Hierarchical Surface Structures Research Articles

Nanoarchitectonics of self-supporting porous carbon electrode with heteroatoms co-doped: For high-performance supercapacitors

Wood possesses a uniform hierarchical porous structure and high mechanical strength, rendering it an excellent precursor for the preparation of self-supporting carbon electrodes without binders and conductive agents. This paper presents an efficient method for synthesizing a self-supporting carbon electrode (HCW-0.7) with high specific surface area, hierarchical pore structure and abundant surface functional groups, utilizing simple hydrothermal pre-treatment and one-step thermochemical conversion process. The HCW-0.7 electrode demonstrates remarkable electrochemical performance, achieving an excellent specific capacitance of 298.52 F g−1 under a current density of 0.5 A g−1. The wood-based symmetrical supercapacitor (HSC) constructed with HCW-0.7 as the electrode has excellent energy density, power density and rate performance. At the power density of 287.5 W kg−1, HSC demonstrates an energy density of 9.43 Wh kg−1, exhibits its excellent electrochemical performance. Notably, even when subject to a higher power density of 5750 W kg−1, the energy density remains at 5.16 Wh kg−1. Furthermore, even after 20,000 charge and discharge cycles, HSC demonstrates a remarkable capacity retention rate of 96.24 %.

Hydrothermally synthetized WO3 coated stainless steel mesh for oil–water separation purposes

To separate oil–water mixtures especially in oil field operations, new energy-efficient methods are urgently required. Conventional separation techniques using demulsifiers for separation of oil–water mixtures or even use of membranes usually suffered from high cost and energy consumption, composition dependency of demulsifiers and fouling or inability of a single membrane to separate all types of oil–water mixtures. This research aimed to synthesize tungsten oxide-coated stainless steel mesh using the hydrothermal method, with a focus on evaluating its effectiveness in oil–water separation. The coating procedure was carried out using hydrothermal techniques, with an emphasis on investigating the impact of precursor concentration, pH levels, reaction temperature and duration, on the separation efficiency of the optimal coating solution. The hydrothermally coated stainless steel mesh was created within a polytetrafluoroethylene reaction vessel, submerged in a 150 ml aqueous solution containing 0.0094 mol of sodium tungstate di-hydrate at pH 3.0, achieved through the addition of hydrochloric acid. Additionally, 1 g of oxalic acid, acting as a chelating agent, was introduced. Subsequently, the mesh underwent a 4 h reaction at 220 °C and was subsequently annealed for 30 min in a 350 °C furnace. Remarkably, the resultant mesh exhibited an exceptional water separation flux of 9870 ± 15 L/hr/m2 when exposed to 1:1 v/v oil–water mixtures. This performance significantly outperformed previous filters designed for similar oil–water separation tasks. The mesh efficiently facilitated the passage of water through the oil–water mixture, achieving an efficiency rate exceeding 98 ± 1%. To gauge its wetting behavior, the hydrophilic/underwater oleophobic filter underwent static contact angle measurements. The filter's wetting mechanism was primarily attributed to its hierarchical surface structure, which enhanced surface hydrophilicity and roughness. Analytical techniques such as XRD, FTIR, and FE-SEM were employed to scrutinize the fabricated filter's composition. These analyses confirmed the successful creation of a nanostructured WO3 coating on both sides of the stainless steel mesh. Moreover, the utilization of commercially available chemicals and straightforward fabrication techniques underscores the promising potential of this approach for large-scale applications.

Cost-effective superhydrophobic ZnO films with adjustable wetting behaviors deposited via solution precursor plasma spray process

In this work, ZnO films featuring hierarchical micron−/nanometer-sized structures were deposited for adjusting wettability by a simple solution precursor plasma spray (SPPS) process using cost-effective zinc acetate solution. The effects of solution flow rate on the surface microstructures, surface roughness, crystalline orientation, and wetting behaviors of the films were investigated comprehensively. The results showed that high solution flow rate facilitated the formation of apparent hierarchical surface structures featuring more uniformly-distributed micron-sized protrusions and higher surface roughness. The increase of solution flow rate also promoted the crystalline growth along the non-polar (100) plane. With the solution flow rate increasing from 10 ml/min to 40 ml/min, the synergy of the surface structures and crystalline growth orientation resulted in a sharp decrease of the surface energy of the films from ~74.4 mJ/m2 to ~12.6 mJ/m2 and a dramatic elevation of water contact angles from ~130° to ~155°. The wetting states of different films were elucidated by correlating the wetting behaviors with the surface structures. The SPPS-deposited ZnO films showed high adhesion to water droplets, similar to the wetting behaviors of the petal effect, which could be used as a “mechanical hand” for non-loss microdroplet transfer. The work shows that SPPS represents a promising method to deposit cost-effective superhydrophobic films with adjustable wetting behaviors.

Direct Fabrication of Te-Doped Black Si with an Enhanced Photoelectric Performance by Femtosecond Laser Irradiation under Water.

Tellurium (Te)-doped black silicon (Si) with enhanced absorption and photoelectric performance over a broad wavelength range of 0.2-2.5 μm was obtained using femtosecond (fs) laser irradiation in liquid water. Prior to laser irradiation, the Si sample was covered with a Te thin film (thickness 200 nm) over an adhesion layer of Cr (thickness 5 nm). Surface analyses by scanning electron microscopy and three-dimensional confocal microscopy evidence the presence of hierarchical surface structures combining quasi-periodic stripes with a spatial period of about 5 μm and subwavelength laser-induced periodic surface structures directed in directions parallel and perpendicular to the direction of the laser polarization, respectively. Moreover, the incorporation of Te generates intermediate levels within the Si bandgap. The Te-doped black Si shows a significant enhancement of the absorption, which reaches values of about 48% in the UV and visible (0.2-1.1 μm) and 70% in the near-infrared (1.1-2.5 μm) spectral ranges, respectively, due to the synergistic effects of multiscale surface structures and Te incorporation. Moreover, the surface reflectance is reduced to almost zero across the entire spectrum. The Te-doped black Si sample is used to realize a photodetector which displays an impressive photoelectric capability, being characterized by a responsivity of 328 mA/W, and an external quantum efficiency of 49.27% at a voltage bias of -10 V for 1064 nm light illumination, with rising and falling times of 55 and 67 ms, respectively. These figures remarkably outperform the response of unprocessed Si under the same experimental conditions.

A REVIEW ON FABRICATION TYPES OF MICRO/NANO HIERARCHICAL STRUCTURES AND THEIR APPLICATIONS IN AEROSPACE ENGINEERING

This review paper discusses various nano/microstructures and fabrication techniques. The nano/ microstructure materials like nano/micropatterned polymer and hierarchical structured surfaces employ different fabrication processes which is the main purpose of this review paper to identify the best technique for Aerospace applications.. The common nano/micro patterned polymer surfaces fabrication technique is by using soft lithography. Hierarchical structured surfaces fabrication techniques are by using soft lithography, self-assembly and by drag reduction from shark skin. They have a special and excellent surface functions namely hydrophobicity, structure color, drag reduction, anti-adhesion, color camouflages and other features. Super hydrophobic surfaces are used for various applications, such as solar panels, cutlery, roof tiles, fabrics, self-cleaning windows, windshields, buildings paints, external paints for ships and others. The main applications in aerospace are the airfoil design, self-cleaning window glasses or paints and anti-corrosion metal surfaces. The methods employed to arrive on our specific applications are description on nano/micro hierarchical structures, useful natural replicas for these strictures, identifying their surface functions and unique benefits as well as the recommended fabrication processes and applications. The best application we found is the riblet fabrication used in airplanes and airfoils geometries. These hierarchical structured surfaces are fabricated by drag reduction from shark skin.

Engineering a hierarchically micro-/nanostructured Si@Au-based artificial enzyme with improved accessibility of active sites for enhanced catalysis.

The active site accessibility and high loading of gold nanoparticles (AuNPs) are key factors affecting the catalytic activity of supported AuNP-based catalysts. However, the preparation of supported AuNP-based catalysts with highly accessible active sites still remains a challenge. Herein, sphere-on-sphere (SoS) silica microspheres with a hierarchical structure, good dispersion and high surface density of thiol groups (10 SH nm-2) are prepared and used as a platform for the growth of high-density AuNPs. The obtained hierarchical Si@Au micro-/nanostructure consisting of 0.55 μm SoS silica microspheres and 7.3 nm AuNPs (SoS-0.55@Au-7.3) is found to show excellent peroxidase-mimicking activity (Km = 0.033 mM and Vmax = 34.6 × 10-8 M s-1) with merits of high stability and good reusability. Furthermore, the as-obtained SoS-0.55@Au-7.3-based system can sensitively detect hydrogen peroxide (H2O2) with a low detection limit of 1.6 μM and a wide linear range from 2.5 μM to 1.0 mM. The high catalytic activity, excellent stability and good reusability of SoS-0.55@Au-7.3 imply its great prospects in biosensing and biomedical analysis.

Advancing biomedical substrate engineering: An eco-friendly route for synthesizing micro- and nanotextures on 3D printed Ti–6Al–4V

This study investigates the impact of a combined approach involving sandblasting and electrochemical surface treatment using a deep eutectic solvent Ethaline, a eutectic mixture of choline chloride and ethylene glycol, on the surface characteristics of Ti–6Al–4V biomedical substrates fabricated through direct selective laser melting (DSLM). Research has focused on surface morphology, topography, chemical composition, and cell adhesion. The novel approach demonstrated the ability to create a hierarchical surface structure with both micro and nanopatterns. The rough edges resulting from the sandblasting process were effectively smoothed through subsequent electrochemical processing. Additionally, the issue of residual sand particles, which commonly arise in sandblasting procedures, was successfully addressed with the new method. The results indicated that Ti alloy samples subjected to sandblasting and electrochemical treatment in Ethaline exhibited improved surface hydrophilicity. In-vitro cell adhesion tests confirmed the potential for bio-inspired properties of DSLM-printed Ti–6Al–4V biomedical substrates achieved through the combination of sandblasting and electrochemical processing in Ethaline.

Multifunctional-regions integrated with Mn-Co-Ni ternary hydroxides as self-assembled electrodes for high-performance hybrid supercapacitors

High-performance supercapacitors require elaborate design for electroactive materials with hierarchical structure and multiple components. In the present work, hierarchical nanoarrays composed of MnCoNi LDH@CoNi LDH (MCNL@CNL) with enoki-mushroom-like structure were constructed by integrating the structural regions with complementary functions. The self-assembled electrodes were fabricated upon MCNL@CNL with MnCo LDH@ZIF-67 as precursor and nickel foam as supporter, which achieved a specific capacitance of 2126.7 F/g at 0.5 A/g. The assembled hybrid supercapacitor exhibited the maximum energy density and power density of 51.4 Wh/kg and 7500 W/kg within the voltage range of 0–1.5 V, respectively, and it provided cycling stability with high capacitance retention (104.1%) and Coulombic efficiency (101.1%) after 10,000 cycles. Based on the characterizations results, MCNL@CNL electrode endowed with fast mass transfer, high conductivity and rich electroactive sites was produced, and its induced synergy effect facilitated charge transfer and promoted specific capacitance. Moreover, the hierarchical structure and rough surface of the fabricated MCNL@CNL accelerated the ions/electrons diffusion, and the cross-growing nanosheets on the surface enhanced the affinity. This work provides a novel approach to designing and fabricating self-assembled electrodes with high-performance and lifetime for supercapacitors.

Hierarchical Surface Pattern on Ni-Free Ti-Based Bulk Metallic Glass to Control Cell Interactions.

Ni-free Ti-based bulk metallic glasses (BMGs) are exciting materials for biomedical applications because of their outstanding biocompatibility and advantageous mechanical properties. The glassy nature of BMGs allows them to be shaped and patterned via thermoplastic forming (TPF). This work demonstrates the versatility of the TPF technique to create micro- and nano-patterns and hierarchical structures on Ti40Zr10Cu34Pd14Sn2 BMG. Particularly, a hierarchical structure fabricated by a two-step TPF process integrates 400nm hexagonal close-packed protrusions on 2.5µm square protuberances while preserving the advantageous mechanical properties from the as-cast material state. The correlations between thermal history, structure, and mechanical properties are explored. Regarding biocompatibility, Ti40Zr10Cu34Pd14Sn2 BMGs with four surface topographies (flat, micro-patterned, nano-patterned, and hierarchical-structured surfaces) are investigated using Saos-2 cell lines. Alamar Blue assay and live/dead analysis show that all tested surfaces have good cell proliferation and viability. Patterned surfaces are observed to promote the formation of longer filopodia on the edge of the cytoskeleton, leading to star-shaped and dendritic cell morphologies compared with the flat surface. In addition to potential implant applications, TPF-patterned Ti-BMGs enable a high level of order and design flexibility on the surface topography, expanding the available toolbox for studying cell behavior on rigid and ordered surfaces.

Wetting-and scaling-resistant superhydrophobic hollow fiber membrane with hierarchical surface structure for membrane distillation

In this study, we address the challenge of wetting and scaling in membrane distillation (MD) by developing a robust superhydrophobic poly(vinylidene fluoride) (PVDF) hollow fiber membrane. To achieve this, we utilized co-extrusion technology and subsequent fluorination treatment to create micro-nanoscale surfaces. The fabrication process involved extruding a SiO2 suspension onto the outermost layer of a triple-orifice spinneret to create a hierarchical structure, followed by 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FAS) modification to lower the membrane surface energy. This resulted in a highly water-repellant membrane, as evidenced by contact angle measurements of 153°, 147°, and 141° for water, sodium dodecyl sulfate (SDS) solution (0.4 mM), and saline SDS solution (0.4 Mm SDS and 35 wt% NaCl), respectively, indicating increased resistance to liquid penetration. Through direct contact membrane distillation (DCMD) experiments, we demonstrated that the PVDF/FAS membrane exhibited excellent wetting resistance to seawater (3.5 wt% of NaCl) with SDS at varying concentrations. Furthermore, the membrane effectively hindered the CaSO4 scaling by reducing both heterogeneous nucleation and the tendency of bulk crystal deposition on the membrane outer surface. Overall, the developed approach for fabrication of superhydrophobic PVDF hollow fiber membrane presents a promising solution for facile and scalable manufacturing of anti-wetting and anti-scaling MD membranes. This advancement has significant implications for enhancing the practical application of MD technology.

Nanocasting technique for imprinting a natural leaf pattern on biomimetic polyaniline to yield an artificial hierarchical surface structure for gas sensing

Hydrogen sulfide (H2S) posed substantial safety risks in industrial settings due to its odorless and toxic nature and necessitated vigilant detection. With the burgeoning importance of H2S gas sensing applications, this study focused on the synthesis and utilization of a novel biomimetic material aimed at advancing gas sensing capabilities. Biomimetic polyaniline (Bio-PANI) with an artificial hierarchical surface structure was fabricated through the innovative nanocasting technique. This technique involved the replication of the surface pattern of a natural Xanthosoma sagittifolium leaf (XSL) onto a PANI coating, achieved using a negative template. In comparison to PANI, Bio-PANI showcased higher specific surface area (160 m2/g versus 41 m2/g of PANI) and exhibited significantly amplified reversible redox and doping–dedoping capacities. The application of Bio-PANI and PANI coatings on interdigitated electrodes (IDEs) allowed for gas-sensing assessments. These evaluations encompassed as-prepared IDE sensor’s responsivity, selectivity, repeatability, and stability. Notably, the Bio-PANI-coated IDE sensor showed larger response (185% versus 27% of PANI toward a 10 ppm concentration of H2S), a consequence of their substantially larger specific surface area and greater electrochemical performances when contrasted with PANI-coated IDE sensor. In addition, Bio-PANI-coated IDE sensor exhibited better selectivity, repeatability, long-term stability, and moisture resistance.

3D Printed Bioinspired Hierarchical Surface Structure with Tunable Wettability

Abstract Nature has examples of impressive surfaces and interfaces with diverse wettability stemming from superhydrophilicity to superhydrophobicity. The multiscale surface structures found in biological systems generally have high geometric complexity, which makes it challenging to replicate their characteristics, especially using traditional fabrication techniques. It is even more challenging to fabricate such complex microstructures with tunable wettability. In this paper, we propose a method to tune the wettability of a micro-scale surface by changing the geometrical parameters of embedded micro-structures in the surface. By taking inspiration from an insect (springtails), we designed micropillar arrays with different roughness by adjusting geometric parameters such as reentrant angle, pitch distance, and the number of spikes and pillars. This study shows that, by changing geometrical parameters in microscale, the apparent contact angle, and hence the surface wettability can be calibrated. The microscale pillars were fabricated using a precise micro direct light processing (uDLP) three-dimensional (3D) printer. Different printing parameters were studied to optimize the geometric parameters to fabricate 3D hierarchical structures with high accuracy and resolution. By controlling the size of different features of the pillar, pillar number, and layout of the mushroom-shaped micropillars, the wettability of the surface is possible to be tuned from a highly nonwetting liquid/material combination to highly wetting material. Such wettability tuning capability expands the design space for many biomedical and thermofluidic applications.

Development of antibacterial neural stimulation electrodes via hierarchical surface restructuring and atomic layer deposition.

Miniaturization and electrochemical performance enhancement of electrodes and microelectrode arrays in emerging long-term implantable neural stimulation devices improves specificity, functionality, and performance of these devices. However, surgical site and post-implantation infections are amongst the most devastating complications after surgical procedures and implantations. Additionally, with the increased use of antibiotics, the threat of antibiotic resistance is significant and is increasingly being recognized as a global problem. Therefore, the need for alternative strategies to eliminate post-implantation infections and reduce antibiotic use has led to the development of medical devices with antibacterial properties. In this work, we report on the development of electrochemically active antibacterial platinum-iridium electrodes targeted for use in neural stimulation and sensing applications. A two-step development process was used. Electrodes were first restructured using femtosecond laser hierarchical surface restructuring. In the second step of the process, atomic layer deposition was utilized to deposit conformal antibacterial copper oxide thin films on the hierarchical surface structure of the electrodes to impart antibacterial properties to the electrodes with minimal impact on electrochemical performance of the electrodes. Morphological, compositional, and structural properties of the electrodes were studied using multiple modalities of microscopy and spectroscopy. Antibacterial properties of the electrodes were also studied, particularly, the killing effect of the hierarchically restructured antibacterial electrodes on Escherichia coli and Staphylococcus aureus-two common types of bacteria responsible for implant infections.

Construction of ZnxCdyS with a 3D Hierarchical Structure for Enhanced Photocatalytic Hydrogen Production from Water Splitting.

The ZnxCdyS has been proven to have unique photoelectric properties, but its synthesis method and photocatalytic water cracking performance need to be further improved. In this paper, Cd-MOF@ZIF-8 with a MOF-on-MOF (MOF = metal-organic framework) structure was prepared by a simple ion adsorption method. Then, a CdS/ZnxCdyS heterojunction with a 3D hierarchical structure was formed by solvothermal sulfidation. The prepared catalysts with different Zn/Cd ratios show an improved hydrogen production performance for photocatalytic water splitting, and the hydrogen evolution rate of Zn1Cd1S can reach up to 29.2 mmol·g-1·h-1. The excellent photocatalytic activity not only benefits from ZnxCdyS strong light conversion ability but also is closely related to the hierarchical structure and large specific surface area. A type II heterojunction also plays an important role in the spatial separation of photogenerated carriers. This paper provides a simple and feasible idea for the synthesis of a photocatalyst with a large specific surface area using a MOF-on-MOF synthesis strategy.

Topography Optimization for Sustainable Dropwise Condensation: The Critical Role of Correlation Length

AbstractAn effective pathway to enhance the heat transfer process is to induce the formation of highly mobile condensate droplets, employing micro‐nanoengineered superhydrophobic surfaces. However, the design of the topography of these surfaces for sustained high performance constitutes a significant scientific and technological challenge. Herein, the critical role of the correlation length of topography is demonstrated as an important factor when designing superhydrophobic surfaces for heat transfer applications. Specifically, it is shown that a) a high correlation length value corresponds to increased space between surface structures and higher lateral distances between nucleating droplets, which results in lower droplet departure diameter and significantly delayed flooding of the surface and b) correlation length has to surpass a critical value for dropwise condensation (DWC) to be sustained in hierarchical structured surfaces, when the droplets are growing in a partial Cassie state. Following this rationale, droplets are categorized in three different energy and wetting states (Wenzel droplets, Cassie droplets of low kinetic energy and high energy jumping droplets), depending on the correlation length of the topography. Heat transfer experiments demonstrate an increase of 126% in the heat transfer coefficient (HTC) of surfaces exhibiting the maximum correlation length when compared to the flat hydrophobic surface.

Constructing MOF-derived V2O5 as advanced cathodes for aqueous zinc ion batteries

Aqueous zinc-ion batteries (AZIBs) have become incremental attention due to its low cost, material abundance and environmental friendliness. Unfortunately, the crucial challenge is to develop cathodes with satisfactory superior Zn2+ storage. Here, a hierarchical porous V2O5 nano-bulk (p-V2O5) was synthesized derived from vanadium-based metal-organic framework via carbonization as cathode for AZIBs. The hierarchical mesoporous structure and elevated specific surface area are conducive to promote ion/electron transport. The prepared cathode delivers a high specific capacity of 115 mAh g−1 even at 3 A g−1. We also demonstrate that the Zn2+ storage mechanism is a reversible Zn2+ insertion/extraction in the open-structured Zn3(OH)2V2O7·2H2O and ZnyV2O5·nH2O in the subsequent cycling. The distinguished Zn2+ storage performance makes p-V2O5 a potential cathode for the next generation AZIBs.

In-situ grown SiO2 on amino-silane modified polyacrylonitrile nanofibrous membranes and its waterproof-breathable and light-shielding properties

Waterproof and breathable (W&B) materials with light-shielding properties are expected to provide new choices for outdoor clothing. Herein, SiO2@PAN nanofibrous membranes were fabricated by a facile and eco-friendly strategy. Firstly, amino-silane modified polyacrylonitrile (PAN-APS) nanofibrous membranes were prepared by electrospinning. Subsequently, a hierarchical rough structure and robust superhydrophobic surface were formed by a one-step in-situ growing SiO2 and coating with hexadecyltrimethoxysilane (HDTMS). The results showed that SiO2@PAN nanofibrous membranes displayed durable water repellency (the water contact angle above 150° and the sliding angle of about 5.3°), and high breathability (the air permeability of 47.23 mm/s and the moisture permeability of 3.92 kg·m−2·d-1). And SiO2@PAN nanofibrous membranes had a certain durability, which water repellency could maintain even after mechanical abrasion, or after 24 h of immersion in acid-base solutions with pH values of 1, 4, 7, 10 and 13. Moreover, SiO2@PAN nanofibrous membranes showed light-shielding properties. After 10 min exposure to sunlight irradiation, the surface temperature of SiO2@PAN membrane was about 10 °C lower than that of PAN membrane and 20 °C lower than the temperature of the surface without covering membrane. This work provides a promising candidate for protective clothing.

Crystalline/amorphous Ni/NixSy supported on hierarchical porous nickel foam for high-current-density hydrogen evolution

Manufacturing efficient and durable electrodes for alkaline water electrolysis under high-current-density conditions is a great challenge. Herein, Ni/NixSy heterostructure was grown on designed porous nickel foam (PNF) to construct Ni/NixSy-PNF electrode by a facile and scalable method for alkaline hydrogen evolution reaction (HER). The hierarchical porous structure and super-hydrophilic surface of Ni/NixSy-PNF accelerate the mass transfer and bubble detachment at high current densities. Theoretical calculations reveals that the enhanced HER activity of Ni/NixSy heterostructure is attributed to the stronger H2O adsorption. The resulting Ni/NixSy-PNF electrode achieves current densities of 100 and 500 mA cm−2 at low overpotentials of 61 and 121 mV, respectively. When applied for overall water splitting, the Ni/NixSy-PNF||Fe-Ni3S2-PNF electrolyser reaches a current density of 10 mA cm−2 at an extremely low voltage of 1.32 V. This work provides an effective strategy for fabricating high-performance electrodes for practical water electrolysis.

Gas foaming guided fabrication of hydrogel beads with controlled phase and porous structure for durable and highly efficient solar-powered water purification

Solar-powered interfacial evaporation has emerged as a reliable and sustainable strategy for clean water production, and accordingly, the rational fabrication of hydrogel-based evaporators has received special attention. The systems with anti-salt accumulation, scalable fabrication and facile use in large areas of water are in urgent need. Herein, MoS2-embedded foam hydrogel beads having hybrid open- and closed-cell structures are constructed via a self-assembly spinning-foaming-crosslinking method. Taking advantage of the internal hierarchical pore structure and spherical surface geometry of hydrogel beads, the assembled “indirect contact” architecture possess efficient in-situ energy utilization strategy, and could induce sufficient Marangoni effect to accelerate water transport and salt ions backflow, leading to prominent salt resistance. Gratifyingly, the improved system achieves an impressive evaporation rate of 3.58 kg m−2 h−1 and photothermal conversion efficiency of 94.7% under one sun illumination, as well as maintain over 3.3 kg m−2 h−1 for 8 cycles (12 h/cycle) even in the 25 wt% brine. As demonstrated by portable solar still prototype, high quality freshwater with production rate of ∼22 L/m−2 day−1 was collected. This study offers a viable strategy for developing the ease of scale, flexible of use, cost-effective and sustainable solar water purification system in real-world applications to mitigate clean water shortages.

In-situ generation of ZnS nanoparticles in quasi-MOFs for efficient eNRR

Inspired by the nitrogenase, transition metal sulfides have made outstanding progress in the field of eNRR. ZnS has emerged in the eNRR due to the strong photoelectric properties. Specially, the physical and chemical properties of ZnS are closely related with the support. In our study, ZIF-8-L was selected as the template to prepared ZnS/quasi-MOFs (ZnS/ZIF-8-L-T (T represents reaction temperature)) catalysts by using partial pyrolysis method. In this reaction process, the metal nodes of ZIF-8-L reacted with BDS to create ZnS nanoparticles, the organic ligands were carbonized to form the N-doped carbon support and partial framework of ZIF-8-L were remained. The hierarchical pore structure and high specific surface area of ZnS/ZIF-8-L-T not only provided a wide space for molecular diffusion, but also improved the adsorption and activation of N2. Additionally, the hydrophobicity of N-doped carbon support inhibited HER and improved FE. When the calcination temperature reached 350 °C, the obtained ZnS/ZIF-8-L-350 catalyst achieved a high NH3 yield (53.44 μg·h−1·mg−1) and a good FE (15.75%) at -0.3 V vs. RHE in 0.05 M H2SO4 solution. This work highlights the importance of support in regulating the physicochemical structure of the catalytic active center and can guide the design of advanced eNRR catalysts.