In Situ Analysis Of Photocatalytic Reactions In Real-time By Probe Electrospray Ionization Mass Spectrometry

The understanding of the mechanism of photocatalytic processes can provide great help for the determination of active sites on photocatalysts and promotion for the development of new high-performance photocatalysts.Although a great deal of efforts has been spent in probing the mechanism of photocatalytic reactions,some key principles and procedures are far from being understood.Thus,real-time monitoring technology for catalytic reactions become more and more popular.The most restricting factor for the monitoring performance of photocatalytic reactions is providing detailed information of chemcial species from reaction process.Probe electrospray ionization mass spectrometry（PESI-MS）technology with high time-resolving ability makes it possible to monitor the photocatalytic reactions due to its unique ability to provide the change of each substance within whole reactions.In this dissertation,a platform for studying heterogeneous photocatalytic reactions was developed by applying PESI-MS with surface-modified probes.Due to the established photocatalytic reaction monitoring platform,the in situ analysis and real-time monitoring of photocatalytic degradation of methylene blue（MB）and brilliant green（BG）by five catalysts（TiO₂,WO₃,ZnS,SnO₂,and SiC）were achieved,respectively.The experimental results in this dissertation demonstrate the potential of PESI-MS for in situ monitoring of heterogeneous photocatalytic reactions occurring in suspensions.PESI-MS can provide continuous sampling and real-time MS results.No time-consuming sample preparation is required in PESI-MS.This method also has other advantages,including good reproducibility and stability（time scale up to180 minutes）,easiness for operation,low sample consumption,high time resolution,and strong tolerance to suspended photocatalyst particles.From the time-resolved mass spectra and ion chromatogram of a certain chemical,it is obvious that photocatalytic degradation reactions are extremely complicated processes.The in situ real-time monitoring method of photocatalytic reaction established in this dissertation is capable for study the mechanism of photocatalytic degradation reactions.By comparison,it can be found that there are some differences in the catalytic performance of different catalysts when degrading the same substrate MB.This founding indicates that PESI-MS can be used to study the characteristic catalysts to the same substrate.The experimental results also indicated that there are certain differences in degradation products when different catalyst were used to the same substrate,promoting us that the in situ monitoring method established in this dissertation can be used to screen catalysts for specific target products.In summary,PESI-MS may be a versatile analytical tool for in situ photocatalytic reaction analysis,and a potential means to evaluate the performance of photocatalysts.In future,more and more time and work will be spent to deeply explore the functions and usefulness of PESI-MS in the fileld of in situ analysis and real-time monitoring of photocatalytic reactions,which will enhance the performance and broaden the applicability of PESI-MS.