
Electrochemical and structural stability of MoS2-based nanomaterials
Beyond catalytical activity, the electrochemical and structural stability is the crucial property that determines the applicability of promising electrocatalysts such as MoS2-based nanomaterials. In our group, we correlate electron microscopy imaging with operando electrochemical techniques to understand and prevent the mechanisms of degradation of MoS2-based electrocatalysts for the hydrogen evolution reaction.
MoS2-based nanomaterials are promising candidates to substitute expensive noble metals as catalyst for the production of green hydrogen through the hydrogen evolution reaction (HER) in acidic media. Despite numerous reports on their activity, the structural and electrochemical stability of MoS2-based nanomaterials has not been thoroughly studied.
In this project, the stability of hydrothermally grown MoS2-based electrocatalysts is investigated by decoupling the effects of the first electrolyte contact, open circuit potential and active HER, all realistic conditions occurring during the lifetime of an electrolyzer. The distinct mechanisms degrading the MoS2 in each stage are elucidated by combining high-end electron microscopy techniques in identical locations to operando electrochemical testing in the scanning flow cell coupled to an inductively coupled plasma mass spectrometer (SFC-ICPMS).
This methodology allows to define the potential stability boundaries for bare MoS2 and how they can be rationally extended by doping with elements such as Re (RexMo1-xS2). As a result, we demonstrate how RexMo1-xS2 do not only possess state-of-the-art activity but also broadened stability regimes for the HER in acid. Future studies will pursue the stability understanding and potential applicability of such materials for direct sea water splitting.
![Figure 1: RexMo1-xS2 nanosheets imaged in a scanning electron microscopy image (Left) and in high angle annular dark field mode at a scanning transmission electron microscope (middle). Note that the Re atoms are visible as shiny dots within the lattice. (Right) Example of operando SFC-ICPMS dataset analyzing the Mo dissolution at different HER potentials. All images are modified from ref. [1].](/5047996/original-1738252404.jpg?t=eyJ3aWR0aCI6MjQ2LCJvYmpfaWQiOjUwNDc5OTZ9--5895f0a3e85bd2df3bd350b0b99b7ae899ca1a96)