Selective Electrosynthesis of Nitrite from NitrateCatalyzed 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.