Tuning the catalytic activity of heterogeneous two-dimensional transition metal dichalcogenides for hydrogen evolution

Using first principles DFT calculations and AIMD simulations, we establish a database for catalytic properties of two-dimensional metal-dichalcogenides (2D-TMDs) toward the hydrogen evolution reaction (HER). In addition to conventionally known active sites of edges, we propose that terrace sites can be substantially activated for the HER even without incorporating defects or heteroatom doping. The key idea is to design a heterogeneous 2D-TMD with a bilayer of catalyst/support configuration. We identify the best candidates, NbS₂/HfSe₂, NbS₂/ZrSe₂, and TaS₂/HfSe₂, via high-throughput computational screening of 256 different heterogeneous 2D-TMDs. The expected HER activity is estimated to be comparable to or even better than that of the conventional Pt/C catalyst. It is shown that the Gibbs free energy of hydrogen adsorption can be tuned to an optimal value of 0 eV using heterogeneous 2D-TMD materials. Careful analysis of the first principles database for 2D-TMDs leads to capturing a universal descriptor for the HER activity of 2D-TMDs regardless of hydrogen coverage and active sites: the adhesion energy difference of the catalyst/support TMDs before and after the hydrogen adsorption. The descriptor is linearly correlated with hydrogen adsorption energy. Our design principle for highly functional 2D-TMD catalysts for the HER is, thus, to identify a heterogeneous 2D-TMD of an optimum hydrogen adsorption energy based on adhesion energy difference, which can be accurately and quickly performed via the analysis of the first principles database and validation through experimental measurements.