Designing spin-selective ZnO-based single-atom catalysts through surface reconstruction engineering

The catalytic performance of single-atom catalysts (SACs) and magnetic single-atom catalysts (MSACs) is strongly influenced by the atomic-scale environment provided by the substrate. Reconstructed polar ZnO(0001) surfaces, stabilized by intrinsic defects, offer distinct chemical and electronic landscapes for anchoring transition metal (TM) atoms. Using spin-polarized density functional theory, we examine Pd, Pt, Rh, and Ru adsorption, incorporation, and substitution into the (2 × 2)-V Zn and (1 × 3)-V O reconstructions. The results reveal a marked contrast between the two surfaces: the (2 × 2)-V Zn reconstruction induces magnetism only in the most stable configuration, when the TM atom replaces a Zn atom, leaving the original Zn vacancy unoccupied, and exhibits positive electrostatic potentials at the TM sites, conditions favorable for spin-selective catalytic activity. In contrast, the (1 × 3)-V O reconstructions only induce magnetism when the Ru atom occupies a Zn site, with all TMs showing nearly neutral electrostatic potentials, suggesting limited catalytic enhancement, but still a possible active site. These findings demonstrate that the interaction between surface reconstruction and TM substitution can selectively tune both spin polarization and local charge environment, providing a pathway for designing ZnO-based SAC and MSAC systems for the oxygen reduction reaction (ORR).