Polycrystalline Pt nanoparticles with controlled ratio of Pt(100) and Pt(110) were adopted to study the surface sensitivity to nitrate reduction. Pt nanoparticles with more Pt(100) oriented surface exhibit higher reactivity to electro-reduction of nitrate. The mechanism studied by a cyclic voltammogram in low nitrate concentration (<= 50 mM) at high scan rate (50 mV s(-1)) indicates that the initial reduction of nitrate ion happens on the short-range order Pt(100) sites, leading to the formation of NOads that acts as the intermediate of the nitrate reduction to ammonia, while Pt(110) is hardly involved in nitrate reduction on this condition. (C) 2015 Elsevier B.V. All rights reserved.