Synthesis of Efficient S-Scheme Heterostructures Composed of BiPO4 and KNbO3 for Photocatalytic N2 Fixation and Water Purification

The preparation of catalysts with heterojunction structures is a strategy to achieve efficient charge separation and high photocatalytic activity of photocatalysts. In this work, BiPO₄/KNbO₃ heterostructure photocatalysts were fabricated by a combination of hydrothermal and precipitation methods and subsequently employed in catalyzing N₂-to-NH₃ conversion and RhB degradation under light illumination. Morphological analysis revealed the effective dispersion of BiPO₄ on KNbO₃ nanocubes. Band structure analysis suggests that KNbO₃ and BiPO₄ exhibit suitable band potentials to form an S-scheme heterojunction. Under the joint action of the built-in electric field at the interface, energy band bending, and Coulomb attraction force, photogenerated electrons and holes with low redox performance are consumed, while those with high redox performance are effectively spatially separated. Consequently, the BiPO₄/KNbO₃ shows enhanced photocatalytic activity. The NH₃ production rate of the optimal sample is 2.6 and 5.8 times higher than that of KNbO₃ and BiPO₄, respectively. The enhanced photoactivity of BiPO₄/KNbO₃ is also observed in the photocatalytic degradation of RhB. This study offers valuable insights for the design and preparation of S-scheme heterojunction photocatalysts.