Synergetic effects of strain engineering and substrate defects on generating highly efficient single-atom catalysts for CO oxidation

Developing highly efficient single-atom catalysts (SACs) containing isolated metal atom monomers dispersed on appropriate substrates has surged to the forefront of heterogeneous catalysis in recent years, driven by both specificity of unique active sites and cost-effectiveness of the approach. Nevertheless, the instability of SACs, i.e., preferential sintering during chemical reactions, dramatically hinders their development and applications. Here, by means of first-principles calculations, taking electronically closed-shell Au2 and open-shell Pd2 (PdAu) on WTe2 as prototypical examples, we investigate the strengthening effect of electronic metal–substrate interactions (EMSI) via a synergetic effect of strain engineering and substrate defects to prevent clustering in the initial stage of SACs. It is noted that on the perfect WTe2 (P-WTe2), both Au and Pd adatoms prefer dimerization to separation. However, when a defect exists on the same WTe2 substrate (D-WTe2), the situation changes considerably. Under tension, relative to the electronically closed-shell Au2 dimer, an electronically open-shell Au monomer at the Te vacancy site (VTe) obtains more charge from the WTe2 substrate, leading to stronger EMSI. However, when an electronically open-shell PdAu (Pd2) dimer is located on the compressively strained D-WTe2, more charge can be transferred to both of the atoms with decreased distances, and therefore the increased Coulomb repulsive interactions separate them to be stable SACs with tunable catalysis for CO oxidation. The present findings demonstrate the importance of substrate engineering in stabilizing SACs and offer a valid approach in fabricating SAC systems.