Cu_2-xS-MoS₂ Nano-Octahedra at the Atomic Scale: Using a Template to Activate the Basal Plane of MoS₂ for Hydrogen Production

Designing and realizing functional nanostructures with specific properties is a demanding challenge. It often requires, beyond the knowledge of the atomic arrangement, assembling a puzzle in order to decipher both the growth mechanism and to explain the measured macroscopic properties. Here, we use the hybrid system of Cu_2-x­S-MoS₂ to present one case study where the structural features, growth mechanism, optical properties and catalytic performance, are all woven into one complete picture. We show a facile synthesis of Cu_2-x­S-MoS₂ hybrids, where Cu_2-x­S serves as a template for a MoS₂ layer. The MoS₂ phase is altered and modified, structurally and electronically, as a result of the contact with Cu_2-xS, according to both experimental HRTEM data and DFT calculations. The electronic reconstruction around the interface activates the outermost S atoms within MoS₂ by tuning of the hydrogen adsorption free energy to a more moderate value, thereby promoting the hydrogen evolution reaction (HER). This concept provides a new design strategy to optimize functional MoS₂ by pairing a 2D layer with a suitable substrate.