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Kinetic and Mechanistic Investigation of the Photocatalyzed Surface Reduction of 4-Nitrothiophenol Observed on a Silver Plasmonic Film via Surface-Enhanced Raman Scattering
摘要： Hot electrons generated by photo-induced plasmon decay from plasmonic metal surface can reduce 4-nitrothiophenol (4-NTP) to 4-aminothiophenol (4-ATP). Comparing to the reduction with a reducing agent such as sodium borohydride, Surface-Enhanced Raman scattering (SERS) measurements were performed here to elucidate the complex molecular mechanism of the reduction in presence of halide ions and hydrogen ions. The SERS measurements were performed using a simply prepared silver plasmonic film (AgPF), which enables monitoring of the reaction in different conditions at a solid-liquid surface, and eliminates the need for use of a reducing agent. As the concentration of H+ and Cl- could controlled, the observation of the reaction under a systematic set of condition was possible. Based on the kinetic traces of the intermediates, a reaction mechanism for the 4-NTP to 4-ATP reduction is suggested. Rate constants for the individual reactions are presented that fit the measured kinetic traces, and the role of hydrogen in each reaction step is characterized. This work provides clarification on the molecular transformation directly using protons as hydrogen source and demonstrates an effective method of applying a simple and low-cost silver surface catalyst for SERS studies. Moreover, the monitoring of Cl--concentration-dependent spectra gained insight into the hot-electron conversion process during the photoreduction and strongly support the formation of AgCl for activation of H+.
关键词： in-situ SERS spectra,kinetic rate constants,reaction mechanism,time-resolved measurements,selective surface photocatalytic reaction
更新于2025-09-23 15:19:57
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Operando Analysis of Electron Accumulation in Titanium(IV) Oxide Particles in an Aqueous Suspension Using a Photoacoustic Spectroscopic Method
摘要： The time course of photoabsorption of an aqueous suspension of titanium(IV) oxide (TiO2) particles was studied using photoacoustic (PA) spectroscopy. In the absence of an electron acceptor and the presence of an electron donor, ultraviolet (UV) irradiation increased PA intensity because photoabsorption of the suspension increased due to trivalent titanium (Ti3+) species generated by electron accumulation in TiO2 particles. In contrast, the addition of methylene blue (MB) as an acceptor caused a decrease in PA intensity, indicating that accumulated electrons were consumed by reduction of MB to colorless leuco-MB. The results for various TiO2 particles indicated that Ti3+ density is determined by this method. Moreover, the measurement can be applicable to quantitative operando analysis for accumulated electrons in a photocatalytic reaction.
关键词： photoacoustic spectroscopy,photocatalytic reaction,Ti3+ density,electron accumulation,titanium(IV) oxide
更新于2025-09-23 15:19:57
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Intrinsic Photo-degradation and Mechanism of Polymer Solar Cells: The crucial role of Non-fullerene Acceptor
摘要： The performances of polymer solar cells (PSCs) based on non-fullerene acceptors (NFAs) have improved remarkably in recent years, but such devices are insufficiently stable for practical applications. Here, we investigated the effects of NFAs on PSC long-term stability. We found that high performance PBDB-T:ITIC solar cells exhibit much lower stability than PTB7:PC71BM devices in the 1 sun light-soaking test; when compared with their initial performances, the performance of PTB7:PCBM-based solar cells remains above 60% for over 4000 h, whereas that of PBDB-T:ITIC-based devices is reduced to one fifth after 1000 h. We demonstrated that the ITIC-based PSCs exhibit poor photo-stability because ITIC at the interface of the ZnO/active film is readily decomposed by a photocatalytic reaction; this poor stability arises because the vinyl group of ITIC is chemically more vulnerable than the stable aromatic units in the organic active materials. The decomposition of ITIC results in the degradation of the electron transport properties of the active materials located close to ZnO, which leads to severe burn-in degradation and reduced FF and VOC under illumination. It is thus highly important to develop intrinsically stable organic materials composed of chemically stable building blocks in order to realize stable and high efficiency PSCs.
关键词： polymer solar cells,photocatalytic reaction,non-fullerene acceptors,photo-stability,ITIC
更新于2025-09-11 14:15:04
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Polyoxometalates/TiO2 Fenton-like photocatalysts with rearranged oxygen vacancies for enhanced synergetic degradation
摘要： Oxygen vacancy modulation has emerged as a prevalent strategy to improve the performance of heterogeneous catalysts. By far, the impact of oxygen vacancy rearrangement on the efficiency of Fenton-like reaction remains largely unknown. In this paper, Fe-containing polyoxometalates were coupled with defect-rearranged TiO2 to construct defective Fenton-like photocatalysts. Experimental characterizations revealed that defect rearrangement facilitated the interfacial transfer of electrons from TiO2 to polyoxometalate molecules. Fenton-like photocatalysts with rearranged defects exhibited 5 and 3.5 times higher activity for the synergetic degradation of toxic dye and 5-Sulfosalicylic acid than pristine TiO2. This enhancement was ascribed to the beneficial role of oxygen vacancy modulation for activating oxygen and H2O2 molecules into ?O2- and ?OH radicals. Our work provides new opportunities for exploring efficient Fenton-like photocatalysts for environmental remediation.
关键词： Photocatalytic reaction,Polyoxometalates,Fenton-like reaction,Titanium Dioxide,Oxygen vacancy rearrangement
更新于2025-09-10 09:29:36
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In situ FTIR reactor for monitoring gas phase products during a (photo)catalytic reaction in the liquid phase
摘要： Various catalytic and photocatalytic reactions in the liquid phase give rise to gas products. Therefore, the identification and quantification of these products are of high importance and even essential for some reactions. In this communication, a new in situ FTIR reactor is designed and used for analyzing the gas headspace of a (photo)catalytic reaction in solution. It allows the identification and quantification of the gas products of a liquid reaction under operating conditions and in real time. The new reactor has been tested in three representative photocatalytic reactions widely studied as model reactions in the liquid phase, i.e., i) decomposition of formic acid, ii) oxidation of Methylene Blue and iii) reduction of CO2. The validity of the results has been confirmed by analyzing the headspace at the end of the reaction using GC. The new reactor opens the possibility to follow on-line the (photo)catalyst activity. This is useful for ensuring the stability of the catalyst and studying the evolution of the selectivity during the reaction. The non-destructive behavior of the FTIR technique allows its coupling with other techniques for obtaining complementary results. The new reactor setup is easy to handle, to ship, and is very efficient which make it very suitable for performing fast and/or preliminary studies.
关键词： gas phase products,photocatalytic reaction,liquid phase,real-time analysis,FTIR reactor
更新于2025-09-10 09:29:36