SATPC0027452 Tab 04 SOW-UTA.2022.pdf

Statement of Work

1.0 ABSTRACT

This Statement of Work provides the details for cathode development by University of Texas

Arlington (UTA) in Arlington, TX. The goal of this effort is to solve the issue of shifting of selectivity towards hydrocarbons due to compositional changes in the cathode electro-catalyst with time for a microfluidic electrochemical reactor. To achieve this, develop an advanced cathode catalyst must be carried out. This statement of work provides the detailed tasks necessary to achieve this goal. Dr. Brian Dennis will serve as the primary point of contact for University of

Texas Arlington.

2.0 STATEMENT OF WORK

Introduction:

The current State of Art (SOA) Environmental Control and Life Support System (ECLSS) oxygen recovery technology is complex, heavy, and power consuming system that recovers approximately 50% of the oxygen from metabolic carbon dioxide (CO2). Lower mass and power consumption, less complexity, and higher oxygen recovery rates are all characteristics of an electrolytic oxygen recovery system, making it a desirable technology to be explored for future long duration missions. In 2016, NASA’s Game Changing Development Program awarded the

University of Texas at Arlington to develop an electrolytic oxygen recovery technology. During this effort, UT Arlington developed and tested a microfluidic electrochemical reactor (MFECR) that converts CO2 and water into oxygen and ethylene with a theoretical oxygen recovery rate of

73%. The MFECR operates at standard conditions, giving it an advantage over other technologies being investigated for future long duration missions which require high temperatures resulting in higher mass reactors and higher power consumption. The MFECR would replace three pieces of hardware: the current Carbon Dioxide Reduction Assembly

(Sabatier reactor), the Plasma Pyrolysis Assembly (PPA), and the Oxygen Generation Assembly

(OGA). It is designed to interface directly with the Carbon Dioxide Removal Assembly (CDRA) and Water Processing Assembly (WPA). This allows for a less complex system and higher reliability than the current SOA as well as reduced power, weight and water consumption of

ECLS systems.

The Engineering Design Unit (EDU) designed and tested by UT Arlington achieved a single loop

CO2 conversion of 37%. Traditional metal electrodes for CO2 electrochemical reduction have issues with CO2 conversion to carbon monoxide instead of conversion to useful hydrocarbons, as well as issues with rapid decrease in CO2 reduction within tens of minutes during electrolysis.

UT Arlington has developed and patented a cathode composed of electrodeposited copper oxide

– copper bromide films on Gas Diffusion Layer, which enhances CO2 conversion to mainly ethylene and generates H2 during the process.

The goal of this project is to continue the development of the advanced cathode catalyst in order to increase CO2 conversion rate. The following are the tasks required in order to advance the development of the cathode catalyst:

Baseline Tasks:

Task 1. Optimization of catalyst deposition on gas diffusion layer (GDL)

The electrochemical deposition method for producing the cathode catalyst on GDL was developed in 2016 for a GDL that is currently no longer in production. An alternative GDL (Sigracet 28 BC) was identified by the team in the previous stage of the project. Preliminary testing of the catalyst deposition with Sigracet 28 BC shows some optimization of the deposition process is going to be required. This will involve modifying the conductive backing that will contact the back of the GDL and create a more uniform current distribution. The deposition conditions will also be modified to increase the thickness and uniformity of the catalyst layer. The resulting depositions will be characterized by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) at various locations across the GDL diameter. The coated GDL will be subjected to hydrostatic pressure tests, which involve placing a GDL sample under a pressurized column of water. The pressure will be controlled by a regulator on a nitrogen gas tank. We will record the pressure where crossover of the liquid water is observed. This critical pressure will be used in the stack design task.

Task 2. Analyses and optimization of performance on cathode materials contacted with alkaline exchange membranes (AEM)

The UTA continuous flow cell will be modified to test the catalyst coated GDLs that are contacted with an AEM to see the impact on current density, product selectivity, and anode corrosion. Three different commercial AEMs will be tested. The GDLs will be prepared according the finding in Task 1. The use of a liquid electrolyte is important for maintaining performance overtime. The tests will be performed in suitable design of the flow electrochemical reactor where the electrolyte solution is constantly flowing and temperature controlled. The hydrodynamic voltammetry will be adjusted for the best performance.

The choice of KOH as electrolyte is our first because of the reaction rate of the competing hydrogen evolution reaction is suppressed in alkaline electrolytes. The Faradaic yields for conversion of CO2 to hydrocarbons will be followed by withdrawing gas aliquots and use online gas chromatography (GC) and gas chromatography –mass spectrometry (GC-MS) detection as a function of the electrolysis time.

Task 3. Testing of alternative electrolyte solution

Electrolytes have been shown to play a major role in the electroreduction of CO2. For example in aqueous solutions, bicarbonate, hydroxide, and alkali salts, such as KHCO3, NaHCO3 , KCl, K2SO4, NaOH, and KOH, are widely used as the supporting electrolytes. However, due to the extreme stability of the CO2 molecule, the low solubility, the potential that is necessary to apply for CO2 electrochemical reduction in water at 25 °C is high: −1.9 V vs. SHE, because the first electron reduction involves the bending of the linear CO2 molecule to form the [•CO2-] radical anion. Therefore, the energy required for the process is usually high, and the energy efficiency as well as yield of the desired product is generally low. The used of organic solvent such as acetonitrile, methanol, and room temperature ionic liquids as electrolyte have clearly showed the ability to lower the energy of the [•CO2-] intermediate thereby decreasing the initial barrier and lowing the overpotential of electrochemical CO2 reduction.

Furthermore, alkaline aqueous solutions (such as KOH and NaOH) at high pH, although shown effective for CO2 reduction, are highly corrosive and not desired. Organic solvents and/or room temperature ionic liquids have the potential to eliminate this concern. Here, we test the performance of the cathode materials in ionic liquids prepared by the NASA team to determine the effect of the electrolytes on the current density and product selectivity during the electroreduction of CO2 at different applied potentials.

Task 4. Fabrication of cathode and anode materials & Support for MFECR Testing

In this final task, UTA will fabricate the cathodes according to the finding in Task 1. UTA will also fabricate composite nickel foam anodes developed in the earlier stages of the project. These will be delivered to NASA for use in their reactor testbed. This task includes technical support required for the integration/installation of the electrodes into the MFECR test bed at NASA, assistance with the analysis of test data and troubleshooting.

Plan of Work

The work involves four tasks. Task 1 includes the optimization of the electrochemical deposition of the catalyst on the Sigracet 28 BC GDL. This task involves the modification of the existing deposition method and reactor in order to ensure to uniform deposition layer across the

GDL. Task 2 involves modifying the continuous flow cell to test the catalyst coated GDLs that are contacted with an AEM to see the impact on current density, product selectivity, and anode corrosion.

Three different commercial AEMs will be tested. The GDLs will be prepared according the finding in Task 1. Online gas chromatography (GC) will be used to determine product selectivity. In Task 3 we test the performance of the cathode materials in ionic liquids prepared by the NASA team to determine the effect of the electrolytes on the current density and product selectivity during the electro-reduction of CO2 at different applied potentials. Task 4 work involves fabrication of the cathodes for Microfluidic Electrochemical reactor (MFECR) and providing technical support required for the integration/installation of the cathodes into the MFECR at NASA MSFC, and providing assistance with the analysis of test data and troubleshooting

The timeline for the tasks is given in the chart below. Milestones are indicated with stars.

Milestone 1: Delivery of optimized cathodes to NASA