Hydrogen Evolution Reaction over Single-Atom Catalysts Based on Metal Adatoms at Defected Graphene and h-BN

In small transition and noble metal particles, commonly used as active parts of heterogeneous industrial catalysts, only a tiny fraction of metal atoms at their surfaces are utilized in relevant chemical reactions. In an effort to use precious metal atoms much more efficiently, the idea of single-atom catalysts (SACs) emerged, where every metal atom would take place in a catalytic process. Applying density functional theory, we carried out a computational search for efficient SACs based on transition metal atoms embedded into monovacancies of graphene and hexagonal boron-nitride (h-BN), where the point defects were used to stabilize metal adatoms and prevent their aggregation into bigger clusters. The efficiency of the catalysts was examined by studying their ability to adsorb H atoms and recombine them into H2 in a thermodynamically neutral manner. The critical steps in the process of the hydrogen evolution reaction (HER) were modeled over nine different metal adatoms embedded into three point defects of graphene and the h-BN, revealing several SACs with nearly flat potential energy landscape for HER, comparable to or even more favorable than the ones found at Pt surfaces.