Electrocatalysis of the Hydrogen Oxidation Reaction on a Platinum-Decorated Nanoporous Gold Surface Studied by Scanning Electrochemical Microscopy

The electrocatalytic activity of a platinum decorated nanoporous gold (Pt-NPG) surface was examined toward the Hydrogen Oxidation Reaction (HOR) using the feedback mode of Scanning Electrochemical Microscopy (SECM). In this system, the proton (H+) reduction and H2 oxidation reactions take place at the tip and the conductive substrate, respectively. Since the H2 oxidation process is highly surface sensitive, the positive feedback current is only observed when the substrate has an excellent electrocatalytic activity to oxidize H2 back to H+. A Pt microelectrode was used as an SECM tip and bare Pt, bare Au, NPG (Nanoporous gold), and Pt-NPG as substrate materials. Positive feedback currents from approach curves were observed for bare Pt and Pt-NPG surfaces, whereas hindered diffusion was noticed for Au and NPG surfaces. The obtained results confirm that the NPG surface is inactive for H2 oxidation, but it becomes active after decoration with a small amount of Pt.