Rational design of solar absorption, heat conversion and water supply for efficient solar steam generation.

Surgical mask is recommended by the World Health Organization for personal protection against disease transmission. However, most of the surgical masks on the market are disposable that cannot be self-sterilized for reuse. Thus, when confronting the global public health crisis, a severe shortage of mask resource is inevitable. In this paper, a novel low-cost electrothermal mask with excellent self-sterilization performance and portability is reported to overcome this shortage. First, a flexible, ventilated, and conductive cloth tape is patterned and adhered to the surface of a filter layer made of melt-blown nonwoven fabrics (MNF), which functions as interdigital electrodes. Then, a graphene layer with premier electric and thermal conductivity is coated onto the MNF. Operating under a low voltage of 3 V, the graphene-modified MNF (mod-MNF) can quickly generate large amounts of heat to achieve a high temperature above 80 °C, which can kill the majority of known viruses attached to the filter layer and the mask surface. Finally, the optimized graphene-modified masks based on the mod-MNF filter retain a relatively high particulate matter (PM) removal efficiency and a low-pressure drop. Moreover, the electrothermal masks can maintain almost the same PM removal efficiency over 10 times of electrifying, suggesting its outstanding reusability.

absorption with noticeable photothermal conversion efficiency have been developed for SSG, [7,8] plasmonic metal, [9][10][11][12][13] semiconductors, [14][15][16][17] and carbon-based materials. [18][19][20][21] However, the high-cost and complex manufacturing processes make it hard to prepare on a large-scale. [22] And the accumulation of salt deposits on the photothermal layers results in a sharp decline in SSG performance, thus lacking sustainability and recyclability. [23] Therefore, the SSG are yet far from industrialization that requires low-cost, scalable, and reusable photothermal materials.Carbonization of rampant plants into carbon materials by the high-temperatureinduced pyrolysis provides an alternative solution to these problems, but it still has great challenges. [24] With the development of this technology, a variety of plants have been explored to synthesis different photothermal layers. [25][26][27][28][29] For instance, Xu et al. [28] demonstrated mushrooms as a solar steam generator for the first time. The unique natural structure of mushroom, porous context, and fibrous stipe, make the conversion efficiency of natural and carbonized mushrooms achieve 62% and 78% under 1 sun illumination. Fang et al. [29] found that the unique macroscopic cone shape and hierarchical porous structures of the carbonized lotus seedpods resulted in an evaporation rate and the corresponding evaporation efficiency under 1 sun irradiation of 1.30 kg m −2 h −1 and 86.5%, respectively. The special structure of plant stem is conducive to improving the SSG ability, which is due to the fact that the plant stem can transport water and other nutrients to the upper layer during the whole plant growth process. [30] However, the prices of the current plants, such as mushroom, lotus seedpods, still need to be further cut down (the cost comparison is shown in Table S1 in the Supporting Information). It is of great significance to explore more abundant and low-cost plants for carbonization. Moreover, the mechanical strength and surface of the plants are destroyed by the high temperature during the carbonization process. It is still a big challenge to uniformly and stably deposit the carbonized species on substrates or assemble them to self-stand films at a large scale. [31][32][33] Most importantly, the steam generation rate and evaporation efficiency are yet to be further increased. Solar steam generation (SSG) based on the photothermal effect has beenconsidered to be a promising avenue for freshwater production. However, the fabrication of highly-efficient photothermal layers, at large-scale and low-cost is still a challenge, hindering practical applications. Herein, it is demonstrated that carbonized towel-gourd sponges (CTGS) are excellent photothermal materials. And a capillarity-driven interfacial self-coating method is developed to prepare the super-hydrophilic CTGS/paper photothermal layer. The SSG device based on the CTGS/paper exhibits a high evaporation rate of 1.53 kg m −2 h −1 with an efficiency of 95.9% under 1 sun i...

Solar steam generation provides a renewable and environmentally friendly approach to solve the water shortage issue. The pursuit of efficient, stable, and cheap photothermal agents is thus of great significance. In this work, Cu nanoparticles (NPs) fabricated simply by a substitution reaction, exhibit a near-unity (∼97.7%) light absorption, covering a broad incident angle and wavelength range (200–1300 nm). Thereby, a high photothermal conversion efficiency of 93% is achieved. The excellent photothermal performance offers a unique opportunity for the development of solar steam generation. By coating the Cu NPs on a cellulose membrane, a solar steam generation efficiency up to 73% is acquired at a low irradiation power density of 2 kW m−2 (1 kW m−2 = 1 sun). Moreover, the Cu NPs are recyclable with the high stability being resistant to heat, photoirradiation and corrosion of brine.

Superwettability materials from existing natural creatures have been widely studied to enable artificial manufacture. Variable wettability states, especially Janus wettability, have attracted particular interest because of the applications in various intelligent systems. However, to date, most of these existing Janus wettability surfaces lack stimuli‐response visualization, which requires the connection of electrical instruments to process and display external stimulus signals. Inspired by the functional performance of lotus leaf and Betta splendens, a multifunctional asymmetric film is designed by using the superhydrophobic/superhydrophilic binary cooperative strategy and tunable structural color feature. Thus, it is demonstrated that the Janus membrane could not only timely report the arrival of the environmental variables via directional migration induced by Marangoni effect, but also quantitively feedback the stimuli through visible structural color variations. These features indicate that the Janus wettability structural color film may open a potential chapter in designing and fabricating the multifunctional robotic environmental detector.