Concave Rhombic Dodecahedral Au Nanocatalyst with Multiple High-Index Facets for CO₂ Reduction

A concave rhombic dodecahedron (RD) gold nanoparticle was synthesized by adding 4-aminothiophenol (4-ATP) during growth from seeds. This shape is enclosed by stabilized facets of various high-indexes, such as (331), (221), and (553). Because it is driven thermodynamically and stabilized by 4-ATP ligands, the concave RD maintains its structure over a few months, even after rigorous electrochemical reactions. We discussed the mechanism of the shape evolution controlled by 4-ATP and found that both the binding energy of Au-S and the aromatic geometry of 4-ATP are major determinants of Au atom deposition during growth. As a possible application, we demonstrated that the concave RD exhibits superior electrocatalytic performance for the selective conversion of CO2 to CO in aqueous solution.