In Situ Characterizations Revealing Ruthenium‐Atom‐Induced Raise of Photocatalytic Performance

Abstract Rational design/fabrication of high‐activity photocatalysts is of central importance to realize solar‐to‐chemical conversion for tackling worldwide energy/environmental issues. Hence, it is desirable to disclose the element/space/time‐resolved charge kinetics and surface species evolution of photocatalysts under realistic conditions using various in situ characterizations. Furthermore, the correlation of the above‐disclosed mechanisms with atomic‐scale compositions/structures of photocatalysts can further direct the atomic‐level design/synthesis of high‐performance photocatalysts. Herein, Ru atoms incorporated CdS quantum dots (QDs) are synthesized using an in situ hot‐injection route. The optimized Ru incorporated CdS QDs (Ru0.1) exhibit excellent photocatalytic evolution rates of H 2 O 2 (8.78 mmol g −1 h −1 ) and benzaldehyde (11.70 mmol g −1 h −1 ), respectively. Four different in situ characterizations demonstrate that in realistic conditions, the incorporated Ru atoms with high oxidation state (+3) effectively attract photo‐generated electrons from bulk to the overall surface of Ru0.1; these directed electron flows also greatly facilitate the transfer of photo‐generated holes from bulk to surface of Ru0.1 via efficiently reducing electron‐hole recombination. in situ diffuse reflectance infrared Fourier transform spectroscopy, electron spin spectroscopy, and species‐trapping experiments further reveal three possible reaction pathways for H 2 O 2 evolution. This work underscores the use of in situ characterizations to reveal the element/space/time‐resolved electrons/holes kinetics and surface‐species generation for photocatalysts in realistic conditions.