Currently, oxygen reduction reaction (ORR) electrocatalysts used within proton-exchange membrane fuel cells (PEMFCs) are primarily platinum (Pt) and Pt-based alloys that are supported on high surface area carbon. At elevated voltages encountered during start-up/shut-down, the corrosion of the carbon support is accelerated which can significantly degrade the long-term stability of the catalyst. Recent work by our group has shown that unsupported (carbon-free) Pt-Ni two-dimensional (2D) nanoframes enable ORR electrocatalysts with significantly improved activity and stability compared with carbon-supported Pt and bimetallic Pt-metal alloy catalysts.¹ The unique nanoframe structure consists of a hierarchical 2D framework composed of a highly catalytically active Pt-metal alloy phase with an interconnected solid and pore network that results in three-dimensional molecular accessibility. The effect of altering the transition metal was investigated as a route to further improve the ORR activity through control of the surface atomic and electronic structure of Pt. Unsupported Pt-metal (metal=Ni, Co) two-dimensional (2D) nanoframes were synthesized through controlled thermal treatments of Pt-decorated metal hydroxide/oxide nanosheets. The structure of the 2D nanoframes were determined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Analysis of XRD and SEM data supports that Co and Ni can be incorporated into Pt-metal 2D nanoframes. Electrochemical characterizing using a rotating disk electrode configuration shows that the Pt-M 2D nanoframes exhibit significantly higher activities compared with Pt/C. The ability to create metallic 2D structures with 3D molecular accessibility opens up new opportunities for the design of high activity and stability carbon-free catalyst nanoarchitectures for numerous electrocatalytic and catalytic applications.

References

1. Godínez-Salomón, F.; Mendoza-Cruz, R; Arellano-Jimenez, M. Jose-Yacaman, M.; Rhodes, C.P; (manuscript submitted).