Reduced Graphene Oxide–Based Spectrally Selective Absorber with an Extremely Low Thermal Emittance and High Solar Absorptance

Abstract

Carbon‐based black materials exhibit strong solar absorptance (αsolar >0.90), which play key roles in transforming solar energy into available power for solar‐thermal, thermophotovoltaic, thermoelectric, and many other systems. However, because of high thermal emittance (>95%), these carbon‐based materials always cause huge energy loss that hinders the solar‐thermal conversion efficiency tremendously. In this study, a reduced graphene oxide–based spectrally selective absorber (rGO‐SSA) is demonstrated, which possesses a recorded low thermal emittance (≈4%) and high solar absorptance (αsolar ≈ 0.92) by easily regulating the reduction level of inner 2D graphene sheets. Compared to conventional carbon‐based black materials, thermal emittance of this rGO‐SSA is largely reduced by ≈95.8% and the cutoff wavelength of rGO‐SSA is broadband‐tunable that can range from 1.1 to 3.2 µm. More importantly, this simply sol‐gel coated rGO‐SSA has high temperature tolerance at 800 °C for 96 h that is hardly achieved by other cermet‐based or photonic‐based SSAs. Based on this rGO‐SSA, ultrafast solar steam escape (0.94 mg cm−2 s−1) under concentrated solar irradiance is achieved directly. The insight from this study will provide a new strategy for constructing thermally stable carbon‐based SSAs and greatly facilitate the solar‐thermal practical significance.

Concentrated Acid‐Induced Dehydration of Fallen Leaves for Efficient, Sustainable, and Self‐Cleaning Solar Steam Generation

“…[ 1–6 ] The development and design of photothermal conversion materials, which can absorb solar irradiation and convert it into heat, is one of the focuses in this field. [ 7–9 ] To date, various types of light absorbers, such as metallic nanoparticles, [ 10–13 ] carbon‐based materials, [ 14–16 ] polymers, [ 17–19 ] and semiconductors [ 20–22 ] have been demonstrated for efficient solar absorption. [ 23,24 ] Among them, carbon‐based materials, including exfoliated graphite, graphene, carbon nanotubes, and other carbon materials have attracted extensive attention due to their high‐efficiency, chemical stability, and excellent broadband solar absorption.…”

Ultrathin Titanium Carbide (MXene) Films for High‐Temperature Thermal Camouflage

“…[6] Reducing the surface temperature and regulating the surface IR emissivity of an object are two main approaches to realize thermal camouflage. [7] Based on these strategies, various materials and systems, such as phase-change materials (PCMs), [2,8] thermal insulation materials, [9][10][11] metal film/coatings, [12][13][14] metasurfaces, [15][16][17][18][19] and several other methods, [20][21][22][23][24][25][26][27] have been developed to date. However, the following problems remain.…”

Calcium-Doped Boron Nitride Aerogel Enables Infrared Stealth at High Temperature Up to 1300 °C

“…The extraordinary high-temperature stability and superior high-temperature heat insulation performance of the Ca-BN aerogel make it useful in high-temperature thermal stealthy [33][34][35][36]. According to the Stefan-Boltzmann law: P = εσT 4 , the thermal radiation of a target is proportional to the surface emittance (ε) and the fourth power of temperature (T) [33][34][35][36][37]. Thermal stealthy is need to blend targets into their surroundings in infrared imaging to evade infrared thermal detection.…”

“…Integrating thermal insulation and desired infrared emission in one architecture, which can further reduce the radiation temperature of high-temperature target to around room temperatures, may provide a chance to achieve superior high-temperature thermal stealthy. Aluminum foil possessed a very low infrared emissivity and high infrared reflectance [29,[37][38][39][40], and it is usually used in thermal stealthy. However, the aluminum foil will be melted or destroyed in the high temperature above 660 °C environment and then brought safety problem or become infrared visible (Fig.…”