Identification of Cu surface active sites for a complete nitrate-to-nitrite conversion with nanostructured catalysts

• Porous Cu-modified electrodes with well-defined surface structures are prepared.
• Nitrate readily adsorbs on Cu-modified electrodes in alkaline electrolyte.
• Adsorption and reduction of nitrates occurs preferentially at Cu(100) surface sites.
• Nitrate is almost exclusively converted to nitrite.

Nitrate reduction on Pt nanostructured films, PtNSF, with an extended surface area (roughness factor of ca. 30), and close to 50% of (100) surface sites modified by Cu adatoms through underpotential deposition (Cuupd/PtNSF), has been studied by means of linear sweep voltammetry (LSV), electrolysis at constant potential, and chemical analysis of the formed products. According to the LSV curves, the adsorption and reduction of nitrates occur preferentially at Cu(100) surface sites and at a potential positive (+0.15 V) of the hydrogen reversible potential. In these conditions, the nitrate-to-nitrite conversion is achieved on the Cu(100) sites, with a faradic efficiency in excess of 95%, and a conversion selectivity of 98%.

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