Photocatalytic water splitting (PWS) has attracted widespread attention as a sustainable method for converting solar to green hydrogen energy. So far PWS research has mainly focused on the development of artificial photocatalytic hydrogen production systems for pure water. It is more practically attractive to create systems for seawater, i.e., to reduce the cost of hydrogen production and make better use of naturally occurring water resources. Herein, brookite, anatase, and rutile TiO₂ nanoparticles are investigated as photocatalysts to explore the feasibility of such thought and have shown attractive hydrogen production performance under full solar spectrum without any sacrificial agent. It is worth noting that, brookite TiO₂, has more suitable band gap position and excellent photoelectric properties compared with anatase and rutile TiO₂, and has higher efficiency and stability in the process of hydrogen production. The photocatalytic hydrogen production rate of brookite TiO₂ can reach up to 1,476 μmol/g/h, the highest value reported for TiO₂-based systems and most other photocatalysts in seawater splitting under full spectrum. As the Cl⁻ ions in seawater go through a cycle of oxidation and reduction, no Cl₂ is detected in the solar hydrogen production from seawater.

Microwave absorbing materials have received considerable interest over the years for their applications in stealth, communications, and information processing technologies. These materials often require functionalization at the nanoscale so to achieve desirable dielectric and magnetic properties which induce interaction with incident electromagnetic radiation. This article presents a comprehensive review on the recent research progress of nanomaterials for microwave absorption, including the basic mechanism of microwave absorption (e.g., dielectric loss, magnetic loss, dielectric/magnetic loss coupling), measurement principle (e.g., fundamentals of analysis, performance evaluation, common interaction pathways: Debye relaxation, Eddy current loss, natural resonance, size and shape factors), and the advances and performance review in microwave absorption (e.g., absorption bandwidth, reflection loss values, absorption peak position) using various nanomaterials, such as carbon nanotubes, carbon fibers, graphenes, oxides, sulfides, phosphides, carbides, polymers and metal organic frameworks. Overall, this article not only provides an introduction on the fundamentals of microwave absorption research, but also presents a timely update on the research progress of the microwave absorption performance of various nanomaterials.

Interactions between incident electromagnetic energy and matter are of critical importance for numerous civil and military applications such as photocatalysis, solar cells, optics, radar detection, communications, information processing and transport et al. Traditional mechanisms for such interactions in the microwave frequency mainly rely on dipole rotations and magnetic domain resonance. In this study, we present the first report of the microwave absorption of Al/H₂ treated TiO₂ nanoparticles, where the Al/H₂ treatment not only induces structural and optical property changes, but also largely improves the microwave absorption performance of TiO₂ nanoparticles. Moreover, the frequency of the microwave absorption can be finely controlled with the treatment temperature, and the absorption efficiency can reach optimal values with a careful temperature tuning. A large reflection loss of −58.02 dB has been demonstrated with 3.1 mm TiO₂ coating when the treating temperature is 700 °C. The high efficiency of microwave absorption is most likely linked to the disordering-induced property changes in the materials. Along with the increased microwave absorption properties are largely increased visible-light and IR absorptions, and enhanced electrical conductivity and reduced skin-depth, which is likely related to the interfacial defects within the TiO₂ nanoparticles caused by the Al/H₂ treatment.