Bottom-up precise synthesis of stable platinum dimers on graphene

Supported metal clusters containing only a few atoms are of great interest. Progress has been made in synthesis of metal single-atom catalysts. However, precise synthesis of metal dimers on high-surface area support remains a grand challenge. Here, we show that Pt₂ dimers can be fabricated with a bottom-up approach on graphene using atomic layer deposition, through proper nucleation sites creation, Pt₁ single-atom deposition and attaching a secondary Pt atom selectively on the preliminary one. Scanning transmission electron microscopy, x-ray absorption spectroscopy, and theoretical calculations suggest that the Pt₂ dimers are likely in the oxidized form of Pt₂O_x. In hydrolytic dehydrogenation of ammonia borane, Pt₂ dimers exhibit a high specific rate of 2800 mol_H2 mol_Pt^-1 min^-1 at room temperature, ~17- and 45-fold higher than graphene supported Pt single atoms and nanoparticles, respectively. These findings open an avenue to bottom-up fabrication of supported atomically precise ultrafine metal clusters for practical applications.