• Mikołajczyk, Alicja
• Pinto, Henry P.
• Winiarski, Michał Jerzy
• Grzyb, Tomasz
• Puzyn, Tomasz
• Strychalska-Nowak, Judyta
• Klimczuk, Tomasz
• Krukowska, Anna
• Lisowski, Wojciech
• Zaleska-Medynska, Adriana

Abstract

Novel rare earth-doped K2Ta2O6 (RE-K2Ta2O6) photocatalysts were successfully synthesized by one-step hydrothermalmethod. The effect of dopant type (RE =Y, Yb, Ho, Pr, Er) and amount of rare earth precursor (2, 4,8 and 10 mol%) on the physicochemical and photocatalytic properties of RE-K2Ta2O6 have been investigated. Allas-prepared materials were subsequently characterized by UV–vis diffuse reflectance spectroscopy (DRS),Brunauer-Emmett-Teller (BET) specific surface area measurement, scanning electron microscopy (SEM) withenergy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy(XPS), Raman spectroscopy, mass magnetic susceptometry and photoluminescence (PL) emission spectroscopy.The photocatalytic activity under UV–vis light irradiation was estimated in phenol degradation in aqueousphase, toluene removal in gas phase and H2 generation from formic acid solution. The experimental results showthat, novel RE-K2Ta2O6 exhibits greatly improved degradation efficiency under UV–vis light irradiation comparedwith pristine K2Ta2O6. The Er-K2Ta2O6 and Pr-K2Ta2O6, obtained by introducing of 2 mol% of RE ionsduring synthesis, reveal the highest photocatalytic activity among prepared samples in aqueous phase (33% ofphenol decomposition after 90 min of irradiation) and gas phase (45% of toluene removal after 60 min of irradiation),respectively. Moreover, both photocatalysts present good stability after subsequent three cycles. Theactive species trapping test shows that %OH and O2% − radicals are significantly involved in phenol oxidationunder UV–vis light irradiation. The amount of H2 evolution increases with increasing addition of Er dopant intoK2Ta2O6 lattice. The highest H2 production is obtained for 10 mol% Er-K2Ta2O6 after 240 min of UV–vis lightirradiation (15.40 μmol/min). Enhanced photoactivity performance can be attributed to incorporation of RE ionsat K+ lattice site in RE-K2Ta2O6, probably leading to formation of new RE 4f states below the conduction band ofK2Ta2O6 structure. To investigate the localization of RE ions in K2Ta2O6 structure, the band structure and partialdensity of the states (PDOS) have been investigated. Computer simulations were performed using plane-wavebased Vienna ab-initio simulation package (VASP) with the generalized gradient approximation (GGA) byPerdew-Burke-Ernzerhof (PBE). Moreover, inclusion of RE ions in K2Ta2O6 causes predominance pyrochlorephase formation over perovskite in regular cubic structure. Summarized, RE-doped K2Ta2O6 is promising materialin photocatalytic degradation of organic pollutants and H2 generation processes. Our work may providevaluable information for rare earth doping semiconductor with improved photocatalytic performance.

Topics

• perovskite
• impedance spectroscopy
• surface
• photoluminescence
• inclusion
• scanning electron microscopy
• x-ray photoelectron spectroscopy
• simulation
• semiconductor
• powder X-ray diffraction
• Energy-dispersive X-ray spectroscopy
• gas phase
• Raman spectroscopy
• band structure
• decomposition
• Specific surface area measurement