This paper reinvestigates the mechanism of HNO(2) and NO(2)(-) reduction on polycrystalline platinum as a function of electrolyte pH and reactant concentration Intermediates and/or reaction products were detected by means of various (combined) techniques RRDE (for NH(2)OH detection) OLEMS (for volatile products) and FTIRS In acidic media HNO(2) is depleted due to homogeneous-phase reactions (accelerated by stirring) that generate NO the latter species which readily forms an adlayer on Pt is reduced in a first wave to N(2)O while HNO(2) is reduced in a following diffusion-limited wave to mainly NH(2)OH The two waves display different reaction orders Loss of HNO(2) (as NO) in the blanketing Ar stream hampered an accurate quantitative evaluation of the product distribution When the pH is Increased NO(2)(-) is reduced in a single peak with a much lower current density than in the previous case In RDE experiments the peak was found to decrease with increasing rotation rates The presence of a sluggishly reduced intermediate (NH(2)OH) has been proposed A general mechanistic scheme including NO HNO(2) and NO(2)(-) is discussed (C) 2010 Elsevier B V All rights reserved