Two-dimensional semiconductor transition metal based chalcogenide based heterostructures for water splitting applications.

Recent research and development is focused in an intensive manner to increase the efficiency of solar energy conversion into electrical energy via photovoltaics and photo-electrochemical reactions. Electrocatalytic and photocatalytic water splitting into hydrogen and oxygen is a promising and emerging technology. Heterogeneous nanostructures based on semiconductor materials have attracted much attention to be used as catalysts, co-catalysts, photocatalysts and photoabsorbers. Development of transition metal dichalcogenide (TMDC) semiconductors with two dimensional (2D) layered structures and peculiar physical and chemical properties are playing a pivotal role in the heterogeneous photocatalytic hydrogen evolution (PHE) reaction. The energy band gap tuning with the thickness of the layers and heterojunction interface formation have given an opportunity to design and develop combinations of both photocatalysts and co-catalysts using semiconductor TMDCs. This contribution summarizes the recent investigations on the 2D semiconductor TMDC (MoS2, WS2, MoSe2 and WSe2) based heterogeneous nanostructures as efficient materials for photocatalytic water splitting applications to produce hydrogen. The literature survey clearly shows that more than 80% of the researchers in this field have worked on MoS2-based heterogeneous nanocomposites, as it is the 2nd most studied material after graphene. It is also evident that among the materials used so far for the PC HER activity, MoS2-based heterogeneous nanocomposites are on top with the highest hydrogen evolution rate and stability. Since the physical and chemical properties of the members are identical, the future research and development would focus on the manipulation of the rest of the TMDC members to achieve the future needs of clean and sustainable energy production.