Preparation and electrocatalytic activity of Rh adlayers on Pt(1 0 0) electrodes: reduction of nitrous oxide

Rhodium adlayers (submonolayer range) have been prepared on Pt(1 0 0) electrodes by electrodeposition from acidic solutions containing an excess of chloride. These Rh/Pt(1 0 0) electrodes give a well-defined voltammetric signal in the hydrogen adsorption region, which gives evidence of a high level of order in the Rh adlayer and allow a reliable estimation of the coverage. The voltammetric behavior of the Rh/Pt(1 0 0) electrodes points to an epitaxial growth with formation of rhodium islands. The well-ordered bimetallic surfaces freshly prepared were tested as electrocatalysts for nitrous oxide reduction and the responses were compared with those of the bulk Pt(1 0 0) and Rh(1 0 0) electrodes. The voltammogram for the bimetallic surface showed well separated N2O reduction signals for Rh and Pt surface zones. An exceptionally high electrocatalytic activity for the Rh adlayer was found for low coverages. This behavior is explained on the basis of a high activity of the rhodium adatoms in the periphery of the islands.