Sustainable Non‐Thermal Plasma‐Assisted Nitrogen Fixation—Synergistic Catalysis

Abstract

In this Minireview, the multiple chemical synergies present in catalytic non‐thermal plasma‐assisted nitrogen fixation (NTPNF) are uncovered through a critical exploration of the underlying mechanisms, during which the catalyst, plasma, and reactants play different roles. For the gas‐phase NTPNF, the synergies consist of different aspects of the catalytic pathways such as electron‐impact dissociation; Zeldovich mechanism in the PNO interactions; and Eley–Rideal, Langmuir–Hinshelwood, surface adsorption, and diffusion mechanisms for the plasma–catalyst interactions. The synergies within the gas–liquid NTPNF involve contributions of plasma and UV excitation to the gas‐phase reactions and the UV excitation of molecules at the liquid–surface interface, which improves synthesis of aqueous nitrate, nitrite, and ammonium products. Based on the various synergistic mechanisms during NTPNF, future potential applications are proposed for how NTPNF could benefit the sustainable nitrogen fixation industry.

Conversion of CO2 by non- thermal inductively-coupled plasma catalysis

“…Research in this scientific field has revealed great potential and progress into using plasma technology to enable endothermic chemical reactions at low reactor temperatures, to improve the properties of catalysts and to synthesize renewable energy materials from greenhouse gases [4, 13 14]. So far different types of plasma technology [16][17][18][19][20][21][22][23][24][25][26] with or without catalysts have been tested on their performance compared to the traditionally thermal chemical processes. Especially a lot of work has been done on Dielectric Barrier Discharge (DBD) generated plasma to dissociate CO2.…”

Plasma-driven catalysis: green ammonia synthesis with intermittent electricity

“…Furthermore, various authors researched plasma-driven ammonia synthesis from CH 4 and N 2 (e.g., the feedstock for the SMR-based Haber-Bosch process), [133][134][135][136] as well as H 2 O and N 2 (e.g., the feedstock for the electrolysisbased Haber-Bosch process). [137][138][139][140][141][142] The challenge with using CH 4 , and even more with using H 2 O, is that the ammonia synthesis becomes endergonic. Although such a reaction can be driven by plasma, the energetically favourable reverse reaction is likely to compromise efficiency.…”

“…Extensive historical accounts can be found in other reviews. 82,84,90,141,261 The aim of this section is to show how recent insights in mechanisms can aid in the development of the field. The energy efficiency and conversion for various plasma reactor types are compared, describing the state of the art.…”

Direct Oxidative Nitrogen Fixation from Air and H2O by a Water Falling Film Dielectric Barrier Discharge Reactor at Ambient Pressure and Temperature

“…[7,8] Several methods of gas-phase NTPNF have been reported, where catalysts were used to improve the performance. [9] However, those methods are still limited by the low energy efficiency, for the nitrogen containing products may partially be decomposed once they are formed in the reactive plasma region, which restricts the nitrogen fixation yield and energy efficiency. [9,10] To overcome this shortcoming, gas-liquid NTPNF is of great interest, as the nitrogen compounds (NH 4 + , NO 2 À NO 3 À ) are directly produced from N 2 and H 2 O, and at the same time the nitrogen fixing products can dissolve in water to avoid decomposition in plasma ( Figure 1).…”

“…[9] However, those methods are still limited by the low energy efficiency, for the nitrogen containing products may partially be decomposed once they are formed in the reactive plasma region, which restricts the nitrogen fixation yield and energy efficiency. [9,10] To overcome this shortcoming, gas-liquid NTPNF is of great interest, as the nitrogen compounds (NH 4 + , NO 2 À NO 3 À ) are directly produced from N 2 and H 2 O, and at the same time the nitrogen fixing products can dissolve in water to avoid decomposition in plasma ( Figure 1). [11] In most of the recent studies on gas-liquid NTPNF, a "pin-toplate" design was adopted, [11,12] where reactions occurred at the small contact area between the plasma jet and the water surface, and only a volume of 10-20 mL can be accommodated by such reactors.…”