Platinum is actually the irreplaceable catalyst for proton-exchange-membrane fuel cells (PEMFCs) and direct-alcohol fuel cells (DAFCs). Due to the high price and rare reserve, further improving the activity while decreasing the loading of Pt catalyst in membrane-electrolyte-assembly (MEA) of fuel cells is crucial. Single atomic Pt layer even single Pt atom catalysts are the most promising and challenging strategy. In this study, catalysts of Pt atomic layers from sub-monolayer to multilayers on Pd tetrahexahedral nanocrystals (THH Pd@Pt_n NCs) with high-index faceted and {111}-faceted Pd NCs were prepared through Pt galvanic displacement of UPD Cu. The results demonstrate that the catalytic activity for ethanol electrooxidation is very low on Pt monolayer (THH Pd@Pt₁ NCs), while the highest activity is measured on Pt 2-layers (THH Pd@Pt₂ NCs) amongst the THH Pd@Pt_n NCs (n<1, =1-5) studied. The catalytic activity of THH Pd@Pt₂ NCs is even higher than that of pure THH Pt NCs. Through in-situ CO-probe FTIR spectroscopic study, it has revealed that both the interaction of Pt layer with Pd nanoparticle (the strain and ligand effects) and the structure of surface atom arrangement play important roles in manipulating the activity of Pt catalyst. The study has thrown insight into design and preparation of high-active and ultra-low loading Pt catalysts for fuel cell applications.

Acknowledgement: This work was supported by Natural Science Foundation of China (21573183, 21621091).

References:

• Li, P. Liu and R. R. Adzic, J. Phys. Chem. Lett., 2012, 3, 3480-3485.
• Liu, D. Gokcen, U. Bertocci and T. P. Moffat, Science, 2012, 338, 1327-1330.
• Yang, J. Kim, Y.J. Tak, A. Soon, H. Lee, Angew. Chem. Int. Ed. 2016, 55, 2058.