Solar Absorption Properties Research Articles

Performance enhancement of a modified solar still with inverted pyramid aluminum basin geometry: Experimental optimization, thermal, and economic assessment

Desalination is a promising solution to address the global challenges of water scarcity and energy demand, aided by industrialization and population growth. This study explores the potential to enhance solar still performance by redesigning the basin into an inverted pyramid shape constructed of aluminium. Aluminium’s superior thermal conductivity and solar radiation absorption properties aim to increase the effective surface area and optimize thermal storage, thereby improving evaporation and condensation processes. Comparative theoretical and experimental investigations between a modified solar still (MSS) and a conventional solar still (CSS) under varying saline water quantities revealed a significant increase in daily water production and thermal efficiency for the MSS. The MSS achieved a 46.67 % higher output (4.40 kg/m2/day at 30 liters) and a 14 % increase in thermal efficiency compared to the CSS (29 %). In terms of exergy efficiency, the calculated daily exergy efficiency for CSS and MSS was 2.0 % and 3.12 %, respectively. The energy payback time of the CSS and MSS was 17.18 and 7.2 years, respectively, and they reduced CO2 emissions by 13.668 tons and 20.05 tons per year. Moreover, the MSS demonstrated a 45.45 % reduction in the cost of freshwater production. Exergo-economic and exergo-environmental analyses further validate the MSS's potential as an efficient and sustainable solution for solar desalination, offering a significant advancement in addressing water scarcity and promoting environmental sustainability.

Biomimetic Ag-modified core-shell nanofibrous membrane with enhanced solar absorption and water replenishment for efficient clean water production and antibacterial activity

Microorganism contamination of evaporators can deteriorate their performance during solar-driven water evaporation. Herein, we developed a biomimetic core-shell nanofibrous membrane with enhanced solar absorption, water replenishment, and antimicrobial properties via modification of silver nanoparticles (Ag-NPs). By mimicking the core-shell structure of natural pine needles, (1) the core of polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) nanofiber, like the xylem of pine needles, can act as a support skeleton for dimensional stability; and (2) the shell of Ag-NPs-modified copper oxide (CuO) crystals (Ag@CuO), like the mesophyll of pine needles (photosynthesis for pine growth), can perform the photothermal and antimicrobial properties. The Ag@CuO nanofibrous membrane achieved increased solar absorption from 92.44 % to 95.88 % and decreased water contact angle from 36.1° to 0° after the incorporation of Ag-NPs. Furthermore, the Ag@CuO nanofibrous membrane exhibited stable evaporation rates of 1.31 kg⋅m−2⋅h−1 for 3.5 wt% saline water and 1.27 kg⋅m−2⋅h−1 for actual dye wastewater. Moreover, the nanofibrous membrane possessed excellent flexibility and robust adhesion of Ag-NPs due to the strong interfacial bonding induced by polydopamine. In addition, inhibition rates above 99.97 % against Staphylococcus aureus and Escherichia coli demonstrated the outstanding antimicrobial properties of the Ag@CuO membrane. In conclusion, the high evaporation performance, excellent flexibility, and outstanding antimicrobial properties enable the Ag@CuO nanofibrous membrane to be a good option for sustainable clean water production by treating evaporation media containing microorganisms.

Synergistic polyimide&ZrO2 flexible films enable low solar absorption and excellent wave-transparency

Carbon fiber epoxy resin (CFRP), as space satellite antenna materials with great application prospects to transmit and receive signals. It is necessary to ensure its normal operation through surface thermal control, which can be achieved by covering with a flexible film. Polyimide (PI) films modified by ceramics particle have been widely studied in the field of flexible devices. However, there is no research on multifunctional PI films with thermal control and wave transmission multifunctional performance. In this study, ZrO2 modified flexible PI films (PI/ZrO2 films) which can be covered on the surface of satellite antenna was prepared, and its solar absorption and wave transmission properties were studied. Prepared films exhibited excellent heat resistance and mechanical properties, and the addition of ZrO2 increased their thermal stability. The solar absorption of films with 50% ZrO2 is the lowest for 0.30, and the highest reflectance can reach to 88.4%. In addition, the maximum dielectric constant of the films was less than 2.5, and the dielectric loss was less than 0.03, showing an excellent wave transmission performance. The films can be covered on the satellite antenna, and also can be used for other space environment or wave transmission requirements.

Improvement on solar selective absorption properties of anodic aluminum oxide photonic crystal films by electrodeposition of silver

Solar selective absorption films based on anodic aluminum oxide (AAO) photonic crystals were prepared by an anodization under periodic current-pulses, subsequently with an alternating current electrodeposition of Co and Ag in sequence. The phase structure, microstructure, and solar selective absorption properties of the Co–Ag electrodeposited film were investigated in comparison with a Co electrodeposited counterpart. Moreover, the stability of the properties against thermal annealing was examined for the two films. A one-dimensional photonic crystal structure was verified for the AAO part in both films, with the first-order photonic bandgap occurring at around 4 μm, while the metals were confirmed to be deposited at the bottom of the AAO part in the form of nanoparticles. For the Co–Ag electrodeposited film, the Ag nanoparticles were deposited over those of Co. The Ag electrodeposition not only was contributive to the solar selective absorption properties, but also substantially improved the stability of the properties against thermal annealing. The Co–Ag electrodeposited film exhibited an infrared emissivity of 0.12, a solar absorptivity of 0.94, and a spectral selectivity of 7.83 before experiencing thermal annealing, while retained a decent spectral selectivity of 6.00 after being annealed in air at 300 °C for 24 h.

Heteropoly Blue/Carbon Nanotubes Nanocomposites as High-Performance Photothermal Conversion Materials.

To realize the direct and full use of the widely distributed solar energy, developing novel materials with superb photothermal conversion capability is essential. Although heteropoly blue has intrinsic outstanding solar absorption and photothermal conversion properties, its spectral absorption in the infrared region is weak. Here, composites of heteropoly blue and carbon nanotubes (HPB/CNTs) are synthesized depending on electrostatic interactions by facile microwave sonication and freeze-drying. The doped CNTs can dramatically improve the spectral absorption performance of HPB ontology in the infrared region. As a result, the light absorption of the optimized HPB/CNTs (20 %) reaches more than 95 % in the range of 200-2400 nm, showing promising prospects as high-performance photothermal conversion material in the applications of solar desalination and wastewater treatment.

Enhanced solar absorption and photoelectrochemical properties of Al-reduced TiO2/TiO2−x/CdS heterojunction nanorods

TiO2/TiO2−x/CdS heterojunction nanorods with high PEC performance were successfully prepared by combining hydrothermal synthesis, Al-reduction and CBD techniques.

New class of high-entropy pseudobrookite titanate with excellent thermal stability, low thermal expansion coefficient, and low thermal conductivity

As a type of titanate, the pseudobrookite (MTi2O5/M2TiO5) exhibits a low thermal expansion coefficient and thermal conductivity, as well as excellent dielectric and solar spectrum absorption properties. However, the pseudobrookite is unstable and prone to decomposing below 1200 °C, which limits the practical application of the pseudobrookite. In this paper, the high-entropy pseudobrookite ceramic is synthesized for the first time. The pure high-entropy (Mg,Co,Ni,Zn)Ti2O5 with the pseudobrookite structure and the biphasic high-entropy ceramic composed of the high-entropy pseudobrookite (Cr,Mn,Fe,Al,Ga)2TiO5 and the high-entropy spinel (Cr,Mn,Fe,Al,Ga,Ti)3O4 are successfully prepared by the in-situ solid-phase reaction method. The comparison between the theoretical crystal structure of the pseudobrookite and the aberration-corrected scanning transmission electron microscopy (AC-STEM) images of high-entropy (Mg,Co,Ni,Zn)Ti2O5 shows that the metal ions (M and Ti ions) are disorderly distributed at the A site and the B site in high-entropy (Mg,Co,Ni,Zn)Ti2O5, leading to an unprecedentedly high configurational entropy of high-entropy (Mg,Co,Ni,Zn)Ti2O5. The bulk high-entropy (Mg,Co,Ni,Zn)Ti2O5 ceramics exhibit a low thermal expansion coefficient of 6.35×10−6 K−1 in the temperature range of 25–1400 °C and thermal conductivity of 1.840 W·m−1·K−1 at room temperature, as well as the excellent thermal stability at 200, 600, and 1400 °C. Owing to these outstanding properties, high-entropy (Mg,Co,Ni,Zn)Ti2O5 is expected to be the promising candidate for high-temperature thermal insulation. This work has further extended the family of different crystal structures of high-entropy ceramics reported to date.

Waste Biomass Selective and Sustainable Photooxidation to High-Added-Value Products: A Review

Researchers worldwide seek to develop convenient, green, and ecological production processes to synthesize chemical products with high added value. In this sense, lignocellulosic biomass photocatalysis is an excellent process for obtaining various outcomes for the industry. One issue of biomass transformation via heterogeneous catalysis into valuable chemicals is the selection of an adequate catalyst that ensures high conversion and selectivity at low costs. Titanium oxide (TiO2), is widely used for several applications, including photocatalytic biomass degradation, depolymerization, and transformation. Graphite carbon nitride (g-C3N4) is a metal-free polymeric semiconductor with high oxidation and temperature resistance and there is a recent interest in developing this catalyst. Both catalysts are amenable to industrial production, relatively easy to dope, and suited for solar light absorption. Recent investigations also show the advantages of using heterojunctions, for biomass derivates production, due to their better solar spectrum absorption properties and, thus, higher efficiency, conversion, and selectivity over a broader spectrum. This work summarizes recent studies that maximize selectivity and conversion of biomass using photocatalysts based on TiO2 and g-C3N4 as supports, as well as the advantages of using metals, heterojunctions, and macromolecules in converting cellulose and lignin. The results presented show that heterogeneous photocatalysis is an interesting technology for obtaining several chemicals of industrial use, especially when using TiO2 and g-C3N4 doped with metals, heterojunctions, and macromolecules because these modified catalysts permit higher conversion and selectivity, milder reaction conditions, and reduced cost due to solar light utilization. In order to apply these technologies, it is essential to adopt government policies that promote the use of photocatalysts in the industry, in addition to encouraging active collaboration between photooxidation research groups and companies that process lignocellulosic biomass.

Investigation of Zr-doped CaMnO<sub>3</sub> perovskite solid solution forhigh-temperature solar thermochemical energy storage

<p indent="0mm">CaMnO₃ perovskite oxide, composed of earth-abundant and cost-effective elements, could store and release heat by the redox reactions over a wide range of temperatures and partial pressures of oxygen (<italic>p</italic>(O₂)). CaMnO₃ perovskite oxide has been regarded as a promising candidate for thermochemical heat storage in concentrated solar power plants. However, CaMnO₃ perovskite oxide is partially decomposed during the high-temperature reduction process, resulting in the incomplete reoxidation of the material, which severely limits its thermochemical energy storage performance. Herein, Zr-doped CaMnO₃ has been proposed as a novel thermochemical energy storage material. Moreover, its phase structure, redox capability, energy storage performance, and solar spectral absorption properties have been thoroughly investigated through experimental and theoretical calculations. The results demonstrated that the CaZr_0.1Mn_0.9O₃ perovskite solid solution could achieve a fully reversible redox cycle while effectively inhibiting decomposition during reduction. However, with the further increase in the Zr doping ratio, the produced side phases would significantly reduce the redox performance of the material. The thermochemical energy storage density of CaZr_0.1Mn_0.9O₃ could reach 390.6±32.8 kJ/kg at 1000°C and <italic>p</italic>(O₂)=10⁻⁵ atm, and the effective doping of Zr could enhance the spectral absorption of CaMnO₃ in the near-infrared region. According to the calculation of density functional theory, the effective doping of Zr could enhance the B–O chemical bond strength of ABO₃ oxides, thus strengthening the structural stability and improving the thermochemical energy storage density. This study provides guidance for the development of perovskites for thermochemical energy storage.

Lowered infrared emittance and enhanced thermal stability of solar selective absorption properties of anodic aluminum oxide photonic crystal coatings

Solar selective absorption coatings based on anodic aluminum oxides (AAO) were prepared via an anodization technique and a subsequent alternating current electrodeposition of Cu-Ni nanoparticles at the bottom. The phase structure, microstructure and solar selective absorption properties of the AAO coatings were investigated with respect to their preparation conditions. Moreover, the dependence of the solar selective absorption properties on thermal annealing history was examined. One-dimensional AAO photonic crystal coatings were produced by anodization under period pulse voltages. The spectral positions of photonic bandgaps were estimated for the AAO photonic crystal coatings. The first-order photonic bandgap was verified to be located in the infrared region. The construction of the photonic crystal structure appreciably lowered the infrared emittance and as a result improved the overall properties of the AAO photonic crystal coatings. A small amount of CuAl2O4 was formed in the electrodeposition layer of AAO photonic crystal coatings by controlling the amplitude of applied electrodeposition voltage at 14 V. The formation of the CuAl2O4 minimized the oxidization of the Cu-Ni nanoparticles at elevated temperatures and thereby enhanced the thermal stability of the solar selective absorption properties. The AAO photonic crystal coating prepared under the electrodeposition voltage showed a solar absorptance of 0.90, an infrared emittance of 0.11 and a spectral selectivity of 8.12 at room temperature, while retaining a spectral selectivity of 6.47 after being annealed at 300 °C for 24 h.

Analysis of Pomegranate Dye Coated Titanium Nanotubes Anode for Solar Cell Application

The titanium nanotube array is termed as titanium nanotubes anode (TNTA). Initially, four samples of TNTA were synthesized using electrochemical anodization method. The titanium nanotube arrays (TNAs) were fixed as anode for dye-sensitized solar cell application. The execution of dye-sensitized solar cells (DSSCs) is found on natural dyes removed out from natural materials. Then, pomegranate dye was exclusively prepared and coated on TNTA samples. These are very affordable and inexpensive and are abundantly available in India. The dye coated TNTAs were distinguished using UV-viewable spectrophotometer and SEM test for their spectral effects. The natural dye showed a wide-ranging absorption performance peak between 300 and 574 nm for the second sample and 300–572 nm for third sample. Their solar absorption property was studied.

Ultralight electrospun fiber foam with tunable lamellar macropores for efficient interfacial evaporation

Solar-driven interfacial evaporation is regarded as one of the most promising technologies to address the critical issue of global water scarcity. However, a great deal of energy is lost via conduction during the interfacial evaporation process. Herein, a self-floating Janus evaporator containing micron-sized isolated bubbles that can enhance heat localization is designed. The evaporator is synthesized by gas foaming polyacrylonitrile (PAN) nanofibers and subsequently depositing polypyrrole (PPy). The hydrophilic PAN nanofiber layer on the bottom of the evaporator with abundant macropores can continuously pump water upward through the capillary force. The hydrophobic PAN@PPy composite nanofiber layer on the top possesses a broadband solar absorption property, converting solar irradiation to heat efficiently. The low thermal conductivity of the isolated micron-sized bubbles enhances the thermal insulation of the obtained PAN foam@PPy Janus evaporator, while the stretching and expanding of the nanofibers induced by the bubbles contribute to its increased mechanical stability. This work offers a simple route to fabricate evaporators that can continuously produce drinking water from brine under sunlight, and provides a fresh idea to enhance the thermal insulation and mechanical properties of the conventional electrospinning-based fiber scaffold.

Graphitic carbon nitride based immobilized and non-immobilized floating photocatalysts for environmental remediation

In solar photocatalysis, light utilization and recycling of powder from reaction solution are the main obstructions that hinder the photocatalytic efficacy of any photocatalyst. In this respect, a floatable system is effective for efficient solar photocatalysis by light utilization. Due to the maximum solar light absorption property, floating nanocomposite photocatalyst is an appealing substitute for effective wastewater treatment. Floating photocatalysts are a non-oxygenated and non-stirred solution that is a good light harvester, stable, non-toxic, biodegradable, naturally abundant in nature. They also have low density, a simple preparation process, no need to stir, and high porosity. Due to these characteristics, floating photocatalysts are widely favored and ideal candidates for practical environmental remediation. Several researchers have come up with new and innovative ways for immobilizing capable photocatalyst on a floatable substrate to produce floating nanocomposite photocatalytic material. In recent decades, g–C3N4–based floating photocatalysts have gained a lot of attention as g-C3N4 is a visible light active photocatalyst with unique and exceptional properties. It also has good photocatalytic activity in waste water treatment and environmental remediation. Many previous reports have studied the logical design and manufacturing method for heterojunction floating photocatalysts and immobilized floating photocatalysts. Based on those studies, we have focused on the g-C3N4 based immobilized and non-immobilized floating photocatalysts for pollutant degradation. We have also categorized immobilized floating photocatalyst based on several lightweight substrates such as expanded perlite and glass microbead. In addition, future challenges have been discussed to maximize solar light absorption and to improve the efficiency of broadband response floating photocatalysts. Floating photocatalysis is an advanced technique in energy conversion and environmental remediation thus requires special consideration.

A Review on the Bioinspired Photocatalysts and Photocatalytic Systems

AbstractAfter long‐term evolution, organisms in nature have achieved optimal structure, organization, and function to adapt to the environment. Some ingenious biological structures have highly efficient solar light absorption, matter transmission, and natural photocatalytic properties, such as leaves, sunflowers, seaweeds, algae, bacteria. Artificial photocatalysis, which involves CO2 reduction and water splitting to obtain green renewable energy or oxygen, is of great significance for solving the problem of energy shortages, achieving carbon neutrality, and building a sustainable society. In order to improve the efficiency of artificial photocatalysis, it is necessary to develop highly efficient photocatalysts by expanding ideas and drawing innovative inspiration from nature. Artificially constructed photocatalysts with bionic structures achieved by simulating natural organisms have gradually become an exciting research field with great potential in recent years. This article reviews bioinspired photocatalysts and photocatalytic systems from the aspects of principle, composition, construction method, and the achieved performance. It is expected that this review will help researchers develop a systematic and in‐depth understanding for the biomimetic design of photocatalysts and photocatalytic systems.

Assessment of Solid Wastes and By‐Products as Solid Particle Materials for Concentrated Solar Power Plants

The revalorization of solid wastes and by‐products to be applied as solid particles in concentrated solar power (CSP) leads to cost savings and progresses toward more sustainable technology. Herein, the physicochemical, morphological, thermal, and solar absorption properties are evaluated for electric arc furnace dust, black slag from the steel industry, and Gossan waste from the Rio Tinto mining industry. The principal objectives of this work are (i) to carry out a thermal aging at 900 °C at different times, (ii) to assess the solid's stability throughout the evaluation of physicochemical, morphological, thermal, and optical properties of the material as received, after 300 and 500 h of thermal aging, and (iii) to determine the most appropriate candidate as a thermal energy storage medium and heat transfer fluid for the CSP concept with solid particles. The results show that electric arc furnace black slag is the most suitable candidate from the three solids studied, as it is the one that optimizes the combination of absorptance, thermal conductivity, and chemical stability after thermal aging.

Effect of Tin Oxide/Black Paint Coating on Absorber Plate Temperature for Improved Solar Still Production: A Controlled Indoor and Outdoor Investigation

The ever-increasing water stress and availability of fresh drinking water are becoming a major challenge in rural and urban communities. The current high-end and large-scale technologies are becoming way more expensive and not friendly to the environment. In this regard, solar still is becoming a prominent and promising future technology due to its environment-friendly nature, less maintenance and operational costs, and simple design. The technological challenge regarding solar still is its low distillate yield. In this study, an attempt has been made to investigate the effect of tin oxide (SnO2) on the absorption surface of solar still towards improvement in sunlight absorption, which would lead to high distillate production rates. Various concentrations of SnO2, i.e., 0.5wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%, 10 wt%, 15 wt%, and 20 wt%, have been mixed in black and applied on the absorber plate to further optimize the suitable concentration. The experiments have been performed in both indoor (simulated) and outdoor conditions. An increase in surface temperature of absorber plate has been observed with increasing concentration of SnO2 under both the indoor and outdoor conditions, which is due to high solar spectrum absorption properties of SnO2 in the ultraviolet (UV) and near to far-infrared (IR) regions. The highest surface temperature of 101.61°C has been observed for specimens containing 15 wt% SnO2 in black paint under indoor conditions at 1000W/m2 irradiation levels, which is 53.67% higher compared to bare aluminum plate and 16.91% higher compared to only black paint coated aluminum plate. On the other hand, the maximum temperature of 74.96°C has been recorded for the identical specimens containing 15 wt% SnO2 under uncontrolled outdoor conditions. The recorded temperature is 47.96% higher than the bare aluminum plate and 14.88% higher than the black paint-coated aluminum plate. The difference of maximum temperatures under indoor and outdoor conditions is due to uncontrolled outdoor conditions and convective losses.

Efficiency Enhancement of GaAs Nano Solar Cell Based on 2D Photonic Crystal Trapping Layer and 2D Index Modulation Layer

In this paper, a nano solar cell structure based on a two-dimensional photonic crystal (2D-PhC) antireflection coating (ARC) trapping layer and a 2D- graded-index (2D-GI) GaAs active layer is presented. These components improve the solar absorption, in-coupling efficiency, quantum efficiency, and optical properties of the active layer. The proposed cell absorption and conversion efficiency were analyzed as a function of the cell layer thickness in comparison with the Lambertian absorption and cell efficiency limits. Additionally, each layer thickness was optimized to enhance the overall solar efficiency. All simulations were conducted in the 300 to 1100 nm range using finite difference time domain (FDTD) analysis, where the 2D-PhC structure was represented by indium tin oxide (ITO) nanorods in an air background. In addition, p-Al(0.85)GaAs/n-Al(0.35)GaAs two-window confinement layers are utilized in contact with the 907-nm GaAs active layer as a perfect match with the 1840-nm ITO-ARC layer to improve the confinement efficiency. Moreover, p-Al(0.85)GaAs/GaAs and GaAs/n-Al(0.35)GaAs 2D-GI active layer structures are used for index modulation to enhance the active layer properties and increase the cell short-circuit current. The main objective of this study is to determine the optimum design of a solar cell that can provide the highest power conversion efficiency using inexpensive semiconductor materials. One of the expected results from this research is the design of a 100- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}^{2}$ </tex-math></inline-formula> nano solar cell with 39.2% conversion efficiency, a short circuit current density of 44.38 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and an open-circuit voltage of 1 V.

Bioinspired design of electrospun nanofiber based aerogel for efficient and cost-effective solar vapor generation

Electrospun nanofiber based aerogels are attracting great attention for solar vapor generation due to their unique three-dimensional (3D) porous structure, light weight, enhanced solar absorption and thermal insulation property. However, the commonly used sophisticated and expensive preparation process, as well as the relatively low solar vapor generation performance, have limited their wide applications. Herein, luffa-inspired electrospun polyacrylonitrile/carbon nanotubes (PAN/CNTs) nanofiber based aerogels with hierarchical pore structure were designed and fabricated in an eco-friendly crosslinking and simple freeze-drying method. The nanofiber based aerogel combined the synergistic photothermal effect of polydopamine (PDA) and CNTs, resulting in a high light absorption of 94.8%. Furthermore, the 3D interconnected structure formed by the electrospun nanofibers greatly reduced the enthalpy of vaporization. The composite aerogel achieved fast evaporation rate of 2.13 kg m-2 h−1 and high solar-vapor conversion efficiency of 94.5% under one sun, superior to most of the reported electrospun nanofiber based solar vapor generators. This scalable, eco-friendly and cost-effective aerogel provides a straightforward approach for producing clean water efficiently.

Strained MoSi2N4 Monolayers with Excellent Solar Energy Absorption and Carrier Transport Properties

The recently synthesized two-dimensional (2D) MoSi2N4 material with a proper band gap and excellent environmental stability promises potential optoelectronic applications. On the basis of first-principles calculations and electron–phonon interaction theory, we systematically analyze the structural, optical, carrier distribution and transport, and photocatalytic water-splitting properties of pristine and strained MoSi2N4 monolayers. They are all found to be dynamically stable. Their optical absorption efficiencies are very high for photon energy larger than the respective band gap. Surprisingly, the optical absorption coefficient of tensile MoSi2N4 is as large as 106 cm–1 across 300–880 nm. To the best of our knowledge, this is the best among optoelectronic materials in the visible region. In addition, compressive strain results in spatial separation of photogenerated electrons and holes, which is beneficial for increasing their separation rates. Transport properties indicate that the lifetime and mean free path (MFP) of photogenerated electrons and holes are, respectively, on the scale of several femtoseconds and within 1.5 nm. Tensile strain notably increases them, becoming comparable to conventional semiconductor Si. Finally, pristine and strained MoSi2N4 monolayers are predicated to be able to photooxidize and photoreduce H2O with proper band edges and H2O adsorption capacities. These systematic characterizations not only deepen understanding of the physical and optoelectronic properties of MoSi2N4 but also indicate promising applications of MoSi2N4 in electronics, optoelectronics, and photocatalytic water splitting.

Thermochemical heat storage performances of fluidized black CaCO3 pellets under direct concentrated solar irradiation

Conventional solar thermochemical heat storage based on indirect surface-heating usually suffers from high heat losses and low solar-chemical efficiency. Here, a different solar thermochemical heat storage system based on direct solar illumination on fluidized black CaCO3 pellets is proposed. A Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model considering irradiation ray tracing, granular flow, heat and mass transfer, and chemical reaction, is built. Black CaCO3 pellets are fabricated via a facile template mixing method, and the solar absorptance is enhanced to 63.9% from 27.9% of traditional pure CaCO3. Effects of gas velocity and irradiative flux on thermochemical heat storage performance in a fluidized volumetric bed are investigated by incorporating measured kinetic and solar absorptance properties of designed black CaCO3 pellets. The peak solar-chemical efficiency reaches a value higher than 43% benefiting from enhanced solar absorptance, higher gas velocity and irradiative flux. This work guides the design of the high-efficiency direct solar thermochemical heat storage system.