Pt on ceria-based catalysts have been extensively investigated in recent years since they could be promising alternatives to Cu-based catalysts for hydrogen production from water gas shift reaction. A core-shell Pt in thin layer ceria prepared by microemulsion technique has earlier been shown to be highly active and selective for WGS reaction as compared to those Pt-ceria catalysts prepared by traditional methods. This paper is to report some optimization parameters including the sequence of adding precursors, aging time, type of reducing agent, support effect, variation in metal core composition and substitution of cerium oxide with other lanthanum metal ions in preparation of desirable metal-support interface for the catalysis. It is reported that a bimetallic core of Pt and Au in a 1:1 ratio at 5 wt% with respect to the ceria shell shows the highest WGS activity. Doping of rare earth metal ions to the ceria coating in the platinum-gold encapsulated does not result in a higher activity. This suggests that the overall catalytic WGS activity of this type of catalysts depends on electronic aspect of metal-ceria interface instead of oxygen mobility and OSC properties of the promoted ceria oxide shell. (C) 2010 Elsevier B.V. All rights reserved.