ABSTRACT (17th)

Artificial photosynthesis is a promising method for producing renewable energy with sunlight. Artificial photosynthesis employing the modified Z-sheme of natural photosynthesis can be exploited both for the oxidation and reduction of water. Oxidation of water is successively achieved by the use of cobalt and manganese oxides with the cations in the 3+ state with one eg electron [1,2]. Hydrogen can be produced by the dye-sensitized photochemical process[3] or by the use of semiconductor heterostructures [4]. In this presentation, ways of splitting water will be presented, followed by recent results obtained on the photochemical generation of hydrogen by different strategies specially those involving semiconductor heterostructures of the type ZnO/Pt/CdS [4] or nanosheets of chalcogenides[3,5] such as MoS2 and MoSe2. Other novel strategies for hydrogen generation such as the solar-thermal route based on oxides[6] will also be examined.

[1] PNAS 110: 11704 (2013)

[2] Chem. Phys. Lett. 591: 277 (2014)

[3] Angew. Chem. Int. Ed. 52: 13057 (2013)

[4] Energy Environ. Sci. 6: 3589 (2013)

[5] Appl. Phys. Lett. (Materials) 2: 092802 (2014)

[6] Phys. Chem. Chem. Phys. 17: 122 (2015)

ABSTRACT (18th)

The discovery of the amazing properties of graphene has stimulated exploration of single- and few-layer structures of layered inorganic materials. Of all the inorganic 2D nanosheet structures, those of MoS2 have attracted great attention because of their novel properties such as the presence of a direct bandgap, good field-effect transistor characteristics, large spin–orbit splitting, intense photoluminescence, catalytic properties, magnetism, superconductivity, ferroelectricity and several other properties with potential applications in electronics, optoelectronics, energy devices and spintronics. MoS2 nanosheets have been used in lithium batteries, supercapacitors and to generate hydrogen. Highlights of the impressive properties of MoS2 nanosheets, along with their structural and spectroscopic features will be discussed in this presentation. MoS2 typifies the family of metal dichalcogenides such as MoSe2 and WS2 and there is much to be done on nanosheets of these materials. Linus Pauling would have been pleased to see how molybdenite whose structure he studied in 1923 has become so important today. Besides MoS2 and related chalcogenides, nanosheets of BN, metal oxides and metal-organic frameworks will be mentioned as well as the novel properties of layered WTe2.

** Chem. Phys. Lett. 609:172 (2014);

ACS Appl. Mater. Interfaces 7:7809 (2015)