Orbital Orientation-based Theoretical Design of Single-Atom Catalysts for the Hydrogen Evolution Reaction

Hydrogen evolution reaction (HER) is regarded as one of the most effective routes to produce H₂, but it usually suffers from the lack of the novel design concept of high-efficiency catalysts, especially in neutral condition. Herein, we report an orbital orientation-based theoretical principle for designing efficient single-atom HER catalysts. Through screening 14 catalysts consisting of the transition-metal single atoms doped into TiO₂ (TM₁@TiO₂) nanosheets, we demonstrate that the d orbital orientation of TM₁–Ti₁ atomic pairs plays a key role in the regulation of catalytic activities. Among them, Pd₁@TiO₂ is screened out as an excellent HER catalyst in neutral media, where the Pd-dx2−y2 orbital tends to be exposed due to the existence of Pd₁–Ti₁ atomic pair and thus promotes OH desorption and the overall hydrogen production. This work provides a new insight through tailoring high-performance orbital catalysts and sheds an orbital-level understanding of the HER mechanism.