Nitric Acid-Mediated Artificial Urea Photo-Synthesis With N₂ And CO₂

Photocatalytic urea synthesis, utilizing N-2 and CO2 as feedstock and sustainable solar energy, represents an environmentally friendly and promising alternative strategy. However, the conventional unidirectional gas phase co-reduction techniques typically employes pose stringent demands for the design of key catalysts, reaction control, mass transfer, and other aspects, due to the disparity in physical properties, structure, and catalytic kinetics between N-2 and CO2. Herein, Ru-TiO2 is synthesized and employed as an effective catalyst for urea photo-synthesis through a nitric acid-mediated pathway combining nitrogen oxidation and subsequent kinetically advantageous nitrate and CO2 co-reduction. A urea yield of 24.95 mu mol h(-1) g(cat)(-1). is obtained through an innovative intermittent illumination method, AQE values of 4.7% and 6.3% at 380 and 420 nm, respectively. The remarkable photo-activity is attributed to its unique oxygen vacancy-anchored Ru nanostructure (Ru-O4Ti1), which effectively activates inert N-2 molecules to minish the disparity of orbital energy levels, facilitates the formation of crucial *NN(OH) intermediates, and serves as an "electronic pump" to avoid electronegativity effect for facilitating electron transfer from nitrogen to TiO2 support for urea photosynthesis. This study presents groundbreaking insights for nitrogen oxidation activation and provides brand-new ideas for the direct resource utilization of nitrogen.