Efficient tandem electroreduction of nitrate into ammonia through coupling Cu single atoms with adjacent Co₃O₄.

Abstract

The nitrate (NO₃^-) electroreduction into ammonia (NH₃) represents a promising approach for sustainable NH₃ synthesis. However, the variation of adsorption configurations renders great difficulties in the simultaneous optimization of binding energy for the intermediates. Though the extensively reported Cu-based electrocatalysts benefit NO₃^- adsorption, one of the key issues lies in the accumulation of nitrite (NO₂^-) due to its weak adsorption, resulting in the rapid deactivation of catalysts and sluggish kinetics of subsequent hydrogenation steps. Here we report a tandem electrocatalyst by combining Cu single atoms catalysts with adjacent Co₃O₄ nanosheets to boost the electroreduction of NO₃^- to NH₃. The obtained tandem catalyst exhibits a yield rate for NH₃ of 114.0 mg <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow></mrow> <mrow> <msub><mrow><mi>NH</mi></mrow> <mrow><mn>3</mn></mrow> </msub> </mrow> </msub> </math> h^-1 cm^-2, which exceeds the previous values for the reported Cu-based catalysts. Mechanism investigations unveil that the combination of Co₃O₄ regulates the adsorption configuration of NO₂^- and strengthens the binding with NO₂^-, thus accelerating the electroreduction of NO₃^- to NH₃.