Abstract:Photoelectrochemical devices integrate the processes of light absorption, charge separation, and catalysis for chemical synthesis. The monolithic design is interesting for space applications, where weight and volume constraints predominate. Hindered gas bubble desorption and the lack of macroconvection processes in reduced gravitation, however, limit its application in space. Physico‐chemical modifications of the electrode surface are required to induce gas bubble desorption and ensure continuous device operat… Show more
“…The dia- and paramagnetic phase separation mechanisms illustrated in this paper may thus enable the design of more efficient (photo-)electrolytic cells where bubbles are efficiently removed from the surface of the electrodes and passively collected using magnetic circuits. In combination with well-designed, hydrophilic (electrode) surfaces 91 , the magnetically induced buoyancy approach could provide a key advancement in low-gravity (photo-)electrolysis, boiling, and phase separation systems, among others, which in turn could represent a step-change in enabling human space exploration.…”
The absence of strong buoyancy forces severely complicates the management of multiphase flows in microgravity. Different types of space systems, ranging from in-space propulsion to life support, are negatively impacted by this effect. Multiple approaches have been developed to achieve phase separation in microgravity, whereas they usually lack the robustness, efficiency, or stability that is desirable in most applications. Complementary to existing methods, the use of magnetic polarization has been recently proposed to passively induce phase separation in electrolytic cells and other two-phase flow devices. This article illustrates the dia- and paramagnetic phase separation mechanism on MilliQ water, an aqueous MnSO4 solution, lysogeny broth, and olive oil using air bubbles in a series of drop tower experiments. Expressions for the magnetic terminal bubble velocity are derived and validated and several wall–bubble and multi-bubble magnetic interactions are reported. Ultimately, the analysis demonstrates the feasibility of the dia- and paramagnetic phase separation approach, providing a key advancement for the development of future space systems.
“…The dia- and paramagnetic phase separation mechanisms illustrated in this paper may thus enable the design of more efficient (photo-)electrolytic cells where bubbles are efficiently removed from the surface of the electrodes and passively collected using magnetic circuits. In combination with well-designed, hydrophilic (electrode) surfaces 91 , the magnetically induced buoyancy approach could provide a key advancement in low-gravity (photo-)electrolysis, boiling, and phase separation systems, among others, which in turn could represent a step-change in enabling human space exploration.…”
The absence of strong buoyancy forces severely complicates the management of multiphase flows in microgravity. Different types of space systems, ranging from in-space propulsion to life support, are negatively impacted by this effect. Multiple approaches have been developed to achieve phase separation in microgravity, whereas they usually lack the robustness, efficiency, or stability that is desirable in most applications. Complementary to existing methods, the use of magnetic polarization has been recently proposed to passively induce phase separation in electrolytic cells and other two-phase flow devices. This article illustrates the dia- and paramagnetic phase separation mechanism on MilliQ water, an aqueous MnSO4 solution, lysogeny broth, and olive oil using air bubbles in a series of drop tower experiments. Expressions for the magnetic terminal bubble velocity are derived and validated and several wall–bubble and multi-bubble magnetic interactions are reported. Ultimately, the analysis demonstrates the feasibility of the dia- and paramagnetic phase separation approach, providing a key advancement for the development of future space systems.
“…Current developments of photoelectrochemical devices for terrestrial applications aim at operation in aqueous electrolytes at near-neutral pH which also represents a safety advantage 34 . Photoelectrolytic half-cells for hydrogen production have been tested in drop tower experiments where they could operate at terrestrial efficiencies 35 , 36 .…”
Section: Application Of Electrolyzer Systems In Spacementioning
confidence: 99%
“…4b . The wettability of plane and modified surfaces with respect to hydrogen and oxygen bubbles in microgravity conditions was studied by Akay et al (2021), Brinkert et al (2018) and Sakuma et al (2008, 2014) 35 , 36 , 46 , 54 . Fig.…”
Section: Electrochemical Gas Bubble Evolutionmentioning
confidence: 99%
“…5b . This decreases the effective area of the electrocatalyst, impedes mass transport and increases the reaction overpotential 36 . To avoid the obvious complexity arising from the interaction of multiple bubbles, several studies on the dynamics of single hydrogen or oxygen bubble were performed on microelectrodes 46 , 63 , 64 .…”
Section: Electrochemical Gas Bubble Evolutionmentioning
Electrochemical energy conversion technologies play a crucial role in space missions, for example, in the Environmental Control and Life Support System (ECLSS) on the International Space Station (ISS). They are also vitally important for future long-term space travel for oxygen, fuel and chemical production, where a re-supply of resources from Earth is not possible. Here, we provide an overview of currently existing electrolytic energy conversion technologies for space applications such as proton exchange membrane (PEM) and alkaline electrolyzer systems. We discuss the governing interfacial processes in these devices influenced by reduced gravitation and provide an outlook on future applications of electrolysis systems in, e.g., in-situ resource utilization (ISRU) technologies. A perspective of computational modelling to predict the impact of the reduced gravitational environment on governing electrochemical processes is also discussed and experimental suggestions to better understand efficiency-impacting processes such as gas bubble formation and detachment in reduced gravitational environments are outlined.
“…Major energy losses are still observable with the direct CO 2 electrolysis set-up due to the high overpotential of the electrochemical CO 2 reduction reaction (CO 2 RR) at the cathode, illustrating that further research into electrocatalysts and electrolyte optimization is required to optimize this system and improve its feasibility for space applications. The powergenerating component for an electrosynthesis device could be ultra-light-weight photovoltaic (PV) modules or integrated photoabsorber-electrocatalyst systems, so-called photoelectrochemical (PEC) devices [60][61][62] . The latter systems provide the possibility of integrating light-absorption, charge separation and catalysis and could represent significant weight and volume advantages.…”
Section: Electrochemistry For Fuel Productionmentioning
Long-term space missions require power sources and energy storage possibilities, capable at storing and releasing energy efficiently and continuously or upon demand at a wide operating temperature range, an ultra-high vacuum environment and a significantly reduced buoyant force. Electrochemical energy conversion systems play already a major role e.g., during launch and on the International Space Station, and it is evident from these applications that future human space missions - particularly to Moon and Mars - will not be possible without them. Here, we will provide an overview of currently existing electrochemical conversion technologies for space applications such as battery systems and fuel cells and outline their role in materials design and fabrication as well as fuel production. The focus lies on the current operation of these energy conversion systems in space as well as the challenges posed on them by this special environment. Future experiment designs which could help elucidating and optimizing their key operating parameters for an efficient and long-term operation are discussed.
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