(729b) Novel Nanoscale Architectures of Pt-Based Electrocatalysts

One grand challenge for the scientists working on the electrocatalysis for proton exchange membrane fuel cells (PEMFCs) is the discrepancy between the catalytic performance of bulk models with extended surfaces and nanoscale materials with high surface area. Pt and Pt-alloy extended surfaces typically exhibit specific activities of an order of magnitude higher than their nanoscale counterparts for the oxygen reduction reaction. The discrepancy has been ascribed to the difference in the coordination number of surface atoms, defects, support, as well as the strain effect in some cases. While it seems formidable to employ bulk crystals in PEMFCs that anyway is not beneficial in terms of mass activity, how to design electrocatalysts achieving or approaching the activity of extended surfaces however has attracted substantial interests in the literature. We discuss here our recent findings in the development of bi- and multimetallic electrocatalysts with the surface structure engineered to mimic the situations on extended surfaces. Specifically, we have made significant progress in producing nanocatalysts with Pt-skin surfaces, which does possess both the high specific activity that can only be accessible by surface segregated extended surfaces and the high surface area of nanocatalysts. Our work is thus insightful for understanding the connection between model and practical heterogeneous catalysts.