Efficient photocatalytic overall water splitting is achieved by the Mo doped ZnIn2S4/Bi4NbO8Cl Z-scheme heterojunction catalyst with full-spectrum response

Photocatalytic overall water splitting (POWS) is an efficient technology that converts solar energy into H 2 energy, holding significant importance in the realms of energy and the environment. As a visible-light photocatalyst, ZnIn 2 S 4 , despite being an ideal low-dimensional semiconductor for photocatalytic overall water splitting, has its performance therein affected by poor charge separation. The present study reports the successful synthesis of a novel Bi 4 NbO 8 Cl/ZnIn 2 S 4 :Mo Z-scheme heterojunction via a hydrothermal method. Under AM 1.5G irradiation, the POWS H 2 evolution rate was measured at 84.8 μmol g −1  h −1 , while the O 2 evolution rate was determined to be 47.0 μmol g −1  h −1 . Under simulated solar light irradiation, Bi 4 NbO 8 Cl/ZnIn 2 S 4 :Mo heterojunction exhibits an apparent quantum efficiency (AQE) of 0.22 % at 420 ± 20 nm and a solar-to-hydrogen (STH) conversion efficiency of 0.026 %. UV–Vis–NIR spectroscopic analysis unequivocally demonstrated a significant enhancement in the utilization efficiency of the Bi 4 NbO 8 Cl/ZnIn 2 S 4 :Mo Z-scheme heterojunction in the near-infrared light region compared to the pristine ZnIn 2 S 4 and Bi 4 NbO 8 Cl. This improvement extends the spectral absorption boundary of the photocatalyst, allowing efficient capture of a considerable proportion of low-energy photons in sunlight. Unique charge transfer mechanism of Z-scheme heterojunction was revealed by in-situ XPS and EPR tests. Z-scheme heterojunction effectively promoted the respective enrichment of electrons and holes generated by photo-excitation in ZnIn 2 S 4 :Mo and Bi 4 NbO 8 Cl, thereby improving the performance of POWS. This study not only establishes an experimental foundation for the design and construction of Z-scheme heterojunctions but also explores a new approach to augment the utilization efficiency of the near-infrared solar spectrum.