Growth of Pt by surface limited redox replacement of underpotentially deposited hydrogen

A surface limited redox replacement (SLRR) protocol for the growth of Pt thin films using adsorbed H or also called underpotentially deposited H (H-UPD) is developed in this work. In contrast to the previously reported studies on SLRR deposition, this work presents the first application of the SLRR protocol in a single-cell configuration using a nonmetal UPD system. Utilizing H-UPD to mediate Pt growth is of significance for green Pt deposition that minimizes the use of environmentally hazardous chemicals by precluding possible mediator metal incorporation reported in standard Pt SLRR protocols. Open circuit chronopotentiometry and quartz-crystal microbalance experiments demonstrate steady displacement kinetics and a yield that is equal to the expected stoichiometric Pt(II)-H exchange ratio (1:2). Cyclic voltammetry characterization of Pt films shows that the growth via SLRR of H-UPD results in increase of the surface roughness with the number of replacement steps. The morphology of as-deposited films has been analyzed by Scanning Tunneling Microscopy. Moreover, the roughness of SLRR deposited Pt films has been compared with films grown in the same solution at two different overpotentials: without adsorbed H (bulk deposition) and with H-UPD floating on the surface i.e. H-surfactant mediated growth (SMG). The results show clear advantages of using the SLRR approach which generates films with nearly two times lower roughness than the ones grown by bulk deposition and SMG. The generality of the proposed approach is validated by growth of Pt films on two types of Pd surfaces: Pd ultrathin films on Au (Pd/Au) and Pd nanocubes. The Pt overlayers grown by 30 replacements on Pd structures have been characterized by H-UPD and their catalytic activity examined by formic acid oxidation reaction. (C) 2013 Elsevier Ltd. All rights reserved.