierarchical Porous Microneedle Arrays

AbstractThe maximizing daily freshwater yield on the ocean surface necessitates all‐day water harvesting technologies and materials. This is realizable by taking advantage of the natural sunlight and humid air, which can drive daytime solar desalination and nighttime fog collection, respectively. To this end, two types of hierarchically porous microneedle array structures, which demonstrate superior capabilities for efficient fog capturing and photothermal evaporation, respectively, are prepared. The gel‐forged microneedle arrays with Janus wettability are fabricated via a simple and controllable top‐down micro‐molding process on a porous platform, and porosity within microneedles is further achieved readily by additional freeze‐drying treatment. The developed microneedle structure shows an ultrahigh fog harvesting rate up to 30.5 kg m−2 h−1, enabling high flux water droplet harvesting from moisture during nighttime. In the daytime, a solar evaporation rate of 2.46 kg m−2 h−1 is realized due to the increased evaporative area of the porous microneedle arrays and enhanced photothermal conversion. By uniting these two water‐harvesting routes, a daily cycle can ideally deliver an overall water yield close to 200 kg m−2, which will offer a promising solution for sustaining future low‐cost and decentralized clean water production.

3D Correlative Imaging of Lithium Ion Concentration in a Vertically Oriented Electrode Microstructure with a Density Gradient.

The performance of Li+ ion batteries (LIBs) is hindered by steep Li+ ion concentration gradients in the electrodes. Although thick electrodes (≥300 µm) have the potential for reducing the proportion of inactive components inside LIBs and increasing battery energy density, the Li+ ion concentration gradient problem is exacerbated. Most understanding of Li+ ion diffusion in the electrodes is based on computational modeling because of the low atomic number (Z) of Li. There are few experimental methods to visualize Li+ ion concentration distribution of the electrode within a battery of typical configurations, for example, coin cells with stainless steel casing. Here, for the first time, an interrupted in situ correlative imaging technique is developed, combining novel, full‐field X‐ray Compton scattering imaging with X‐ray computed tomography that allows 3D pixel‐by‐pixel mapping of both Li+ stoichiometry and electrode microstructure of a LiNi0.8Mn0.1Co0.1O2 cathode to correlate the chemical and physical properties of the electrode inside a working coin cell battery. An electrode microstructure containing vertically oriented pore arrays and a density gradient is fabricated. It is shown how the designed electrode microstructure improves Li+ ion diffusivity, homogenizes Li+ ion concentration through the ultra‐thick electrode (1 mm), and improves utilization of electrode active materials.

A bi-functional Co–Ni layered double hydroxide three-dimensional porous array electrode derived from ZIF-L(Co)@ZIF-L(Co, Ni) for oxygen evolution reaction and supercapacitors

Developing high-efficiency bifunctional materials for electro-catalysis and supercapacitors are urgently needed but challenging. Herein, we develop a self-supporting Co–Ni LDH electrode prepared by in-situ growing ZIF-L(Co)@ZIF-L(Co, Ni) on carbon paper followed by a pseudomorphic transformation. The optimized Co–Ni LDH/carbon paper electrodes (CN-2/CP) exhibit excellent electrochemical activity and stability in oxygen evolution reactions (OER) and supercapacitors. The CN-2/CP electrode displays a low overpotential of 230 mV at 10 mA cm −2 and superior stability at 40-h chronopotentiometry for OER. For supercapacitor, the CN-2/CP electrode delivers a high specific capacitance of 1346 F g −1 at 1 A g −1 and maintains a capacitance of 88.5% after 7000 charge/discharge cycles at 20 A g −1 . Based on the physical and chemical characterization results, the high performance originates from the in-situ electrochemical conversion of metal hydroxide, improved conductivity, fast charge transfer at the interface and unique layered cross morphology providing more active sites. • In-situ synthesis of Co–Ni LDH 3D porous array on carbon paper. • The self-supported electrode exhibits high OER performance and stability. • The large surface area and high porosity of CoNi LDH provide abundant active sites.

Rational construction of hierarchical porous FeP nanorod arrays encapsulated in polypyrrole for efficient and durable hydrogen evolution reaction

Employing an environmentally friendly and economical approach to significantly improve the electrocatalytic activity for hydrogen evolution reaction (HER) has attracted widespread attention because of its enormous value and challenge. Herein, we report a series of FeP nanorod arrays (FeP NRAs) with polypyrrole (PPy) shell coating on carbon textiles (CTs) to improve the HER performance. The composite combines the high conductivity of PPy and synergistic effect between FeP and PPy, where the PPy coating remarkably reduces the apparent activation energy for HER and increases the turnover frequency of catalysts, thus the electrocatalytic performance of [email protected]/CTs hybrid nanorod arrays is significantly improved. Among them, the [email protected]/CTs-5 h catalyst exhibit superior HER performance with a low onset over-potential of 103.1 mV and a small Tafel slope of 49.2 mV/dec at 10 mA cm−2, and as well as an excellent long-term stability during operation for 46 h. Notably, it shows efficient HER performance during various bending status, demonstrating that the stability and flexibility of [email protected]/CTs catalysts. The excellent electrocatalytic performance is promising for applications as a cost-effective non-noble-metal HER catalyst during electrochemical water splitting for large-scale hydrogen fuel production.

Study on Spectral Selective Manipulation Characteristics of Surface Multilevel Micro-Nano Structures by FDTD Simulation.

The optical filter based on the micro–nano structure on the material surface is an important optical device, which is widely used in many fields. The filter is fabricated on the substrate with different shapes and sizes of micro–nano array structure, and the wavelength selectivity is realized by adjusting the processing parameters. In this paper, the finite-difference time-domain (FDTD) method is used to simulate the spectral properties of periodic array structures on the Au surface, and the spectral response characteristics of different surface structural parameters to the incident light are obtained. The simulation results show that the periodic pore array has a directional modulation function on the reflectivity and transmittance of the material surface. In the same circular aperture array structure, the wavelength selection ability is proportional to the interval distance of the array period, but the transmission peak linewidth decreases with the increase of the interval distance. The structural spectrum of the cylindrical array is closely related to the structural period. The period of the array structure increases in proportion, the center wavelengths of the reflection and transmission peak of the spectrum are red-shifted. When the height of the array structure increases proportionally, the positions of the center wavelengths of the reflection and transmission peak remain almost unchanged. When the period of the array structure increases, the center wavelength of the reflection and transmission peaks appear red-shifted, and the line width is also narrowed. For the periodic ring array structure, as the inner diameter increases, the reflection peak is significantly red-shifted, and the smaller the ring width, the faster the red-shift of the reflection peak with the wavelength. By controlling the ratio of inner diameter-to-outer diameter, the spectral characteristics of the structured surface can be effectively controlled. These simulation results provide a basis for the preparation of optical filters in the future and a new idea for the study of micro–nano characteristic structures on the surface of materials.

Ion-transfer electrochemistry at arrays of nanoscale interfaces between two immiscible electrolyte solutions arranged in hexagonal format

• Nanoscale interfaces between two immiscible electrolyte solutions were studied. • Arrays of pores were formed by focused ion beam milling. • Hexagonal array format was characterised by ion transfer voltammetry. • Comparison of experiment and numerical simulation was undertaken with good agreement. • nanoITIES arrays in hexagonal format reach independent diffusion at large separations. The electrochemical behaviour of hexagonally arranged nanopore arrays was studied by simple ion transfer across the interface between two immiscible electrolyte solutions (ITIES) formed between water and 1,2-dichloroethane. The hexagonal nanoITIES arrays were supported at nanopores fabricated by focused ion beam milling into 50 nm thick silicon nitride films. Six arrays with different pore centre-to-centre distance ( r c ) to radius ( r a ) ratios were prepared. Within these arrays, the diffusion-limited steady-state currents ( i ss ) of tetrapropylammonium cation (TPrA + ) ion transfer increased concomitantly with increasing r c / r a ratio, reaching a plateau at r c / r a ≥ 96, which is greater than that previously reported for square-patterned nanoITIES arrays ( r c / r a ≥ 56). The diffusion regime and i ss associated with simple ion transfer across a nanopore array was also examined using numerical simulations, via COMSOL Multiphysics software, incorporating a 3-dimensional geometry and employing finite element analysis. Simulated linear sweep voltammograms of TPrA + transfer demonstrated a unique diffusional behaviour dependent on hexagonal nanopore spacing and the r c / r a ratio, analogous to the experimental voltammograms. Overlay of simulated and experimental voltammograms for each r c / r a ratios showed good agreement. These results indicate that a new design criterion is required to achieve independent diffusion at hexagonal nanointerface arrays, in order to maximize nanodevice performance in electrochemical sensor technologies.

Interfacial coupling porous cobalt nitride nanosheets array with N-doped carbon as robust trifunctional electrocatalysts for water splitting and Zn-air battery

Compositional and structural engineering of high-performance catalysts is vital for electrochemical catalysis, but challenges remain in their facile synthesis and efficient controls. Herein, a novel vaporization-nitridation synthesis strategy with simple operation is developed to prepare hierarchically porous cobalt nitride hybrid nanosheets grown on Ni foam by coupling cobalt nitride with N-doped carbon (CoN@NC). Benefitting from the highly open 3D hierarchical porous architecture and strong coupling effect between CoN and NC, the obtained CoN@NC electrode possesses accelerated ion and electron transfer. Moreover, the transform from CoN to CoOOH during water oxidation is confirmed by in-situ Raman characterizations, which together with NC and CoN species afford multiple active sites. The optimized CoN@NC-300 exhibits remarkable trifunctional catalytic activity towards OER, HER and ORR. Consequently, a two-electrode electrolyzer based on CoN@NC-300 needs only a voltage of 1.53 V to achieve the current density of 10 mA cm−2. Moreover, the flexible Zn-air battery assembled with CoN@NC exhibits high performance and superior durability. This work offers a novel method for designing metal nitride hybrids as highly efficient multifunctional electrocatalysts towards electrocatalysis and energy storage.

Nanofluid Flow of Alumina–Copper/Water Through Isotropic Porous Arrays of Periodic Square Cylinders: Mixed Convection and Competent Array Shape

Abstract The flow of hybrid alumina–copper/water nanofluid with mixed convection heat transfer from multiple square cylinders arranged in three different types of arrays, namely equilateral triangle (ET), rotated square (RS), and rotated rhombus (RR) in a heat exchanger, has never been studied before the present study. Navier–Stokes and energy equations with a periodic boundary condition in the transverse direction for all three array types having the same porosity are solved with the finite volume methodology. The combined effect of aiding buoyancy (Richardson number 0–2), the configuration of square cylinders, and hybrid nanoparticle volume fraction (0-0.06) on the flow dynamics and their impact on the overall heat transfer phenomenon through three different array configurations is thoroughly elucidated. The arrays’ overall drag and friction coefficient increases with an increase in the strength of aiding buoyancy and nanoparticle volume fraction. An increment in Richardson number, and nanoparticle volume fraction, causes thermal boundary layer thinning and results in higher heat transfer rates across all three arrays. With an increase in Ri from 0 to 2 at a nanoparticle volume fraction of 0.06, the mean Nusselt number of ET, RS, and RR arrays is increased by 161%, 5%, and 32%, respectively. While, with an increase in nanoparticle volume fraction from 0 to 0.06 at Ri = 2, the mean Nusselt number of ET, RS, and RR arrays is augmented by 17%, 6%, and 9%, respectively. Finally, the efficient array configuration in terms of fluid-thermal behavior is proposed to design various heat-exchange systems under differing operating conditions.

Design of new porous supramolecular arrays from flavyliums derivative linker. A theoretical assemble toward surface properties

Here, we attempt to design novel microporous framework materials, in this sense, such designs were carried out taking flavylium derivatives as corresponding linkers, which are assembled with the chosen well-known secondary building units SBUs such as Zn4O(CO2)6 and MIL-53 respectively. The linkers and SBUs are put together by means of topological simulations taking advantage of the powerful AutoGraFS tool, which allows a screening of feasible supramolecular frameworks, and therefore, these initial designs are validated from the molecular mechanics until highly accurate quantum mechanics techniques. Therefore, we selected the most stable structures through tight binding DFTB and DFT periodic computations, this finding enables us to obtain the lattice vectors and the unit cell parameter [a,b,c], achieving the simulation of their overall structural accurate description. Later the grand canonical Monte Carlo simulations (GCMC) give rise to the best elucidation of the active surface properties, including surface area, pore volume, and size, and several calculations to the host-guest gas adsorption characteristics and thus contrast the intrinsic capacities and applications of such novel designs. Additionally, these frameworks depict favorable candidates for a post-synthetic work that is bearing by a strategic cutting-edge research.

Strong Magnetic-Field-Engineered Porous Template for Fabricating Hierarchical Porous Ni-Co-Zn-P Nanoplate Arrays as Battery-Type Electrodes of Advanced All-Solid-State Supercapacitors.

The sluggish charge transport kinetics that exist in the energy storage process of all-solid-state supercapacitors (ASSSCs) can be improved by designing open hierarchical porous structures for binder-free electrodes. Herein, a template-directed strategy is developed to fabricate open hierarchical porous Ni-Co-Zn-P nanoplate arrays (NCZP6T) through phosphating the electrodeposited NiCo-LDH nanosheets loaded on a template. At first, porous conductive NiZn alloy nanoplate arrays are rationally devised as the template by a strong magnetic field (SMF)-assisted electrodeposition. The Lorentz force caused by coupling the SMF with the electrical current induces a magnetohydrodynamic (MHD) flow (including the micro-MHD flow), which homogenizes the deposition coating, tunes the nucleation and growth of the NiZn alloy, and produces pores in the nanoplates. The open hierarchical porous structure offers a larger specific surface area and pore volume for accelerating charge transport and gives a synergistic effect between the inner porous conductive NiZn array template and the outer electrochemical active phosphides for high-performance hybrid ASSSCs. Accordingly, the battery-type electrode of NCZP6T shows a much higher specific capacitance of 3.81 F cm-2 at 1 mA cm-2, enhanced rate capability, and remarkable cycling stability at progressively varying current densities. Finally, the NCZP6T//FeS ASSSC delivers a high energy density of 77 μW h cm-2 at a large power density of 12 mW cm-2, outperforming most state-of-the-art supercapacitors.

Spherical Co3S4 grown directly on Ni–Fe sulfides as a porous nanoplate array on FeNi3 foam: a highly efficient and durable bifunctional catalyst for overall water splitting

Spherical Co3S4 grown directly on Ni–Fe sulfides as porous nanoplate array on FeNi3 foam: a highly efficient and durable bifunctional catalyst for overall water splitting.

Plasma-induced defect engineering of porous metal-organic framework nanosheet arrays for efficient water splitting.

Herein, we present a facile plasma-induced strategy to introduce plentiful oxygen vacancies in porous metal-organic framework nanosheet arrays (Ov-Fe MOF/IF). The pore structure and coordinatively unsaturated metal sites endow the Ov-Fe MOF/IF with more active sites and accelerated reaction kinetics, thereby exhibiting a low potential of 1.51 V at 10 mA cm-2 for water splitting, which outperforms most MOF-based electrocatalysts.

Correction: Spherical Co3S4 grown directly on Ni–Fe sulfides as a porous nanoplate array on FeNi3 foam: a highly efficient and durable bifunctional catalyst for overall water splitting

Correction for ‘Spherical Co3S4 grown directly on Ni–Fe sulfides as a porous nanoplate array on FeNi3 foam: a highly efficient and durable bifunctional catalyst for overall water splitting’ by Jun Shen et al., J. Mater. Chem. A, 2022, 10, 5442–5451, DOI: 10.1039/d1ta07504g.

NiCoP nanoparticle-decorated carbon nanosheet arrays assembled on nickel nanowires for volumetric energy-dense supercapacitors

Structures with NiCoP nanoparticle-decorated porous carbon nanosheet arrays integrated on Ni nanowires were assembled. The hierarchical structure of Ni@C–NiCoP accounts for its enhanced electrochemical performance as a supercapacitor electrode.

Seed layer-free hydrothermal synthesis of porous tungsten trioxide nanoflake arrays for photoelectrochemical water splitting.

The simple preparation of efficient nano-photoanodes has been a key issue in the development of photoelectrochemical water splitting. In this work, a convenient and seed layer-free hydrothermal approach has been developed to synthesize vertically aligned porous WO3 nanoflakes on a fluorine-doped tin oxide conductive glass substrate. The morphology of WO3 nanoflakes could be manipulated by changing the annealing time, which further affected the performance of WO3 nanoflakes as photoanodes. Under optimum conditions, the obtained photoanode can lead to a high photocurrent density of 2.34 mA cm−2 at 1.4 V vs. Ag/AgCl under one sun irradiation (100 mW cm−2) and an incident photon to current conversion efficiency of 60% at 300 nm. The excellent photoelectrochemical performance can be mainly attributed to the larger active surface area, single crystal structure with an optimum thickness and the exposed highly active facets.

Growth mechanism of aligned porous oxide layers on titanium by anodization in electrolyte containing Cl-

In recent times, fluoride-free electrolyte-based titanium dioxide nanotubes (TNTs) have been considered as the fourth generation synthesis method employing HCl, HClO4, H2O2 solution and their mixture. In the present investigation, aligned porous oxide layers were achieved using chloride-based electrolyte in combination with polyethylene glycol and hydrogen peroxide through electrochemical anodization. In this method, H2O2 was used instead of H2O as an oxygen source. It was observed that oxidation of titanium was rapid in PEG/NH4Cl/H2O2 electrolyte. The fabricated oxide layer showed an amorphous structure. These amorphous porous oxide layers were then transformed into crystallized form by annealed at 500 °C for 2 h. The structural, morphological, and elemental analyses were carried out by X-ray diffraction, Field emission - scanning electron microscopy and Energy dispersive X-ray fluorescence. The X-ray diffraction pattern confirmed mixed phases of titania, and the average crystallite size was 31.72 nm. The Field emission - scanning electron microscopy morphologies showed aligned porous oxide arrays with smooth walls, and bundles of nanostructures were also observed. The EDX spectra indicated that the main components are O and Ti, with low content of Cl. It was observed that anodization in a chloride-containing organic electrolyte under a specific condition can be used to obtain higher-order titania nanostructure.

Highly Dispersed Pt/Cuo Nanoclusters in N-Doped Porous Carbon Array for Superior Hydrogen Evolution

Highly Dispersed Pt/Cuo Nanoclusters in N-Doped Porous Carbon Array for Superior Hydrogen Evolution

Ruthenium nanoparticles integrated bimetallic metal-organic framework electrocatalysts for multifunctional electrode materials and practical water electrolysis in seawater.

There is still a significant technical hurdle in the integration of better electrocatalysts with coordinated functional units and morphological integrity that improves reversible electrochemical activity, electrical conductivity, and mass transport capabilities. In this work, ruthenium-integrating porous bimetallic transition metal nanoarrays are efficiently generated from metal-organic framework-covered three-dimensional platforms such as carbon cloth using a simple solution-based deposition technique followed by calcination. Heterostructure ruthenium-cobalt-iron hollow nanoarrays are built to permit exceptionally effective multifunctional activities in reactions including the oxygen evolution reaction, hydrogen evolution reaction, and oxygen reduction reaction. As presumed, the as-synthesized porous nanostructured arrays show remarkable electrochemical performance due to the benefits of copious active reaction sites, and efficient electron and ion transport channels. The oxygen reduction reaction of the porous nanostructured array electrocatalyst has a half-wave potential of 0.875 V vs. reversible hydrogen electrode and can achieve a current density of 10 mA cm-2 at low overpotentials of 220 and 50 mV for the oxygen and hydrogen evolution reactions, respectively, and the needed cell voltage for total water splitting is just 1.49 V at a current density of 10 mA cm-2. The fabricated electrolyzer coupling splits seawater at relatively low cell voltages of 1.54 V at ambient temperature.