Durable Self-Cleaning Radiative Cooling Coatings for Building Energy Efficiency.

Passive daytime radiative cooling (PDRC) is an energy-saving technology without an additional energy supply or environmental pollution. At present, most PDRC coatings for buildings are only aiming at high solar reflectivity (RS) and high mid-infrared emissivity (EMIR) while ignoring practicalities such as adhesion strength, scalability, and durability. In this work, modified calcined kaolin/(ethylene trifluorochloroethylene copolymer-polydimethylsiloxane) (MK/(FEVE-PDMS)) coating with super practicability is prepared by using MK as a filler, FEVE as an adhesive, and PDMS as a hydrophobic modifier. The RS and EMIR of the coating are 92.5 and 94.6%, respectively. The MK/(FEVE-PDMS) coating exhibits superhydrophobicity, with an advancing contact angle (ACA) of 160.2° and a hysteresis contact angle of 7.3°. At an average solar irradiance of 742.78 W m-2, the coating achieved a temperature drop of 13.12 °C (shielded with PE film) and 3.09 °C (without shielding), respectively, relative to the environment. The coating adheres firmly to the substrate with an adhesion strength of class 2. The superhydrophobicity of the coating provides excellent durability and ease of repair, which can resist UV aging and mechanical damage. The durable superhydrophobicity gives the coating long-term stability in PDRC performance. Additionally, the cheap raw materials and the preparation process, consistent with the production of existing paints, show excellent scalability. Moreover, the energy consumption simulation results show that the energy saving ratio of the coating is more than 10% in the densely populated Yangtze River Delta and Pearl River Delta. The durable self-cleaning radiative coating developed in this work has potential application prospects in areas where the demand for cooling in summer is large and the demand for heating in winter is small.

Innovative Solid Slippery Coating: Uniting Mechanical Durability, Optical Transparency, Anti-Icing, and Anti-Graffiti Traits.

Slippery coatings, such as the slippery liquid-infused porous surface (SLIPS), have gained significant attention for their potential applications in anti-icing and anti-fouling. However, they lack durability when subjected to mechanical impact. In this study, we have developed a robust slippery coating by blending polyurethane acrylate (PUA) with methyltriethoxysilane (MTES) and perfluoropolyether (PFPE) in the solvent of butyl acetate. The resulting mixture is homogeneous and allows for uniform coating on various substrates using a drop coating process followed by drying at 160 °C for 3 h. The cured coating exhibits excellent water repellency (contact angle of ~108° and sliding angle of ~8°), high transparency (average visible transmittance of ~90%), exceptional adherence to the substrate (5B rating according to ASTMD 3359), and remarkable hardness (4H on the pencil hardness scale). Moreover, the coating is quite flexible and can be folded without affecting its wettability. The robustness of the coating is evident in its ability to maintain a sliding angle below 25° even when subjected to abrasion, water jetting, high temperature, and UV irradiation. Due to its excellent nonwetting properties, the coating can be employed in anti-icing, anti-graffiti, and anti-sticking applications. It effectively reduces ice adhesion on aluminum substrates from approximately 217 kPa to 12 kPa. Even after 20 cycles of icing and de-icing, there is only a slight increase in ice adhesion, stabilizing at 40 kPa. The coating can resist graffiti for up to 400 cycles of writing with an oily marker pen and erasing with a tissue. Additionally, the coating allows for easy removal of 3M tape thereon without leaving any residue.

Novel SLIPS based on the photo-thermal MOFs with enhanced anti-icing/de-icing properties.

A photo-thermal anti-icing/de-icing SLIPS coating is designed based on porous light-responsive MOFs. Due to the strong light absorption and high light-thermal conversion, the as-synthetic SCMOFs exhibited prolonged freezing delay time and depressed water crystallization point under light irradiation. Meantime, the SCMOFs exhibit good deicing properties. With the irradiation, the half-melted ice slips off quickly.

Durable Superhydrophobic Wood via One-Step Immersion in Composite Silane Solution.

A superhydrophobic coating endows pristine hydrophilic wood with excellent water/moisture repellency and thus prolongs its service life. Generally, the superhydrophobic coating on wood is fabricated by a two-step process in which the nanoparticles are first introduced onto the surface and then modified by low-surface-energy molecules. Herein, for the first time, we have fabricated the superhydrophobic wood via a one-step process free of nanoparticles by immersing the pristine hydrophilic wood, such as pine, balsawood, and basswood, into a composite silane solution of hexadecyltrimethoxysilane and methyltrimethoxysilane. The wood remains superhydrophobic or highly hydrophobic after long-term exposure to mechanical damage (such as abrading, knife-cutting, and tape-peeling), chemical damage (such as immersion in acid, alkali, or ethanol), and environmental impacting (such as UV irradiation and low/high-temperature exposure).

Water and mildew proof SiO2 & ZnO/silica sol superhydrophobic composite coating on a circuit board.

In order to improve the waterproof and mildew resistance of electronic equipment, a superhydrophobic coating was prepared on a circuit board. First, hexadecyl trimethoxysilane was used to modify the nano silica and nano zinc oxide particles, and then the modified nanoparticles were mixed with the silica sol. Then the superhydrophobic coating was prepared on the surface of the printed circuit board by a spraying process. The preparation technology and physical and chemical properties of the coating were studied. The contact angle of the final sample can reach 169.47°, the sliding angle can reach 1.2°, it has good acid and alkali corrosion resistance, resistance to NaCl, self-cleaning performance and antimildew performance.

Single Pt Atoms Confined into a Metal-Organic Framework for Efficient Photocatalysis.

It is highly desirable yet remains challenging to improve the dispersion and usage of noble metal cocatalysts, beneficial to charge transfer in photocatalysis. Herein, for the first time, single Pt atoms are successfully confined into a metal-organic framework (MOF), in which electrons transfer from the MOF photosensitizer to the Pt acceptor for hydrogen production by water splitting under visible-light irradiation. Remarkably, the single Pt atoms exhibit a superb activity, giving a turnover frequency of 35 h-1 , ≈30 times that of Pt nanoparticles stabilized by the same MOF. Ultrafast transient absorption spectroscopy further unveils that the single Pt atoms confined into the MOF provide highly efficient electron transfer channels and density functional theory calculations indicate that the introduction of single Pt atoms into the MOF improves the hydrogen binding energy, thus greatly boosting the photocatalytic H2 production activity.

Metal-Organic Framework-Derived FeCo-N-Doped Hollow Porous Carbon Nanocubes for Electrocatalysis in Acidic and Alkaline Media.

Metal-organic frameworks (MOFs) are ideal precursors/ templates for porous carbons with homogeneous doping of active components for energy storage and conversion applications. Herein, metalloporphyrinic MOFs, PCN-224-FeCo, with adjustable molar ratio of FeII /CoII alternatively residing inside the porphyrin center, were employed as precursors to afford FeCo-N-doped porous carbon (denoted as FeCo-NPC) by pyrolysis. Thanks to the hollow porous structure, the synergetic effect between highly dispersed FeNx and CoNx active sites accompanied with a high degree of graphitization, the optimized FeCo2 -NPC-900 obtained by pyrolysis at 900 °C exhibits more positive half-wave potential, higher diffusion-limited current density, and better stability than the state-of-the-art Pt/C, under both alkaline and acidic media. More importantly, the current synthetic approach based on MOFs offers a rational strategy to structure- and composition-controlled porous carbons for efficient electrocatalysis.

Porphyrinic Metal-Organic Framework-Templated Fe-Ni-P/Reduced Graphene Oxide for Efficient Electrocatalytic Oxygen Evolution.

The sluggish kinetics of oxygen evolution reaction (OER) hampers the H2 production by H2O electrolysis, and it is very important for the development of highly efficient and low-priced OER catalysts. Herein, a representative metalloporphyrinic MOF, PCN-600-Ni, integrated with graphene oxide (GO), serves as an ideal precursor and template to afford bimetallic iron-nickel phosphide/reduced graphene oxide composite (denoted as Fe-Ni-P/rGO-T; T represents pyrolysis temperature) via pyrolysis and subsequent phosphidation process. Thanks to the highly porous structure, the synergetic effect of Fe and Ni elements in bimetallic phosphide, and the good conductivity endowed by rGO, the optimized Fe-Ni-P/rGO-400 exhibits remarkable OER activity in 1 M KOH solution, affording an extremely low overpotential of 240 mV at 10 mA/cm2, which is far superior to the commercial IrO2 and among the best in all non-noble metal-based electrocatalysts.