Oxygen Generation by Carbon Dioxide Glow Discharge and Separation by Permeation Through Ultrathin Silver Membranes

Abstract

A six Torr CO2 glow discharge in combination with a heated W mesh‐reinforced ultrathin Ag membrane is used to generate molecular oxygen. The Ag membrane is a commercially available 25‐μm‐thick Ag foil backed by a 25‐μm‐thick W electroformed mesh. The permeation flux is inversely dependent on the membrane thickness and exponentially dependent on the membrane temperature. Calculations show that a pressure differential of 1 atmosphere can be supported by the W mesh/Ag foil membrane at temperatures up to 350 °C. In this work, a glow discharge for pressures between 2 and 15 Torr CO2 and temperatures up to 500 °C were reported. The DC glow discharge was produced initially with a solid Ag rod cathode, 2 mm in diameter, and then with a 7‐mm‐diameter Ag rod machined into a hollow cathode, located 5 mm from, and normal to, the Ag membrane anode. The voltage was varied from 440 to 620 VDC with currents up to 41 mA. A stable flux of 1.61 × 1015 O2 molecules·cm−2·s−1 is observed for a membrane temperature of 450 °C and a CO2 pressure of 6 Torr. With ~4‐m2 surface area, this approach is competitive with the present mission qualified Mars Oxygen In‐Situ Resource Utilization Experiment (MOXIE) system planned by National Aeronautics and Space Administration (NASA) for the 2020 Mars rover mission which generates ≈12 g/hr O2. The proof of concept technique presented herein can be substantially improved by further reduction of the membrane thickness, refinement of the cathode, and glow discharge plasma.

Advances in non-equilibrium $$\hbox {CO}_2$$ plasma kinetics: a theoretical and experimental review

“…In the shock layer of atmospheric entry body, there is a high temperature plasma, cooling while diffusing toward the low temperature surface [348,349]. An interesting application of the present section can be also to explore the possibility to create O 2 on the Mars soil from CO 2 taken from Mars atmosphere and transforming the CO 2 in CO and O 2 by using plasma discharges [2,[37][38][39].…”

“…J. D (2021) 75 :237 quency (RF) discharges [1][2][3][4], from few Torr to tens of Torr with RF and microwave discharges (MW) [5][6][7][8], at atmospheric pressure with gliding arc [9][10][11], dielectric barrier discharges (DBD) [12][13][14] or micro-hollow cathode discharges [15] and even above atmospheric pressure with nanosecond discharges [16,17].…”

“…The interest on CO 2 plasma, however, has a long history starting from the 1960s with a wide variety of applications, ranging from CO 2 lasers [18], to astrophysical observations [19,20], surface treatment processes on carbon-containing substrates [21][22][23][24][25][26] and polymer deposition [27][28][29], or the design of spacecraft shields for planetary atmosphere entry [30,[30][31][32][33][34][35][36]. Recently, also the possibility of in situ oxygen production from the CO 2 present locally in the atmosphere is being developed for futuristic human mission to Mars [2,[37][38][39].…”

“…From an experimental point of view, the majority of the works dedicated to conversion efficiency of CO 2 by plasma uses complex reactor configurations for which only the conversion rate α, defined as n CO /(n CO +n CO2 ), and the conversion energy efficiency η are measured. Several review papers [42][43][44][45] already compare the different plasma sources from [1][2][3][4][5][6][7][8][9][10][11][12][13][14]16,17] and others in terms of α and η. However, these two parameters are insufficient to gain a deep understanding of CO 2 plasma kinetics and a similar dissociation rate α can be calculated with very different kinetic schemes because of the complexity of the energy transfers taking place between excited states of CO 2 and its byproducts.…”

Oxygen atom kinetics in CO2 plasmas ignited in a DC glow discharge

“…This experimental approach can then be used as a basis for validating kinetic models and the knowledge acquired is essential to optimise the actual discharges to be used in future applications. Following this approach, we previously measured the vibrational temperatures of CO 2 and CO in a pulsed DC discharge for different pressures (1)(2)(3)(4)(5) and currents (10-50 mA) [53,54]. These first measurements showed a good agreement with a kinetic model describing the vibrational kinetics of CO 2 under conditions of very low dissociation rate (pulsed plasma at low repetition rate) in which the quantities of CO and O can be neglected [55,56].…”