Direct Generation of Oxygen via Electrocatalytic Carbon Dioxide Reduction with an Ionic Liquid

Holquist, Jordan Barr

Graduate Thesis Or Dissertation

Direct Generation of Oxygen via Electrocatalytic Carbon Dioxide Reduction with an Ionic Liquid Public Deposited

Analytics

Download PDF

Citations

Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/73666478n

Abstract

The feasibility of long duration crewed space exploration missions will depend on the supply of consumables, such as oxygen, to keep the crew alive. Air revitalization is a function of environmental control and life support systems (ECLSS) employed on any crewed spacecraft. On longer duration missions, such as on the International Space Station (ISS), resource regeneration reduces the amount of consumables that must be provided for the mission. Systems on the ISS recover O₂ from metabolically produced CO₂, which itself is collected from the ISS cabin where astronauts live and work. The current state-of-the-art for O₂ recovery onboard the ISS can only recover up to 54% of the O₂ available in respired CO₂ and relies on the resupplied H₂O to the ISS. An alternative O₂ generation process is solvated electrochemical CO₂ reduction, enabled in spacecraft environments by using a non-volatile ionic liquid (IL) solvent, electrolyte, and catalysis promoter. An electrochemical CO₂ reduction system (ECRS) could improve O₂ recovery from CO₂ by up to 70%, or it could function to recover 50% O₂ from CO₂ without a net water loss, which can be advantageous in missions where in-situ resource utilization (ISRU) of Martian atmospheric CO₂ is desired. Ionic liquid supported electrochemical CO₂ reduction is evaluated to determine its feasibility for space applications. The requirements, sizing, and challenges of including an ECRS are considered for various possible ECLSS or ISRU architectures. The current state-of-the-art for IL supported CO₂ electrolysis is reviewed, and selections of ILs studied experimentally in this work are presented and justified. Thermophysical properties of the ILs as neat and aqueous solutions are measured to aid in understanding and design of the ILs themselves and in systems using them. Aqueous IL solutions are studied using cyclic voltammetry and constant potential electrolysis with gaseous product analysis to determine if and how the selected ILs promote electrochemical CO₂ reduction. A concept for a vacuum-assisted product removal (VAPR) CO₂ electrolyzer is presented as a possible solution to space application environmental conditions and requirements, and the concept is demonstrated through the design and testing of a prototype electrolyzer.

Creator