Screening of Heterogeneous Photocatalysts for Water Splitting

In this contribution, a simple method for the screening of photocatalytic activity of catalyst materials is presented. The method is based on two steps the immobilization of the photocatalyst and the subsequent testing of their photocatalytic activity, using the gas evolution at the solid liquid interface. Up to four catalysts can be tested under the same conditions. The observed gas evolution for selected photocatalysts is consistent with trends reported in the literature from conventional photocatalytic reactor

Protonated Imine Linked Covalent Organic Frameworks for Photocatalytic Hydrogen Evolution

Covalent organic frameworks COFs have emerged as an important class of organic semiconductors and photocatalysts for the hydrogen evolution reaction HER from water. To optimize their photocatalytic activity, typically the organic moieties constituting the frameworks are considered and the most suitable combinations of them are searched for. However, the effect of the covalent linkage between these moieties on the photocatalytic performance has rarely been studied. Herein, we demonstrate that donor acceptor D A type imine linked COFs can produce hydrogen with a rate as high as 20.7 mmol g 1 h 1 under visible light irradiation, upon protonation of their imine linkages. A significant red shift in light absorbance, largely improved charge separation efficiency, and an increase in hydrophilicity triggered by protonation of the Schiff base moieties in the imine linked COFs, are responsible for the improved photocatalytic performanc

Constitutional isomerism of the linkages in donor acceptor covalent organic frameworks and its impact on photocatalysis

When new covalent organic frameworks COFs are designed, the main efforts are typically focused on selecting specific building blocks with certain geometries and properties to control the structure and function of the final COFs. The nature of the linkage imine, boroxine, vinyl, etc. between these building blocks naturally also defines their properties. However, besides the linkage type, the orientation, i.e., the constitutional isomerism of these linkages, has rarely been considered so far as an essential aspect. In this work, three pairs of constitutionally isomeric imine linked donor acceptor D A COFs are synthesized, which are different in the orientation of the imine bonds D C N A DCNA and D N C A DNCA . The constitutional isomers show substantial differences in their photophysical properties and consequently in their photocatalytic performance. Indeed, all DCNA COFs show enhanced photocatalytic H2 evolution performance than the corresponding DNCA COFs. Besides the imine COFs shown here, it can be concluded that the proposed concept of constitutional isomerism of linkages in COFs is quite universal and should be considered when designing and tuning the properties of COF

Case Report - Epidermolytic hyperkeratosis with rickets

A 6-year-old child presented with generalized hyperkeratosis, most marked over the flexures; windswept deformity of the legs; and limping since 3 years. On the basis of the clinical, histopathologic and biochemical findings, he was diagnosed as a case of epidermolytic hyperkeratosis with rickets. He was treated with parenteral vitamin D3 and calcium supplements orally. Nutritional rickets has been reported in children with various types of ichthyosis like lamellar and X-linked types. We report this case of epidermolytic hyperkeratosis with rickets for its rarity

Influence of MoS2 on activity and stability of carbon nitride in photocatalytic hydrogen production

MoS2/C3N4 (MS-CN) composite photocatalysts have been synthesized by three different methods, i.e., in situ-photodeposition, sonochemical, and thermal decomposition. The crystal structure, optical properties, chemical composition, microstructure, and electron transfer properties were investigated by X-ray diffraction, UV-vis diffuse reflectance spectroyscopy, X-ray photoelectron spectroscopy, electron microscopy, photoluminescence, and in situ electron paramagnetic resonance spectroscopy. During photodeposition, the 2H MoS2 phase was formed upon reduction of [MoS4]2− by photogenerated conduction band electrons and then deposited on the surface of CN. A thin crystalline layer of 2H MoS2 formed an intimate interfacial contact with CN that favors charge separation and enhances the photocatalytic activity. The 2H MS-CN phase showed the highest photocatalytic H2 evolution rate (2342 µmol h−1 g−1, 25 mg catalyst/reaction) under UV-vis light irradiation in the presence of lactic acid as sacrificial reagent and Pt as cocatalyst