Selective Electrosynthesis of Nitrite from Nitrate Catalyzed by Perovskite Hydroxide CuSn(OH)₆

Nitrite (NO₂^-) is an important nitrogenous compound widely used in the chemical and pharmaceutical industries. The electrochemical reduction of earth-abundant nitrate (NO₃^-) is an appealing strategy for the sustainable synthesis of NO₂^-, but its practical use is limited by poor selectivity due to the lack of effective electrocatalysts. Herein, the perovskite hydroxide CuSn(OH)₆ is developed as an efficient electrocatalyst for the selective electrosynthesis of NO₂^- from NO₃^-. The Cu and Sn cations of CuSn(OH)₆ work cooperatively for efficient catalysis, in which the NO₃^- is preferentially adsorbed by the Sn sites and then catalyzed to NO₂^- by the Cu sites. Because the robust Sn(OH)₆ octahedrons in the perovskite hydroxide prevent the Cu²⁺ from being reconstructed into metallic Cu with strong hydrogenation activity, further reduction of NO₂^- is eliminated. Consequently, the efficient and selective conversion of NO₃^- to NO₂^- is achieved over Sn(OH)₆. Even though the electrode potential is as negative as −0.7 V, CuSn(OH)₆ shows a high NO₂^- yield of 145.8 μmol h^-1 mg_cat^-1 (6851.1 μg h^-1 mg_cat^-1) and selectivity of 97% with excellent stability in 100 mM Na₂SO₄ electrolyte containing 10 mM NaNO₃. This study offers an efficient catalyst for selective electrosynthesis of NO₂^- from NO₃^- and also a novel technique for designing and regulating Cu-based catalysts for diverse applications.