Improved Borohydride Oxidation Reaction Activity and Stability for Carbon-Supported Platinum Nanoparticles with Tantalum Oxyphosphate Interlayers

Abstract

Platinum electrocatalysts are active for the borohydride oxidation reaction (BOR) in an alkaline environment. However, high surface area carbon-supported platinum (Pt/C) electrodes are not viable long term in alkaline solutions at 60 °C, because Pt nanoparticles are dislodged from the C surface over time due to carbonate formation and the Pt is poisoned by intermediates in the BOR, causing a significant loss in activity. We demonstrate that platinum has increased BOR activity and durability when supported on a tantalum oxyphosphate (TaOPO4) interlayer on Vulcan carbon (VC) (Pt/[TaOPO4/VC]). Pt/[TaOPO4/VC] is compared to Pt/VC electrocatalysts at the anode of a hydrogen peroxide direct borohydride fuel cell (H2O2-DBFC) and using rotating disk electrode (RDE) voltammetry in a half cell measurements. Accelerated stress testing with rotating disk electrode voltammetry is carried out in both 0.10 M NaOH at 25 °C and 0.05 M NaBH4 + 1 M NaOH at 60 °C. The TaOPO4 interlayer between the Pt and VC improves performance and durability in the range of 10 to 20%, suggesting that this is a promising approach for stabilizing Pt in aggressive alkaline environments.