A multi-site Ru-Cu/CeO2 photocatalyst for boosting C-N coupling toward urea synthesis

Abstract

Photocatalytic urea production from nitrogen (N₂) and carbon dioxide (CO₂) is a sustainable and eco-friendly alternative to the Bosch-Meiser route. However, it remains a significant challenge in developing highly efficient photocatalysts for enhancing C-N coupling to high-yield urea synthesis. Herein, we propose a multi-site photocatalyst concept to address the concern of low yield by simultaneously improving photogenerated carrier separation and reactant activation. As a proof of concept, a well-defined multi-site photocatalyst, Ru nanoparticles and Cu single atoms decorated CeO₂ nanorods (Ru-Cu/CeO₂), is developed for efficient urea production. The incorporation of Ru and Cu sites is crucial not only to generate high-density photogenerated electrons, but also to facilitate N₂ and CO₂ adsorption and conversion. The in situ formed local nitrogen-rich area at Ru sites increases the encounter possibility with the carbon-containing species generated from Cu sites, substantially promoting C-N coupling. The Ru-Cu/CeO₂ photocatalyst exhibits an impressive urea yield rate of 16.7 μmol g⁻¹ h⁻¹, which ranks among the best performance reported to date. This work emphasizes the importance of multi-site catalyst design concept in guaranteeing rapid C-N coupling in photocatalytic urea synthesis and beyond.