The optimal ∆G H * value has traditionally been taken as 0 eV but more recent studies have shown that the optimal binding energy is slightly endothermic, ∼ 0.1-0.2 eV, at zero overpotential. The hydrogen adsorption free energies at different sites on the top and edge sides of the LDH heterostructures are depicted in Figures and show that the top and Fe sites bind hydrogen weakly and are expected to be catalytically inactive towards HER, while the other sites have near optimal hydrogen binding. In particular, the MoS 2 @Ni 6 Fe 2 Co 1 -Mo(doped) heterostructure catalyst has a near optimal hydrogen binding energy of 0.32 eV on the Co sites. Contrasting these computational results with the electro-catalytic activity tests in Figure -c shows that the hydrogen binding energies can be used as a reliable descriptor for the HER activity: the incorporation of Mo and MoS 2 -QDs in the Fe/Ni/Co LDHs leads to near optimal hydrogen energies, which correlate veery well with the experimentally observed lower overpotentials, smaller Tafel slopes, and smaller charge transfer resistances on the MoS 2 @NiFeCo-Mo(doped)-LDH. The computational results show that both Mo and MoS 2 -QDs significantly enhance the HER activity of the Fe/Ni/Co-catalysts.