Oxygen evolution electrocatalysts with high activity and stability are needed for proton-exchange membrane (PEM) electrolyzers. Iridium oxide (IrO_x) has been shown to exhibit both high activity and stability for the oxygen evolution reaction (OER) under acidic conditions. Based on the high cost and limited supply of IrO_x, approaches that increase the activity of Ir-based OER catalysts are of significant interest. Recent work has shown that incorporation of Ni within the IrO_x structure increases the OER activity.¹ Further, the activity of IrO_x has been shown to depend on specific surface structures (i.e. edges, corners and facets).² As an approach to provide high activity OER catalysts, we investigated a unique self-supported IrNi_xO_y two-dimensional (2D) nanoframe structure that allows the combination of (i) incorporation of a non-noble transition metal within the structure to tune the surface atomic and electronic structure, (ii) expression of specific facets and edges, and (iii) an interconnected, carbon-free three-dimensional matrix that allows molecular accessibility. The IrNi_xO_y 2D nanoframes were synthesized by using nickel hydroxide/oxide nanosheets that were decorated with Ir and then treated under controlled temperature/atmosphere treatments to facilitate Ir-Ni interaction. The development of IrNi_xO_y 2D nanoframes extends our group’s recent work on bimetallic Pt-Ni 2D nanoframes which were shown to exhibit high stabilities and activities for the oxygen reduction reaction.³ The 2D nanoframe structure provides an architecture that expresses highly catalytically active surfaces within an interconnected solid and pore network that faciliates molecular access to the reactive surface. The structure of the IrNi_xO_y 2D nanoframes was determined using X-ray diffraction, scanning transmission microscopy, and scanning transmission electron microscopy. Oxygen evolution activities and stabilities were determined using rotating ring disk electrode configuration and will be presented. The ability to combine highly catalytically active surfaces within a 3D nanoarchitecture provides the opportunity to design OER catalysts with improved activity and stability.

References

1. Sen, F. G.; Kinaci, A.; Narayanan, B.; Gray, S. K.; Davis, M. J.; Sankaranarayanan, S.; Chan, M. K. Y. J. Mater. Chem. A 2015, 3, 18970-18982.

2. Reier, T.; Pawolek, Z.; Cherevko, S.; Bruns, M.; Jones, T.; Teschner, D.; Selve, S.; Bergmann, A.; Nong, H. N.; Schlogl, R.; Mayrhofer, K. J. J.; Strasser, P. J. Am. Chem. Soc. 2015, 137, 13031-13040.

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