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Heat dissipation is a severe barrier for ever‐smaller and more functionalized electronics, necessitating the continuous development of accessible, cost‐effective, and highly efficient cooling solutions. Metals, such as silver and copper, with high thermal conductivity, can efficiently remove heat. However, ultralow infrared thermal emittance (<0.03) severely restricts their radiative heat dissipation capability. Here, a solution‐processed chemical oxidation reaction is demonstrated for transfiguring “infrared‐white” metals (high infrared thermal reflectance) to “infrared‐black” metametals (high infrared thermal emittance). Enabled by strong molecular vibrations of metal‐oxygen chemical bonds, this strategy via assembling nanostructured metal oxide thin films on metal surface yields infrared spectrum manipulation, high and omnidirectional thermal emittance (0.94 from 0 to 60°) with excellent thermomechanical stability. The thin film of metal oxides with relatively high thermal conductivity does not hinder heat dissipation. “Infrared‐black” meta‐aluminum shows a temperature drop of 21.3 °C corresponding to a cooling efficiency of 17.2% enhancement than the pristine aluminum alloy under a heating power of 2418 W m⁻². This surface photon‐engineered strategy is compatible with other metals, such as copper and steel, and it broadens its implementation for accelerating heat dissipation.

 

Passive radiative cooling, drawing heat energy of objects to the cold outer space through the atmospheric transparent window, is significant for reducing the energy consumption of buildings. Daytime and nighttime radiative cooling have been extensively investigated in the past. However, radiative cooling which can continuously regulate its cooling temperature, like a valve, according to human need is rarely reported. In this study, we propose a reconfigurable photonic structure, based on the effective medium theory and semi-analytical calculations, for the adaptive radiative cooling by continuous variation of the emission spectra in the atmospheric window. This is realized by the deformation of a one-dimensional polydimethylsiloxane (PDMS) grating and nanoparticle-embedded PDMS thin film when subjected to mechanical stress/strain. The proposed structure reaches different stagnation temperatures under certain strains. A dynamic tuning in emissivity under different strains results in a continuously variable “ON”/“OFF” mode in a particular atmospheric window that corresponds to the deformation-induced fluctuation of the operating temperatures of the reconfigurable nanophotonic structure.

 

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⁻²h⁻¹under 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.

 

Passive daytime radiative cooling (PDRC) is a promising energy-saving cooling method to cool objects without energy consumption. Although numerous PDRC materials and structures have been proposed to achieve sub-ambient temperatures, the technique faces unprecedented challenges brought on by complicated and expensive fabrication. Herein, inspired by traditional Chinese oil-paper umbrellas, we develop a self-cleaning and self-cooling oil-foam composite (OFC) made of recycled polystyrene foam and tung oil to simultaneously achieve efficient passive radiative cooling and enhanced thermal dissipation of objects. The OFCs show high solar reflectance (0.90) and high mid-infrared thermal emittance (0.89) during the atmospheric transparent window, contributing to a sub-ambient temperature drop of ∼5.4 °C and cooling power of 86 W m −2 under direct solar irradiance. Additionally, the worldwide market of recycled packaging plastics can provide low-cost raw materials, further eliminating the release of plastics into the environment. The OFC offers an energy-efficient, cost-effective and environmentally friendly candidate for building cooling applications and provides a value-added path for plastic recycling. 

Thermophotovoltaics is a promising technology for heat recovery and has garnered tremendous attention in the past decades. In a thermophotovoltaic system, a selective emitter is required to convert the incoming light in order to emit appropriate photons matched with the bandgap of the PV cell, both avoiding low-energy useless photons and thermalization loss caused by high-energy photons. This work aims to design a metal-based photonic narrowband emitter, and it is composed of tungsten, a refractory material which can withstand the high working temperature of the thermophotovoltaic system. Besides, the advantage of an all-metal emitter is that there is no concern of thermal expansion mismatch. Hexagon and square patterned arrays are numerically analyzed and a parametric study is conducted for different feature sizes, gaps, and pattern heights, leading to an emission peak shift and bandwidth change. Besides, a photonic metal-based emitter is fabricated using a photolithography method, optically characterized and compared with the calculated emissivity spectra. This work sheds light on the research of high-temperature thermal management, energy harvesting and power generation. 

Configured with a rapid evaporation rate and a high photothermal conversion efficiency, solar-driven interfacial evaporation displays considerable promise for seawater desalination. Inspired by the versatility and deployability of origami-based structures, we demonstrate a portable waterbomb origami pattern-based tower-like structure, named an “origami tower”, as a convertible photothermal evaporator floating on water for efficient solar-driven interfacial desalination. The origami tower has predictable deformability, featuring reversible radial expansion and contraction radially accompanied by small changes in the axial direction. The reversible adjustability of the origami tower offers convenience for transportation and storage, while the quick expansion into its tower shape provides rapid deployment capabilities. Benefiting from an enlarged evaporation surface, excellent light trapping ability, and heat localization, the origami-tower photothermal evaporator yields an evaporation rate of 2.67 kg m −2 h −1 under one sun illumination. This reversible 3D origami-based photothermal evaporator opens a new avenue for building a portable and efficient solar thermal desalination system.