2D porous hexaniobate-bismuth vanadate hybrid photocatalyst for photodegradation of aquatic refractory pollutants

Metal oxide semiconductors are highly promising due to their excellent photocatalytic performance in the photodegradation of industrial waste containing refractory chemical compounds. A hybrid structure with other semiconductors provides improved photocatalytic performance. In this work, porous and two-dimensional (2D) hexaniobate-bismuth vanadate (Nb₆-BiVO₄) Z-scheme hybrid photocatalysts are synthesized by chemical solution growth (CSG) of BiVO₄ over electrophoretically deposited Nb₆ thin films. The structural and morphological analysis of Nb₆-BiVO₄ hybrid thin films evidenced the well-crystalline uniform growth of monoclinic scheelite BiVO₄ over lamellar Nb₆ nanosheets. The Nb₆-BiVO₄ hybrid thin films exhibit a highly porous randomly aggregated nanosheet network, creating the house-of-cards type morphology. The Nb₆-BiVO₄ hybrid thin films display a strong visible light absorption with band gap energy of 2.29 eV and highly quenched photoluminescence signal, indicating their visible light harvesting nature and intimate electronic coupling between hybridized species beneficial for photocatalytic applications. The visible-light-driven photodegradation performance of methylene blue (MB), rhodamine-B (Rh-B) dyes, and tetracycline hydrochloride (TC) antibiotic over Nb₆-BiVO₄ hybrid are studied. The best optimized Nb₆-BiVO₄ thin film shows superior photocatalytic activity for photodegradation of MB, Rh-B dyes, and TC antibiotic with photodegradation rates of 87.3, 92.8, and 64.7 %, respectively, exceptionally higher than that of pristine BiVO₄. Furthermore, the mineralization study of Nb₆-BiVO₄ thin film is conducted using chemical oxygen demand (COD) analysis. The optimized Nb₆-BiVO₄ thin film shows superior percentage COD removal of 83.33, 85.42, and 61.36 % for MB, Rh-B dyes and TC antibiotic, respectively. The present results highlight the expediency of hybridization in enhancing the photocatalytic activity of pristine BiVO₄ by minimizing its charge recombination rate and improving chemical stability.