The electron bridge of Ti–O–Cu on well-integrated core–shell TiO₂@Cu nanorod for efficient and stable photocatalytic urea synthesis

The photocatalytic co-reduction of CO₂ and NO₃⁻ is a sustainable method for urea synthesis under mild condition. However, the low photocatalytic yield of urea is a challenge, due to the sluggish kinetics of the C–N coupling reaction. Herein, we successfully designed a TiO₂ nanoparticle modified Cu nanorod photocatalyst (TiO₂@Cu) for simultaneously promoting the NO₃⁻ reduction and CO₂ reduction reaction in the photocatalytic synthesis of urea. The TiO₂ nanoparticles were uniformly covered onto the surface of the Cu nanorod via a simple one-pot strategy, and the as-prepared well-integrated core–shell TiO₂@Cu showed excellent activity in photocatalytic urea synthesis, reaching up to 72.8 μmol·g⁻¹·h⁻¹ of urea yield. The turnover frequency of TiO₂@Cu is 30.1 times higher than that of pure TiO₂. Furthermore, the photocatalytic performance of TiO₂@Cu remains stable after 10 cycles, with no significant decline in urea yield. The remarkable photoactivity is attributed to the unique Ti–O–Cu bond in heterojunction interface of TiO₂@Cu, and Ti–O–Cu bond provides a favorable electron transfer pathway from TiO₂ to Cu, which accelerates the transfer of photogenerated charge and reduces the recombination of hole and electron. Meanwhile, the introduction of Cu alters the energy band structure of TiO₂, resulting in a smaller band gap and further improving the utilization of light. The energy barrier of the C–N coupling reaction in Ti–O–Cu site (−3.22 eV) is much lower than that of individual Cu site (1.21 eV). This work provides important inspiration and guiding significance towards highly efficient photocatalytic synthesis of urea.