Photoexcited Electron Dynamics of Nitrogen Fixation Catalyzed by Ruthenium Single-Atom Catalysts

Abstract

It is still a grand challenge to exploit efficient catalysts to achieve sustainable photocatalytic N2 reduction under ambient conditions. Here, we developed a ruthenium-based single-atom catalyst anchored on defect-rich TiO2 nanotubes (denoted Ru-SAs/Def-TNs) as a model system for N2 fixation. The constructed Ru-SAs/Def-TNs exhibited a catalytic efficiency of 125.2 μmol g–1 h–1, roughly 6 and 13 times higher than those of the supported Ru nanoparticles and Def-TNs, respectively. Through ultrafast transient absorption and photoluminescence spectroscopy, we revealed the relationship between catalytic activity and photoexcited electron dynamics in such a model SA catalytic system. The unique ligand-to-metal charge-transfer state formed in Ru-SAs/Def-TNs was found to be responsible for its high catalytic activity because it can greatly promote the transfer of photoelectrons from Def-TNs to the Ru-SAs center and the subsequent capture by Ru-SAs. This work sheds light on the origin of the high performance of SA catalysts from the perspective of photoexcited electron dynamics and hence enriches the mechanistic understanding of SA catalysis.

Single-atom catalysts for photocatalytic energy conversion

“…99 Distinctively, the covalent coordination between the isolated metal sites and host semiconductor materials makes the single-atom photocatalyst Schottky-barrier free, enabling the electron transfer to be unrestricted and more effective. 100 Benefiting from the modern characterization techniques, several electron pump models and local electron trap states induced by isolated metal sites have been found to reveal the charge separation/transfer manner in single-atom photocatalysts.…”

Recent advances in photocatalytic nitrogen fixation: from active sites to ammonia quantification methods

“…have good nitrogen xation effects. In addition, research on single-atom catalysts 22 and layered double hydroxide (LDH) catalysts 23,24 has gradually increased in recent years. Photoinduced electrons from these semiconductors are used to reduce N 2 to NH 3 .…”

Photocatalytic nitrogen reduction to ammonia: Insights into the role of defect engineering in photocatalysts

“…Another interesting work from Zhang and coworkers showed that the introduction of OVs and Ru single atoms (SAs) in TiO2 cooperatively accelerated electron and hole separation and suppressed their recombination, prolonging the lifetime of photogenerated carriers to 0.73 ns ± 0.03 ns (Figs. 13(a)-13(f)) [254]. Note that the defects in semiconducting photocatalysts is a double-edged sword for charge-carrier separation.…”