Application of Pulsed Laser Deposition in Reactive Gaseous Media to Fabricate an Effective Hybrid MoSx/WOy Catalyst for the Reaction of Hydrogen Evolution

Abstract

To fabricate an electrocatalyst containing nanostructured layers of WOy and MoS_x, a sequential formation of tungsten oxide and molybdenum sulfide thin films is performed by means of the pulsed laser deposition of W and Mo in low-pressure air and hydrogen sulfide media, respectively. The reactive medium pressure and the substrate (glassy carbon) temperature are varied during and after the deposition. WOy thin films of various morphologies and structures determining certain differences in their catalytic properties in the reaction of hydrogen evolution in acidic solutions are obtained. However, the catalytic efficiency of the obtained WO_y nanoelements (spheres, needles, and sheets) with amorphous and crystalline structures appears to be insufficient. Additional deposition of MoS_x with an amorphous structure results in a significant improvement of the catalytic properties. Sulfur atoms in the MoSx amorphous matrix cause the formation of catalytically active sites, while the developed surface of the WO_y stimulates an increase in the catalyst total active area. Penetration of hydrogen effectively formed on MoS_x into the bulk of thin films of WO_y provides a crucial electrocatalysis condition—low current resistance in the support layer with a large exposed surface area.