Reasonable Design of MXene-Supported Dual-Atom Catalysts with High Catalytic Activity for Hydrogen Evolution and Oxygen Evolution Reaction: A First-Principles Investigation.

MXene-supported single-atom catalysts (SACs) for water splitting has attracted extensive attention. However, the easy aggregation of individual metal atoms used as catalytic active centers usually leads to the relatively low loading of synthetic SACs, which limits the development and application of SACs. Herein, by performing first-principles calculations for Pt and 3d transition metal single atoms immobilized on a two-dimensional (2D) Mo 2 TiC 2 O 2 MXene surface, we systematically studied the performance of heterogeneous dual-atom catalysts (h-DACs) in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Significantly, h-DACs exhibit higher metal atom loading and more flexible active sites compared to SACs. Benefiting from these features, we found that Pt/Cu@Mo 2 TiC 2 O 2 heterogeneous DACs exhibits excellent HER activity with ultra-low overpotential |ΔG H ∗ | (0.04 eV), lower than the corresponding Pt@Mo 2 TiC 2 O 2 (0.14 eV) and Cu@Mo 2 TiC 2 O 2 (0.33 eV) SACs, and even lower than that of Pt (0.09 eV). Meanwhile, Pt/Ni@Mo 2 TiC 2 O 2 exhibits superior OER activity with ultra-low overpotential η OER (0.38 V), lower than that of Pt@Mo 2 TiC 2 O 2 (1.11 V) and Ni@Mo 2 TiC 2 O 2 (0.57 V) SACs, and even lower than that of RuO 2 (0.42 V) and IrO 2 (0.56 V). Our finding paves the way for the rational design of h-DACs for HER and OER with excellent activity, which provides guidance for other catalytic reactions.