Iodide as Terminating Agent for Platinum Electrodeposition

“Approximate” Pt layers hold great promise to be highly active and durable oxygen reduction reaction (ORR) catalysts. Electrodeposition of such layers on relevant catalyst supports, for example TiO x , requires the application of a “Pt-on-Pt” deposition limiter to keep layers thin and leave no atom behind for catalysis. Classic Pt-on-Pt deposition limiting agents like CO and over-potential deposited hydrogen (H opd ) work reliably on gold but fail on TiO x substrates. Iodide, in contrast, is a new “Pt-on-Pt” deposition limiting agent that shows substantial Pt layer thickness reduction during electrodeposition on gold as well as TiO x substrates. Graphical Abstract Limitations are not always a bad thing: The addition of NaI during Pt electrodeposition from Ar-saturated 0.1 mM K 2 PtCl 4 + 0.1 M HClO 4 solution limits the Pt deposition amount and leads to a substantial reduction in Pt layer thickness and a concurrent increase in ORR mass activity.