Ultra‐Black Pinecone for Efficient Solar Steam Generation under Omnidirectional Illumination

Abstract

It has been a goal to create artificial evaporators that have highly efficient solar steam generation (SSG) performance under omnidirectional illumination to solve the global drinking water crisis. Although some evaporators with high evaporation rates and efficiencies have been reported, their inefficient performance under oblique illumination conditions remain to be overcome. Pinecones, with their delicate transpiration channels, photo‐thermal moisture‐sensitive deployable structure, and 3D Fibonacci helically‐arranged scales, inspire the design of this efficient evaporator under omnidirectional illumination. Herein, ultra‐black pinecone (UBP) with multi‐branched, arterially porous, and hierarchical structures shows excellent SSG performance under omnidirectional illumination. UBP achieves a high evaporation rate and efficiency of 1.86 kg m−2 h−1 and 97.85% respectively, under one sun illumination. The SSG performance under oblique incidence conditions of UBP are not degraded but improved (2.194 g h−1 under incident angle of 90°) because the UBP can recover reflection and radiation energy losses, avoid cosine energy losses, and absorb heat from the warm environment. The UBP also exhibits high evaporation rate in real weather and good durability and salt resistance in concentrated brine, which ensures its great potential applications in wastewater treatment and solar desalination.

State‐of‐the‐Art Advances, Development, and Challenges of Metal Oxide Semiconductor Nanomaterials for Photothermal Solar Steam Generation

“…[11] To improve the calculation of 3D evaporators on solar-thermal conversion efficiency, some authors proposed the consideration of steady-state energy balance in a SSG system. [11,13,130] Heat losses in the form of light reflection and scattering, conduction, convection, and radiation are included for a more precise calculation. To account for the effect of light reflection and scattering, the total received Figure 19.…”

“…Convection heat loss occurs from photoabsorber to ambient air can be represented by Newton's law of cooling [13,130] conv,air evap PTM env…”

“…Low thermal conductivity of carbonized corn cob also favors the SSG process. Other rational design of solar evaporators inspired from natural products such as Monstera, [11] Magnolia, [12] pinecone, [13] lotus seedpod, [14] sunflower head, [15,16] and loofah [17] have also gained great attention in recent development of SSG system. A simple SSG system consists of four main components: photoabsorber, substrate, water reservoir, and incoming sunlight.…”

Recent Progress on the Solar‐Driven Interfacial Evaporation Based on Natural Products and Synthetic Polymers

“…Li and coworkers [ 109 ] reported a novel double‐layer PM based on attapulgite/polyacrylamide composite (APAC); the APAC‐based SSGD was prepared by simple flame treatment. The thin carbon layer had excellent light adsorption, the APAC‐based SSGD had an evaporation rate of 1.20 kg m −2 h −1 under 1 sun irradiation, and the corresponding solar steam conversion efficiency was 85.0%.…”

Ultrablack Poly(vinyl alcohol)‐Graphite Composite Xerogel with Vertically Arranged Pores for Highly Efficient Solar Steam Generation and Desalination

“…In the past few years, some efficient evaporators based on different ultrablack materials such as metal nanoparticles, [23][24][25] semiconductors, [26][27][28] carbon materials, [29][30][31][32][33][34] polymers, [35][36][37] and others [38][39][40][41][42] have been reported. However, there are still one or more disadvantages of these evaporators in practical application, such as the use of expensive metals, the strict and complex chemical synthesis process to achieve high absorbance, synthesis process involving high temperature and pressure, and poor durability.…”