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 (KTaO 3 )/pyrochlore-type (K 2 Ta 2 O 6 ) photocatalysts were successfully prepared by facile hydrothermal incorporation of RE ions into KTaO 3 /K 2 Ta 2 O 6 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-KTaO 3 and MNPs/RE-K 2 Ta 2 O 6 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 KTaO 3 /K 2 Ta 2 O 6 , which resulted in greatly improved photocatalytic performance compared with that of pristine KTaO 3 /K 2 Ta 2 O 6 . Inclusion of RE ions into KTaO 3 /K 2 Ta 2 O 6 lattices probably leads to formation of RE4 f states below the conduction band levels to electron transition by lower photon excitation energy, while photoreduction of MNPs on the RE-KTaO 3 /RE-K 2 Ta 2 O 6 surface causes localized surface plasmon resonance and activates surface by adsorption for both O 2 and H 2 O molecules. The highest visible-light-induced photoactivity was observed for the Au/Er-KTaO 3 sample (16.48%) in phenol solution degradation and for the Pt/Pr-K 2 Ta 2 O 6 photocatalyst (36.13%) in gaseous toluene removal, respectively. Active species-trapping tests indicate that O 2 − radicals are meaningfully involved in phenol oxidation under visible light irradiation. The largest amount of H 2 evaluation was observed for the Pt/Pr-K 2 Ta 2 O 6 sample (93.16 µmol/min) under UV–vis irradiation, which also showed a relatively good lifetime in recycling. The present study describes noble- and rare-earth-metal-modified KTaO 3 /K 2 Ta 2 O 6 as an advanced material in photocatalysis.