Passive daytime radiative cooling (PDRC) involves cooling down an object by simultaneously reflecting sunlight and thermally radiating heat to the cold outer space through the Earth's atmospheric window. However, for practical applications, current PDRC materials are facing unprecedented challenges such as complicated and expensive fabrication approaches and performance degradation arising from surface contamination. Herein, we develop scalable cellulose-fiber-based composites with excellent self-cleaning and self-cooling capabilities, through air-spraying ethanolic poly-(tetrafluoroethylene) (PTFE) microparticle suspensions embedded partially within the microsized pores of the cellulose fiber to form a dual-layered structure with PTFE particles atop the paper. The formed superhydrophobic PTFE coating not only protects the cellulose-fiberbased paper from water wetting and dust contamination for real-life applications but also reinforces its solar reflectivity by sunlight backscattering. It results in a subambient cooling performance of 5 °C under a solar irradiance of 834 W/m 2 and a radiative cooling power of 104 W/m 2 under a solar intensity of 671 W/m 2 . The self-cleaning surface of composites maintains their good cooling performance for outdoor applications, and the recyclability of the composites extends their life span after one life cycle. Additionally, dyed cellulose-fiber-based paper can absorb appropriate visible wavelengths to display specific colors and effectively reflect nearinfrared lights to reduce solar heating, which synchronously achieves effective radiative cooling and esthetic varieties.

Solar-driven steam generation, whereby solar energy is harvested to purify water directly, is emerging as a promising approach to mitigate the worldwide water crisis. The scalable application of conventional 3D evaporators is hindered by their complex spatial geometries. A 2.5D structure is a spatial extension of a 2D structure with an addition of a third vertical dimension, achieving both the feasibility of 2D structure and the performance of 3D structure simultaneously. Here, an interconnected open-pore 2.5D Cu/CuO foam-based photothermal evaporator capable of achieving a high evaporation rate of 4.1 kg m −2 h −1 under one sun illumination by exposing one end of the planar structure to air is demonstrated. The micro-sized open-pore structure of Cu/CuO foam allows it to trap incident sunlight, and the densely distributed blade-like CuO nanostructures effectively scatter sunlight inside pores simultaneously. The inherent hydrophilicity of CuO and capillarity forces from the porous structure of Cu foam continuously supply sufficient water. Moreover, the doubled working sides of Cu/CuO foam enlarge the exposure area enabling efficient vapor diffusion. The feasible fabrication process and the combined structural features of Cu/CuO foam offer new insight into the future development of solar-driven evaporators in large-scale applications with practical durability.

Solar-driven interfacial steam generation provides an opportunity for solar harvesting and freshwater yield as a promising and eco-friendly technology. Here, we demonstrate a sustainable, nontoxic, and highly efficient fully biomass-based GG/CI hydrogel evaporator consisting of gellan gum (GG) hydrogel as the matrix and cuttlefish ink (CI) as the photothermal material. Induced by the ice-template method and freeze-drying method, vertically aligned microchannels are generated along the ice crystal growth direction. Efficient photothermal conversion is enabled by the natural black cuttlefish ink powder and enhanced by the light trapping effect within vertical microchannels. The hydrophilic property of the gellan gum hydrogel and water capillary force in those microchannels boost water pumping to the top interfacial evaporation region. Effective rapid salt self-cleaning behavior is achieved due to the rapid ion diffusion within vertical microchannels. An evaporation rate of 3.1 kg m–2 h–1 under one sun irradiance is demonstrated by this fully biomass-based GG/CI hydrogel evaporator. This work offers a promising alternative for eco-friendly and sustainable freshwater generation with abundant natural biomasses.

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Solar-driven interfacial evaporation shows great prospects for seawater desalination with its rapid fast evaporation rate and high photothermal conversion efficiency. Here, a sustainable, biodegradable, non-toxic, and highly efficient full ocean...

Passive radiative cooling, radiating energy from objects to the outer space through the Earth's atmospheric window, offers promising solutions for passive building cooling and renewable energy harvesting. However, static passive radiative cooling systems with a fixed thermal emissivity cannot automatically regulate emission in response to varying ambient temperature. Here, we propose an intelligent cooling system composed of nanoporous polyethylene, which acts as a solar reflector and a nanograting radiative cooler using the phase-transition material vanadium dioxide (VO2) and polydimethylsiloxane (PDMS). The top reflector enables the cooling system to reflect solar irradiation during the daytime, and the bottom cooler plays the role of switching radiative cooling in the spectrum band (8  μm < λ < 13  μm) due to the phase transition characteristic of VO2, contributing to the temperature of radiative cooler near a critical temperature. Meanwhile, continuous stretching of the material can achieve dynamic radiative cooling via deformation of the elastic PDMS substrate to realize different desired cooling temperatures. The proposed VO2-PDMS-driven radiative cooling system can not only intelligently switch between “on” and “off” radiative cooling modes but also adjust thermal comfort in its on mode in response to changes in the ambient temperature. This work has a great potential to be applied in the intelligent temperature regulation of buildings, vehicles, and utilities.

The increasing demand for freshwater and the intensification of environment pollution have driven the exploration of high-performance photothermal conversion materials for the solar-driven interfacial evaporation (SIE) to produce fresh water....

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