Monometallic nanoparticles decorated and rare earth ions doped KTaO3/K2Ta2O6 photocatalysts with enhanced pollutant decomposition and improved H2 generation

New, monometallic nanoparticles (MNPs) decorated surface and rare earth (RE) ions doped lattice of perovskite-type (KTaO3)/pyrochlore-type (K2Ta2O6) photocatalysts were successfully prepared by facile hydrothermal incorporation of RE ions into KTaO3/K2Ta2O6 lattices followed by photodeposition of MNPs. The impact of noble metal type (MNPs = Au, Pt, Rh) and rare earth dopant type (RE = Er, Pr) on the physicochemical properties correlated with photoactivity of MNPs/RE-KTaO3 and MNPs/RE-K2Ta2O6 has been examined. All as-prepared photocatalysts were systematically characterized by UV-vis diffuse reflectance spectroscopy, photoluminescence emission spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, fast Fourier transform, powder X-ray diffraction, and X-ray photoelectron spectroscopy. The crystal structure was presented using VESTA software. Photocatalytic activity of samples under visible light irradiation was determined by pollutant decomposition, while UV-vis induced activity was estimated by H-2 generation efficiency. The experimental results suggested a synergistic effect between MNPs and RE-ions-modified KTaO3/K2Ta2O6, which resulted in greatly improved photocatalytic performance compared with that of pristine KTaO3/K2Ta2O6. Inclusion of RE ions into KTaO3/K2Ta2O6 lattices probably leads to formation of RE4f states below the conduction band levels to electron transition by lower photon excitation energy, while photoreduction of MNPs on the RE-KTaO3/RE-K2Ta2O6 surface causes localized surface plasmon resonance and activates surface by adsorption for both O-2 and H2O molecules. The highest visible-light-induced photoactivity was observed for the Au/Er-KTaO3 sample (16.48%) in phenol solution degradation and for the Pt/Pr-K2Ta2O6 photocatalyst (36.13%) in gaseous toluene removal, respectively. Active species-trapping tests indicate that O-2(center dot-) radicals are meaningfully involved in phenol oxidation under visible light irradiation. The largest amount of H-2 evaluation was observed for the Pt/Pr-K2Ta2O6 sample (93.16 mu mol/min) under UV-vis irradiation, which also showed a relatively good lifetime in recycling. The present study describes noble- and rare-earth-metal-modified KTaO3/K2Ta2O6 as an advanced material in photocatalysis. (C)2018 Elsevier Inc. All rights reserved.