Promoting electrocatalytic CO₂ and nitrate coreduction for urea synthesis by co-loading TiO₂ with In₂O₃ and Bi₂O₃

Electrocatalytic coreduction of CO₂ and nitrate ions (NO₃^-) enables the directional transformation of greenhouse gases and nitrogen-containing pollutants into urea, providing an innovative approach to traditional urea synthesis and facilitating carbon reduction and resource recycling in line with sustainability. However, low urea yield, poor selectivity, and ambiguous mechanisms restrict its application and development. In this study, a synergistic catalytic system composed of p-block and d-block elements was constructed, and Bi₂O₃-In₂O₃/TiO₂ electrocatalytic materials were designed and prepared. By rationally regulating the molar ratio of Bi to In, the catalytic material achieved a urea production rate of 37.78 μmol h^-1 cm^-2 and a urea Faraday efficiency (FE_Urea) of 40.79 % at -0.90 V vs. RHE. Meanwhile, Bi₂O₃-In₂O₃/TiO₂ exhibited a significant inhibitory effect on the formation of toxic and harmful by-products NO₂^- and N₂H₄. Mechanistic studies revealed that *CO₂ and *NO₂ undergo spontaneous adsorption and stabilization on the surface of In₂O₃, and the subsequent hydrogenation step is difficult to proceed, which promoted the early C-N coupling to form the key intermediate *CO₂NO₂. Additionally, Bi₂O₃-In₂O₃/TiO₂ reduced the high reaction energy barrier for the dehydroxylation of *COOHNH₂, facilitating the continuous and stable production of urea on the catalytic surface. This research not only presents a practical and potential solution for efficient electrocatalytic urea synthesis but also provides theoretical support and direction for the design and performance improvement of subsequent catalysts.