Chemical vapor deposition synthesis of transition metal dichalcogenides for water electrolysis

Significant raise of carbon dioxide level in the atmosphere since the beginning of the industrial revolution has led to global warming and consequently rapid climate changes. In addition to that, rapid increase of the world polulation as well as the depletion of fossil fuels necessitate the transition to renewable energy sources. Hydrogen, an alternative to fossil fuels, is a clean energy carrier. Hydrogen can be produced by water electrolysis using renewable energy sources. Catalysts are employed to make the electrolysis process more efficient. Platinum is the best known catalyst for hydrogen evolution reaction. However, large scale use of platinum seems impossible due to its low abundancy and high cost. Recently, transition metal dichalcogenides has emerged as promising catalysts for hydrogen evolution reaction. Yet, their inactive basal plane and poor electrical conductivity hinder their catalytic performance. In this thesis, the effect of varying amount of Ni doping on the hydrogen evolution reaction performance of MoSe2 was investigated. Ni doped MoSe2 films were prepared by the thermal selenization of the sputter deposited Ni-Mo alloy films. Electrochemical measurements indicate that Ni doping enhances the catalytic activity of the MoSe2 by lowering the overpotential and Tafel slope. Furthermore, oxidation inhibitor role of hydrogen in the selenization reaction was studied by using nitrogen/hydrogen gas mixture as the carrier gas. Various physicochemical characterization results show that hydrogen decreases or completely prevents the oxide formation. This effect has been found to be more prominent at 800 oC selenization.