The oxygen reduction reaction (ORR) can be greatly improved when the traditional used Pt catalyst is alloyed with yttrium. According to density functional theory calculations, the activity of polycrystalline Pt₃Y electrodecan be enhanced relative to pure Pt by afactor of 6-10.^[1] Experimental preparation of PtY alloy is limited to physical method such as gas aggregation^[2] ormagnetron co-sputtering. ^[3] The mass activity of ORR at 0.9V_RHE is as high as 3.05A mg_Pt^-1obtained from a Pt_xY particle of 9nm in diameter.^[2]However there is no firm evidence of the possibility of mass production of PtY alloy with high catalytic performance in ORR from chemical method because yttrium reacts with even trace amount of water and oxygen.

To solve this problem, electrodeposition is considered to be a possibility. It is well known that yttrium is extremely basic metal with a reduction potential -2.43V_RHE and electroplating of yttrium from aqueous solutions is believedto be unattainable due to intensive hydrogen evolution at such large over potentials. This problem can be solved using ionic liquids as solvent and electrolyte. They are appropriate medium for the electrodeposition of yttrium and its alloys, because the area of electrochemical stability of ionic liquids overlaps the range of reduction potentials of yttrium.^[4]

We selected 1-ethyl-3-methylimidazolium tetrafluoroborate to electrodeposit yttrium on glassy carbon substrate.^[5]A controlled method is applied to form PtY alloy based on the electrodeposited yttrium. The ORR activity is evaluated by both half cell and full cell characterizations.

References:

[1] J. Greeley, I. E. L. Stephens, A. S. Bondarenko, T. P. Johansson, H. A. Hansen, T. F. Jaramillo, J. Rossmeisl, I. Chorkendorff, J. K. Nørskov, Alloys of platinum and early transition metals as oxygen reduction electrocatalysts, Nature Chemistry, 2009, 1, 552-556.

[2]P. H. Fernandez,F.Masini,D. N. McCarthy,C. E. Strebel,D.Friebel,D.Deiana,P.Malacrida,A.Nierhoff,A.Bodin,A. M. Wise,J. H. Nielsen,T. W. Hansen,A.Nilsson,I. E. L. Stephens, I.Chorkendorff, Mass-selected nanoparticles of PtxY as model catalysts for oxygenelectroreduction, Nature Chemistry, 2014, 6, 732-738

[3]S. J.Yoo , K. S. Lee , S. J. Hwang, Y. H. Cho, S. K. Kim,J. W. Yun, Y. E. Sung, T. H. Lim, Pt₃Y electrocatalyst for oxygen reduction reaction in protonexchange membrane fuel cells, International Journal of Hydrogen Energy,2012, 37, 9758-9765.

[4]L. M. Glukhov, A. A. Greish, and L. M. Kustov, Electrodeposition of Rare Earth Metals Y, Gd, Yb in Ionic Liquids, Russian Journal of Physical Chemistry A, 2010, 84, 104-108.