Self-terminating electrodeposition of ultrathin Pt films on Ni: An active, low-cost electrode for H2 production

Self-terminating electrodeposition was developed for depositing ultrathin Pt overlayers on segmented electrodeposited Ni films supported on Au. The partitioned substrates provided an internal reference, namely, Pt on Au versus Pt on Ni, for every growth experiment. Deposition at large overpotentials yielded a Pt overlayer approximately 1 ML thick on Au or 2 to 3 ML thick on Ni as determined by X-ray photoelectron spectroscopy (XPS). Ion scattering spectroscopy (ISS) indicated that Pt covered 60% of the Ni surface forming a Pt50Ni50 surface alloy stabilized by excess Pt-Ni bond enthalpy supplemented by O- and H-induced Ni segregation. The Pt deposition rate on Ni was constrained by Ni oxide reduction while self-termination was mediated by the formation of a layer of adsorbed hydrogen (H-upd) on the Pt-Ni surface. Multi-cycle Pt deposition on Ni involved emersion and rapid water rinsing in air to oxidize the Hupd followed byre-immersion for additional Pt deposition. Four deposition cycles resulted in a Pt-terminated surface. The electrocatalytic activity for hydrogen production in alkaline media was significantly enhanced on the Pt-Ni monolayer film relative to Pt. The Pt-Ni electrode deactivated with time although intermittent oxidation at, or above, 1 V-RHE restructured the electrode to form an active Pt-Ni(OH)(2) composite surface. Published by Elsevier B.V.