Studies On The Photocatalytic Hydrogen Production And Catalytic Combustion Performance Of Flame Spray Pyrolysis Synthesized Pt-based Single Atom Catalysts

In recent years,photocatalytic hydrogen production and catalytic combustion technologies have attracted widespread attention,and the core issue of catalytic reactions is the development of efficient and stable catalysts.Noble metal catalysts show good activity in a variety of catalytic reactions,but the cost is relatively high.Single atom catalysts（SACs）can achieve extremely high activity by improving the utilization of atoms and forming uniform active sites,thereby reducing the cost of noble metal catalysts.Flame spray pyrolysis（FSP）has many advantages in many methods of synthesizing nanoparticles,but there is a lack of research reports on the synthesis of single atom catalysts.In this paper,flame spray pyrolysis is used to synthesize Pt/TiO₂,Pt/ZrO₂,Pt/Zn O and Pt/Mg O single atom catalysts with isolated Pt atoms on the surface of different supports.The key to this FSP process is that the saturated vapor pressures between the two components are very different.When quenched to ambient temperature,gaseous Pt O₂will be deposited on the surface of the support nanoparticles.Combining XPS and HAADF-STEM characterization,it is determined that Pt atoms are dispersed and anchored on the catalyst surface.By controlling the loading at an ultra low level,a single atom catalyst with Pt dispersed at the atomic level can be prepared well.This work tests the photocatalytic water splitting hydrogen production activity of Pt/TiO₂single atom catalyst.0.1Pt/TiO₂（The atomic ratio of Pt:Ti is 0.1%.）has the highest hydrogen production rate,which is 108.5 times that of the benchmark TiO₂ sample（P25）,and has good stability.It has been discovered through various characterization means that the isolated oxidation state Pt atoms supported on the surface that have a strong interaction with the support are the main active centers for photocatalytic hydrogen production.The loading of Pt promotes the separation of photo-generated charges and the transfer of hydrogen ions,which improves the activity.At the same time,the large specific surface area and fine dispersion increase the number of active sites.This work further studies the performance of Pt/TiO₂ and other single atom catalysts in the catalytic combustion reaction.Pt/TiO₂ exhibits the highest activity in the CO catalytic combustion reaction,of which 0.2Pt/TiO₂（The atomic ratio of Pt:Ti is 0.2%.）sample has the highest turnover frequency（TOF）,and the 90%conversion temperature(T₉₀)of carbon monoxide of the 0.5Pt/TiO₂（The atomic ratio of Pt:Ti is 0.5%.）sample is 105°C,which has a much higher activity than Pt/TiO₂ with similar loadings prepared by other methods.The high activity is mainly due to the higher amount of active oxygen on the surface of Pt/TiO₂ and better reducibility.For CH₄ catalytic combustion activity and thermal stability,the loading of Pt greatly improves the CH₄ catalytic combustion activity of TiO₂.0.5Pt/TiO₂ sample decreases the 90%conversion temperature(T₉₀)of methane to about 500°C,and the final conversion rate reaches more than 99%.The improvement of lattice oxygen desorption performance at high temperature is the main reason for the improvement of activity.In addition,The Pt/TiO₂ single atom catalyst exhibits good thermal stability under long-term high temperature conditions.