The Ta2O5-modified Pt electrode, which was prepared by electrodeposition of Ta on a Pt electrode from 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPTFSI) ionic liquid and subsequent calcination, possesses excellent electrocatalytic activity toward the oxidation of formaldehyde to CO2 in 0.5 M H2SO4 solution compared with the bare Pt electrode. This significant improvement in catalytic performance may be attributed to the strong metal-oxide interaction as well as hydroxide spillover effect of the modified electrode. A possible reaction mechanism is proposed.