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Mechanistic reaction pathway for hexafluoropropylene oxide pulsed plasma deposition of PTFE-like films
摘要： The pulsed plasma deposition of PTFE-like thin films using hexafluoropropylene oxide (HFPO) precursor has been investigated by time-resolved in situ mass spectrometry. Electron-impact and electron-attachment ionisation modes have been employed to monitor neutral plasma species; whilst electrical discharge negative and positive ions have been detected by switching-off the mass spectrometer electron-impact ionisation source. The relative concentrations of neutral versus ionic plasma species were found to rise for shorter pulse duty cycles. Mechanistically, HFPO molecules undergo pulsed plasma-initiated decomposition to form difluorocarbene (:CF2) radical species, and these can combine to form tetrafluoroethylene (CF2=CF2) molecules, which subsequently polymerise leading to the growth of PTFE-like ([–CF2–]n) perfluoroalkyl chains. Shorter pulsed plasma duty cycles enhance the growth of linear PTFE-like perfluoroalkyl chains.
关键词： pulsed plasma,PTFE,mechanistic reaction pathway,nanofilms
更新于2025-09-23 15:23:52
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Kinetic effects and oxidation pathways of sacrificial electron donors on the example of the photocatalytic reduction of molecular oxygen to hydrogen peroxide over illuminated titanium dioxide
摘要： Sacrificial electron donors are frequently used in photocatalytic reactions to enhance the performance of the reaction, typically short-chain alcohols as well as their respective aldehydes and acids are used. This study focuses on the differences between the individual electron donors regarding their oxidation rates, mechanistic pathways, the influence of the intermediates and their direct impact on the H2O2 generation. The individual H2O2 formation rates of 16 different electron donors, photonic and faradaic efficiencies for H2O2 production are carefully discussed. Furthermore, a new multi-reaction pathway for t-butanol oxidation is postulated and critically examined.
关键词： Alcohol oxidation,Reaction kinetics,Reaction pathway,Hydrogen peroxide,Photocatalysis,Sacrificial electron donors
更新于2025-09-23 15:22:29
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Reaction Pathway for Efficient CZTSe Solar Cells from Alloyed Cu-Sn Precursor via a Cu-Rich Selenization Stage
摘要： A detailed reaction pathway for efficient CZTSe solar cells from alloyed Cu-Sn precursor via a Cu-rich selenization stage is presented. The study focuses on the selenization of stacked elemental metallic layers (Cu-Sn-Zn), a commonly reported approach in kesterite Cu2ZnSnSe4 (CZTSe) processing. The high volatility of binary selenides, such as SnSe2-x, at necessary annealing temperatures (500 – 550 °C) makes this reaction pathway prone to Sn loss, which challenges the control of the composition and quality of the grown material. The present work reports an approach based on stacked elemental and alloyed precursors, discussing the benefits of using a Zn/Cu-Sn/Zn configuration. The absence of non-alloyed elemental Sn helps in suppressing the formation and subsequent evaporation of SnSe2-x phases, preventing Sn loss from the film during selenization. This reaction pathway involves a process scheme which i) starts with the growth of CZTSe in a Cu-rich environment, ii) includes a shift of the composition by supply of SnSe2-x vapor, and iii) terminates in the Cu-poor regime, leading to device efficiencies above 10%. This composition shift in the presented process appears similar to the final stage of the commonly known CIGSe three-stage co-evaporation.
关键词： Reaction pathway,Selenization,Kesterite,Alloying
更新于2025-09-23 15:19:57
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Plasmonic Switching of the Reaction Pathway: Visible‐Light Irradiation Varies the Reactant Concentration at the Solid–Solution Interface of a Gold–Cobalt Catalyst
摘要： Product selectivity of alkyne hydroamination over catalytic Au2Co alloy nanoparticles (NPs) can be made switchable by a light-on/light-off process, yielding imine (cross-coupling product of aniline and alkyne) under visible-light irradiation, but 1,4-diphenylbutadiyne in the dark. The low-flux light irradiation concentrates aniline on the catalyst, accelerating the catalytic cross-coupling by several orders of magnitude even at a very low overall aniline concentrations (1.0 X 10@3 mol L@1). A tentative mechanism is that Au2Co NPs absorb light, generating an intense fringing electromagnetic field and hot electrons. The sharp field-gradient (plasmonic optical force) can selectively enhance adsorption of light-polarizable aniline molecules on the catalyst. The light irradiation thereby alters the aniline/alkyne ratio at the NPs surface, switching product selectivity. This represents a new paradigm to modify a catalysis process by light.
关键词： product selectivity,reaction pathway,selective adsorption,visible-light photocatalysis,plasmonic metal nanoparticles
更新于2025-09-19 17:13:59
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Degradation of dimethyl phthalate using a liquid phase plasma process with TiO2 photocatalysts
摘要： The liquid phase plasma (LPP) method with a TiO2 photocatalyst and hydrogen peroxide was used to decompose dimethyl phthalate (DMP). As the applied voltage, pulse width, and frequency were increased, the rate of decomposition was increased and the decomposition rate was 63% for 180 min under plasma optimum conditions. The addition of TiO2 photocatalyst and hydrogen peroxide increased the DMP decomposition reaction rate, but an excess cause a decrease in decomposition rate due to a decrease in conductivity, blocking of ultraviolet light, and scavenger effect. When the TiO2 photocatalyst and hydrogen peroxide were used together, the decomposition reaction rate of DMP was greatly improved by using LPP single process alone. Also, when all the processes were used at the same time, the decomposition reaction rate was improved to about 2.8 times. DMP undergoes bond cleavage and ultimately decomposes into CO2 and H2O via dimethyl 4-hydroxyphthalate and methyl salicylates due to hydroxyl radicals and various active species generated by the LPP reaction.
关键词： Synergy effect,Hydrogen peroxide,Hydroxyl radicals,Decomposition rate,Degradation reaction pathway
更新于2025-09-09 09:28:46
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Nitrogen-Doping Chemical Behavior of Graphene Materials with Assistance of Defluorination
摘要： Heteroatom-doping reactions are essential to achieve advanced graphene-based materials for energy and biological areas. Unfortunately, considerably less is known regarding the detailed reaction pathways up to now. Here, we focus on investigating the nitrogen (N) doping process of fluorinated graphene (FG) under the assistance of defluorination based on modified in situ fourier transform infrared spectroscopy. It was demonstrated FG possesses a higher and more effective reactivity with ammonia in comparison with other graphene derivatives, which enable N-doping to proceed efficiently with assistance of defluorination even at a lower temperature (16.8 at % of N at 300 °C, 19.9 at % of N at 400 °C). Combining with Density functional theory, it was proved that, at the initial reaction step of N-doping, ammonia molecule attacked and substituted the C-F of FG by the new C-NH2. Sequentially, amino group was cyclized to the three-membered ring of ethylenimine. More importantly, the dissociation and migration of C-F bonds facilitates the dissociating of C-C bonds and the recombining of C-N bonds, thus significantly promoting the N atom in ethylenimine ring to transform to the pyridinic-N or graphitic-N in graphene skeleton.
关键词： Fluorinated graphene,Reaction pathway,Defluorination,Nitrogen doping,Two-dimensional chemistry
更新于2025-09-04 15:30:14