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Mars In Situ Oxygen Production, 18-9065

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Principal Investigators
Danny M. Deffenbaugh
Michael A. Miller
Steven T. Green

Inclusive Dates: 01/01/98 - 01/01/99

Background - The discovery of evidence of life in meteoritic rocks from Mars has renewed interest in sample return missions and in a manned mission to Mars. Although initial plans for a Mars mission were formulated during the Apollo program, no funding was provided to implement those ambitious plans. More recently, a number of studies have rekindled interest in a Mars mission. NASA plans an extensive exploration of Mars, including manned missions, in the early 21st century. One of the main goals of NASA’s Human Exploration and Development of Space enterprise is to establish a long-term human presence on Mars at a reasonable cost. To meet this objective, the launch mass of the Mars spacecraft must be significantly reduced. The initial propellant load of today’s spacecraft is over 90 percent of the total launch mass. If the fuel for the return trip were produced on Mars, the spacecraft’s mass could be reduced to one-sixth of its previous mass, enabling a launch with current technology. The challenge is to produce the needed return fuel on Mars using Martian resources.

Approach - The objective of this project is to develop and demonstrate in the laboratory a simple, reliable, low-power catalytic process for converting carbon dioxide (CO2) into carbon monoxide (CO) and oxygen. The conceptual approach is based on the electrochemical reduction of CO2 at a catalytic surface under potentiostatic conditions with selective separation of product gases. This approach involves developing an electrochemical cell (shown in the illustration) that comprises a solid electrolyte for oxygen conduction sandwiched between porous working and counter electrodes. The working electrode affects the electrochemical reaction that is facilitated by the catalytic properties of the electrode material and by the potential applied between this electrode and a counter electrode. From an electrochemical viewpoint, the reduction of CO2 is the reverse endoenergetic reaction that occurs in a low-temperature CO/O2 fuel cell. The reverse reaction is to be exploited in the present effort through careful choice of a catalytic surface for which only a slightly cathodic potential is needed to drive the electrochemical reduction.

Accomplishments - The energy burden for the electrochemical reduction of CO2 to oxygen and carbon monoxide may be reduced to a practical level through the appropriate design and selection of catalytic electrode materials and solid electrolytes. A number of electrocatalytic materials have been synthesized, and a select few have been shown by thermal desorption and recoiling mass spectrometry to be active in the heterogeneous reduction of CO2 at relatively low temperatures (ca. 150°C). These catalysts have been combined with electrically conductive support materials to form a porous working electrode. Support materials containing a proprietary mixture of an actinide oxide have remarkably efficient charge-transfer properties and low interfacial impedance. Ceramic electrolytes have been prepared as solid wafers through a pressing and sintering process that yields an oxygen-deficient microstructure for selective conduction of oxygen ions.

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SwRI-developed electrochemical cell is designed to produce
fuel-grade oxygen from carbon dioxide.

Chemistry and Chemical Engineering Program
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