Tuning the Interaction between Ruthenium Single Atoms and the Second Coordination Sphere for Efficient Nitrogen Photofixation

Orienting the migration of photogenerated electrons to the target active single atoms instead of dissipation at inert sites is crucial to improve the photocatalytic activity of single-atom catalysts, but remains a challenge. Herein, it is demonstrated that the strong interaction between Ru single atoms and the second coordination sphere significantly enriches photogenerated electrons at Ru active sites and boosted N-2 photofixation activity. The extra Ru-Co coordination from the strong interaction with the second coordination sphere is observed over CoO-supported Ru single atoms (RuO+Co/CoO) relative to the weakly interacting ones (Ru-O/CoO). For N-2 photofixation, RuO+Co/CoO exhibits an ammonia production rate of 306 mu mol g(cat.)(-1) h(-1) without any sacrificial agents at room temperature, which is 4.6 times that of Ru-O/CoO. Mechanistic studies reveal that Ru-Co coordination in RuO+Co/CoO serves as an additional photoelectron transfer channel. Such channel promotes the accumulation of photoelectrons that excite from O to Co atoms on Ru active sites, facilitating the photoreduction of N-2 into NH3 process. The concept of the second coordination sphere modulation offers a powerful platform toward rational design of highly efficient single-atom catalysts for N-2 fixation and beyond.

Automated summary

This study demonstrates that the strong interaction between Ru single atoms and the second coordination sphere can enrich photogenerated electrons at Ru active sites and enhance N-2 photofixation activity. Mechanistic studies reveal that Ru-Co coordination serves as an additional photoelectron transfer channel, facilitating the photoreduction of N-2 into NH3.