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Investigations into Flow Cell Electrolyzers for CO2 Reduction.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Investigations into Flow Cell Electrolyzers for CO2 Reduction./
作者:	Jeng, Emily.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
面頁冊數:	113 p.
附註:	Source: Masters Abstracts International, Volume: 82-10.
Contained By:	Masters Abstracts International82-10.
標題:	Chemical engineering. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28317444
ISBN:	9798597087887

Investigations into Flow Cell Electrolyzers for CO2 Reduction.
Jeng, Emily.

Investigations into Flow Cell Electrolyzers for CO2 Reduction. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 113 p.

Source: Masters Abstracts International, Volume: 82-10.

Thesis (M.S.)--University of Delaware, 2021.

This item must not be sold to any third party vendors.

The switch to renewable energy from fossil fuels as a source of electricity means that the issue of its intermittency must be addressed. One possible solution is to produce chemicals and fuels through electrochemical CO2 reduction, as a way of energy storage in the form of chemicals. For CO2 electroreduction to be feasible and practical in industrial applications, high current densities, or reaction rates, must be obtained. Therefore, developing electrolyzers, or reactors, for CO2 reduction has been receiving more attention recently, as a way to boost current densities. In this thesis, I will be discussing work involving different types of CO2 electrolyzers and various aspects that have been studied for further understanding of these electrolyzers.In the first chapter, I discuss the single-pass conversion for CO2 electrolyzers, a figure-of-merit that receives little attention in comparison to other figures-of-merits that are normally investigated (Faradaic efficiency, voltage, current densities, etc.). I mainly focus on the single-pass conversion of CO2 to CO in MEA-type electrolyzers, investigating how different parameters such as gas flow rate and temperature affected the overall single-pass conversion. A lower gas inlet flow rate (15, 30 mL/min) would result in a higher conversion, whereas higher gas inlet flow rates (greater than 80 mL/min) were limited by the gas diffusion through the GDL, which resulted in partial current densities being controlled by mass transport limitations. Increasing the temperature from room temperature up to 60 C improved the gas diffusivity, which resulted in higher partial current densities at lower voltages. However, regardless of gas inlet flow rate or temperature, the highest single-pass conversion to CO obtained was 43%. This conversion is limited by the CO2 being consumed by the side product hydroxide to form carbonates, resulting in an overall conversion of 95% for CO2 and thus less CO2 available. In addition, I also show that this consumption of CO2 by hydroxide affects the effluent stream of the electrolyzer, in which a maximum of 80% CO can be obtained at the single-pass conversion limit.In the next chapter, I switch to focusing on the three-compartment cell configuration, looking into the aspects for fabricating electrodes for that type of electrolyzer. Two different copper catalyst deposition methods onto the Gas Diffusion Layer (GDL) were compared: electron beam (E-beam) deposition and magnetron sputtering. The E-beam deposited copper showed better performance for CO2 electrolysis, as the copper deposited by magnetron sputtering had penetrated into the PTFE layer of the GDL, resulting in less hydrophobicity and thus more prone to flooding and shifting the selectivity to H2. The effect of catalyst loading was also investigated with E-beam deposited copper samples. Lower thicknesses (100 nm and 200 nm) showed worse performance due to less catalytic area available for CO2 electrolysis. However, too much catalyst loading (800 nm thickness) resulted in the copper catalyst starting to aggregate, with less porosity and catalytic surface area. The 400 nm E-beam deposited copper had shown the best performance of all the copper samples tested.While the work done in these chapters had provided insights into different aspects of CO2 electrolyzers, there is still work that needs to be done for further improvement of CO2 electrolyzers. For instance, for both of these electrolyzers, improved water management is still an issue that needs to be resolved, as flooding the catalyst would result in poor selectivity and stability. Looking into improving GDLs and flow fields for gas delivery would help in preventing flooding. In addition, CO2 forming carbonates as a side reaction is another challenging issue, as it limits the overall single-pass conversion for CO2 to other products, and can also result in poor stability from the salt formation blocking gas delivery. These are some of the issues that should be solved going forward in the development of CO2 electrolyzers.

ISBN: 9798597087887Subjects--Topical Terms:

560457
Chemical engineering.
Subjects--Index Terms:

Catalysts

Investigations into Flow Cell Electrolyzers for CO2 Reduction.
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100 1 $a Jeng, Emily. $3 3683836
245 1 0 $a Investigations into Flow Cell Electrolyzers for CO2 Reduction.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2021
300 $a 113 p.
500 $a Source: Masters Abstracts International, Volume: 82-10.
500 $a Advisor: Jiao, Feng.
502 $a Thesis (M.S.)--University of Delaware, 2021.
506 $a This item must not be sold to any third party vendors.
520 $a The switch to renewable energy from fossil fuels as a source of electricity means that the issue of its intermittency must be addressed. One possible solution is to produce chemicals and fuels through electrochemical CO2 reduction, as a way of energy storage in the form of chemicals. For CO2 electroreduction to be feasible and practical in industrial applications, high current densities, or reaction rates, must be obtained. Therefore, developing electrolyzers, or reactors, for CO2 reduction has been receiving more attention recently, as a way to boost current densities. In this thesis, I will be discussing work involving different types of CO2 electrolyzers and various aspects that have been studied for further understanding of these electrolyzers.In the first chapter, I discuss the single-pass conversion for CO2 electrolyzers, a figure-of-merit that receives little attention in comparison to other figures-of-merits that are normally investigated (Faradaic efficiency, voltage, current densities, etc.). I mainly focus on the single-pass conversion of CO2 to CO in MEA-type electrolyzers, investigating how different parameters such as gas flow rate and temperature affected the overall single-pass conversion. A lower gas inlet flow rate (15, 30 mL/min) would result in a higher conversion, whereas higher gas inlet flow rates (greater than 80 mL/min) were limited by the gas diffusion through the GDL, which resulted in partial current densities being controlled by mass transport limitations. Increasing the temperature from room temperature up to 60 C improved the gas diffusivity, which resulted in higher partial current densities at lower voltages. However, regardless of gas inlet flow rate or temperature, the highest single-pass conversion to CO obtained was 43%. This conversion is limited by the CO2 being consumed by the side product hydroxide to form carbonates, resulting in an overall conversion of 95% for CO2 and thus less CO2 available. In addition, I also show that this consumption of CO2 by hydroxide affects the effluent stream of the electrolyzer, in which a maximum of 80% CO can be obtained at the single-pass conversion limit.In the next chapter, I switch to focusing on the three-compartment cell configuration, looking into the aspects for fabricating electrodes for that type of electrolyzer. Two different copper catalyst deposition methods onto the Gas Diffusion Layer (GDL) were compared: electron beam (E-beam) deposition and magnetron sputtering. The E-beam deposited copper showed better performance for CO2 electrolysis, as the copper deposited by magnetron sputtering had penetrated into the PTFE layer of the GDL, resulting in less hydrophobicity and thus more prone to flooding and shifting the selectivity to H2. The effect of catalyst loading was also investigated with E-beam deposited copper samples. Lower thicknesses (100 nm and 200 nm) showed worse performance due to less catalytic area available for CO2 electrolysis. However, too much catalyst loading (800 nm thickness) resulted in the copper catalyst starting to aggregate, with less porosity and catalytic surface area. The 400 nm E-beam deposited copper had shown the best performance of all the copper samples tested.While the work done in these chapters had provided insights into different aspects of CO2 electrolyzers, there is still work that needs to be done for further improvement of CO2 electrolyzers. For instance, for both of these electrolyzers, improved water management is still an issue that needs to be resolved, as flooding the catalyst would result in poor selectivity and stability. Looking into improving GDLs and flow fields for gas delivery would help in preventing flooding. In addition, CO2 forming carbonates as a side reaction is another challenging issue, as it limits the overall single-pass conversion for CO2 to other products, and can also result in poor stability from the salt formation blocking gas delivery. These are some of the issues that should be solved going forward in the development of CO2 electrolyzers.
590 $a School code: 0060.
650 4 $a Chemical engineering. $3 560457
650 4 $a Chemistry. $3 516420
650 4 $a Alternative energy. $3 3436775
650 4 $a Sustainability. $3 1029978
653 $a Catalysts
653 $a Chemical reactions
653 $a Carbon dioxide reduction
653 $a Electrochemistry
653 $a Reactor design
653 $a Reactor engineering
653 $a Flow cell electrolyzers
690 $a 0542
690 $a 0485
690 $a 0640
690 $a 0363
710 2 $a University of Delaware. $b Chemical Engineering. $3 3178390
773 0 $t Masters Abstracts International $g 82-10.
790 $a 0060
791 $a M.S.
792 $a 2021
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28317444