Direct Observation of Plasma-Stimulated Activation of Surface Species Using Multimodal In Situ/Operando Spectroscopy...

Area of Science:

• Plasma Science
• Surface Chemistry
• Catalysis

Background:

• Nonthermal plasmas (NTPs) offer unique reactive environments for chemical transformations at low temperatures.
• Integrating NTPs with conventional catalysis shows promise for novel chemical reactions.
• Understanding plasma-surface interactions is crucial for optimizing plasma-catalytic processes.

Purpose of the Study:

• To develop and utilize a multimodal spectroscopic instrument for in situ investigation of plasma-surface interactions.
• To correlate plasma-phase chemistry with surface and gas-phase products during plasma catalysis.
• To elucidate the mechanisms of carbonaceous species activation by NTP on different surfaces.

Main Methods:

• A novel multimodal spectroscopic instrument combining polarization-modulation infrared reflection-absorption spectroscopy (PM-IRAS), mass spectrometry, and optical emission spectroscopy (OES) was designed.
• The instrument was used to study NTP-promoted nonoxidative coupling of methane and subsequent activation of deposited carbonaceous species.
• Experiments were conducted on nickel (Ni) and silicon dioxide (SiO2) surfaces using an atmospheric pressure argon plasma jet.

Main Results:

• The instrument successfully monitored plasma-surface interactions during methane coupling and carbonaceous species activation.
• For the first time, the direct activation of carbonaceous surface species by NTP on Ni and SiO2 surfaces was observed.
• Formation of hydrogen gas and C2 hydrocarbons from activated carbonaceous species was detected, with evidence suggesting different formation pathways.

Conclusions:

• The developed multimodal spectroscopic tool provides unprecedented insight into plasma-surface interactions in plasma catalysis.
• Direct observation of carbonaceous species activation by NTP opens new avenues for understanding plasma-catalytic mechanisms.
• This capability can facilitate the rational design of advanced plasma-stimulated catalytic processes.