Photocatalytic Generation of H 2 O 2 Via a Hydrogen-Abstraction Pathway by Bi 2.15 WO 6 under Visible Light.

Photocatalytic technology is a popular research area for converting solar energy into environmentally friendly chemicals and is considered the greenest approach for producing H 2 O 2 . However, the corresponding reactive oxygen species (ROS) and pathway involved in the photocatalytic generation of H 2 O 2 by the Bi 2.15 WO 6 -glucose system are still not clear. Quenching experiments have established that neither • OH nor h + contribute to the formation of H 2 O 2 , and show that the formed surface superoxo (≡Bi-OO • ) and peroxo (≡Bi-OOH) species are the predominant ROS in H 2 O 2 generation. In addition, various characterizations indicate the enhanced electron-transfer on the surface of Bi 2.15 WO 6 with increasing contents of glucose via the ligand-to-metal charge transfer pathway, confirming H-transfer from glucose to ≡Bi-OO • or ≡Bi-OOH. The increased production of H 2 O 2 with decreasing bond dissociation energy (BDE O-H ) values of various phenolic compounds again supports the H-transfer mechanism from phenolic compounds to ≡Bi-OO • and then to ≡Bi-OOH. DFT calculations further reveal that on the Bi 2.15 WO 6 surface, oxygen is sequentially reduced to ≡Bi-OO • and ≡Bi-OOH, while H-transfer from H 2 O or glucose to ≡Bi-OO • and ≡Bi-OOH, resulting in the production of H 2 O 2 . The lower energy barrier of H-transfer from adsorbed glucose (0.636 eV) than that from H 2 O (1.157 eV) indicates that H-transfer is more favorable from adsorbed glucose. This work gives new insight into the photocatalytic generation of H 2 O 2 by Bi 2.15 WO 6 in the presence of glucose/phenolic compounds via the H-abstraction pathway.