Unveiling the photocatalytic dye degradation potential of high-entropy perovskite (Bi0.2K0.2Na0.2Ca0.2Ba0.2)TiO3 ceramics

High-entropy ceramics (HEC), have emerged as promising alternative owing to their exceptional properties in diverse functional and structural applications. Recently, these HEC have been documented for their promising potential in water-treatment using catalytic technology. However, the use of HECs for catalytic based water-treatment is relatively new and very less explored. With this motivation, this paper unveils the photocatalytic dye degradation performance of high-entropy perovskite ceramics (HEPC) under indoor artificial lights as well as outdoor sunlight conditions and elucidate its underlying mechanism. A HEPC, (Bi0.2K0.2Na0.2Ca0.2Ba0.2)TiO3 (BKNCBT), was successfully synthesized using traditional and facile solid-state reaction approach. This multi-principal elemental HEPC adopted a stable single-phase distorted-cubic perovskite structure owing to its high configurational entropy as confirmed from X-ray diffraction (XRD) and Raman spectroscopy analysis. X-ray photoelectron spectroscopy (XPS) confirmed the surface chemical composition and provided oxidation states of different elements. XPS also evidenced a notable increment of high oxygen vacancies in HEPC BKNCBT sample in comparison to reference BaTiO3 (BT) sample. Scanning Electron microscope (SEM) images displayed the random morphology of HEPC BKNCBT powder particles with three-fold increment in average particle size in comparison to reference BT perovskite. A weaker photoluminescence (PL) intensity was observed in HEPC BKNCBT sample in comparison to reference BT sample, that signified the lower electron-hole pairs recombination rates in HEPC BKNCBT over reference BT, however the band gap energy remained same (similar to 3.2 eV) for both HEPC BKNCBT and reference BT samples. The photocatalytic performance of HEPC BKNCBT sample was analysed in comparison to reference BT sample under indoor ultraviolet (UV) lights and outdoor sunlight conditions for varying concentrations and volumes of model pollutant, i.e. Methylene Blue (MB) dye. The photocatalytic activity of HEPC BKNCBT was found to be significantly higher than that of BT sample, with degradation rates of 4.7 x 10(-3) and 9.8 x 10(-3) min(- 1) over BT sample that showed degradation rates of 0.8 x 10(-3) and 4.6 x 10(-3) min(- 1) under artificial UV light and sunlight, respectively. It was correlated to higher oxygen vacancies and lattice distortion in HEPC BKNCBT sample over reference BT sample, which led to lower electron-hole pair recombination in HEPC sample and thus allowed more charge carriers to participate in photocatalytic redox reactions. Finally, scavenger tests confirmed that the hydroxyl radicals (OH center dot) as the dominant reactive species driving the photocatalytic reaction. Thus, this study elucidated that high configurational entropy is an efficient approach to boost photocatalytic performance of perovskite ceramics.