Synthesis of Ultrathin and Continuous Layers of Nanoporous Au on Glassy Carbon Substrates

Abstract

Thin continuous films of platinized nanoporous Au (Pt-NPG) catalyst have been synthesized by all-electrochemical routines including successive AgxAu (1-x) deposition and de-alloying. However, when deposited on inexpensive substrates like glassy carbon (GC), the alloy precursor grows in isolated clusters. This constitutes a challenge addressed in the present work by using a Pd seeding process to promote continuity in NPG films on GC. The approach relies on electroless seeding of an ultra high density Pd cluster network that facilitates the coalescence at very low thickness of the deposited alloy precursor. The seeding has been performed in both naturally aerated and de-oxygenated PdCl2 solutions on Sn 2+ sensitized GC electrodes. Also, the alloy deposition process has been studied in the presence and absence of O 2 and with different supporting electrolytes. The O 2 content of both seeding and deposition solutions has been identified as a key factor in controlling the densification of the NPG-based catalyst. Electrochemical and SEM characterizations have been used to assess the outcome of the densification process. The alloy compositional homogeneity has been examined by de-alloying polarization curves. The surface area evolution has been studied by Pb UPD. Optimum conditions for achieving continuity of the deposit have been elucidated and further discussed. © 2014 The Electrochemical Society.