Nanoparticle Shape Effect Study as an Efficient Tool to Reveal the Structure Sensitivity of Olefinic Alcohol Hydrogenation

Monodisperse Pd nanocubes of 20 nm rib length and Pd nanospheres of 3.0 nm diameter were synthesized in the presence of cetyltrimethylammonium bromide and used to investigate the structure sensitivity of three-phase 2-methyl-3-buten-2-ol hydrogenation. Turnover frequencies per all surface atoms were found as 2.58 s(-1) for the cubes and 3.86 s(-1) for the spheres at 313 K, indicating that (100) atoms of the cubes comprising similar to 98% of all surface atoms have lower activity than other surface atoms of the spheres, composed of atoms on (111), (100) terraces, edges, and vertices. Apparent activation energies of 23 kJ/mol for the cubes and 17 kJ/mol for the spheres in the verified kinetic regime confirmed the reaction structure sensitivity. Assuming that only (100) and (III) atoms are active on the sphere surface, a hypothetical most active Pd nanostructure was predicted as a tetrahedron allowing twice higher activity per Pd loading as compared to a spherical particle.