High‐Performance Large‐Scale Solar Steam Generation with Nanolayers of Reusable Biomimetic Nanoparticles

Abstract

is currently based on structures floating on water. [11,13,17,[19][20][21][22] By using graphite membranes, the highest solar thermal efficiency (see Equation (4)) of 85% has been reported under an equivalent solar intensity of 10 suns. [13] One of the main drawback of this approach, besides the large light intensity requirement, lies in the fact that carbon-based systems (both graphite and graphene) are vulnerable to the contamination of pollutants or salt in the water, thus limiting the recyclability of the membrane after prolonged use.In this article, we developed a different approach, which makes use of a flat-optics metasurface [23][24][25][26][27][28] composed of suitably engineered plasmonic nanoparticles. [29,30] Plasmonics structures, thanks to the possibility of localizing light energy at the nanoscale, have demonstrated a great potential in converting light energy into heat for a variety of photothermal applications. [31][32][33][34] In plasmonic steam generation, the best results have been obtained with porous films, which reported efficiencies of ≈60% under 1 sun. [19,20] The efficiency limits of these structures originate from the resonant nature of classical plasmonic materials, which usually harvest energy only at characteristic frequencies of the solar spectrum. In our metasurface, we overcome this problem by using a completely new mechanism of heat generation supported by biomimetic nanoparticles that behave as an almost ideal blackbody. These nanoparticles mimic the shell of an Asian specie of beetle that possesses an exceptional ability in controlling light reflection. [29] Even when these nanoparticles are used in extremely small volumes, they completely absorb input photons at all frequencies and polarizations. By suitably dispersing these nanoparticles in a paper film, we created a metasurface with a remarkable ability in transforming light energy into heat, leading to a dramatic increase of solar thermal generation efficiency if compared to classical structures. Our nanoparticles are fully recyclable from the paper substrate and invulnerable to saline water corrosion, representing an ideal system for solar steam generation. [35] 2. Results Sample Design and Fabrication

Fast‐Growing Field of Interfacial Solar Steam Generation: Evolutional Materials, Engineered Architectures, and Synergistic Applications

“…The green shaded area corresponds to the standard deviation of the absorbance; and the solid orange area represents the solar irradiation spectrum. Reproduced with permission . Copyright 2017, Wiley‐VCH.…”

“…By mimicking the shell of an Asian species of beetle (Figure e), Fratalocchi's group designed a flat‐optical metasurface, acquiring an evaporation efficiency of 87% upon exposure to sunlight with an intensity of only 2.3 kW m −2 . The as‐designed flat‐optical metasurface consists of the absorbing layer (gold plasmonic nanostructures made by a nanorod connected with a nanosphere) and the supporting layer (filter paper).…”

Efficient Solar Evaporation by [Ni(Phen)3][V14O34Cl]Cl Hybrid Semiconductor Confined in Mesoporous Glass

“…[11] In general, solar evaporation processes include the key steps of solar absorbance and subsequent conversion into heat on absorbers, water supply to illuminated absorbers, and vapor generation,a sw ell as vapor condensation and collection. The four predominant factors that determinet he performance of solar evaporation are the efficiency of solar-thermal conversion of the absorber,h eat management of the system,water supply,a nd the vapor evacuation system.T ypical solar absorber materials, such as graphene oxide (GO), [12] ultrablack absorbers, [13] plasmonic nanoparticles, [14] and thermalconcentrating ceramics, [15] have displayed excellent capability for enhancing the local heat concentrationb ys olar-thermal conversion.A sw ater evaporation is as urface processa tt he very thin water-air interface, minimizing the heat dissipation into the environmenta nd the parasitic heat loss into bulk water is critical for improving solare vaporation performance in terms of heat management. With the assistance of at wo-dimensional water supply path,t he solar evaporation efficiency under 1sun illumination reaches up to 80 %, owing to the minimized heat loss.…”

“…Theg eneratori sf loated in water by supporting it on ad omestic melamine-formaldehyde (MF) foam to ensure evaporation att he water-air interface. The porous structures and poor thermalc onductivities of the meso-glass and MF foam contribute to enabling ac onsistentw ater supply, strong solart hermal localization,a nd less heatd issipation and convection.A ssociated with the strong photothermal role of NiV 14 ,t heses ynergistic effects lead to aw ater evaporation rate of 14.38 kg m À2 h À1 with total water evaporation efficiency of 111.4% under 6suns and ad aily solar water purification yield of 42.00 Lm À2 under 1sun irradiation. This solar evaporation system shows great promise forh igh-efficiency water purification application.…”

“…Essentially,t he intrinsic photothermal properties of the active materials are the core for developing efficient solar evaporation devices.W es ynthesized the hybridi onic compound [Ni(Phen) 3 termined its crystal structure by single-crystal X-ray diffraction. [21] Many reported materials with similars tructures to NiV 14 have been used in photocatalysis and radiodynamic therapy. [22,23] In this work, we have taken advantage of the excellent photothermal properties of NiV 14 and developed ah ighly efficient solar evaporation generator,i nw hich the solar-thermal materialN iV 14 is embedded in the pores of mesoporous glass (denoteda sm eso-glass) with ap ore size distribution of 20-30 nm and ah ydrophilic wall ( Figure 1a).…”