(345b) Support Interactions in MoS2 for Hydrogen Evolution

Increased global energy consumption and the threat of climate change have led to major efforts in alternative energy research. One key class of catalysts for these environmental applications is MoS₂, which is being studied as a catalyst for hydrogen evolution (HER) in the production of hydrogen fuels. Since the best catalyst for this reaction is currently Platinum (Pt), a costly precious metal, a cheaper and abundant catalyst such as MoS₂ shows great promise. Insight into the nature of its reactivity can lead to the design and discovery of even better catalysts for alternative energy applications.

Though van der Waals (vdW) interactions are usually assumed to be insignificant in DFT calculations, they cannot be completely ignored for MoS₂. First of all, MoS₂ is a layered catalyst where each layer is held together by weak vdW interactions. Furthermore, it is known that the interaction between certain catalysts and their supports affects their reactivity and morphology. Since vdW interactions are important in the adsorption of the MoS₂ catalyst onto the support, they must be taken into account to accurately predict catalytic behavior.

In this work, we employ the newly developed Bayesian error estimation van der Waals functional (BEEF-vdW) to describe the vdW interactions between MoS₂ catalyst layers and their interactions with various catalyst supports. We find that the hydrogen binding energy is weaker when the support interactions are stronger. This explains the lower than expected exchange current densities of support MoS₂ in electrochemical H₂ evolution. More generally, a deeper understanding of the support effects can lead to new strategies for tuning the catalytic activity.