(569dw) Active Sites of the Oxygen Reduction Reaction on Stepped Pt(111) Surfaces

For the electrochemical oxygen reduction reaction (ORR) on Pt group metal surfaces, the classic model categorizes active sites based on surface motifs, such as terraces and steps. However, this simplistic approach often leads to orders of magnitude errors in catalyst activity predictions and qualitative uncertainties of active sites, thus limiting opportunities for catalyst design. Using stepped Pt(111) surfaces and ORR as examples, we will illustrate that the root cause of larger errors and uncertainties is such a simplified categorization overlooks atomic site-specific reactivity driven by surface stress release. Specifically, we will show how surface stress release at steps introduces inhomogeneous strain fields, resulting in distinct electronic structures and reactivity for terrace atoms with identical local coordination. This phenomenon leads to a cluster of active sites flanking both sides of the step edge. We will demonstrate strategies to enhance ORR activity by leveraging this effect, such as varying terrace widths,^[1] adjusting the thickness of 2D nanosheets^[2] or controlling external stress.^[3]

[1] G. Liu, A. J. Shih, H. Deng, K. Ojha, X. Chen, M. Luo, I. T. McCrum, M. T. M. Koper, J. Greeley, Z. Zeng, Nature 2024, 626, 1005-1010.

[2] L. Wang, Z. Zeng, W. Gao, T. Maxson, D. Raciti, M. Giroux, X. Pan, C. Wang, J. Greeley, Science 2019, 363, 870-874.

[3] K. J. Sawant, Z. Zeng, J. P. Greeley, Angew. Chem., Int. Ed. 2024, 63, e202312747.