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 mgcat–1 (6851.1 μg h–1 mgcat–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.