CeO_x-Integrated dual site enhanced urea electrosynthesis from nitrate and carbon dioxide.

Abstract

Electrocatalytic urea synthesis via the co-reduction of <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>NO</mi></mrow> <mrow><mn>3</mn></mrow> <mrow><mo>-</mo></mrow> </msubsup> </math> and CO₂ as a promising option to the conventional Bosch-Meiser remains challenged by regulating desired intermediates to simultaneously achieve a high yield and Faradaic efficiency. Here, we integrate the substrate material (SiO₂) and functionally atomic sites (Cu and Sn) utilizing CeO_x nanoclusters as 'adhesive', in which the CeO_x and SiO₂ form the composite carrier (CS) construct Cu and Sn diatomic electrocatalyst (CuSn/CS-1). Spectroscopic techniques and density functional theory calculations reveal that overall charge redistribution in the CeO_x-CuSn modules forms bifunctional active sites with unique electronic properties and abundant oxygen vacancies. The Cu sites mediate the conversion of CO₂ to *CO through a single carbon-coordinated structure with *CO₂^-, while Sn sites regulate the reduction of <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>NO</mi></mrow> <mrow><mn>3</mn></mrow> <mrow><mo>-</mo></mrow> </msubsup> </math> to stabilize the formation of *NH₂, broadening the C-N coupling route. Oxygen vacancies provide additional electron storage sites and promote the electron flow during the electrocatalytic process. CuSn/CS-1 achieves a urea yield of 55.81 mmol g^-1_cat. h^-1 with a Faradaic efficiency of 79.27% in H-cell at -0.7 V versus the reversible hydrogen electrode. This work overcomes the traditional trade-off between urea yield and Faradaic efficiency, providing a feasible and sustainable strategy.