Bifunctional Pt–Ni Electrocatalyst Synthesis with Ultralow Platinum Seeds for Oxygen Evolution and Reduction in Alkaline Medium

Abstract

Pt–Ni polyhedral nanoparticles (NPs) are extensively studied as electrocatalysts, mainly for oxygen reduction reaction (ORR), but they display a poor activity for the oxygen evolution reaction (OER). Here, ultralow platinum Pt@Ni@Pt core–bishell nanorods were designed (less than 1 wt % of Pt), synthesized, and characterized to yield bifunctional electrocatalysts with high efficiency toward ORR and OER in alkaline media. Ultralow platinum Pt@Ni@Pt core–bishell nanorods achieve an unprecedented (for a Pt-based catalyst) overpotential of 0.29 V at 10 mA cm–2 and current density of 162 mA μg–1Pt at 1.6 V (vs RHE) for the OER, while still maintaining a very decent value of 0.32 A mg–1Pt at 0.85 V for the ORR. These values outperform the standard Pt catalyst for the ORR and the Ni catalyst for the OER, using less than 1 wt % Pt. We describe the two-step synthesis of the Pt@Ni@Pt nanorods, demonstrating the adjustment of their structural properties by a combination of dimethylformamide (DMF) and benzyl alcohol in a solvothermal reaction. We found that the solvent ratio controls the Pt-core size, Ni-shell thickness, and morphology. The combination of high performance and structure control via synthesis makes Pt@Ni@Pt nanorods promising candidates for further applications and opens a door for their further investigation.