The Art of Decoration: Rhodium-Modified Platinum Films with Preferential (100) Orientation as Electrocatalysts for Nitrate Reduction and Dimethyl Ether Oxidation

Nanostructured platinum films with a preferential (100) orientation were decorated with a rhodium adlayer through potentiodynamic electrodeposition. The Rh surface coverage was controlled by varying the number of electrodeposition cycles, and the growth of the Rh layer was followed by means of the distinct hydrogen adsorption/desorption peaks pertaining to Rh. The bimetallic electrodes were tested for their catalytic activity toward a set of electrochemical reactions of the carbon and nitrogen cycles (nitrate reduction, CO oxidation, and DME oxidation) in H2SO4. At the same time, these reactions provided further insight into the surface structure of the Rh deposits: thus, it was found that Rh deposition occurs mostly at (100) sites, creating ordered Rh islands. It was shown that DME oxidation at Pt(100) can be further promoted by minimum Rh coverages, at which the highly active (100) terraces remain mostly free. On the other hand, the activity toward nitrate reduction can be enhanced by increasing amounts of Rh. Finally, we succeeded in directing Rh deposition through the partial stripping of adsorbed CO, using this molecule as a site-blocking adlayer protecting wide (100) terraces, thus achieving the maximum enhancement for DME oxidation.