This review describes the history and development of plasma-assisted catalysis focussing mainly on the use of atmospheric pressure, non-thermal plasma. It identifies the various interactions between the plasma and the catalyst that can modify and activate the catalytic surface and also describes how the catalyst affects the properties of the discharge. Techniques for in situ diagnostics of species adsorbed onto the surface and present in the gas-phase over a range of timescales are described. The effect of temperature on plasma–catalysis can assist in determining differences between thermal catalysis and plasma-activated catalysis and focuses on the meaning of temperature in a system involving non-equilibrium plasma. It can also help to develop an understanding of the gas-phase and surface mechanism of the plasma–catalysis at a molecular level. Our current state of knowledge and ignorance is highlighted and future directions suggested.

http://iopscience.iop.org/article/10.1088/0022-3727/49/24/243001/pdf

Plasma–catalysis: the known knowns, the known unknowns and the unknown unknowns

Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, CH4 activation into hydrogen, higher hydrocarbons or oxygenates, and NH3 synthesis Other applications are already more established, such as for air pollution control, eg volatile organic compound remediation, particulate matter and NOx removal In addition, plasma is also very promising for catalyst synthesis and treatment Plasma catalysis clearly has benefits over 'conventional' catalysis, as outlined in the Introduction However, a better insight into the underlying physical and chemical processes is crucial This can be obtained by experiments applying diagnostics, studying both the chemical processes at the catalyst surface and the physicochemical mechanisms of plasma-catalyst interactions, as well as by computer modeling The key challenge is to design cost-effective, highly active and stable catalysts tailored to the plasma environment Therefore, insight from thermal catalysis as well as electro- and photocatalysis is crucial All these aspects are covered in this Roadmap paper, written by specialists in their field, presenting the state-of-the-art, the current and future challenges, as well as the advances in science and technology needed to meet these challenges

/pdf/the-2020-plasma-catalysis-roadmap-4nij6g176p.pdf

The 2020 plasma catalysis roadmap

Catalyst preparation with plasmas is increasingly attracting interest A plasma is a partially ionized gas, consisting of electrons, ions, molecules, radicals, photons, and excited species, which are all active species for catalyst preparation and treatment Under the influence of plasma, nucleation and crystal growth in catalyst preparation can be very different from those in the conventional thermal approach Some thermodynamically unfavorable reactions can easily take place with plasmas Compounds such as sulfides, nitrides, and phosphides that are produced under harsh conditions can be synthesized by plasma under mild conditions Plasmas can produce catalysts with smaller particle sizes and controllable structure Plasma is also a facile tool for reduction, oxidation, doping, etching, coating, alloy formation, surface treatment, and surface cleaning in a simple and direct way A rapid and convenient plasma template removal has thus been established for zeolite synthesis It can operate at room tempera

Catalyst Preparation with Plasmas: How Does It Work?

The Co3O4 and Mn-doped Co3O4 nanoparticle were synthesized by a co-precipitation method and used as selective catalytic reduction of NO with NH3 (NH3-SCR) catalysts. After the doping of manganese oxides, the NH3-SCR activity of Mn0.05Co0.95Ox catalyst is greatly enhanced. The NO oxidation ability of two catalysts is compared, and the X-ray diffraction results demonstrate that Mn has been successfully doped into the lattice of Co3O4. The X-ray photoelectron spectroscopy and temperature-programmed reduction with H2 results confirmed that there is a strong interaction between Mn and Co in the Mn0.05Co0.95Ox catalyst. Their adsorption and desorption properties were characterized by temperature-programmed desorption with NH3 or NO + O2 and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTs). These results indicated that the doping of manganese could provide more acid sites on the catalysts, and bidentate nitrates species originated from NOx adsorption are obviously activated on...

In Situ DRIFTs Investigation of the Low-Temperature Reaction Mechanism over Mn-Doped Co3O4 for the Selective Catalytic Reduction of NOx with NH3

CO2 hydrogenation to methanol is a promising process for CO2 conversion and utilization. Despite a well-developed route for CO hydrogenation to methanol, the use of CO2 as a feedstock for methanol synthesis remains underexplored, and one of its major challenges is high reaction pressure (usually 30–300 atm). In this work, atmospheric pressure and room temperature (∼30 °C) synthesis of methanol from CO2 and H2 has been successfully achieved using a dielectric barrier discharge (DBD) with and without a catalyst. The methanol production was strongly dependent on the plasma reactor setup; the DBD reactor with a special water-electrode design showed the highest reaction performance in terms of the conversion of CO2 and methanol yield. The combination of the plasma with Cu/γ-Al2O3 or Pt/γ-Al2O3 catalyst significantly enhanced the CO2 conversion and methanol yield compared to the plasma hydrogenation of CO2 without a catalyst. The maximum methanol yield of 11.3% and methanol selectivity of 53.7% were achieved ov...

Atmospheric Pressure and Room Temperature Synthesis of Methanol through Plasma-Catalytic Hydrogenation of CO2

Atmospheric pressure nonthermal-plasma-activated catalysis for the removal of NOx using hydrocarbon selective catalytic reduction has been studied utilizing toluene and n-octane as the hydrocarbon reductant. When the plasma was combined with a Ag/Al2O3 catalyst, a strong enhancement in activity was observed when compared with conventional thermal activation with high conversions of both NOx and hydrocarbons obtained at temperature ≤250 °C, where the silver catalyst is normally inactive. Importantly, even in the absence of an external heat source, significant activity was obtained. This low temperature activity provides the basis for applying nonthermal plasmas to activate emission control catalysts during cold start conditions, which remains an important issue for mobile and stationary applications.

/pdf/ambient-temperature-hydrocarbon-selective-catalytic-42sly98ukk.pdf

Ambient Temperature Hydrocarbon Selective Catalytic Reduction of NOx Using Atmospheric Pressure Nonthermal Plasma Activation of a Ag/Al2O3 Catalyst

The current paper reports on a newly developed DRIFTS-MS system for the investigation of non-thermal plasma (NTP) assisted heterogeneously catalyzed reactions. Specifically, this methodology has been utilized to investigate the surface changes during the NTP-activated hydrocarbon selective catalytic reduction (HC-SCR) deNOx reaction over a silver-based catalyst at ambient temperature using simulated diesel fuels (toluene and n-octane). The experimental setup and the methods used to investigate the plasma activation operating with helium as the carrier gas in order to examine low-temperature reactions are described. The technique has identified the importance, even at low temperatures, of isocyanate species in the HC-SCR deNOx reaction as well as the critical role of water in the formation of N2.

Probing a Non-Thermal Plasma Activated Heterogeneously Catalyzed Reaction Using in Situ DRIFTS-MS

An experimental diagnostic based on a nanosecond-intensified charged coupled device camera and optical emission spectroscopy (OES) are proposed to observe the interfacial region between the plasma plume and liquid surfaces. The study is simulating the investigations of using non thermal atmospheric pressure plasma jets for the eradication of bacterial biofilms. The spatially and temporally resolved images are focused on the contact region in the open air between the nozzle of the reactor and liquid targets. The emission intensity from one discharge cycle is captured and accumulated over several cycles to investigate the formation and the kinetic evolution of the plasma during the interaction. Moreover, the emission intensity of the helium plasma jet and plasma behaviour with different samples are observed. It is found that some dynamic of the plasma discharge has changed during the interaction with different targets. The method can be used to improve the need of understanding of the physics and chemistry of plasma jet during the interaction with liquid surfaces. Different types of species that arrived to the samples were studied and compared with the free jet mode using OES.

Investigation of a non-thermal atmospheric pressure plasma jet in contact with liquids using fast imaging

Comparison Study of Two Atmospheric Pressure Plasma Jet Configurations for Plasma-Catalyst Development

Non-thermal atmospheric pressure plasma jets APPjs are a promising new field of research which are beneficial to many associated technologies, such as material treatment and biomedical applications [1],[2]. The use of non-thermal plasmas for the eradication and control of bacterial infection and contamination are acquired great attention in biomedical applications [3]. The effects of non-thermal plasma operating conditions on the bacterial inactivation rate have been investigated in many previous studies. In this study a kHz-driven APPj source of a structure similar to that designed by Teschke et al in 2005 [4], which has been studied recently by many research groups in different configurations [5]. The experimental setup simulates the activity of a APPj against biofilms of Bacillus cereus to investigate the influence of APPj. The method improves the understanding of the interaction mechanism between the plasma jet and the liquid biological samples.

http://ieeexplore.ieee.org/iel7/7154561/7179488/07179968.pdf

Wameedh Adress

Papers

Ambient Temperature Hydrocarbon Selective Catalytic Reduction of NOx Using Atmospheric Pressure Nonthermal Plasma Activation of a Ag/Al2O3 Catalyst

Probing a Non-Thermal Plasma Activated Heterogeneously Catalyzed Reaction Using in Situ DRIFTS-MS

Investigation of a non-thermal atmospheric pressure plasma jet in contact with liquids using fast imaging

Comparison Study of Two Atmospheric Pressure Plasma Jet Configurations for Plasma-Catalyst Development

Investigation of non-thermal atmospheric pressure plasma jet in contact with liquids-using ICCD camera