Electrochemical synthesis of tetrahexahedral rhodium nanocrystals with extraordinarily high surface energy and high electrocatalytic activity.

Noble metal nanocrystals (NCs) enclosed with high-index facets hold a high catalytic activity thanks to the high density of low-coordinated step atoms that they exposed on their surface. Shape-control synthesis of the metal NCs with high-index facets presents a big challenge owing to the high surface energy of the NCs, and the shape control for metal Rh is even more difficult because of its extraordinarily high surface energy in comparison with Pt, Pd, and Au. The successful synthesis is presented of tetrahexahedral Rh NCs (THH Rh NCs) enclosed by {830} high-index facets through the dynamic oxygen adsorption/desorption mediated by square-wave potential. The results demonstrate that the THH Rh NCs exhibit greatly enhanced catalytic activity over commercial Rh black catalyst for the electrooxidation of ethanol and CO.