Photoelectrochemical water splitting represents an attractive technological solution to harvest and then store the solar energy which is abundant but intermittent. It can be achieved by employing a photoelectrochemical cell, also called an artificial leaf. In order to construct viable photoeclectrochemical cells, efforts are being dedicated to engineer robust and efficient photocathodes for solar H 2 generation and photoanodes for solar water oxidation reaction. In this article, we discuss on the recent achievements and current perspectives in engineering of viable hybrid photocathodes. The state of the art on the design of a hybrid photocathode, its performance as well as the current understanding of its mechanistic operation will be first described. We then discuss on the technical strategies that are currently being developed to enhance the robustness and performance of a hybrid photocathode.

Abstract:Orchidaceae is one of the most valuable plant groups all over the world, and is also an impressively large and complex family of flowering plants. Effective molecular tools used for the identification of orchid species should be developed to support traditional morphological approaches. This study reviews most of the DNA fragments that have been used as taxon identifiers in researches conducted on Orchidaceae in order to assess potential molecular markers and metric measurements for the identification of orchid species.

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Transition metal spinel oxides have recently been suggested for the creation of efficient photovoltaic cells or photocatalysts. These compounds can be easily tuned by doping to adapt their electronic or magnetic properties. However, their cation distribution is very complex and band structures are still a subject of controversy. We propose a complete density functional theory investigation of MnCoO compounds, using different approximations in order to explain the variation of these properties as a function of composition (for 0 ≤ x ≤ 3) and determine the electronic structure over the whole solid solution range. A detailed study of their atomic structure, magnetic properties and electronic structure is given and compared with experimental data. The unit cell volume calculated for each composition is in agreement with the volume obtained experimentally in ceramics, while a cubic-to-tetragonal structural transition is predicted at x = 2.0. An antiferromagnetic to ferrimagnetic behavior is observed at the lowest ordering temperature depending on the composition. The band gap, deduced from our band structure calculations, strongly decreases upon doping of the end members CoO and MnO, but is partly restored by the tetragonal distortion. A direct band gap, close to 0.5-0.8 eV, is calculated for 0.25 ≤ x ≤ 2.25, justified by inter-metal transitions from Mn ions on octahedral sites.