Defect Structure Analysis of Heterointerface between Pt and CeO_x Promoter on Pt Electro-Catalyst

Pt-CeOx/C (1.5 ≤ x ≤ 2) electro-catalyst is one of the most promising cathode materials for use in polymer membrane electrolyte fuel cells. To clarify the microstructure of Pt-CeOx heterointerface, we prepared Pt-loaded CeOx thin film on conductive SrTiO3 single crystal substrate by using a stepwise process of pulse laser deposition method for the preparation of epitaxial growth CeOx film followed by an impregnation method which loaded the Pt particles on the CeOx film. The electrochemistry observed for the Pt-loaded CeOx thin film on the conductive single crystal substrate was examined by using cyclic voltammetry in 0.5 M H2SO4 aqueous solution, and a cross-sectional image of the aforementioned Pt-CeOx thin film electrode was observed using a transmission electron microscope. The electrochemistry observed for Pt-CeOx thin film electrode clearly showed the promotion effect of CeOx. Also, the microanalysis indicated that unique, large clusters that consisted of C-type rare-earth-like structures were formed in the Pt-CeOx interface by a strong interaction between Pt and CeOx. The present combination analysis of the electrochemistry, microanalysis, and atomistic simulation indicates that the large clusters (i.e., 12 (PtCe''-Vo(••)) + 2 (PtCe''-2Vo(••)-2CeCe')) that were formed into the Pt-CeOx interface promoted the charge transfer between Pt surface and CeOx, suggesting that the oxygen reduction reaction activity on Pt can be maximized by fabrication of C-type rare-earth-like structure that consists of the aforementioned large clusters in the Pt-CeOx interfaces.