Light-Driven De/Rehydrogenation of a LiH Surface under Ambient Conditions.

Lithium hydride (LiH), a saline hydride with a hydrogen density of 12.6 wt %, is highly thermostable, which hinders its extensive application in hydrogen storage. In this study, we demonstrate a distinct photodecomposition of LiH under ambient conditions. Ultraviolet-visible (UV-vis) illumination induces hydrogen release and creates surface hydrogen vacancies on LiH. The subsequent H- migration enables hydrogen desorption and the accumulation of vacancies at the subsurface, resulting in the generation of metallic Li clusters. Rehydrogenation, on the contrary, can be charged under UV-vis illumination in 1 bar H2. Such phenomena show that the thermodynamic and kinetic limits in the re/dehydrogenation of LiH can be broken under illumination, which allows hydrogen storage over the LiH surface at temperatures ∼600 K lower than those of the corresponding thermal process. This work provides new insights into the interaction of semiconducting hydrides and photons and opens an avenue for the development and optimization of materials for hydrogen storage and related photodriven reactions.

Light-driven ammonia synthesis under mild conditions using lithium hydride.

Photon-driven chemical processes are usually mediated by oxides, nitrides and sulfides whose photo-conversion efficiency is limited by charge carrier recombination. Here we show that lithium hydride undergoes photolysis upon ultraviolet illumination to yield long-lived photon-generated electrons residing in hydrogen vacancies, known as F centres. We demonstrate that photon-driven dehydrogenation and dark rehydrogenation over lithium hydride can be fulfilled reversibly at room temperature, which is about 600 K lower than the corresponding thermal process. As light-driven F centre generation could provide an alternative approach to charge carrier separation to favour chemical transformations that are kinetically or thermodynamically challenging, we show that light-activated lithium hydride cleaves the N≡N triple bond to form a N-H bond under mild conditions. Co-feeding a N2/H2 mixture with low H2 partial pressure leads to photocatalytic ammonia formation at near ambient conditions. This work provides insights into the development of advanced materials and processes for light harvesting and conversion.

[Removal of algae using local soils and sediments].

Removal of algal blooms using modified local soils and sediments was studied. It was found that the local soils and sediments modified by chitosan removed algae effectively. The component of local soils and sediments, the organic matter in local soils and sediments had no effect on algae removal. Organic matter content (TOC < or = 40 mg/L) in water had a little negative effect on removal of algal cells. Field experimental results suggested that chitosan-modified local soils could be highly effective and quick for emergency needs to clear up harmful cyanobacterial blooms in fresh waters. In enclosures in Meiliang Bay of Taihu Lake, a loading of 0.025 g/L or 53 g/m2 chitosan-modified local soils removed 98.6% chlorophyll-a while secchi depth increased from 15 cm to 90 cm.