SAD–GLAD Pt–Ni@Ni Nanorods as Highly Active Oxygen Reduction Reaction Electrocatalysts

Abstract

Vertically aligned catalysts comprised of platinum–nickel thin films on nickel nanorods (designated as Pt–Ni@Ni-NR) with varying ratios of Pt to Ni in the thin film were prepared by magnetron sputtering and evaluated for their oxygen reduction reaction (ORR) activity. A glancing angle deposition (GLAD) technique was used to fabricate the Ni nanorods (NRs) and a small angle deposition technique for growth of a thin conformal coating of Pt–Ni on the Ni-NRs. The Pt–Ni@Ni-NR structures were deposited on glassy carbon for evaluation of their ORR activity in an aqueous acidic electrolyte using the rotating disk electrode technique. The Pt–Ni@Ni-NR catalysts showed superior area-specific and mass activities for ORR compared to those of Pt–Ni alloy nanorod catalysts prepared using the GLAD technique and compared to those of conventional large-surface area Pt and Pt–Ni alloy nanoparticle catalysts.

Core–Shell-Structured Low-Platinum Electrocatalysts for Fuel Cell Applications

“…And after 10,000 cycling tests, the Au@PtNi nanoparticles exhibited a roughly 11.7 mV smaller negative potential shift than Au@Pt nanoparticles (12.7 mV). Various studies have also reported that if PtNi alloy shells are used with other cores such as Pd, Ni, and PtPb, good catalytic activities and stabilities for ORRs can also be obtained [160,388,[559][560][561]. Wang et al [562] also reported that the use of PtCo alloy shells on Pd cores can produce better ORR activities than other samples of Pt/C, Pd/C and Pd@Pt/C, and increased stability in which the maximum power density of Pd@Pt 3 Co/C showed almost no obvious decay in experimental testing.…”

The effect of the core/shell nanostructure arrays on PEM fuel cells: a short review

“…[45][46][47] Through controlling the roughness factor-that is the ratio of the active surface area to the geometric surface area, promoting single-crystal property, and optimizing FCC orientation, the electrochemical activity of PEM fuel cells can potentially be enhanced. [44][45][46][47][48][49][50][51][52][53] An additional cause for loss in efficiency in operating PEM FCs are cathode catalyst layers. The issue is that utilizing optimally the catalyst material accounts for a large fraction of the overall cost of the fuel cell system.…”

“…However, researchers are still working on designing a fuel cell with reduced use of Pt but decreased limitations and issues. [50][51][52]55 The Department of Energy (DOE) is the primary authority that outlines future goals for fuel cell development-especially PEM FCs. The DOE's targets for 2020 are, "14$/kWnet, 5000 hours of durability with cycling, 300 mA/cm 2 performance at 0.8 V, 1000 mW/cm 2 performance at rated power; 20$/m 2 cost, 0.125 mg/cm 2 , g/ kW electrode for [Pt] PEM total loading (both electrodes) less than 40% loss in mass activity.…”

“…How to prepare Pt-group catalysts-especially Pt alloyed with other less precious metals-for optimal reactions has been a key focus of fuel cell research. 48,50,52 Thermal evaporation and thin-film sputtering depositions have been two traditional methods used to prepare supported nanostructure catalysts. These approaches have been liberally used in order to prepare metal catalysts on support materials.…”

“…Developing thin-films of high-active and stable catalysts coated on vertically aligned nanorod arrays of conductive and stable support is the main strategy of these core/shell nanostructures. Kariuki NN et al, 52 worked on vertically aligned catalysts comprised of platinumnickel (Pt-Ni) thin-films on core nickel (Ni) nanorods with varying ratios of Pt to Ni in the shell thin-films. The Pt-Ni@Ni-Nanorod(NR) catalysts showed superior area-specific and mass activities for ORR compared to those of conventional large-surface area Pt nanoparticle catalysts.…”