Unveiling the highly disordered NbO6 units as electron-transfer sites in Nb2O5 photocatalysis with N-hydroxyphthalimide under visible light irradiation

ABSTRACT Although different NbO x units are present in Nb 2 O 5 -based catalysts, the correlations between these structures and activity remain unclear, which considerably hinders the further development of Nb 2 O 5 photocatalysis . Herein, we utilized N- hydroxyphthalimide (NHPI) as the probe molecule to distinguish the role of different NbO x units in the activation of C–H bond under visible light irradiation. With the addition of NHPI, Nb 2 O 5 catalysts with highly disordered NbO 6 units exhibited higher activities than that with slightly disordered NbO 6 units (419–495 vs . 82 μmol·g −1 ·h −1 ) in photocatalytic selective oxidation of ethylbenzene . Revealed by Raman spectra, electron paramagnetic resonance spectra, and transmission-electron-microscopy images, highly disordered NbO 6 units were confirmed to act as the active sites for the transfer of photogenerated electrons from NHPI, promoting the generation of phthalimide- N -oxyl (PINO) radicals for the enhanced conversion of ethylbenzene under visible light irradiation. This study provides guidance on the role of local NbO x units in Nb 2 O 5 photocatalysis.