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) Mo₂TiC₂O₂ 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@Mo₂TiC₂O₂ heterogeneous DACs exhibits excellent HER activity with ultra-low overpotential |ΔG_H^∗| (0.04 eV), lower than the corresponding Pt@Mo₂TiC₂O₂ (0.14 eV) and Cu@Mo₂TiC₂O₂ (0.33 eV) SACs, and even lower than that of Pt (0.09 eV). Meanwhile, Pt/Ni@Mo₂TiC₂O₂ exhibits superior OER activity with ultra-low overpotential η^OER (0.38 V), lower than that of Pt@Mo₂TiC₂O₂ (1.11 V) and Ni@Mo₂TiC₂O₂ (0.57 V) SACs, and even lower than that of RuO₂ (0.42 V) and IrO₂ (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.