Engineering a Versatile Spectrally Selective Absorber for Moderate‐ and Low‐Temperature Application with Gradient High‐Entropy Nitride Nanofilms

Abstract

Spectrally selective absorber with superior thermal stability and optical properties is crucial for photothermal conversion applications, including evaporation, anti‐icing, medical sterilization, photothermal catalysis, and solar‐thermal power. Efforts are being made to develop entropy‐stabilized high‐entropy ceramics as high‐performance functional materials, which promise a wide range of potential applications in the fields of energy storage and conversion owing to their diverse compositions and outstanding physical and chemical properties. Herein, an entropy‐stabilized strategy is used to boost the performance of spectrally selective absorbers by carefully choosing a high‐entropy alloy (TiVCrAlZr) target with a reasonable element design, which exhibits a good solar absorptance (α = 96.1%) and low thermal emittance (ϵ = 7.8%). Long‐term thermal stability investigation demonstrates that the entropy‐stabilized absorber could endure at 400 °C for 168 h. Under the irradiation of simulated sunlight, the surface temperature of the absorber can reach up to 105 °C, which is essential for middle‐ and low‐temperature applications. Overall, this work provides significant insights into the spectral selectivity of high‐entropy alloy nitrides and offers a new strategy for designing and developing moderate and low solar selective absorbing coatings via a high‐entropy strategy.

Efficient Warming Textile Enhanced by a High‐Entropy Spectrally Selective Nanofilm with High Solar Absorption

“…The optical properties of ZrNbMo‐Al‐N film can be tuned by changing the N 2 flow rate. According to the previous report, [ 31 ] a high N 2 flow rate leads to increased dielectric properties of the film. Accordingly, we devised an optical gradient triple‐layer SSF, comprising a high metal volume fraction (HMVF) ZrNbMo‐Al‐N layer as the main absorption layer, a low metal volume fraction (LMVF) ZrNbMo‐Al‐N layer that facilitates destructive interference, and a dielectric Si 3 N 4 as an antireflection layer.…”

“…High‐entropy nitride is a category of up‐and‐coming photothermal materials due to its unique and fascinating structural characteristics, and large compositional space. [ 30 , 31 , 32 ] It remains, however, a significant challenge to achieve desired spectral selectivity on rough and porous substrates.…”

Enabling Highly Enhanced Solar Thermoelectric Generator Efficiency by a CuCrMnCoAlN-Based Spectrally Selective Absorber

“…In this context, a spectrally selective absorber (SSA), which allows for high solar absorptance (α) in the solar spectrum (0.3–2.5 μm), but low thermal emittance (ε) in the infrared region (2.5–20 μm), is an ideal candidate for the increment of heat side temperature. − In contrast, nonselective solar absorbers have inferior solar energy harvesting ability because of their significant IR thermal loss . Under identical solar intensities, the SSA will capture a higher balance temperature compared to the nonselective counterpart, making it more suitable for the enhancement of STEG performance . For example, notwithstanding CuO nanoflakes reaching a prominent solar absorptance (97.5%), the temperature difference between heat and cold sides is only 5.3 °C .…”

“…14 Under identical solar intensities, the SSA will capture a higher balance temperature compared to the nonselective counterpart, making it more suitable for the enhancement of STEG performance. 15 For example, notwithstanding CuO nanoflakes reaching a prominent solar absorptance (97.5%), the temperature difference between heat and cold sides is only 5.3 °C. 16 As a comparison, the Bi 2 Te 3 /Cu-based SSA (α = 89%; ε = 5%) could boost the surface temperature from 93 to 317 °C under the same solar radiation flux in vacuum.…”

Uninterrupted Self‐Generation Thermoelectric Power Device Based on the Radiative Cooling Emitter and Solar Selective Absorber

“…He et al [25] adjusted the nitrogen content of the high-entropy ceramic AlCrWTaNbTiN to design and fabricate an ultrathin multilayer solar absorbing coating, which exhibits a high solar absorptance of 93% and a low emittance of 6.8% at 82 C. Under the irradiation of simulated sunlight, they obtained the surface temperature of 105 C by a TiVCrAlZr layer with gradient high-entropy nitride nanofilms. [26] Wu et al [27] proposed to replace the pure dielectric layer of the laminated interference coating with a cermet coating film to prepare a composite structure of W/W-SiO 2 /W/W-SiO 2 /Al 2 O 3 / SiO 2 . The performance of cermet-based SSA is stable, and the preparation of double-layer ceramic membranes is simpler than textured surface coatings [28,29] or laminated interference coatings, [30,31] and is suitable for mass production.…”