Pt Single-Atom Modified BaTiO₃:Contaminants Removal And Hydrogen Evolution

Photocatalytic water splitting has attracted wide research interest due to its key role in solving energy crisis and environmental problems.Incorporating co-catalyst is an effective approach to boost the photocatalytic reaction process,which can not only inhibit charge carrier recombination,but also can provide abundant active sites for proton reduction and electron capture.Platinum（Pt）was usually regarded as the most efficient hydrogen evolution co-catalyst;however,only exposed surface atoms can be used as active sites to participate in the photocatalytic hydrogen evolution process,there is still a lot of research space to improve the atomic utilization efficiency.Downsizing the size of noble metals to subclusters or single atoms is an ideal way to maximize atomic efficiency.In this study,we modified barium titanate（BTO）perovskite via loading Pt single atoms,and the main work is as follows:（1）BTO was synthesized by hydrothermal method,and then BTO supported with highly dispersed Pt single atoms（Pt SA-BTO）was obtained by simple wet impregnation.The results of transmission electron microscopy（TEM）showed that the morphology of the material was irregular spherical particles with an average diameter of 50 nm.High-angle annular dark-field scanning transmission electron microscopy（HAADF-STEM）was further employed to obtain the atomic structure of as-prepared catalyst,we found that Pt atoms exist as highly dispersed individual atoms.X-ray absorption fine structure（XAFS）fitting results show that Pt atoms replaced Ti atoms in BaTiO₃ in the form of Pt-O₆ coordination,which confirmed the successful synthesis of Pt single atoms catalyst Pt-SA BTO.（2）The Pt SA-BTO catalyst has excellent photocatalytic activity for hydrogen production.The maximum hydrogen evolution rate 1.61 mmol g^-1h^-1（with 1 wt%loading content）was reached,which was 120 and 9.5 folds over the original BTO and Pt nanoparticles loaded BTO,respectively,indicating the extremely high atom utilization efficiency of Pt single atoms.After 12 hours cycle test,the hydrogen production performance maintained above 90%,which proved the good stability of Pt SA-BTO.（3）Through UV-Vis absorption spectra,it is found that the intrinsic absorption edge of the Pt SA-BTO catalyst is red-shifted from 406 nm of the BTO catalyst to 442 nm,and the band gap was reduced from 3.28 e V to 3.10 e V,which effectively enhanced the visible light absorption ability of the catalyst.Time-resolved photo-induced luminence decay spectra confirmed that the photogenerated carrier lifetime of Pt SA-BTO catalyst was 1.5 times over BTO.Meanwhile,Pt SA-BTO has a smaller electrochemical impedance radius and a stronger transient photocurrent response（6 times that of BTO）.It was proved that Pt single atom greatly promoted the separation and migration of carriers in BTO,which contributed to the improvement of photocatalytic hydrogen evolution activity.