One-step facile fabrication of hydrophobic SiO2 coated super-hydrophobic/super-oleophilic mesh via an improved Stöber method to efficient oil/water separation

Hydrophobicity and Improved Corrosion Resistance of Weathering Steel via a Facile Sol-Gel Process with a Natural Rust Film

Weathering steel, which has a protective corrosion product film, is widely used in various construction and landscaping applications. However, it causes metal contamination in the receiving ecosystem via corrosion-induced metal dissolution and rust runoff. Traditional corrosion prevention methods, such as surface coating, also suffer from environmental pollution and high maintenance costs. In this study, we propose a novel method to make the rust film hydrophobic to prevent corrosion while retaining its original appearance. The crystalline rust is used as a natural skeleton, and nano-SiO2 particles are synthesized in situ on it by a facile sol-gel method. The microscopic analysis shows that the flower-like rust flakes provide a primary structure (micrometric scales) and the nano-SiO2 particles form a secondary structure (nanoscale bumps), which is the essential micronanostructure for forming a hydrophobic surface. The as-synthesized film shows strong corrosion resistance, with the corrosion current density being 4 orders of magnitude lower than that of the samples without hydrophobicity. The hydrophobic surface not only prevents corrosive substances from penetrating into the rust layer but also reduces the risk of contamination through its self-cleaning properties. Therefore, the weathering steel with a hydrophobic rust film can be more stable and environmentally friendly for multiscenario applications.

Facile Preparation of Durable and Eco-Friendly Superhydrophobic Filter with Self-Healing Ability for Efficient Oil/Water Separation

The superhydrophobic feature is highly desirable for oil/water separation (OWS) operation to achieve excellent separation efficiency. However, using hazardous materials in fabricating superhydrophobic surfaces is always the main concern. Herein, superhydrophobic filters were prepared via an eco-friendly approach by anchoring silica particles (SiO2) onto the cotton fabric surface, followed by surface coating using natural material-myristic acid via a dip coating method. Tetraethyl orthosilicate (TEOS) was used in the synthesis of SiO2 particles from the silica sol. In addition, the impact of the drying temperature on the wettability of the superhydrophobic filter was investigated. Moreover, the pristine cotton fabric and as-prepared superhydrophobic cotton filters were characterised based on Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) and contact angle (CA) measurement. The superhydrophobic cotton filter was used to perform OWS using an oil-water mixture containing either chloroform, hexane, toluene, xylene or dichloroethane. The separation efficiency of the OWS using the superhydrophobic filter was as high as 99.9%. Moreover, the superhydrophobic fabric filter also demonstrated excellent durability, chemical stability, self-healing ability and reusability.

Special wettable Azadirachta indica leaves like microarchitecture mesh filtration membrane produced by galvanic replacement reaction for layered oil/water separation

The oil/water separation has received significant attention due to its critical environmental impact. The special wettable surfaces are highly desired to deal with the oil/water mixtures. This work demonstrates a simple two-step method to develop a superhydrophobic Azadirachta indica leaves like Ag-decorated electrochemically copper-coated stainless-steel mesh (SH-AIL-Ag-EC-Cu-Mesh) for efficient separation of oil/water mixtures. In the first step, the electrodeposition of the copper took place on the mesh surface at a suitable applied potential. In the second step, the galvanic replacement reaction between the Ag⁺ and electrodeposited Cu produced the fascinating superhydrophobic Ag leaves on the mesh surface. The SH-AIL-Ag-EC-Cu-Mesh was thoroughly characterized by the X-ray photoelectron spectroscopy (XPS), Energy Dispersive X-Ray Spectroscopy (EDX), elemental mapping, surface wettability analysis, and the contact analyzer. The morphological analysis has shown the unique leafy structures of the reduced Ag on the surface of the mesh. The XPS analysis has confirmed that most of the Ag present on the surface is in zerovalent form. The combination of the electrodeposition and the displacement reaction between the copper and the silver turned the surface superhydrophobic, and the water contact angle was significantly improved from 115° to 158°. The designed SH-AIL-Ag-EC-Cu-Mesh has shown excellent selectivity for oil in oil/water mixtures with a separation efficiency of 99.1% with an exceptionally high flux of 8963 L m^-2h^-1. The SH-AIL-Ag-EC-Cu-Mesh has shown excellent reusability, and after 15 cycles of separation, no significant decrease in the oil/water separation efficiency was observed.

Triple-Phase Interface Engineered Hierarchical Porous Electrode for CO2 Electroreduction to Formate

The aqueous electrochemical CO₂ reduction to valuable products is seen as one of the most promising candidates to achieve carbon neutrality yet still suffers from poor selectivity and lower current density. Highly efficient CO₂ reduction significantly relies on well-constructed electrode to realize efficient and stable triple-phase contact of CO₂ , electrolyte, and active sites. Herein, a triple-phase interface engineering approach featuring the combination of hierarchical porous morphology design and surface modification is presented. A hierarchical porous electrode is constructed by depositing bismuth nanosheet array on copper foam followed by trimethoxy (1H,1H,2H,2H-heptadecafluorodecyl) silane modification on the nanosheet surface. This electrode not only achieves highly selective and efficient CO₂ reduction performance with formate selectivity above 90% over wide potentials and a partial current density over -90 mA cm^-2 in H-cell but also maintains a superior stability during the long-term operation. It is demonstrated that this remarkable performance is attributed to the construction of efficient and stable triple-phase interface. Theoretical calculations also show that the modified surface optimizes the activation path by lowering thermodynamic barriers of the key intermediates *OCHO for the formation of formate during electrochemical CO₂ reduction.

A practical strategy for fabrication of transparent, robust and environmentally friendly superhydrophobic surfaces for toys and games

Abstract

This work presents a practical strategy for fabrication of transparent, robust and environmentally friendly superhydrophobic surfaces for toys and games by a one-step spray coating method. A type of commercial stringed silica nanoparticles (NPs) is chemically modified by a mixture of two fluorine-free silanes, tetraethyl orthosilicate (TEOS) and dodecyltrimethoxysilane (DDTMS) via a sol–gel process with the aid of ammonia as a basic catalyst and a small amount of water in ethanol, resulting in the formation of an amphiphilic solution, suitable for coating a variety of substrate materials such as glass, ceramics, wood, metal, plastics and paper and so on. Polyarylic acid (PAA) is used as a binder to improve the mechanical robustness of the superhydrophobic coating. Effects of silica NPs concentration, mixing order, TEOS/DDTMS ratio, PAA amount and catalyst on the transparency, uniformity, mechanical robustness and superhydrophobicity of the resultant coatings deposited on the glass slides are investigated. The mechanisms for the superhydrophobicity and water-resistance as well as the effects of catalyst and mixing order are discussed. Furthermore, an example of the superhydrophobic surfaces as toys is presented. This work will pave the way for expanding wide applications of the superhydrophobic surfaces towards toys and games.

Article Highlights

Fabrication of Superhydrophobic Ni-Co-BN Nanocomposite Coatings by Two-Step Jet Electrodeposition

The stability of hydrophobic surface has an important influence on the application of superhydrophobic function. The destruction of hydrophobic micro-nano structures on the material surface is the main factor leading to the loss of superhydrophobic property. In order to improve the corrosion resistance of superhydrophobic surface, Ni-Co-BN nanocomposite coatings with superhydrophobic property were prepared on 45 steel by two-step jet electrodeposition. The surface morphology, water contact angle, and corrosion resistance of the samples were measured and characterized by scanning electron microscope, surface contact angle measuring instrument, and electrochemical workstation. The results of electrochemical analysis show that the superhydrophobic property improved the corrosion resistance of Ni-Co-BN nanocomposite coating. The enhanced corrosion resistance is of great significance to the integrity of the microstructure and the durability of the superhydrophobic function.