We report here the significant enhancement of catalytic activity of Ag-Pd bimetallic nanocatalysts with the formation of Ag-Pd catalysts having an average diameter of 4.2 AE 1.5 nm on TiO 2 nanoparticles using a two-step microwave (MW)-polyol method. Data obtained using XRD and STEM-EDS indicated that Ag-Pd bimetallic nanocatalysts consisted of Ag 82 Pd 18 alloy core and about 0.5 nm thick Pd shell, denoted as AgPd@Pd. The hydrogen production rate of AgPd@Pd/TiO 2 from formic acid, 16.00 AE 0.89 L g À1 h À1 , was 23 times higher than that of bare AgPd@Pd prepared under MW heating at 27 C. It was even higher by 2-4 times than the best Ag@Pd and CoAuPd catalysts at 20-35 C reported thus far. The apparent activation energy of the formic acid decomposition reaction using AgPd@Pd catalyst decreased from 22.8 to 7.2 kJ mol À1 in the presence of TiO 2 . Based on negative chemical shifts of the Pd peaks in the XPS data and the measured activation energies, the enhancement of catalytic activity in the presence of TiO 2 was explained by the lowered energy barrier in the reaction pathways because of the strong electron-donating effects of TiO 2 to Pd shells, which enhance the adsorption of formate to the catalyst and dehydrogenation from formate. † Electronic supplementary information (ESI) available: Temperature proles of reagent solutions in each experiment and STEM and STEM-EDS images of bare AgPd@Pd nanoparticles. See