Atom-level design strategy for hydrogen evolution reaction of transition metal dichalcogenides catalysts

Two-dimensional transition metal dichalcogenides are among the most promising materials for water-splitting catalysts. While a variety of methods have been applied to promote the hydrogen evolution reaction on the transition metal dichalcogenides, doping of transition metal heteroatoms have attracted much attention since it provides effective ways to optimize the hydrogen adsorption and H2 generation reactions. Herein, we provide in-depth and systematic analyses on the trends of the free energy of hydrogen adsorption ({\Delta}GH*), the most well-known descriptor for evaluating hydrogen evolution reaction performance, in the doped transition metal dichalcogenides. Using the total 150 doped transition metal dichalcogenides, we carried out the atom-level analysis on the origin of {\Delta}GH* changes upon the transition metal heteroatom doping, and suggest two key factors that govern the hydrogen adsorption process on the doped transition metal dichalcogenides: 1) the changes in the charge of chalcogen atoms where hydrogen atoms adsorbed for the early transition metal doped structures, and 2) the structural deformation energies accompanying in introduced dopants for the late transition metal doped structures. Based on our findings, we interpret from a new perspective how vacancies in the TM-doped TMDs can provide optimal {\Delta}GH* in HER. We suggest electrostatic control for early TM doped systems and structural control for late TM doped systems as the effective strategies for the thermoneutral {\Delta}GH* in TMD.