Broadband solar energy harvesting enabled by micro and nanostructured materials

In der kommenden Ära des "Carbon Peak und der Kohlenstoffneutralität" ist es besonders wichtig, neue Energietechnologien zu entwickeln, die kostengünstig, umweltfreundlich und im industriellem Maßstab herstellbar sind, um die herkömmlichen fossilen Brennstoffe zu ersetzen, die weithin als Verursacher des Treibhauseffekts und häufiger extremer Wetterlagen gelten. Solarenergie ist sozusagen eine unerschöpfliche Energieform, die jedem Land der Erde kostenlos zur Verfügung steht. Daher ist sie im Vergleich zu Kernenergie, Windenergie und blauer Energie die vielversprechendste Alternative zu fossiler Energie. In dieser Arbeit werden breitbandige Materialien zur Gewinnung von Solarenergie als Lichtabsorber für Anwendungen zur Umwandlung von Solarenergie, wie Stromerzeugung, Wasserdampferzeugung und Wasserstofferzeugung, vorgestellt. Zunächst wird schwarzes Silizium (b-Si) mit einer Vielzahl von Mikro-Nanostrukturen durch reaktives Ionenätzen (RIE) hergestellt. Die so hergestellten b-Si-Proben mit ultra-breitbandiger Lichtabsorption können für die photo-thermoelektrische (P-TE) Stromerzeugung, die photothermische (PT) Wasserverdampfung und die photoelektrochemische (PEC) Wasserreduktion verwendet werden, was die Leistung der Solarenergieumwandlung aufgrund ihrer hervorragenden Lichtabsorption im gesamten Sonnenspektrum verbessert. Darüber hinaus wurde eine metastabile Atomlagenabscheidung (MS-ALD) mit Selbstorganisation zur Herstellung großflächiger plasmonischer 3D-Ag@SiO2 Hybrid-Nanostrukturen entwickelt. Diese zeigen auch eine ultrabreitbandige sehr hohe Absorption im gesamten Sonnenspektrum. Wenn sie für die P-TE- und PT-Wasserverdampfung verwendet werden, verbessert sich die Leistung der Solarenergieumwandlung im Vergleich zu b-Si-Proben.In the current era of "Carbon Peak and Carbon Neutrality", it is particularly important to develop low-cost, environmentally-friendly, and industrial-scale energy technologies to replace the traditional fossil fuels, which are widely considered to cause the greenhouse effect and frequent extreme weathers. Solar energy is a kind of energy that lasts forever and is freely available for all countries all over the world. Therefore, it is the most promising alternative to fossil energy compared to nuclear energy, wind energy, and blue energy (Energy that comes from ocean, such as tidal energy, salinity gradient energy). In this work, broadband solar energy harvesting materials are produced and demonstrated to serve as light absorbers for solar energy conversion applications, such as electric power generation, water steam generation and hydrogen generation. Firstly, black silicon (b-Si) with micro-nanostructures is fabricated by reactive ion etching (RIE). The as-prepared b-Si samples with ultra-broadband light absorption can be used for photo-thermoelectric (P-TE) power generation, photothermal (PT) water evaporation and photoelectrochemical (PEC) water reduction, which enhances solar energy conversion performance due to their excellent broadband light absorption. In addition, a metastable atomic layer deposition (MS-ALD) self-assembly strategy for fabricating large area 3D Ag@SiO2 hybrid plasmonic nanostructures was developed. They also demonstrate an ultra-broadband super-high absorption over the whole solar spectrum. When they are further used for P-TE and PT water evaporation, the solar energy conversion performances are improved compared with b-Si samples

Synthesis of Dinitrogen‐Fused Spirocyclic Heterocycles via Organocatalytic 1,3‐dipolar Cycloaddition of 2‐Arylidene‐1,3‐indandiones and an Azomethine Imine

An efficient 1,3‐dipolar cycloaddition of 2‐arylidene‐1,3‐indandiones with an azomethine imine has been developed to furnish spiroindane‐1,3‐dione‐pyrazolidinones in generally good to high yields with excellent diastereoselectivity under mild conditions.On an upward spiro: An efficient cycloaddition between 2‐arylidene‐1,3‐indandiones and an azomethine imine has been developed for the construction of dinitrogen‐fused spirocyclic heterocycles.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137534/1/ajoc201500529.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137534/2/ajoc201500529-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137534/3/ajoc201500529_am.pd

A review on photothermal conversion of solar energy with nanomaterials and nanostructures: from fundamentals to applications

Solar energy is a green, sustainable, and de facto inexhaustible energy source for mankind. The conversion of solar energy into other forms of energy has attracted extensive research interest due to climate change and the energy crisis. Among all the solar energy conversion technologies, photothermal conversion of solar energy exhibits unique advantages when applied for water purification, desalination, high-temperature heterogeneous catalysis, anti-bacterial treatments, and deicing. In this review, the various photothermal conversion mechanisms based on different forms of heat release are summarized and some of the latest examples are presented. In addition, the necessary prerequisites for solar-driven photothermal materials toward their practical applications are also discussed. Further, the latest advances in photothermal conversion of solar energy are discussed, focusing on different types of photothermal applications. Finally, a summary is given and the challenges and opportunities in the photothermal conversion of solar energy are presented. This review aims to give a comprehensive understanding of emerging solar energy conversion technologies based on the photothermal effect, especially by using nanomaterials and nanostructures

Human Semantic Segmentation using Millimeter-Wave Radar Sparse Point Clouds

This paper presents a framework for semantic segmentation on sparse sequential point clouds of millimeter-wave radar. Compared with cameras and lidars, millimeter-wave radars have the advantage of not revealing privacy, having a strong anti-interference ability, and having long detection distance. The sparsity and capturing temporal-topological features of mmWave data is still a problem. However, the issue of capturing the temporal-topological coupling features under the human semantic segmentation task prevents previous advanced segmentation methods (e.g PointNet, PointCNN, Point Transformer) from being well utilized in practical scenarios. To address the challenge caused by the sparsity and temporal-topological feature of the data, we (i) introduce graph structure and topological features to the point cloud, (ii) propose a semantic segmentation framework including a global feature-extracting module and a sequential feature-extracting module. In addition, we design an efficient and more fitting loss function for a better training process and segmentation results based on graph clustering. Experimentally, we deploy representative semantic segmentation algorithms (Transformer, GCNN, etc.) on a custom dataset. Experimental results indicate that our model achieves mean accuracy on the custom dataset by $\mathbf{82.31}\%$ and outperforms the state-of-the-art algorithms. Moreover, to validate the model's robustness, we deploy our model on the well-known S3DIS dataset. On the S3DIS dataset, our model achieves mean accuracy by $\mathbf{92.6}\%$, outperforming baseline algorithms

Tuning the electronic properties of monolayer and bilayer PtSe\u3csub\u3e2\u3c/sub\u3e \u3ci\u3evia\u3c/i\u3e strain engineering

The recently synthesized monolayer PtSe2 belongs to the class of two-dimensional transition metal dichalcogenide (TMDC) materials (Nano Lett., 2015, 15, 4013). Based on first-principles calculations, we show that the band gaps of monolayer and bilayer PtSe2 can be tuned over a wide range via strain engineering. Both isotropic and uniaxial strains are investigated. For bilayer PtSe2, the vertical out-of-plane strain is also considered. In most cases, the strain can reduce the band gap except for the bilayer PtSe2 under the isotropic strain (Ɛ≤ 4%) for which the band gap can be slightly enlarged. Importantly, the monolayer can be transformed from the indirectgap to the direct-gap semiconductor at the compressive strain of Ɛy = -8%. Moreover, the bilayer can undergo the semiconductorto- metal (S–M) transition at a critical vertical strain due to the chemical interaction (p orbital coupling) between the Se atoms of the two opposite layers. Overall, the ability to modulate the band gap of monolayer and bilayer PtSe2 over an appreciable range of strains opens up new opportunities for their applications in nanoelectronic devices

Tuning the electronic properties of monolayer and bilayer PtSe\u3csub\u3e2\u3c/sub\u3e \u3ci\u3evia\u3c/i\u3e strain engineering

The recently synthesized monolayer PtSe2 belongs to the class of two-dimensional transition metal dichalcogenide (TMDC) materials (Nano Lett., 2015, 15, 4013). Based on first-principles calculations, we show that the band gaps of monolayer and bilayer PtSe2 can be tuned over a wide range via strain engineering. Both isotropic and uniaxial strains are investigated. For bilayer PtSe2, the vertical out-of-plane strain is also considered. In most cases, the strain can reduce the band gap except for the bilayer PtSe2 under the isotropic strain (Ɛ≤ 4%) for which the band gap can be slightly enlarged. Importantly, the monolayer can be transformed from the indirectgap to the direct-gap semiconductor at the compressive strain of Ɛy = -8%. Moreover, the bilayer can undergo the semiconductorto- metal (S–M) transition at a critical vertical strain due to the chemical interaction (p orbital coupling) between the Se atoms of the two opposite layers. Overall, the ability to modulate the band gap of monolayer and bilayer PtSe2 over an appreciable range of strains opens up new opportunities for their applications in nanoelectronic devices

A novel hybrid propulsion system configuration and power distribution strategy for light electric aircraft

Similar to the electrification of the automotive industry, the growing concerns with the shortage of fossil fuels has also called for a paradigm shift in aviation industry. To promote the aviation electrification process, it is necessary to develop an efficient energy storage system and a stable power transmission system to improve the reliability and extend the endurance of electric aircraft. This paper designs a novel propulsion system topology and power distribution algorithm for light manned electric aircraft. Firstly, a novel aircraft hybrid propulsion system topology is designed, in which the battery energy storage system can work synergistically with the fuel cell to provide power to the aircraft electric engine. Then, an adaptive energy management framework is developed to distribute the aircraft power requirement between energy storage devices. Meanwhile, an aircraft power balance state recognizer is designed to enhance the dynamic performance of the aircraft and adjust the working state of the propulsion system. The proposed hybrid propulsion system configuration and power distribution algorithm are verified under a prototype two-seater electric aircraft: Alpha Electro. Numerical analysis results indicate that the developed methods can dynamically meet the power requirement of aircraft under fast-charging and peak power requirement scenarios. With the developed hybrid propulsion system, most of the fuel cell high-power working points are moved to the medium and low area, which indicates that the fuel cell is effectively protected. Furthermore, the quantified hydrogen consumption can be reduced by 7.63% comparing to fuel cell electric aircraft.</p